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METHOD 514.8

METHOD 514.8
VIBRATION
NOTE: Tailoring is essential. Select methods, procedures, and parameter levels based on the tailoring process
described in Part One, paragraph 4, and Part One, Annex C. Apply the general guidelines for laboratory test methods
described in Part One, paragraph 5 of this standard. For vibration schedule development, see Annex F.
The vibration profiles provided in Annexes B through E of this Method are default curves that are generally
developed as a composite of multiple locations acquired from multiple vehicles of a similar construct. For
technical guidance / contact information regarding the existence and availability of either item-specific or location-
specific vibration profiles that may reside in various archives, see Part One, page iii, for Service points-of-contact. In
addition, Test Operations Procedure (TOP) 01-2-601 (paragraph 6.1, reference d), includes an assortment of specific
ground vehicle vibration data and TOP 01-2-603 (paragraph 6.1 reference xx) includes several specific helicopter
vibration data.

Organization. The main body of this Method is arranged similarly to the other methods of MIL-STD-810H. A
considerable body of supplementary information is included in the Annexes. With the exception of Table 514.8-I, all
tables and figures for the entire method are in Annexes B through F. Annex A provides definitions and engineering
guidance useful in interpreting and applying this Method. Annexes B through F provide guidance for estimating
vibration levels and durations and for selection of test procedures. Reference citations to external documents are at
the end of the main body (paragraph 6). It is highly recommended that users read Annex A before applying the
vibration schedules in Annexes B through E or the vibration schedule development process in Annex F. The
Annexes are as follows:
ANNEX A – ENGINEERING INFORMATION
ANNEX B – MANUFACTURE / MAINTENANCE TAILORING GUIDANCE FOR VIBRATION EXPOSURE
DEFINITION
ANNEX C – TRANSPORTATION TAILORING GUIDANCE FOR VIBRATION EXPOSURE DEFINITION
ANNEX D – OPERATIONAL TAILORING GUIDANCE FOR VIBRATION EXPOSURE DEFINITION
ANNEX E – SUPPLEMENTAL TAILORING GUIDANCE FOR VIBRATION EXPOSURE DEFINITION
ANNEX F – DEVELOPMENT OF LABORATORY VIBRATION TEST SCHEDULES

1. SCOPE.
1.1 Purpose.
The purpose of this Method is to provide guidance for defining vibration environments materiel may be exposed to
throughout a life cycle and to provide guidance for the conduct of laboratory vibration tests. Vibration tests are
performed to:
a. Develop materiel to function in and withstand the vibration exposures of a life cycle including synergistic
effects of other environmental factors, materiel duty cycle, and maintenance.
b. Verify that materiel will function in and withstand the vibration exposures of a life cycle.
1.2 Application.
a. General. Use this Method for all types of materiel except as noted in Part One, paragraph 1.3, and as stated
in paragraph 1.3 below. For combined environment tests, conduct the test in accordance with the applicable
test documentation. However, use this Method for determination of vibration test levels, durations, data
reduction, and test procedure details.
b. Purpose of test. The test procedures and guidance herein are adaptable to various test purposes including
development, reliability, qualification, etc. See Annex A for definitions and guidance.

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c. Vibration life cycle. Table 514.8-I provides an overview of various life cycle situations during which some
form of vibration may be encountered, along with the anticipated platform involved. Annex A provides
definitions and engineering guidance useful in interpreting and applying this Method. Annexes B - E provide
guidance for estimating vibration levels and durations and for selection of test procedures. Test Operations
Procedure (TOP) 01-2-601 (paragraph 6.1, reference d), includes an assortment of specific ground vehicle
data. TOP 01-2-603 (paragraph 6.1, reference xx) includes a few specific helicopter profiles and will be
updated as more data become available.
d. Manufacturing. The manufacture and acceptance testing of materiel involves vibration exposures. These
exposures are not directly addressed herein. It is assumed that materiel undergoes environmental testing
during the manufacturing and acceptance process and this process produces the same environmental damage
for any deliverable materiel. Thus the tests described in this Method are designed to verify the field life of
the delivered materiel. When a change is made to the manufacturing process that involves increased vibration
exposure, evaluate this increased vibration exposure to ensure the field life of subsequent materiel is not
shortened. An example might be pre-production materiel completely assembled in one building, whereas
production units are partially assembled at one site and then transported to another site for final assembly.
Changes in the manufacturing vibration environment should be evaluated with regard to the need for design
and (re)qualification. (See Annex B)
e. Environmental Stress Screening (ESS). Many materiel items are subjected to ESS, burn-in, or other
production acceptance test procedures prior to delivery to the government, and sometimes during
maintenance. As in basic production processes, it is assumed that both the test units and the field units receive
the same vibration exposures, so that environmental test results are valid for the field units. Where units do
not necessarily receive the same exposures, such as multiple passes through ESS, apply the maximum
allowable exposures to the items used for environmental test as pre-conditioning for the environmental tests.
(See Annex A, paragraph 2.1.6, and Annex B, paragraph 2.3.)

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1.3 Limitations.
a. Safety testing. This Method may be used to apply specific safety test requirements as coordinated with the
responsible safety organization. However, vibration levels or durations for specific safety related issues
are not provided or discussed.
b. Platform/materiel interaction. In this Method, vibration requirements are generally expressed as inputs to
materiel that is considered to be a rigid body with respect to the vibration exciter (platform, shaker, etc.).
While this is often not true, it is an acceptable simplification for smaller materiel items. This method does
not attempt to address the validity of this assumption and leaves it to the user to determine proper treatment
of a given materiel item/platform. The guidance below addresses typical platform/material interaction
scenarios. Additional discussion of platform/materiel interaction is provided in Annex A, paragraph 2.4.
(1) Where impedance mismatch between platform/materiel and laboratory vibration exciter/test
item are significantly different, force control or acceleration limiting control strategies may be
required to avoid unrealistically severe vibration response (see paragraph 4.2). The use of
control limits should be based upon field data measurements and the sensitivity of the materiel
to excessive vibratory loading (e.g., a resonance condition).
(2) In certain cases in which the field measured response is well defined on a small component and
the duration of the vibration is short, execution of the laboratory test under open loop waveform
control based upon the field measured data is an option.
(3) For large materiel items, it is necessary to recognize that the materiel and the exciter vibrate as
a single flexible system and may be difficult to control as a laboratory vibration test. An
example is a shelter transported to the field as a pre-assembled office, laboratory, etc. A suitable
test for such systems would be the large assembly transport test (Procedure III) of
paragraph 4.4.3.
(4) Proper treatment of a given materiel item may vary throughout the life cycle. An example
might be a galley designed for an aircraft. For the operational environment (installation on an
operating aircraft), consider the galley structure as aircraft secondary structure, and design and
test accordingly. Design subassemblies within the galley (e.g., coffee maker) for vibration
levels based on guidance of Annex D, and tested in accordance with Procedure I. When
packaged for shipment, the packaging, galley, and subassemblies are considered a single
materiel item, and tested accordingly.
c. Environmental Stress Screening (ESS). This Method does not contain guidance for selection of ESS
exposures. Some discussion is in Annex A, paragraph 2.1.6, and Annex B, paragraph 2.3.
d. Multiple Exciter Testing. This Method is limited to consideration of one mechanical degree-of-freedom
based on a spectral reference. Refer to Method 527 for further guidance on multiple exciter testing, and
Method 525 for time waveform replication.
e. Synergistic Effects. Combine the guidance of this Method with the guidance of Part One and other methods
herein to account for environmental synergism.
2. TAILORING GUIDANCE
2.1 Selecting this Method.
Essentially all materiel will experience vibration, whether during manufacture, transportation, maintenance, or
operational use. The procedures of this Method address most of the life cycle situations during which vibration is
likely to be experienced. Select the procedure or procedures most appropriate for the materiel to be tested and the
environment to be simulated. See Table 514.8-I for a general listing of vibration exposures and test procedures as
related to environmental life cycle elements. See Annexes B-F for guidance on determining vibration levels and
durations.
a. Fidelity of the laboratory test environment. As noted in Part I (Paragraph 1.3), laboratory test methods are
limited in their abilities to simulate synergistic or antagonistic stress combinations, dynamic (time

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sequence) stress applications, aging, and other potentially significant stress combinations present in natural
field/fleet service environments. Use caution when defining and extrapolating analyses, test criteria, and
results. An assessment of the test article vulnerabilities should be used to determine the environmental
variables that are essential to the laboratory test and potential for increased margin to compensate for
deficiencies in the test environment. Reduction in test environment fidelity may lead to an increased risk
to material life and function in the fielded environment.
b. Conservatism with measured data. The guidance in this document encourages the use of materiel-specific
measured data as the basis for vibration criteria. Due to limitations in numbers of transducers, accessibility
of measurement points, linearity of data at extreme conditions, and other causes, measurements do not
include all extreme conditions. Further, there are test limitations such as single axis versus multi-axis, and
practical fixtures versus platform support. Apply margin to measured data in deriving test criteria to
account for these variables. When sufficient measured data are available, use statistical methods as shown
in Annex F.
c. Conservatism with default or enveloped data. Annexes B - E of this Method provide information that can
be used to generate default criteria for those cases where measured data are unavailable. These data are
based on envelopes of wide ranges of cases and are conservative for any one case. Additional margin is
not recommended. Use caution when conducting vibration test with default or enveloped vibration data if
non-linear behavior is expected or observed at full test level. If non-linear behavior is a concern, a ramp
up step should be added to the test schedule. The vibration amplitude of this additional ramp up step shall
have an exaggeration factor of unity. This unity ramp up step duration should be at least 10 minutes. The
data measured during full test level and the unity ramp up step can be used to evaluate the linearity of the
materiel during accelerated test. If materiel is determined to behave non-linearly using the above
technique, the organization responsible for the materiel under test shall be notified. Test options should be
explored and a proposed path forward should be identified. The test options and proposed path forward
should be sent to the appropriate test authority for concurrence prior to proceeding.

NOTE: The materiel’s anticipated Life Cycle Environmental Profile (LCEP) may reveal other vibration
scenarios that are not specifically addressed in the procedures. Tailor the procedures as necessary to capture
the LCEP variations, but do not reduce the basic test requirements reflected in the below procedures without
proper justification. (See paragraph 2.3 below.)

2.1.1 Effects of environment.

Vibration results in dynamic deflections of and within materiel. These dynamic deflections and associated velocities
and accelerations may cause or contribute to structural fatigue and mechanical wear of structures, assemblies, and
parts. In addition, dynamic deflections may result in impacting of elements and/or disruption of function. Some
typical symptoms of vibration-induced problems follow. This list is not intended to be all-inclusive:
a. Chafed wiring.
b. Loose fasteners/components.
c. Intermittent electrical contacts.
d. Electrical shorts.
e. Deformed seals.
f. Failed components.
g. Optical or mechanical misalignment.
h. Cracked and/or broken structures.
i. Migration of particles and failed components.
j. Particles and failed components lodged in circuitry or mechanisms.

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k. Excessive electrical noise.

l. Fretting corrosion in bearings.
2.1.2 Sequence.
Use the anticipated life cycle sequence of events as a general sequence guide (see Part One, paragraph 5.5).
a. General. The accumulated effects of vibration-induced stress may affect materiel performance under other
environmental conditions such as temperature, altitude, humidity, leakage, or electromagnetic interference
(EMI/EMC). When evaluating the cumulative environmental effects of vibration and other environments,
expose a single test item to all environmental conditions, with vibration testing generally performed first.
If another environment (e.g., temperature cycling) is projected to produce damage that would make the
materiel more susceptible to vibration, perform tests for that environment before vibration tests. For
example, thermal cycles might initiate a fatigue crack that would grow under vibration or vice versa.
b. Unique to this Method. Generally, expose the test item to the sequence of individual vibration tests that
follow the sequence of the life cycle. For most tests, this can be varied if necessary to accommodate test
facility schedules, or for other practical reasons. Complete all manufacture associated preconditioning
(including ESS) before any of the vibration tests. Complete any maintenance associated preconditioning
(including ESS) prior to tests representing mission environments. Perform tests representing critical end-
of-mission environments last.
2.2 Selecting Procedures.
Identify the environments of the materiel life cycle during the tailoring process as described in Part One, paragraph 4.
Table 514.8-I provides a list of vibration environments by category versus test procedure. Descriptions of each
category listed in this table are included in Annexes B - E, along with information for tailoring the test procedures of
paragraph 4 below, and alternate test criteria for use when measured data are not available. In general, test the materiel
for each category to which it will be exposed during an environmental life cycle. Tailor test procedures to best
accomplish the test purpose (see Annex A, paragraph 2.1), and to be as realistic as possible (see Annexes B-E,
paragraphs 1.2).
2.2.1 Procedure selection considerations.
Vibration test profiles may be omitted from an overall test series depending on relative profile severity. Profile
severity comparisons shall include fatigue damage potential (test duration and bandwidth), vibration amplitude, and
spectral content within the profile bandwidth. Analytical estimates of fatigue damage potential should be made on
the basis of simple, well-understood models of the materiel, when and if possible.
Another method for reducing test duration is through a combination of spectra techniques. Combinations of random
vibration test profiles may be performed if the reference spectra and bandwidths are similar by either employing the
fatigue damage spectrum (FDS) or via statistical methods (refer to Annex F). Combination of vibration tests should
not be performed with dissimilar spectra or spectra with dissimilar bandwidths. Examples of dissimilar spectra are
random, sine, sine on random, sweeping sine on random, or sweeping random on random. For example, combining a
broadband random (e.g. wheeled vehicle) spectrum with a sine-on-random spectrum (e.g. helicopter) should be
avoided. Observe that the FDS example provided in Annex F is quite liberal in combining spectral shapes. Factors
such as vibration magnitudes and unit under test (UUT) robustness should always be considered in establishing
combined spectra based requirements.
Extreme caution should be used if test schedule compression is used to combine tests. Too much compression could
result in entering non-linear regions of mechanical response which is undesirable. Highly conservative specifications
with no correlation to actual discrete environmental conditions can lead to unnecessary overdesign. Furthermore,
combining spectra can result in the inability to relate a failure mechanism to a discrete vibration environment. Finally,
careless combination of spectra has the potential to yield a test that is difficult to conduct and control. Additionally,
enveloping or combining spectra could result in the loss of vehicle anti-resonances which may be necessary for
laboratory replication. These considerations are especially important for multi-axis test setups and profile definitions.
In evaluation of the relative severity of environments, include the differences in transportation configuration
(packaging, shoring, folding, etc.) and application configuration (mounted to platform, all parts deployed for service,

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etc.). In addition, transportation environments are usually defined as inputs to the packaging, whereas application
environments are expressed as inputs to the materiel mounting structure or as response of the materiel to the
environment.
a. Transportation vibration more severe than application environment. Transportation vibration levels are
often more severe than application vibration levels for ground-based and some shipboard materiel. In this
case, both transportation and platform vibration tests are usually needed because the transportation test is
performed with the test item non-operating, and the platform test is performed with the test item operating.
b. Application vibration more severe than transportation vibration. If the application vibration levels are more
severe than the transportation levels, it may be feasible to delete transportation testing. It may also be
feasible to change the application test spectrum shape or duration to include transportation requirements in
a single test. In aircraft applications, a minimum integrity test (see Annex E, paragraph 2.1) is sometimes
substituted for transportation and maintenance vibration requirements.
c. Any omission or combination of spectra techniques employed should be agreed to by the responsible test
authority prior to the conduct of testing and should be thoroughly documented in the test report.
2.2.2 Difference among procedures.
a. Procedure I - General Vibration. Use Procedure I for materiel to be transported as secured cargo or
deployed for use on a vehicle. This procedure applies to ground vehicles as well as fixed and rotary wing
aircraft. For this procedure, the test item is secured to a vibration exciter, and vibration is applied to the
test item as an input at the fixture/test item interface. Steady state or transient vibration may be applied as
appropriate.
b. Procedure II - Loose Cargo Transportation. Use this procedure for materiel to be carried in/on trucks,
trailers, or tracked vehicles and not secured to (tied down in) the carrying vehicle. The test severity is not
tailorable, and represents loose cargo transport in military vehicles traversing rough terrain.
c. Procedure III - Large Assembly Transportation. This procedure is intended to replicate the vibration and
shock environment incurred by large assemblies of materiel installed or transported by wheeled or tracked
vehicles. It is applicable to large assemblies or groupings forming a high proportion of vehicle mass, and
to materiel forming an integral part of the vehicle. In this procedure, use the specified vehicle type to
provide the mechanical excitation to the test materiel. The vehicle is driven over surfaces representative
of service conditions, resulting in realistic simulation of both the vibration environment and the dynamic
response of the test materiel to the environment. Generally, measured vibration data are not used to define
this test. However, measured data are often acquired during this test to verify that vibration and shock
criteria for materiel subassemblies are realistic.
d. Procedure IV - Assembled Aircraft Store Captive Carriage and Free Flight. Apply Procedure IV to fixed
wing aircraft carriage and free flight portions of the environmental life cycles of all aircraft stores, and to
the free flight phases of ground or sea-launched missiles. Use Procedure I, II, or III for other portions of
the store’s life cycle as applicable. Steady state or transient vibration may be applied as appropriate. Do
not apply Procedure I to fixed wing aircraft carriage or free flight phases.
2.3 Determine Test Levels and Conditions.
Select excitation form (steady state or transient), excitation levels, control strategies, durations and laboratory
conditions to simulate the vibration exposures of the environmental life cycle as accurately as possible. Whenever
possible, acquire measured data as a basis for these parameters. Annexes B - E include descriptions of various phases
typical of an environmental life cycle, along with discussions of important parameters and guidance for developing
test parameters. Annex A has further guidance in interpretation of technical detail.
2.3.1 Climatic conditions.
Many laboratory vibration tests are conducted under standard ambient test conditions as discussed in Part One,
paragraph 5. However, when the life cycle events being simulated occur in environmental conditions significantly
different than standard conditions, consider applying those environmental factors during vibration testing. Individual
climatic test methods (Methods 501.6 and 502.6) of this Standard include guidance for determining levels of other

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environmental loads. For temperature-conditioned environmental tests, (high temperature tests of explosive or
energetic materials in particular), consider the materiel degradation due to extreme climatic exposure to ensure the
total test program climatic exposure does not exceed the life of the materiel. (See Part One, paragraph 5.19.)
2.3.2 Test item configuration.
Configure the test item for each test as it will be in the corresponding life cycle phase. In cases representing
transportation, include all packing, shoring, padding, or other configuration modifications of the particular shipment
mode. The transportation configuration may be different for different modes of transportation.
a. Loose cargo. The procedure contained herein is a general representation based on experience as well as
measurement, and is not tailorable (see Annex C, paragraph 2.2 for details). The most realistic alternative
for truck, trailer, or other ground transportation is to use Procedure II that requires the transportation vehicle
and a full cargo load. In this test, the cargo has freedom to bounce, scuff and collide with other cargo and
with the sides of the vehicle. The loose cargo environment includes conditions experienced by cargo
transported in a vehicle traversing irregular surfaces. This test replicates the repetitive impact environment
incurred by cargo transported under these conditions.
b. Secured cargo. Procedure I assumes no relative motion between the vehicle cargo deck or cargo
compartment and the cargo. This applies directly to materiel that is tied down or otherwise secured such
that no relative motion is allowed considering vibration, shock, and acceleration loads. When restraints
are not used or are such as to allow limited relative motions, provide allowance in the test setup and in the
vibration excitation system to account for this motion. Procedure III is an alternative for ground
transportation.
c. Stacked cargo. Stacking or bundling of sets or groups of materiel items may affect the vibration transmitted
to individual items. Ensure the test item configuration includes appropriate numbers and groupings of
materiel items.
2.3.3 Multiple Exciter Consideration.
Method 527.1 addresses scenarios in which the test item size requires use of more than one exciter or test fidelity
requires more than one mechanical degree-of-freedom. In general, if a test facility has the capability to address more
than one mechanical degree-of-freedom, and if such testing can be conducted in a time and cost effective manner,
multiple axis testing should be considered as a test option. If the default curves provided within various categories of
Method 514.8 are used as reference curves in a multiple-axis test, it should be recognized that Cross Spectral Density
(CSD) terms will be undefined. Method 527 recommends that the coherence terms be near zero. Some reduction in
levels (e.g., lower conservatism factors) may be justified if it can be shown that the multiple degree-of-freedom
(MDOF) test produces significantly higher stress levels or lower fatigue life than the sequential single degree-of-
freedom (SDOF) tests.

2.4 Test Item Operation.

Where vibration tests are conducted to determine operational capability while exposed to the environment, operate
the test item during the vibration test. Otherwise, verify operation before and after the vibration test. Use caution when
applying combined or enveloped vibration profiles during operational tests as the levels may not be representative of
any particular operational environment. During operational vibration tests, monitor and record sufficient data to define
the achieved performance and sensitivity of the materiel to the vibration environment. See Annex A, paragraph 2.1.2.1
for additional functional test considerations.

3. INFORMATION REQUIRED.
The following information is required to conduct and document vibration tests adequately. Tailor the lists to the
specific circumstances, adding or deleting items as necessary. Although generally not required in the past, perform
fixture and materiel modal surveys when practical. These data are useful in evaluating test results, and in evaluating
the suitability of materiel against changing requirements or for new applications. These data can be particularly
valuable in future programs where the major emphasis will be to use existing materiel in new applications. (When

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modal survey is ruled out for programmatic reasons, a simple resonance search can sometimes provide useful
information.)
3.1 Pretest.
The following information is required to conduct vibration tests adequately.
a. General. See Part One, paragraphs, 5.7 and 5.9, and Part One, Annex A, Task 405 of this Standard.
b. Specific to this Method (applicable to Procedures I through IV).
(1) Test schedule(s) and duration of exposure(s).
(2) Locations and specifications for all control and/or response transducers.
(3) Test equipment limitations. Assure that test requirements (force, acceleration, velocity, displacement)
can be met. Seek approval for variation if required. Document any variation.
(4) Test shutdown procedures for test equipment or test item problems, failures, etc. (See paragraph 4.3).
(5) Test interruption recovery procedure. (See paragraph 4.3).
(6) Test completion criteria.
(7) Allowable adjustments to test item & fixture (if any); these must be documented in test plan and the
test report.
c. Tailoring, Necessary variations in the basic test parameters/testing materials to accommodate LCEP
requirements and/or facility limitations.
d. Specific to Procedure.
(1) Procedure I and IV- General and captive carriage/free flight vibration.
i. Test fixture requirements.
ii. Test fixture modal survey requirements / procedure.
iii. Test item / fixture modal survey requirements / procedure.
iv. Vibration exciter control strategy.
v. Test tolerances.
vi. Test temperature conditioning requirements.
vii. Combined environment requirements (e.g., temperature, humidity).
viii. Axes of exposure.
(2) Procedure II - Loose cargo vibration.
i. Orientation of test item(s) in relation to the axis of throw of the test table
ii. Number of possible test item orientations.
iii. Test time per orientation.
iv. Test item temperature conditioning requirements.
v. Test fixture requirements.
(3) Procedure III - Large assembly transport.
i. Test vehicle(s).
ii. Vehicle load configuration(s).
iii. Required road surface(s).
iv. Required distance(s) on each road surface.
v. Required speed(s) on each road surface.
vi. Vehicle suspension configuration(s) i.e., tire pressures (or Central Tire Inflation System

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(CTIS) settings), suspension settings (as applicable) etc.

NOTE: Modal surveys of both test fixtures and test items can be extremely valuable. Large test items
on large complex fixtures are almost certain to have fixture resonances within the test range. These
resonances may result in significant overtests or undertests at specific frequencies and locations within a
test item. Where fixture and test item resonances couple, the result can be catastrophic. Similar problems
often occur with small test items, even when the shaker/fixture system is well designed because it is very
difficult and often impractical to achieve a lowest fixture resonant frequency above 2000 Hz. In cases
where the fixture/item resonance coupling cannot be eliminated, consider special vibration control
techniques such as acceleration or force limit control.

3.2 During Test.

Document the following information during conduct of the test:
a. Collect the information listed in Part One, paragraph 5.10, and in Part One, Annex A, Tasks 405 and 406
of this Standard. Document any adjustments to the test item and fixture identified by the test plan,
including planned stopping points. (See also paragraph 4.3.)
b. Document the vibration exciter control strategy used, e.g., single point response, multipoint response, force
limit, waveform, etc.
c. Refer to the test-specific plan to address any additional data that may be required during the test phase.
3.3 Post-Test.
The following post test data, if applicable, shall be included in the test report.
a. General. See Part One, paragraph 5.13, and Part One, Annex A, Task 406 of this Standard.
b. Specific to this Method.
(1) Summary and chronology of test events, test interruptions, and test failures.
(2) Discussion and interpretation of test events.
(3) Functional verification data.
(4) Test item modal analysis data.
(5) All vibration measurement data.
(6) Documentation of any test requirement variation (paragraph 3.1 b (7))
(7) Any changes from the original test plan.
(8) Record of combined environment parameters (i.e., temperature and humidity).
4. TEST PROCESS.
Tailor the following paragraphs as appropriate for the individual program.
4.1 Test Facility.
Use a test facility, including all auxiliary equipment, capable of providing the specified vibration environments and
the control strategies and tolerances discussed in paragraph 4.2. In addition, use measurement transducers, data
recording and data reduction equipment capable of measuring, recording, analyzing, and displaying data sufficient to
document the test and to acquire any additional data required. Unless otherwise specified, perform the specified
vibration tests and take measurements at standard ambient conditions as specified in Part One, paragraph 5.1.
4.1.1 Procedure I - General vibration.
This procedure uses standard laboratory vibration exciters (shakers), slip tables, and fixtures. Choose the specific
exciters to be used based on:
a. the size and mass of test items and fixtures;

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b. the frequency range required;

c. the force, acceleration, velocity, and displacement required.
4.1.2 Procedure II - Loose cargo transportation.
Simulation of this environment requires use of a package tester (Annex C, Figure 514.8C-8) that imparts a 25.4 mm
(1.0 inch) peak-to-peak, circular synchronous motion to the table at a frequency of 5 Hz. This motion takes place in
a vertical plane. The figure shows the required fixturing. This fixturing does not secure the test item(s) to the bed of
the package tester. Ensure the package tester is large enough for the specific test item(s) (dimensions and weight).
4.1.3 Procedure III - Large assembly transport.
The test facility for this Procedure is a test surface(s) and vehicle(s) representative of transportation and/or service
phases of the environmental life cycle. The test item is loaded on the vehicle and secured or mounted to represent the
life cycle event. The vehicle is then driven over the test surface in a manner that reproduces the transportation or
service conditions. The test surfaces may include designed test tracks (e.g., test surfaces at the US Army Aberdeen
Test Center (paragraph 6.1, reference b), typical highways, or specific highways between given points (e.g., a specified
route between a manufacturing facility and a military depot)). Potentially, such testing can include all environmental
factors (vibration, shock, temperature, humidity, pressure, etc.) related to wheeled vehicle transport.
4.1.4 Procedure IV - Assembled aircraft store captive carriage and free flight.
This procedure uses standard laboratory vibration exciters (shakers) driving the test item directly or through a fixture.
The test item is supported by a test frame independent of the vibration exciters (see paragraph 4.4.4). Select the
specific exciters based on size and mass of test items and fixtures, frequency range, and low frequency stroke length
(displacement) required.
4.2 Controls, Tolerances, and Instrumentation.
The accuracy in providing and measuring vibration environments is highly dependent on fixtures and mountings for
the test item, the measurement system and the exciter control strategy. Ensure all instrumentation considerations are
in accordance with the best practices available (see paragraph 6.1, reference c). Careful design of the test set up,
fixtures, transducer mountings and wiring, along with good quality control will be necessary to meet the tolerances of
paragraph 4.2.2 below.
4.2.1 Control strategy.
For Procedures I and IV, select a control strategy that will provide the required vibration at the required location(s) in
or on the test item. Base this selection on the characteristics of the vibration to be generated and platform/materiel
interaction (see paragraph 1.3b above and Annex A, paragraph 2.4). Generally, a single strategy is appropriate. There
are cases where multiple strategies are used simultaneously.
4.2.1.1 Acceleration input control strategy.
The vibration excitation is controlled to within specified bounds by sampling the vibratory motion of the test item at
specific locations. These locations may be at, or in close proximity to, the test item fixing points (controlled input) or
at defined points on the test item (controlled response). The vibratory motions may be sampled at a single point (single
point control), or at several locations (multi-point control). The control strategy will be specified in the Test Plan.
However, it should be noted that it could be influenced by:
a. The results of preliminary vibration surveys carried out on materiel and fixtures;
b. Meeting the test specifications within the tolerances of paragraph 4.2.2;
c. The capability of the test facility.
In view of the possibility of frequency drift, it is essential when conducting fixed frequency sinusoidal "resonance
dwell" tests that the frequency be constantly adjusted to ensure a maximum response. Two methods are available:
a. Search for the maximum dynamic response;
b. Maintain the phase between the control and monitoring points.

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METHOD 514.8

4.2.1.1.1 Single Point Control Option

This option can be used when the preliminary vibration survey indicates a rigid vibration fixture, or when one control
accelerometer accurately represents an average of the inputs at each fixing point. However, given the increased risk
associated with transducer or instrumentation failure and/or calibration or scaling error attributable to a single channel,
this option is not recommended. A single control point is selected:
a. Either from among the fixing points;
b. Or, in such a way that it provides the best possible solution for achieving the tolerances at the fixing points.
4.2.1.1.2 Multiple Point Control (average) Option.
This option can be used when the preliminary vibration survey shows that inputs to the test item vary significantly
between fixing points. The control points, usually two or three, will be selected using the same criteria listed in
paragraph 4.2.1.1.1 for the single control point option. However, the control for:
a. Random will be based on the average of the ASD of the control points selected.
b. Sine will be based on the average of the peak response values of the control points selected.
4.2.1.1.3 Multiple Point Control (maximum) Option
This option can be used when responses are not to exceed given values, but care is needed to avoid an undertest.
Preliminary vibration survey results are used to aid the definition of the control points on the test item at which
maximum response motions occur. The control points, usually two or three, will be selected using the same criteria
listed in paragraph 4.2.1.1.1 for the single point option. However, the control for:
a. Random, will be based on the maximum spectrum response at any of the selected control points.
b. Sine, will be based on the maximum peak response at any of the selected control points.
4.2.1.2 Force control strategy.
Dynamic force gages are mounted between the exciter/fixture and the test item. Exciter motion is controlled with
feedback from the force gages to replicate field measured interface forces. This strategy is used where the field
(platform/materiel) dynamic interaction is significantly different from the laboratory (exciter/test item) dynamic
interaction. This form of control inputs the correct field-measured forces at the interface of the laboratory vibration
exciter and test item. This strategy is used to prevent overtest or undertest of materiel mounts at the lowest structural
resonances that may otherwise occur with other forms of control.
4.2.1.3 Acceleration limit strategy.
Input vibration criteria are defined as in paragraph 4.2.1.1. In addition, vibration response limits at specific points on
the materiel are defined (typically based on field measurements). Monitoring transducers (typically accelerometers
or strain gages) are located at these points. The test item is excited as in paragraph 4.2.1.1 using test item mounting
point accelerometer signals to control the exciters. The input criteria are experimentally modified as needed to limit
responses at the monitoring transducers to the predefined limits. Changes to the specified input criteria are limited in
frequency bandwidth and in level to the minimum needed to achieve the required limits.
4.2.1.4 Acceleration response control strategy.
Vibration criteria are specified for specific points on, or within the test item. Control accelerometers are mounted at
the vibration exciter/fixture interface. Monitoring accelerometers are mounted at the specified points within the item.
Low level vibration, controlled with feedback from the control accelerometers is input to the test item. The input
vibration is experimentally adjusted until the specified levels are achieved at the monitoring accelerometers. This
strategy is commonly used with assembled aircraft stores where store response to the dynamic environment is
measured or estimated. It is also applicable for other materiel when field measured response data are available.
4.2.1.5 Waveform control strategy.
This strategy is discussed in Methods 525.1 and 527.1.

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METHOD 514.8

4.2.2 Tolerances.
Use the following tolerances unless otherwise specified. In cases where these tolerances cannot be met, achievable
tolerances should be established and agreed to by the cognizant engineering authority and the customer prior to
initiation of test. Protect measurement transducer(s) to prevent contact with surfaces other than the mounting
surface(s).
4.2.2.1 Acceleration spectral density.
The test facility should be capable of exciting the test item to the random vibration conditions specified in the Test
Plan. The motion induced by the random vibration should be such that the fixing points of the test item move
substantially parallel to the axis of excitation. In these conditions the amplitudes of motion should exhibit a normal
distribution. The tolerances defined in Table 514.8-II below should be used and checked with the test item installed.
The tolerances associated with the test severity parameters are not to be used to overtest or undertest the test item.
Any deviations to the test or test tolerances from the values in Table 514.8-II must be approved by the appropriate test
authority and must be clearly documented. In addition to the tolerances specified in Table 514.8-II, the following
factors should also be considered:
a. Vibration environment. The following discussion relates the measured vibration level to the specification
level and, like the control system, does not consider any measurement uncertainty. The test tolerance
should be kept to the minimum level possible considering the test item, fixturing and spectral shape. Test
tolerances of less than ±3 dB are usually readily attainable with small, compact test items (such as small
and medium sized rectangular electronic packages), well-designed fixtures, and modern control equipment.
When test items are large or heavy, when fixture resonances cannot be eliminated, or when steep slopes
(>20 dB/octave) occur in the spectrum, these tolerances may have to be increased. When increases are
required, exercise care to ensure the selected tolerances are the minimum attainable, and that attainable
tolerances are compatible with test objectives.
b. Vibration measurement. Use a vibration measurement system that can provide acceleration spectral
density measurements within ±0.5 dB of the vibration level at the transducer mounting surface (or
transducer target mounting surface) over the required frequency range. Do not use a measurement
bandwidth that exceeds 2.5 Hz at 25 Hz or below, or 5 Hz at frequencies above 25 Hz. Use a frequency
resolution appropriate for the application (i.e., generally in wheeled vehicles a resolution of 1 Hz is
sufficient).
c. Statistical degrees of freedom. Since the control loop time depends on the number of degrees of freedom
and on the analysis and overall bandwidths, it is important to select these parameters so that test tolerances
and control accuracy can be achieved. If possible, ensure the number of statistical degrees of freedom is
greater than 120. Swept narrow-band random on random vibration tests may require lesser degrees of
freedom due to sweep time constraints.
d. Root mean square (RMS) “g.” Do not use RMS g as the sole parameter defining or controlling vibration
tests because it contains no spectral information. RMS levels are useful in monitoring vibration tests since
RMS can be monitored continuously, whereas measured spectra are available on a delayed, periodic basis.
Also, RMS values are sometimes useful in detecting errors in test spectra definition. Do not use random
vibration RMS g as a comparison with sinusoidal peak g. These values are unrelated.
e. When possible, an identical analysis bandwidth should be used for both control and monitoring. When this
is not possible, adequate allowance should be made to the results of the monitoring analysis.
f. For swept narrow band random tests, the tolerances on the swept components of the test requirement
should, wherever possible, be the same as for a wide band random component. However, at some sweep
rates, these tolerances may not be achievable. Therefore, the tolerance requirements for these components
shall be stated in the Test Plan.
g. The complete test control system including checking, servoing, recording, etc., should not produce
uncertainties exceeding one third of the tolerances listed in Table 514.8-II.

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h. The tolerances associated with the test severity parameters are not to be used to overtest or undertest the
test item. If tolerances are not met, the difference observed should be noted in the test report.
Table 514.8-II. Random Vibration Test Tolerances.
Specific Tolerances For All Random Vibration Tests (including the broadband component of mixed
random and sinusoidal vibration tests and the fixed and swept narrowband components of mixed broadband
and narrowband random vibration tests)
Parameter Tolerance
Number (n) of independent statistical degrees of n > 120
freedom (DOF) for control of the specified ASD.
Composite Control: Maximum deviation of the ± 3 dB below 500 Hz
composite control ASD in relation to the ± 6 dB above 500 Hz
specified ASD. 1
± 10% overall grms
Multi-point Control: Maximum deviation of any Average Control Extremal Control
individual control channel ASD in relation to the ± 6 dB below 500 Hz - 6 dB / + 3 dB below 500 Hz
specified ASD.2, ± 9 dB above 500 Hz - 9 dB / + 6 dB above 500 Hz
± 25% overall grms ± 25% overall grms
Cross-axis Motion: ASD measured with the same Less than 50% below 500 Hz
number of DOF as in the test axis, along the Less than 100% above 500 Hz
mutually orthogonal directions, in relation to the Less than the relevant specified ASD for the given
in-axis specified ASD. cross-axis.
Frequency sweep rate ± 10% of stated rate
Test time duration ± 5% of stated duration
Amplitude distribution of the instantaneous Nominally Gaussian (Refer to paragraph 2.4 for
values of the random vibration measured at the amplitude distribution discussion)
drive signal.
1
Composite Control is defined as: The ASD computed as either the average, maximum, or minimum
(depending on control method) of all feedback channels deemed as control channels in a multi-point control
scenario or the single control channel in a single-point control scenario. As discussed in paragraph 4.2.1.1
multi-point control is encouraged.
2
If using minimum control, the negative tolerance will be that of the Composite Control.

The default assumption for all ASD references provided in this document is that the associated probability density
function (pdf) is of Gaussian form. Generally, unless documentation from field data indicates otherwise, the drive-
limiting option (often referred to as three-sigma clipping) should not be invoked. However, it is recognized that there
are scenarios such as test equipment displacement limitations or power amplifier voltage or current limitations that
could be resolved by invoking the drive limiting control parameter. When invoking the drive signal limiting feature
on a Gaussian drive signal, the limiting threshold should never be set to less than three standard deviations (3-sigma).
In addition, the test engineer or program engineer responsible for the test article should approve the operation and it
should be properly documented within the test report.
When an ASD is being generated to serve as a reference for a vibration test, careful examination of field measured
response probability density information should be performed. The probability density/distribution function should be
estimated and compared with that of a theoretical Gaussian probability density/distribution. If there is strong evidence
of departure from the Gaussian distribution then an accurate estimate of the higher moments – primarily kurtosis and
skewness should be made, cognizant of the substantial increased amount of measurement information needed to
estimate higher order moments accurately. Skewness and kurtosis are the third and fourth standardized moments
about the mean computed as:

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METHOD 514.8

 ( x − µ )3   ( x − µ )4 
Skewness = E   and Kurtosis = E   , where
 σ  σ
3 4
 
E = expectation operator
x = individual acceleration values
µ = mean acceleration value
σ = acceleration standard deviation
A Gaussian process has a skewness equal to 0 and a kurtosis equal to 3. Skewness is a measure of the asymmetry of
the probability distribution of a random variable while kurtosis is a measure of “peakedness” or “flatness” of the
distribution.
If analysis shows the data to be highly non-Gaussian, one may consider either of the following:
(1) Employing TWR techniques (that will generally preserve the measured pdf and the distribution in time
of the time history characteristics e.g., peaks and valleys, that provide for kurtosis differing from the
Gaussian theoretical value).
(2) Employing a control algorithm capable of drive signal synthesis per user defined kurtosis and “matching”
the measurement pdf within some level of statistical confidence. All control systems do not necessarily
assume the same model for generating non-Gaussian input and most control system software ignore the
form of the pdf. Use of a control system that does not take account of the form of the pdf is discouraged
unless it can be demonstrated that the pdf of the synthesized data is comparable (via statistical test) to
that of the measured data upon which the test reference is based. This assumes a single measured test
reference with non-Gaussian behavior. When several measured test references are present the overall
non-Gaussian behavior may be due to “mixture distribution” effects, in which case an analyst must be
consulted for recommendations as to a way to proceed.
In the event TWR or user defined kurtosis options as defined above are employed to address non-Gaussian scenarios,
the time compression techniques outlined in Annex A paragraph 2.2 are not applicable.
The test engineer or program engineer responsible for the test article should approve any deviation from the standard
Gaussian process and any deviations should be properly documented within the test report by time history plots,
skewness/kurtosis estimates and probability density function estimate plots.
4.2.2.2 Peak sinusoidal acceleration.
The test facility should be able to excite the materiel as specified in the Test Plan. The motion should be sinusoidal
and such that the fixing points of the test item move substantially in phase with and parallel to the excitation axis. The
sinusoidal tolerances and related characteristics defined in Table 514.8-III should be used and checked with the test
item installed. Only under exceptional circumstances should a Test Plan need to specify different tolerances. The
complete test control system should not produce uncertainties exceeding one third of the tolerances listed in
Table 514.8-III. The tolerances associated with the test severity parameters are not to be used to overtest or undertest
the test item. If tolerances are not met, the difference observed should be noted in the test report.

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METHOD 514.8

Table 514.8-III. Sinusoidal Vibration Test Tolerances.

Specific Tolerances For All Sinusoidal Tests (including fixed, swept and stepped sine tests as well as the fixed
and swept sinusoidal components of mixed random and sinusoidal tests)
Parameter Tolerance
Frequency ± 0.1 %
Composite Control: Maximum deviation of ± 10%
the composite control1 tone level(s) in relation
to the specified tone level(s).
Multi-point Control: Maximum deviation of Average Control Maxi Control
the individual control channel tone levels in ± 25% below 500 Hz +10% / -25% below 500 Hz
relation to the specified tone level(s).2 ± 50% above 500 Hz +10% / -50% above 500Hz
Cross-axis Motion: Tone levels measured Less than 50% below 500 Hz
along the mutually orthogonal directions, in Less than 100% above 500 Hz
relation to the in-axis specified level(s). Less than the relevant specified levels for the given cross-axis.
Frequency sweep rate ± 10% of stated rate
Test time duration ± 5% of stated duration
Difference between the unfiltered signal and ± 5% on the grms values4
filtered acceleration signal 3

1
Composite Control is defined as: The Line Spectrum computed as either the average, maximum, or minimum
(depending on control method) of all feedback channels deemed as control channels in a multi-point control
scenario or the single control channel in a single-point control scenario. As discussed in paragraph 4.2.1.1
2
If using minimum control, the negative tolerance will be that of the Composite Control.
3
Distortion of the sinusoidal signal can occur particularly when using hydraulic actuators. If distortion of the
sinusoidal signal is suspected, the unfiltered signal and filtered acceleration signal should be compared. A
signal tolerance of ±5 percent corresponds to a distortion of 32 percent by utilization of the formula:

2
�𝑎𝑎𝑡𝑡𝑡𝑡𝑡𝑡 − 𝑎𝑎12
𝑑𝑑 = × 100
𝑎𝑎1
where: 𝑎𝑎1 = grms value of acceleration at the driving frequency;
𝑎𝑎𝑡𝑡𝑡𝑡𝑡𝑡 = total grms of the applied acceleration (including the value of 𝑎𝑎1 ).
4
The grms of a sinusoid equals 0.707 times peak g. It is not related to grms of a random (g2/Hz) spectrum; do
NOT use this to compare sine criteria (g) to random criteria (g2/Hz).

4.2.2.3 Frequency measurement.

Ensure the vibration measurement system provides frequency measurements within ± 1.25 percent at the transducer
mounting surface (or transducer target mounting surface) over the required frequency range.
4.2.2.4 Cross axis accelerations.
In a single axis vibration test, cross axis vibration acceleration in two axes mutually orthogonal and orthogonal to the
drive axis should be less than or equal to the values specified in Table 514.8-II for the cross axis of concern. If
measured cross axis vibration accelerations exceed these values, the source of the vibration should be identified and
addressed. The following common sources of cross axis vibration should be considered:
a. Test fixture resonance. Prior to test, a test fixture survey should be conducted to ensure that the structural
characteristics of the test fixture do not introduce uncontrollable resonances into the test setup. The survey
may be experimental or analytical. If problematic resonances are identified, modifications should be made
to the test fixture to shift the resonance beyond the frequency range of the test or to dampen the resonance
in order to minimize the effect on the test.
b. Test article resonance. Cross axis resonances of the test article may be characteristic of the test article
structure and not necessarily a product of test fixture or restraint. As long as the test item is secured in a

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METHOD 514.8

manner consistent with the environment being tested, and the test fixture is not introducing unrealistic
resonance, the following options should be considered in limiting the cross axis vibration:
(1) Response Limit - A limit spectrum may be applied to the cross axis response of the test article in order
to effectively notch the control spectrum in the drive axis. This limit spectrum should be defined in
terms of the test profile for the cross axis of concern. For example, if the transverse response to vertical
axis test is excessive, the transverse response should be limited to some factor of the corresponding
transverse profile. In a random vibration test, the cross axis resonances are often narrow frequency
bands, the notching may be within acceptable tolerances.
(2) Multi-axis Test - If the test article structure is such that the cross axis vibration response to a single
axis vibration test is beyond acceptable levels, it may be necessary to conduct the test as a multi-axis
in order to simultaneously control multiple axes of vibration to the required test profiles. Method
527.1 discusses the technical details associated with multi-axis vibration testing.
4.2.3 Instrumentation.
In general, acceleration will be the quantity measured to meet the vibration specification. On occasion, other devices
may be employed, e.g., strain gage, linear displacement/voltage transducer, force gage, laser velocimeter, rate gyro,
etc. In these cases, give special consideration to the instrument specification to satisfy the calibration, measurement,
and analysis requirements. Calibrate all measurement instrumentation to traceable national calibration standards (see
Part One, paragraph 5.3.2). The measurement device and its mounting will be compatible with the requirements and
guidelines provided in paragraph 6.1, reference c.
a. Accelerometer. In the selection of any transducer, one should be familiar with all parameters provided on
the associated specification sheet. Key performance parameters for an accelerometer follow:
(1) Frequency Response: A flat frequency response within ± 5 percent across the frequency range of
interest is required.
(2) Transverse sensitivity should be less than or equal to 5 percent.
(3) Nearly all transducers are affected by high and low temperatures. Understand and compensate for
temperature sensitivity deviation as required. Temperature sensitivity deviations at the test
temperature of interest should be no more than ±5 percent relative to the temperature at which the
transducer sensitivity was established.
(4) Base Strain sensitivity should be evaluated in the selection of any accelerometer. Establishing
limitations on base strain sensitivity is often case specific based upon the ratio of base strain to
anticipated translational acceleration.
b. Other measurement devices. Any other measurement devices used to collect data must be demonstrated
to be consistent with the requirements of the test.
c. Signal conditioning. Use only signal conditioning that is compatible with the instrumentation requirements
of the test, and is compatible with the requirements and guidelines provided in paragraph 6.1, reference c.
In particular, filtering of the analog voltage signals will be consistent with the time history response
requirements (in general, demonstrable linearity of phase throughout the frequency domain of response),
and the filtering will be so configured that anomalous acceleration data caused by clipping will not be
misinterpreted as response data.
4.3 Test interruption.
Test interruptions can result from multiple situations. The following paragraphs discuss common causes for test
interruptions and recommended paths forward for each. Recommend test recording equipment remain active during
any test interruption if the excitation equipment is in a powered state.
4.3.1 Interruption due to laboratory equipment malfunction.
a. General. See Part One, paragraph 5.11, of this Standard.
b. Specific to this Method. When interruptions are due to failure of the laboratory equipment, analyze the
failure to determine root cause. It is also strongly advised that both control and response data be evaluated

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to ensure that no undesired transients were imparted to the test item during the test equipment failure. If
the test item was not subjected to an over-test condition as a result of the equipment failure, repair the test
equipment or move to alternate test equipment and resume testing from the point of interruption. If the
test item was subjected to an over-test condition as a result of the equipment failure, the test engineer or
program engineer responsible for the test article should be notified immediately. A risk assessment based
on factors such as level and duration of the over-test event, spectral content of the event, cost and
availability of test resources, and analysis of test specific issues should be conducted to establish the path
forward. See Annex A, paragraph 2.1 for descriptions of common test types and a general discussion of
test objectives.
4.3.2 Interruption due to test item operation failure.
Failure of the test item(s) to function as required during operational checks presents a situation with several possible
options. Failure of subsystems often has varying degrees of importance in evaluation of the test item. Selection of
option a through c below will be test specific.
a. The preferable option is to replace the test item with a “new” one and restart the entire test.
b. An alternative is to replace / repair the failed or non-functioning component or assembly with one that
functions as intended, and restart the entire test. A risk analysis should be conducted prior to proceeding
since this option places an over-test condition on the entire test item except for the replaced component. If
the non-functioning component or subsystem is a line replaceable unit (LRU) whose life-cycle is less than
that of the system test being conducted, proceed as would be done in the field by substituting the LRU, and
continue from the point of interruption.
c. For many system level tests involving either very expensive or unique test items, it may not be possible to
acquire additional hardware for re-test based on a single subsystem failure. For such cases, a risk
assessment should be performed by the organization responsible for the system under test to determine if
replacement of the failed subsystem and resumption of the test is an acceptable option. If such approval is
provided, the failed component should be re-tested at the subcomponent level.

NOTE: When evaluating failure interruption, consider prior testing on the same test item and
consequences of such.

4.3.3 Interruption due to a scheduled event.

There are often situations in which scheduled test interruptions will take place. For example, in a tactical
transportation scenario, the payload may be re-secured to the transport vehicle periodically (i.e., tie-down straps may
be re-secured at the beginning of each day). Endurance testing often represents a lifetime of exposure; therefore it is
not realistic to expect the payload to go through the entire test sequence without re-securing the tie-downs as is done
in a tactical deployment. Similarly, items mounted on rubber isolation systems may require monitoring of the isolator
temperature with planned test interruptions to prevent overheating and unnatural failure of the isolator. Many other
such interruptions, to include scheduled maintenance events, are often required over the life-cycle of materiel. Given
the cumulative nature of fatigue imparted by dynamic testing, it is acceptable to have test interruptions that are
correlated to realistic life-cycle events. All scheduled interruptions should be documented in the test plan and test
report.
4.3.4 Interruption due to exceeding test tolerances
Exceeding the test tolerances defined in paragraph 4.2.2, or a noticeable change in dynamic response may result in a
manual operator initiated test interruption or an automatic interruption when the tolerances are integrated into the
control strategy. In such cases, the test item, fixturing, and instrumentation should be checked to isolate the cause.
a. If the interruption resulted from a fixturing or instrumentation issue, review the data leading up to the test
interruption and assess the extent of over/under test, if any. If an over/under test condition is identified,
document the incident and obtain approval from the organization responsible for the system under test to
correct the problem and resume the test.

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b. If the interruption resulted from a structural or mechanical degradation of the test item, the problem will
generally result in a test failure and requirement to re-test unless the problem is allowed to be corrected
during testing by the organization responsible for the system under test. If the test item does not operate
satisfactorily, see paragraph 5 for failure analysis, and follow the guidance in paragraph 4.3.2 for test item
failure.
4.4 Test Setup.
See Part One, paragraph 5.8. For standardization purposes, major axes are defined as vertical (perpendicular to level
ground); longitudinal (parallel to vehicle fore and aft movement), and transverse (perpendicular to vertical and
longitudinal movement).
4.4.1 Procedure I - General vibration.
a. Test Configuration. Configure the test item appropriately for the life cycle phase to be simulated.
i. Transportation. Configure the test item for shipment including protective cases, devices,
and/or packing. Mount the test item to the test fixture(s) by means of restraints and/or tie
downs dynamically representative of life cycle transportation events.
ii. Operational service. Configure the test item for service use. Secure the test item to the test
fixture(s) at the mounting point(s) and use the same type of mounting hardware as used during
life cycle operational service. Provide all mechanical, electrical, hydraulic, pneumatic or
other connections to the materiel that will be used in operational service. Ensure these
connections dynamically simulate the service connections and that they are fully functional
unless otherwise specified.
b. Instrumentation. Installation and location of the control accelerometer(s) can significantly affect test
outcome. It is recommended to mechanically attach (i.e., screw mount) control accelerometer(s) to the
vibration test fixture near the test item interface(s) or at the location(s) used to derive the test specification.
Additional control and/or response instrumentation may be attached with screws or adhesives to other
locations on the vibration table or test item as specified in the test plan. All instrumentation locations should
be described in the test plan and in the specification derivation report. Examples are presented in Annex C.
4.4.2 Procedure II - Loose cargo transportation.
The loose cargo test can be considered as being of two types that differ from one another only in the installation
conditions of the materiel. Two different setups of fencing are required depending on the type of test item. The two
types are those that are more likely to slide on the test surface or “rectangular cross section items” (typically packaged
items), and those most likely to roll on the surface or “circular cross section items.” See paragraph 4.5.3 for details
of the test procedure. Fencing information is presented in Annex C, paragraph 2.2. Because part of the damage incurred
during testing of these items is due to the items impacting each other, the number of test items should be greater than three
where the size of the item is such that more than three items in a typical cargo truck bed. Although the loose cargo
transportation simulators are typically operated at fixed rates of rotation, it is recommended to monitor and record an
accelerometer on the table surface in order to (1) provide measurable verification of the table motion and (2) detect any
change in the test setup caused by degradation of the fencing or damage to the test article.
4.4.3 Procedure III - Large assembly transport.
Install the test item in/on the vehicle in its intended transport or service configuration. If the test assembly is to be
contained within a shelter, or if other units are attached to the materiel assembly in its in-service configuration, also
install these items in their design configuration.
a. Test surfaces. When setting up the test, consider the test surfaces available at the particular test location
(see paragraph 6.1, reference b). Also, ensure the selection of test surfaces, test distances, and test speeds
are appropriate for the specified vehicles and their anticipated use as defined in the vehicle OMS/MP.
b. Test loads. Response of the vehicle to the test terrain is a function of the total load and the distribution of
the load on the vehicle. In general, a harsher ride occurs with a lighter load, while a heavier load will result

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in maximum levels at lower frequencies. Multiple test runs with variations in load may be required to
include worst case, average, or other relevant cases.
c. Tie-down/mounting arrangements. During the test, it is important to reproduce the more adverse
arrangements that could arise in normal use. For example, during transportation, relaxation of tie-down
strap tension could allow the cargo to lift off the cargo bed and result in repeated shock conditions.
Excessive tightening of webbing straps could prevent movement of test items and thereby reduce or
eliminate such shocks.
4.4.4 Procedure IV - Assembled aircraft store captive carriage and free flight.
a. Captive carriage test fixture. Suspend the test item (store) from a structural support frame by means of the
operational service store suspension equipment (bomb rack, launcher, pylon, etc.). Ensure the flexible
modes of the support frame are as high as practical, at least twice the first flexible frequency of the store,
and that they do not coincide with store modes. Include and load (torque, clamp, latch, etc.) sway braces,
lugs, hooks or other locking and load carrying devices that attach the store to the suspension equipment
and the suspension equipment to the carrier aircraft, as required for captive carriage in service. Ensure the
layout of the structural support frame and the test area is such that there is adequate access for the vibration
exciters and test materiel.
(1) Configure the assembled store for captive carriage and mount it to the structural support frame. Softly
suspend the structural support frame within the test chamber. Ensure that rigid body modes of the
store, suspension equipment, and structural support frame combination are between 5 and 20 Hz, and
lower than one half the lowest flexible mode frequency of the store. Use structural support that is
sufficiently heavy and of sufficient pitch and roll inertias to approximately simulate carrier aircraft
dynamic reaction mass. If the structural support is too heavy or its inertia too large, the store
suspension equipment and store hardback will be over-stressed. This is because unrealistically high
dynamic bending moments are needed to match acceleration spectral densities. Conversely, if the
structural support is too light or its inertia too low, there will be an undertest of the suspension
equipment and store hardback.
(2) Do not use the structural support to introduce vibration into the store. Hard-mounting stores to large
shakers has proven to be inadequate. Test experience with F-15, F-16, and F/A-18 stores indicates
that including a structural support/reaction mass greatly improves the match between flight measured
data and laboratory vibrations, particularly at lower frequencies.
(3) In cases in which the frequency requirements in (1) and (2) cannot be met, consider force control
strategy (see paragraph 4.2.1.2).
b. Free flight test fixture. Configure the assembled test store for free flight and softly suspend it within the
test chamber. Ensure rigid body modes of the suspended store are between 5 and 20 Hz and lower than
one half the lowest flexible mode frequency of the store.
c. Orientation. With the store suspended for test, the longitudinal axis is the axis parallel to the ground plane
and passing through the longest dimension of the store. The vertical axis is mutually perpendicular to the
ground plane and the longitudinal axis. The transverse axis is mutually perpendicular to longitudinal and
vertical axes.
d. Vibration excitation. Store longitudinal vibration is typically less than vertical and transverse vibration.
Vertical and transverse excitation of store modes usually results in sufficient longitudinal vibration. When
a store is relatively slender (length greater than 4 times the height or width), drive the store in the vertical
and transverse axes. In other cases, drive the store in the vertical, transverse, and longitudinal axes. If a
store contains material that is not vibration tested except at assembled store level, or the store contains
components that are sensitive to longitudinal vibration, include longitudinal excitation.
(1) Transmit vibration to the store by means of rods (stingers) or other suitable devices running from
vibration exciters to the store. Separate drive points at each end of the store in each axis are
recommended. Ideally, the store will be driven simultaneously at each end. However, it can be driven
at each end separately. A single driving point in each axis aligned with the store aerodynamic center

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has also been successful. Use drive points on the store surfaces that are relatively hard and structurally
supported by the store internal structure or by test fixture(s) (usually external rings around the local
store diameter) that distribute the vibratory loads into the store primary structure.
(2) There are many signal forms available to drive the vibration exciters. Some of the most popular are
uncorrelated random, sinusoidal and transient (burst random or sine) excitation. Consideration of the
characteristics of the store structure, the suspension equipment, general measurement considerations,
and the desired data resolution will dictate selection of the driving signals. Uncorrelated random
excitation and burst random excitation should be accomplished such that the signals are driven
periodically within each data acquisition block in order to improve the data quality of the derived
frequency response functions (FRFs). Use of more than one vibration exciter with random excitation
will assist in minimizing the influence of non-linear behavior and allows the structure to be uniformly
excited and allow for better FRFs. In turn, sinusoidal excitation should be used to characterize non-
linearities in the system. For suspension systems involving carriage of multiple stores, the relative
phase characteristics between stores should be defined and efforts made to replicate relative phasing
in the laboratory setting to the maximum degree possible. It is acknowledged that there may not be
sufficient excitation degrees-of-freedom to have full control authority over the phase characteristics
of multiple stores. When more than one vibration exciter is used simultaneously, knowledge of
multiple exciter testing techniques that include specification of the vibration exciter cross-spectral
density matrices is required (reference Method 527.1). The auto and cross-spectral density
characteristics should be made available as part of the test specification. In the absence of measured
cross-spectral data, the cross-spectrum will need to be either estimated via model, or assumed to be
uncorrelated. Additional information regarding specification of cross-spectral parameters is addressed
in paragraph 6.1, reference gg. For the case in which the cross-spectral density between drive points
is assumed to be zero, recognize that due to coupling between the vibration exciters via the
store/suspension structure, some level of correlation between the control points will generally exist.
e. Instrumentation. Mount transducers on the store and/or the store excitation devices to monitor compliance
of vibration levels with requirements, to provide feedback signals to control the vibration exciter, and to
measure materiel function. Additionally, it is usually important to overall program objectives to add
transducers to measure the local vibration environment throughout the store. Note the vibration exciter
control strategy used, e.g., single point response, multipoint response, force limit, waveform, etc. Also
note the relationship between field measurement data and laboratory measurement data.
(1) Mount accelerometers to monitor vibration levels at the forward and aft extremes of the primary load
carrying structure of the store. Do not mount these accelerometers on fairings, unsupported areas of
skin panels, aerodynamic surfaces, or other relatively soft structures. In some cases (see paragraph
4.4.4c above), transducers are required in the vertical and transverse directions. In other cases,
transducers are required in vertical, transverse, and longitudinal directions. Designate these
transducers as the test monitor transducers.
(2) An alternate method is to monitor the test with strain gages that are calibrated to provide dynamic
bending moment. This has proven successful where integrity of the store primary structure is a major
concern. Flight measured dynamic bending moment data is required for this Method. Also, use
accelerometers positioned as discussed above to verify that general vibration levels are as required.
(3) As feedback control transducers, use either accelerometers on or near the store/vibration transmission
device(s)/vibration exciter interface, force transducer(s) in series with the store/vibration transmission
device(s)/vibration exciter, or dynamic bending moment strain gages. A clear understanding of the
vibration exciter control strategy and its effects on the overall measurements is necessary.
4.5 Test Execution.
The following steps, alone or in combination, provide the basis for collecting necessary information concerning the
durability and function of a test item in a vibration environment.

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4.5.1 Preparation for test.

4.5.1.1 Preliminary steps.
Before starting a test, review pretest information in the test plan to determine test details (procedure(s), test item
configuration(s), levels, durations, vibration exciter control strategy, failure criteria, item operational requirements,
instrumentation requirements, facility capability, fixture(s), etc.).
a. Select appropriate vibration exciters and fixtures.
b. Select appropriate data acquisition system (e.g., instrumentation, cables, signal conditioning, recording,
analysis equipment).
c. Operate vibration equipment without the test item installed to confirm proper operation.
d. Ensure the data acquisition system functions as required.
4.5.1.2 Pretest standard ambient checkout.
All items require a pretest standard ambient checkout to provide baseline data. Conduct the pretest checkout as
follows:
Step 1. Examine the test item for physical defects, etc. and document the results.
Step 2. Prepare the test item for test, in its operating configuration if required, as specified in the test plan.
Step 3. Examine the test item/fixture/exciter combination for compliance with test item and test plan
requirements.
Step 4. If applicable, conduct an operational checkout in accordance with the test plan and document the
results for comparison with data taken during or after the test. If the test item does not operate as
required, resolve the problems and repeat this step.
4.5.2 Procedure I - General vibration.
Step 1. Conduct a fixture modal survey or resonance search, if required, and verify that fixture design is
compliant with recommended practices, and meets any test defined requirements that may have been
provided in the item-specific test plan (see paragraph 6.1, references aa, dd, and ee).
Step 2. Mount the test item to the test fixture in a manner dynamically representative of the life cycle event
simulated.
Step 3. Install sufficient transducers on or near the test item/fixture/vibration exciter combination to measure
vibration at the test item/fixture interface, to control the vibration exciter as required by the control
strategy, and measure any other required parameters. Mount control transducer(s) as close as possible
to the test item/fixture interface. Ensure that the total accuracy of the instrumentation system is
sufficient to verify that vibration levels are within the tolerances of paragraph 4.2.2, and to meet
additionally specified accuracy requirements.
Step 4. Conduct a test item modal survey or resonance search, if required.
Step 5. Perform a visual inspection of the test setup.
Step 6. Apply low level vibration to the test item/fixture interface. If required, include other environmental
stresses.
Step 7. Verify that the vibration exciter, fixture, and instrumentation system function as required.
Step 8. Apply the required vibration levels to the test item/fixture interface. Apply additional environmental
stresses as required.
Step 9. Monitor vibration levels and, if applicable, test item performance continuously through the exposure.
If levels shift or a failure occurs, shut down the test in accordance with the test interruption procedure
(paragraph 4.3.2). Determine the reason for the shift and proceed in accordance with the test
interruption recovery procedure (paragraph 4.3.2).

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Step 10. When the required duration has been achieved, stop the vibration.
Step 11. If the test plan calls for additional exposures, repeat Steps 5 through 10 as required by the test plan
before proceeding.
Step 12. Inspect the test item, fixture, vibration exciter, and instrumentation. If failure, wear, looseness, or
other anomalies are found, proceed in accordance with the test interruption recovery procedure
(paragraph 4.3.2).
Step 13. Verify that the instrumentation functions as required, and perform an operational check of the test
item as required per the test plan. If the test item fails to operate as intended, follow the guidance in
paragraph 4.3.2 for test item failure.
Step 14. Repeat Steps 1 through 13 for each required excitation axis.
Step 15. Remove the test item from the fixture and inspect the test item, mounting hardware, packaging, etc.,
for any signs of visual mechanical degradation that may have occurred during testing. See paragraph
5 for analysis of results.
4.5.3 Procedure II - Loose cargo transportation
Step 1. Place the test item(s) on the package tester within the restraining fences in accordance with paragraph
2.2 of Annex C.
Step 2. Install instrumentation to measure the rotational speed of the package tester. Ensure the total accuracy
of the instrumentation system is sufficient to meet specified accuracy requirements.
Step 3. After determining the number of possible test item orientations and corresponding test time (paragraph
3.1d), operate the package tester for the prescribed orientation duration (Annex C, paragraph 2.2).
Step 4. Perform a visual inspection of the test item and an operational check. If the test item fails to operate
as intended, follow the guidance in paragraph 4.3.2 for test item failure. Otherwise, proceed to Step
5.
Step 5. Reorient the test item(s) and/or the fencing/impact walls in accordance with paragraph 3.1d(1) and
Annex C, paragraph 2.2b.
Step 6. Operate the package tester for the next prescribed duration.
Step 7. Perform a visual inspection of the test item and an operational check. If the test item fails to operate
as intended, see paragraph 5 for analysis of results, and follow the guidance in paragraph 4.3.2 for test
item failure.
Step 8. Repeat Steps 5-7 for the total number of orientations.
Step 9. Perform a final visual inspection of the test item and an operational check. See paragraph 5 for
analysis of results.
4.5.4 Procedure III - Large assembly transport.
Step 1. Mount the test item(s) on/in the test vehicle as required in the test plan.
Step 2. If required, install transducers on or near the test item sufficient to measure vibration at the test
item/vehicle interface, and to measure any other required parameters. Protect transducers to prevent
contact with surfaces other than the mounting surface.
Step 3. Subject the vehicle containing the test item to the specified test conditions in Annex C, paragraph 2.3,
or as otherwise specified in the test plan.
Step 4. Perform a visual inspection of the test item and an operational check. If the test item fails to operate
as intended, follow the guidance in paragraph 4.3.2 for test item failure.
Step 5. Repeat Steps 1 through 4 for additional test runs, test loads, or test vehicles as required by the test
plan.

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Step 6. Perform a final visual inspection of the test item and an operational check. See paragraph 5 for
analysis of results.
4.5.5 Procedure IV - Assembled aircraft store captive carriage and free flight.
Step 1. With the store suspended within the test chamber and the instrumentation functional, verify that the
store suspension system functions as required by measuring the suspension frequencies.
Step 2. If required, conduct a test item modal survey.
Step 3. If required, place the test item in an operational mode and verify that it functions properly. Perform
a visual inspection of the test setup.
Step 4. Apply low level vibration to the vibration exciter/store interface(s) to ensure the vibration exciter and
instrumentation system function properly. For acceleration feedback control, use an initial input level
12 dB down from the required forward test monitor transducer spectrum. For force feedback control,
use a flat force spectrum where the response at the test monitor accelerometer is at least 12 dB below
the required test monitor value at all frequencies. For bending moment feedback control, use an initial
input level that is 12 dB down from the required test monitor transducer spectrum.
Step 5. Adjust the vibration exciter(s) such that the test monitor transducers in the excitation axis meet the
test requirements. For acceleration control, identify the test monitor transducer spectrum peaks that
exceed the input spectrum by 6 dB or more (frequencies may differ fore and aft). For force feedback
control, identify major peaks from the force measurements to check monitor accelerometer transfer
functions. For both cases, equalize the input spectra until the identified peaks equal or exceed the
required test levels. The identified peaks shall include at least the first 3 structural elastic modes of
the store airframe, any local mode frequencies for subsystem structure of significant mass, and any
frequencies which correspond with subassembly local modes which are critical for store performance.
Additionally, the input spectra should be equalized at all frequencies up to the first flexible bending
mode peak of the store to achieve the required test levels for ensuring the aircraft suspension
equipment / store interface is adequately stressed. The resulting input spectra should be as smooth
and continuous as possible while achieving the required peak responses. (It is not necessary to fill in
valleys in the test monitor transducer spectra; however, it is not acceptable to notch out the input in
these valleys.) For bending moment control raise and shape the input spectrum until it matches the
required spectrum (peaks and valleys).
Step 6. When the input vibration is adjusted such that the required input response (R1) is achieved, measure
the off-axis response(s) (R2, R3). Verify that off-axis response levels are within requirements using
the following equations. If the result obtained from the equation is greater than the value established
for the equation, reduce the input vibration level until the achieved input and off-axis response levels
are less than or equal to the appropriate constant. Apply these equations at each peak separately. Use
the first equation for testing that requires vibration application in two separate mutually perpendicular
axes, and use the second equation for testing that requires vibration application in three separate
mutually perpendicular axes. Refer to paragraph 4.2.2.4 for additional guidance.
(R1/A1 + R2/A2) ≤2
or
(R1/A1 + R2/A2 + R3/A3) ≤3
Where

Ri = Response level in g2/Hz or (N-m)2/Hz or (in-lb)2/Hz for i = 1 - 3, and

Ai = Test requirement level in g2/Hz or (N-m)2/Hz or (in-lb)2/Hz for i = 1 - 3

For example:
For testing that requires vibration application in three, separate, mutually-perpendicular axes, and
the vibration is being applied in the vertical axis, use the equation below as follows:
(R1/A1 + R2/A2 + R3/A3) ≤3

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METHOD 514.8

Where:

R1 = Vertical axis response level

A1 = Vertical axis requirement level
R2 = Transverse axis response level
A2 = Transverse axis requirement level
R3 = Longitudinal axis response level
A3 = Longitudinal axis requirement level.

For vibration being applied in either the transverse or longitudinal axis, repeat the above process.
(R1/A1 + R2/A2 + R3/A3) ≤3

Step 7. Verify that vibration levels are as specified. If the exposure duration is 1/2 hour or less, accomplish
this step immediately after full levels are first applied, and immediately before scheduled shut down.
Otherwise, accomplish this step immediately after full levels are first applied, every half-hour
thereafter, and immediately before scheduled shut down.
Step 8. Monitor the vibration levels and test item performance continuously through the exposure. If levels
shift, performance deviates beyond allowable limits, or failure occurs, shut down the test in
accordance with the test shut down procedure (paragraph 4.3). Determine the reason for the anomaly
and proceed in accordance with the test interruption recovery procedure (paragraph 4.3).
Step 9. When the required duration has been achieved, stop the vibration.
Step 10. If the test plan calls for additional exposures, repeat Steps 3 through 9 as required by the test plan
before proceeding.
Step 11. Inspect the test item, fixture, vibration exciter, and instrumentation. If failure, wear, looseness or
other anomalies are found, proceed in accordance with the test interruption recovery procedure
(paragraph 4.3).
Step 12. Verify that the instrumentation functions as required and perform an operational check of the test item
for comparison with data collected in paragraph 4.5.1.2. If the test item fails to operate as intended,
follow the guidance in paragraph 4.3.2 for test item failure.
Step 13. Repeat Steps 1 through 12 for each required excitation axis.
Step 14. Remove the test item from the fixture and inspect the test item, mounting hardware, packaging, etc.,
for any signs of visual mechanical degradation that may have occurred during testing. See paragraph
5 for analysis of results.
5. ANALYSIS OF RESULTS.
In addition to the guidance provided in Part One, paragraph 5.14, the following is provided to assist in the evaluation
of the test results.
5.1 Physics of Failure.
Analyses of vibration related failures must relate the failure mechanism to the dynamics of the failed item and to the
dynamic environment. It is insufficient to determine that something broke due to high cycle fatigue or wear. It is
necessary to relate the failure to the dynamic response of the materiel to the dynamic environment. Thus, include in
failure analyses a determination of resonant mode shapes, frequencies, damping values and dynamic strain
distributions, in addition to the usual material properties, crack initiation locations, etc. (See paragraph 6.1, references
ll and mm, and Annex A, paragraph 2.5.)
5.2 Qualification Tests.
When a test is intended to show formal compliance with contract requirements, recommend the following definitions:

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a. Failure definition. “Materiel is deemed to have failed if it suffers permanent deformation or fracture; if
any fixed part or assembly loosens; if any moving or movable part of an assembly becomes free or sluggish
in operation; if any movable part or control shifts in setting, position or adjustment, and if test item
performance does not meet specification requirements while exposed to functional levels and following
endurance tests.” Ensure this statement is accompanied by references to appropriate specifications,
drawings, and inspection methods.
b. Test completion. “A vibration qualification test is complete when all elements of the test item have
successfully passed a complete test. When a failure occurs, stop the test, analyze the failure, and either
repair the test item or replace with a modified test item. Continue or repeat the test until all fixes have
been exposed to a complete test. Each individual element is considered qualified when it has successfully
passed a complete test (see paragraph 4.3). Qualified elements that fail during extended tests are not
considered failures, and can be repaired to allow test completion.”
5.3 Other Tests.
For tests other than qualification tests, prepare success and/or failure criteria and test completion criteria that reflect
the purpose of the tests.
6. REFERENCE/RELATED DOCUMENTS
6.1 Referenced Documents.
a. Methodology Investigation, Final Report of the TECOM Package Tester Characterization, DTIC AD No.
B217688, September 1996.
b. Test Operations Procedure (TOP) 01-1-011A, Vehicle Test Facilities at Aberdeen Test Center Yuma Test
Center, 27 February 2012; DTIC AD No. ADA557002. "Vehicle Test Facilities at Aberdeen Test Center
and Yuma Test Center"
c. Handbook for Dynamic Data Acquisition and Analysis, IEST-RD-DTE012.2; Institute of Environmental
Sciences and Technology, Arlington Place One, 2340 S. Arlington Heights Road, Suite 100, Arlington
Heights, IL 60005-4516; Institute of Environmental Sciences and Technology Website.
d. Test Operations Procedure (TOP) 01-2-601, Ground Vehicle Laboratory Vibration Schedules. 18 May
2015.
e. International Test Operating Procedure (ITOP) 1-1-050. Development of Laboratory Vibration Test
Schedules. 6 June 1997. DTIC AD No B227368.
f. Tevelow, Frank L., The Military Logistical Transportation Vibration Environment: Its Characterization
and Relevance to MIL-STD Fuse Vibration Testing. Harry Diamond Laboratories, December 83. HDL-
SR-83-11.
g. Connon, William H. (III). Methodology Investigation, Final Report, Ground Vehicle - Loose Cargo
Vibration Schedules. January 1987. DTIC AD No. B1114819L.
h. White, George O., Methodology Investigation, Final Report, Loose Cargo Testing of Unpackaged Separate
Loading Projectiles. May 1990, DTIC AD No. B144437.
i. Wafford, J.H. and J. F. Dreher, Aircraft Equipment Vibration Test Criteria Based on Vibration Induced by
Jet and Fan Engine Exhaust Noise. Shock and Vibration Bulletin 43, Part 3, 1973, pp. 141-151. Shock &
Vibration Information Analysis Center (SAVIAC), PO Box 165, 1104 Arvon Road, Arvonia, VA 23004.
j. Dreher, J. F., Aircraft Equipment Random Vibration Test Criteria Based on Vibration Induced by
Turbulent Air Flow Across Aircraft External Surfaces. Shock and Vibration Bulletin 43, Part 3, 1973, pp.
127-139. Shock & Vibration Exchange (SAVE), 1104 Arvon Road, Arvonia, VA 23004.
k. Hinegardner, W. D., et al., Vibration and Acoustics Measurements on the RF-4C Aircraft. Wright-
Patterson AFB, OH: ASD Systems Engineering Group, 1967, TM-SEF-67-4.

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l. Bartel, H. W and J. M. McAvoy, Cavity Oscillation in Cruise Missile Carrier Aircraft. Air Force Wright
Aeronautical Laboratories, June 1981. AFWAL-TR-81-3036; DTIC No. ADA108610.
m. Tipton, A. G., Weapon Bay Cavity Noise Environments Data Correlation and Prediction for the B-1
Aircraft. Air Force Wright Aeronautical Laboratories, June 1980. AFWAL-TR-80-3050.
n. Thomas, C. E., Flight Survey of C-130A Aircraft. March 1962. ASD-TR-62-2167. DTIC No. AD-274-
904.
o. Bolds, P. G., Flight Vibration Survey C-133 Aircraft. April 1962. ASD-TDR-62-383. DTIC No. AD-
277-128.
p. Kuhn, D. L., Analysis of the Vibration Environment for Airborne Reconnaissance Integrated Electronics
System (ARIES) Installed on EP-3E Aircraft. Indianapolis: Naval Avionics Center 443, 1975. Document
No. ESL-163.
q. Kuhn, D. L. and R. M. Johnson., Evaluation of the Vibration Environment for the Doppler Ranging
Information System. Indianapolis: Naval Avionics Center 443, 1982. Document No. ESL-420.
r. Analysis of the Vibration Environment for TACAMO IV B System Installed on ED-130 Aircraft.
Indianapolis: Naval Avionics Center 443, 1976. Document No. ESL-199.
s. Kuhn, D. L., Evaluation of Flight Data for the Big Look Antenna System OE-319/APS Installed on EP-3E
aircraft. Indianapolis: Naval Avionics Center 443, 1981. Document No. ESL-418.
t. Kuhn, D. L., Analysis of Flight Data for Deepwell System Installed in EP-3E Aircraft. Indianapolis: Naval
Avionics Center 443, 1975. Document No. ESL-169.
u. Dreher, J. F., E. D. Lakin, and E. A. Tolle, Vibroacoustic Environment and Test Criteria for Aircraft Stores
During Captive Flight. Shock and Vibration Bulletin 39, Supplement (1969), pp. 15-40. Shock &
Vibration Exchange (SAVE), 1104 Arvon Road, Arvonia, VA 23004.
v. Dreher, J. F., Effects of Vibration and Acoustical Noise on Aircraft/Stores Compatibility. Aircraft Store
Symposium Proceedings, Vol. 6, November 1969.
w. Piersol, A. G., Vibration and Acoustic Test Criteria for Captive Flight of Externally Carried Stores,
December 1971. AFFDL-TR-71-158. DTIC No. AD-893-005L.
x. Frost, W. G., P. B. Tucker, and G. R. Waymon, Captive Carriage Vibration of Air-to-Air Missiles on
Fighter Aircraft. Journal of Environmental Sciences, 21:15, (September/October 1978), pp. 11-15.
Institute of Environmental Sciences and Technology, Arlington Place One, 2340 S. Arlington Heights
Road, Suite 100, Arlington Heights, IL 60005-4516.
y. Mechanical Vibrations; Den Hartog, J. P., Fourth Edition, McGraw-Hill Book Company. 1956.
z. A Modern Course in Aeroelasticity. Dowell, E. H., et al, Second Edition, Kluwer Academic Publisher,
1989.
aa. Shock and Vibration Handbook, Fifth Edition, Edited by Harris, Cyril M. and Piersol, Allan G.; McGraw-
Hill Book Company.
bb. Bendat, Julius S., and Piersol, Allan G., Engineering Applications of Correlation and Spectral Analysis,
2nd Edition, John Wiley & Sons, Inc., New York, 1993. Wiley Interscience, ISBN 0471570554, 1993.
cc. Allemang, Randall J. and David L. Brown, Experimental Modal Analysis and Dynamic Component
Synthesis - Measurement Techniques for Experimental Modal Analysis. Vol. 2. December 1987.
AFWAL-TR-87-3069, DTIC No. ADA195145.
dd. Allemang, Randall J. and David L. Brown, Experimental Modal Analysis and Dynamic Component
Synthesis - Modal Parameter Estimation. Vol. 3. December 1987. AFWAL-TR-87-3069, DTIC No.
ADA195146.

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ee. Allemang, Randall J. and David L. Brown, Experimental Modal Analysis and Dynamic Component
Synthesis - System Modeling Techniques. Vol. 6. December 1987. AFWAL-TR-87-3069, DTIC No.
ADA195148.
ff. Airplane Aerodynamics, Dommasch, Daniel O, Sidney S. Sherby and Thomas F. Connolly, Pitman
Publishing Corporation, 1958.
gg. Smallwood, David, Multiple Input Multiple Output (MIMO) Linear Systems Extreme Inputs/Outputs.
Shock and Vibration 13 (2006) 1-25, Manuscript number SAV-05-058; IOS Press, Inc., 4502 Rachael
Manor Drive, Fairfax, VA 22032
hh. NATO STANAG 4370, Environmental Testing.
ii. NATO Allied Environmental Conditions and Test Publication (AECTP) 400, Mechanical Environmental
Testing, Method 401.
jj. NATO Allied Environmental Conditions and Test Publication (AECTP) 240, Mechanical Environmental
Testing.
kk. U.S. Standard Atmosphere, 1976; DTIC No. ADA035728.
ll. NATO STANAG 4570, Evaluating the Ability of Materiel to Meet Extended Life Requirements; 2004;
Information Handling Services.
mm.NATO Allied Environmental Conditions and Test Publication (AECTP) 600, A Ten Step Method for
Evaluating the Ability of Materiel to Meet Extended Life Requirements; December 2004; Leaflet 604;
Information Handling Services.
nn. Ehlers, E.L., and Cline, H.T., "Methodology Investigation Final Report Improvement of Shock and
Vibration Testing - Schedules for Transport of Loose, Restrained and Restrained Cargo," Report No. APG-
MT-5521, September 1981, ADB060211.
oo. Foley, J.T., M. B. Gens, C. G. Magnuson, and R. A. Harley; “Transportation Dynamic Environment
Summary,” Sandia Laboratories, EDB 1354, January 1973b.
pp. Barry, M., “Test Record, Composite Wheeled Vehicle Vibration Schedule Development,” USAADSS No.
2005-DT-ATC-SNIMT-D0079, US Army Aberdeen Test Center, Report No. 06-AID-115, October 2006.
qq. The Shock and Vibration Monograph Series, SVM-8, "Selection and Performance of Vibration Tests,"
1971; Shock & Vibration Exchange (SAVE), 1104 Arvon Road, Arvonia, VA 23004.
rr. Robinson, J.A., Final Report, Methodology Investigation “Cargo Configuration and Restraint in Military
Ground Vehicles,” TECOM-Project No. 7-CO-RD8-AP1-002; US Army Aberdeen Proving Ground,
Report No. APG-MT-5319, November 1979.
ss. Ehlers, E.L. and Cline, H.T., Final Report, Methodology Investigation, “Realistic Vehicle Mileages for
Installed Equipment in Ground Vehicles,” TECOM Project No. T-CO-RD2-AP1-003; US Army Aberdeen
Proving Ground, Report No. APG-MT-5804, December 1983.
tt. Baily, R.D., Corr, J.R., Final Report, Methodology Investigation, “Realistic Test Schedules for Restrained
Cargo in Military Vehicles, Groups I and II,” TECOM Project No. T-CO-RD3-AP1-002; US Army
Aberdeen Proving Ground, Report No. APG-MT-5948, January 1984.
uu. US TOP 2-2-506A, “Wheeled and Tracked Vehicle Endurance Testing”, 2 October 2014, ADA610880.
vv. Baily, R.D., Final Report, Methodology Investigation, “Realistic Vibration Schedules for Equipment
Installed in Military Vehicles,” TECOM Project No. 7-CO-R86-APO-003, US Army Aberdeen Proving
Ground. Report No. USACSTA 6656, March 1988.
ww. Kim, Steven S., “How to Use MIL-STD-810 Helicopter Vibration Test Procedures,” Report Number IHTR
2011, Indian Head Division, Naval Surface Warfare Center, 18 August 1997.

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xx. Test Operations Procedure (TOP) 01-2-603, Rotorcraft Laboratory Vibration Test Schedules, 12 June
2017; DTIC AD No. AD1035102.
yy. SST-EAS-0581 Issue 1, Assessment Report, Munition Vibration and Shock Environments Experienced
During Transportation by Hercules C130J Mk 5, June 2005
zz. ESG-TN-0397 Issue 6, Technical Note, Derivation of Vibration test Severities for the Transport of Material
in C130K and C130J Aircraft, 26 May 2005
6.2 Related Documents.
a. Dynamic Environmental Criteria, NASA Technical Handbook, NASA-HDBK-7005, 2001.
b. Force Limited Vibration Testing, NASA Technical Handbook, NASA-HDBK-7004, 2003.
c. Egbert, Herbert W. “The History and Rationale of MIL-STD-810 (Edition 2),” January 2010; Institute of
Environmental Sciences and Technology, Arlington Place One, 2340 S. Arlington Heights Road, Suite
100, Arlington Heights, IL 60005-4516.
d. The Shock and Vibration Monograph Series, SVM 9, "Equivalance Techniques for Vibration Testing,”
1972. Shock & Vibration Exchange (SAVE), 1104 Arvon Road, Arvonia, VA 23004.
e. McConnell, Kenneth, Vibration Testing: Theory and Practice, Wiley Interscience, ISBN 0471304352,
1995.
f. Nelson, Wayne, Accelerated Testing Statistical Models, Test Plans, and Data Analyses, Wiley Interscience,
ISBN 0471522775, 1990.
g. Ewins, D. J., Modal Testing, Theory, Practice and Application, Research Study Press LTD., ISBN
0863802184, 2000.
h. Bendat, Julius S., Piersol, Allan, G., Random Data Analysis and Measurement Procedures, Wiley
Interscience, ISBN 0471317730, 3d edition, 2000.
i. Lalanne, Christian, Specification Development (Mechanical Vibration and Shock), CRC, ISBN
1560329904, 2002.
j. Dodson, Bryan and Schwab, Harry, Accelerated Testing: A Practitioner's Guide to Accelerated And
Reliability Testing, SAE International, ISBN 0768006902, 2006.
k. Porter, Alex, Accelerated Testing and Validation, Amsterdam; Newnes, ISBN 0750676531, 2004.
l. MIL-STD-167-1A, Mechanical Vibrations of Shipboard Equipment (Type I – Environmental and Type II
– Internally Excited).
m. Tustin, Wayne, Random Vibration & Shock Testing, Measurement, Analysis & Calibration, Equipment
Reliability Institute, ISBN: 0-9741466-0-9, 2005.
(Copies of Department of Defense Specifications, Standards, and Handbooks, and International
Standardization Agreements are available online at https://assist.dla.mil.

Requests for other defense-related technical publications may be directed to the Defense Technical Information Center
(DTIC), ATTN: DTIC-BR, Suite 0944, 8725 John J. Kingman Road, Fort Belvoir VA 22060-6218,
1-800-225-3842 (Assistance--selection 3, option 2), http://www.dtic.mil/dtic/; and the National Technical
Information Service (NTIS), Springfield VA 22161, 1-800-553-NTIS (6847), http://www ntis.gov/.

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METHOD 514.8 ANNEX A

METHOD 514.8, ANNEX A

Engineering Information
NOTE: Unless specifically noted, all document references refer to paragraph 6.1 in the front part
of this Method.

1. SCOPE.
1.1 Purpose.
This Annex provides information intended to be useful in interpreting Method 514.8.
1.2 Application.
The following discussions concern basic engineering information. They are intended as a quick introduction to the
subject matter and are offered without detailed explanations, mathematics, or references. If further information or
understanding is required, the technical literature and engineering textbooks should be consulted. Paragraph 6.1,
reference aa, is recommended as a starting point.
1.3 Limitations.
See paragraph 1.3 in the front part of this Method.
2. ENGINEERING INFORMATION.
2.1 Vibration Test Types.
The following presents discussions of general types of vibration tests. Other test types, definitions, and names will be
found in practice. All of these test types may not be applied to a given materiel item. A typical materiel development
might include development testing and durability testing, while another might include qualification and reliability
testing. Environmental worthiness testing is included when needed. Environmental Stress Screening (ESS) is a part
of most current DOD acquisitions. All of the tests, including ESS, consume vibratory fatigue life. In many cases, a
qualification test, a durability test, or a reliability test consumes so much of the fatigue life of the test article that it is
not suitable for field deployment. However, there are instances in which the same tests are conducted to only a portion
of the fatigue life in the conduct of a system level version of an ESS test. Similarly, development tests and worthiness
tests may or may not consume a complete life depending on the specific test goals. It is important to ensure ESS
consumes only an appropriate, hopefully negligible, portion of total life, and that this portion is accounted for in the
total life cycle of vibration exposures. In all cases, it is vital to tailor test methodology and requirements to achieve
the desired results.
2.1.1 Development test.
Development testing is used to determine characteristics of materiel, to uncover design and construction deficiencies,
and to evaluate corrective actions. Begin as early as practical in the development, and continue as the design matures.
The ultimate purpose is to assure developed materiel is compatible with the environmental life cycle, and that formal
testing does not result in failure. The tests have a variety of specific objectives. Therefore, allow considerable freedom
in selecting test vibration levels, excitation, frequency ranges, and durations. Typical programs might include modal
analysis to verify analytical mode shapes and frequencies, and sine dwell, swept sine, transient, or random vibration
to evaluate function, fatigue life, or wear life. The test types, levels, and frequencies are selected to accomplish
specific test objectives. Levels may be lower than life cycle environments to avoid damage to a prototype, higher to
verify structural integrity, or raised in steps to evaluate performance variations and fragility.
2.1.2 Qualification test.
Qualification testing is conducted to determine compliance of a materiel with specific environmental requirements.
Such tests are commonly a contractual requirement and will include specific test specifications. Qualification tests
should be conducted using an excitation that has the same basic characteristics as the anticipated service environment.
For most items, this consists of a functional test and an endurance test (sometimes combined). The functional test
represents the worst case vibration (or envelope of worst case conditions) of the operational phases of the
environmental life cycle. The endurance test is a fatigue test representing an entire life cycle. When separate
functional and endurance tests are required, split the functional test duration, with one half accomplished before the
endurance test, and one half after the endurance test (in each axis). The duration of each half should be sufficient to

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fully verify materiel function. This arrangement has proven to be a good way of adequately verifying that materiel
survives endurance testing in all respects.
2.1.2.1 Functional test.
Functional testing is conducted to verify that the materiel functions as required while exposed to no less than the worst
case operational vibration for a particular segment(s) of a mission profile. Functional vibration levels typically do not
include time compression but may include some level of conservatism. Tailor the vibration level for each segment of
the mission profile based on measured data, when available, or derived from the operational state of the vehicle
platform.. This is the maximum vibration environment where the unit under test is expected to function. Fully verify
function at the beginning, middle and end of each test segment. Monitor basic function at all times during each test
run. In some cases, materiel that must survive severe worst case environments may not be required to function or
function at specification levels during worst case conditions. Typically "operating" and "non-operating" envelopes
are established. Tailor functional tests to accommodate non-operating portions by modifying functional monitoring
requirements as appropriate.
2.1.2.2 Endurance test.
Endurance testing is conducted to reveal time-dependent failures. In many cases the test is accelerated in order to
produce the same damage as the entire duration of the required service life. Generally, it is not required to have an
item powered-up during the endurance phase of test. Refer to paragraph 2.1.2.1 for functional testing. Use the
simplified fatigue relationship in paragraph 2.2 below to scale the less severe vibration levels to the maximum service
levels that occur during the service life. This, in turn, will define the test time at maximum service levels (functional
levels) that are equivalent to a vibration lifetime (levels vary throughout each mission). Use the equivalent time as
the functional test duration, thereby combining functional and endurance tests. There may be cases when this test
duration is too long to be compatible with program restraints. In these cases, use as long of a test duration as is
practical and use the fatigue relationship to define the test level. While this approach does not completely eliminate
nonlinearity questions, it does limit levels to more realistic maximums. Generally, the test item will not be in a
powered-up state during the endurance (“non-operating”) phase of testing; particularly in a situation in which the test
levels have been exaggerated beyond maximum measured values in order to significantly compress the test duration.
2.1.3 Durability test.
Durability testing is a real-time (non-exaggerated) simulation of the environmental life cycle to a high degree of
accuracy. A durability analysis precedes the test and is used to determine which environmental factors (vibration,
temperature, altitude, humidity, etc.) must be included in the test to achieve realistic results. Although the test is
intended to be a real time simulation of the life cycle, it may be shortened by truncation if feasible. Truncation is the
elimination of time segments that are shown by the durability analysis to be benign with regard to materiel function
and life. Durability analyses should use fatigue and fracture data applicable to each material, rather than the simplified
expressions of paragraph 2.2 below.
a. Worst case levels. Mission portions of the environmental life cycle are represented in the durability test
by mission profiles. Mission profiles are statistical definitions of environmental stress and materiel duty
cycle versus time. Mission profiles often do not include worst case environmental stresses because they
are encountered too rarely to be significant statistically. However, it is important to verify that materiel
will survive and function as needed during extreme conditions. Therefore, insert maximum environmental
levels into the durability test, in a realistic manner. For example, in the case of a fighter airplane, the
maximum levels would be inserted during an appropriate combat mission segment rather than a more
benign segment such as cruise.
b. Success criteria. Pass/fail criteria for durability tests are established for the particular effort. Criteria could
include no failures, a maximum number of failures, a maximum amount of maintenance to fix failures, or
some combination of these.
2.1.4 Reliability test.
Reliability testing is accomplished to obtain statistical definitions of materiel failure rates. These tests may be
development tests or qualification tests. The accuracy of the resulting data is improved by improving realism of the
environmental simulation. Test requirements are developed by engineers responsible for materiel reliability. Specific
definitions for reliability test as discussed in paragraph 6.1, reference aa, are provided below.

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2.1.4.1 Statistical Reliability test.

A statistical reliability test is a test performed on a large sample of production items for a long duration to establish or
verify an assigned reliability objective for the equipment operating in its anticipated service environment, where the
reliability objective is usually stated in terms of a mean-time-to-failure (MTTF), or if all failures are assumed to be
statistically independent, a mean-time-between-failures (MTBF) or failure rate (the reciprocal of MTBF). To provide
an accurate indication of reliability, such tests must simulate the equipment shock and vibration environments with
great accuracy. In some cases, rather than applying stationary vibration at the measured or predicted maximum levels
of the environment, even the non-stationary characteristics of the vibration are reproduced, often in combination with
shocks and other environments anticipated during the service life (see Annex A of Method 516.8). The determination
of reliability is accomplished by evaluating the times to individual failures, if any, by conventional statistical
techniques.
2.1.4.2 Reliability Growth test.
A reliability growth test is a test performed on one or a few prototype items at extreme test levels to quickly cause
failures and, thus, identify weaknesses in materiel design. In many cases, the test level is increased in a stepwise
manner to clearly identify the magnitude of the load needed to cause a specific type of failure. Design changes are
then made and the failure rate of the materiel is monitored by either statistical reliability tests in the laboratory or
valuations of failure data from service experience to verify that the design changes produced an improvement in
reliability. Unlike statistical reliability tests, reliability growth tests do not simulate the magnitudes of the service
environments, although some effort is often made to simulate the general characteristics of the environments; for
example, random vibration would be used to test materiel exposed to a random vibration service environment.
2.1.5 Worthiness test.
When unqualified materiel is to be evaluated in the field, verification that the materiel will function satisfactorily is
normally required for safety and/or test efficiency reasons. This is accomplished by environmental worthiness test.
The worthiness test is identical to a qualification test except that it covers only the life cycle of the field evaluation.
Levels are usually typical operating levels unless safety is involved; then maximum operating levels are necessary.
Durations are either equivalent to a complete system/subsystem test, long enough to check materiel function, or an
arbitrary short time (5 or 10 minutes). For safety driven worthiness test, the test item is considered to be consumed
by the test (the test item may not be used in the field). An identical item of hardware is used in the field evaluation.
When safety is not an issue, an item may be subjected to a minimum time functional test and then used in the field
evaluation. When it is required to evaluate the cumulative environmental effects of vibration and environments such
as temperature, altitude, humidity, leakage, or EMI/EMC, a single test item should be exposed to all environmental
conditions. For air worthiness testing, a three step approach may be required. For example, this could include
conducting an initial laboratory vibration test, followed by experimental flight testing to acquire the actual exposure
levels, and ending with a qualification test based on the measured field data.
2.1.6 Environmental Stress Screening (ESS).
ESS is not an environmental simulation test representative of a life cycle event and is not a substitute for a
qualification test. It is a production or maintenance acceptance inspection technique designed to quickly induce
failures due to latent defects that would otherwise occur later during service. However, it is an environmental life
cycle event and should be included as preconditioning or as part of the test as appropriate. Materiel may be subject to
multiple ESS cycles, and maintenance ESS vibration exposures may differ from production acceptance exposures.
ESS should be included in development tests only as appropriate to the test goals. The vibration environment is
sometimes applied using relatively inexpensive, mechanically or pneumatically driven vibration testing machines
(often referred to as impact or repetitive shock machines) that allow little or no control over the spectrum of the
excitation. Hence, the screening test environment generally does not represent an accurate simulation of the service
environment for the materiel.
2.2 Test Time Compression and the Fatigue Relationship.
The major cause of items failing to perform their intended function is material fatigue and wear accumulated over a
time period as a result of vibration-induced stress. It is preferable for materiel to be tested in real-time so the effects
of in-service conditions are simulated most effectively. However, in most instances real-time testing cannot be
justified based on cost and/or schedule constraints and, therefore, it is customary to compress the service life
environment into an equivalent laboratory test. For vibration environments that vary in severity during the materiel’s

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METHOD 514.8 ANNEX A

service life, the duration of the environment can often be reduced for testing by scaling the less severe segments of
the vibration environment to the maximum levels of the environment by use of an acceptable algorithm. In many
cases, scaling less severe segments to the maximum levels may still yield a test duration that is still too long to be
practical. In such cases, the same algorithm may be used to further reduce test duration by increasing test amplitude.
Provided that fatigue is a significant potential failure criterion for the materiel under test, this practice is acceptable
within strict limits, notably that test amplitudes are not over exaggerated (or accelerated) simply to achieve short test
durations. Such excessive amplitudes may lead to wholly unrepresentative failures, and cause suppliers to design
materiel to withstand arbitrary tests rather than the in-service conditions.
The most commonly used method for calculating a reduction in test duration is the Miner-Palmgren hypothesis that
uses a fatigue-based power law relationship to relate exposure time and amplitude. The mathematical expression and
variable descriptions for this technique are illustrated below in Equations (1) and (4).
m
t 2  S1 
=  Equation (1)
t1  S 2 

where
t1 = equivalent test time
t2 = in-service time for specified condition
S1 = severity (rms) at test condition
S2 = severity (rms) at in-service condition
[The ratio S1/S2 is commonly known as the exaggeration factor.]
m = a value based on (but not equal to) the slope of the S-N curve for the appropriate material, where S
represents the stress amplitude, and N represents the mean number of constant amplitude load
applications expected to cause failure.
Fatigue damage can be calculated using either a stress life or strain life process. For the strain life technique, the
number of cycles to failure, N f , is computed from:

σ'f
εa = (2 N f )b + ε ' f (2 N f )c Equation (2)
E
where
εa = test or environment strain amplitude
σ’f = fatigue strength coefficient (material property)
E = modulus of elasticity (material property)
Nf = number of cycles to failure
b = fatigue strength exponent (material property)
ε’f = fatigue ductility coefficient (material property)
c = fatigue ductility exponent (material property)
The fatigue strength portion of the equation represents the elastic portion of the S-N curve and the fatigue ductility
portion of the equation represents the plastic portion. The stress life technique uses only the linear (elastic) portion of
the curve (below yield) and is written as:

S a = σ ' f (2 N f )
b
Equation (3)

Where
Sa = test or environment stress amplitude
Equation (3) is valid only in the finite life region with elastic nominal stresses (generally 1000 to 10,000,000 cycles

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METHOD 514.8 ANNEX A

to failure). Fatigue damage outside this region can be described by a power law model in the form of Equation (1)
with an exponent “m” that is not equal to “b.” The value of “m” is strongly influenced by the material S-N curve, but
fatigue life is also influenced by the surface finish, the treatment, the effect of mean stress correction, the contributions
of elastic and plastic strain, the waveshape of the strain time history, etc. Therefore, the value of “m” is generally
some proportion of the negative reciprocal of the slope of the S-N curve, known as the fatigue strength exponent and
designated as “-1/b.” Typical values of “m” are 80 percent of “-1/b” for random waveshapes, and 60 percent of “-1/b”
for sinusoidal waveshapes. Historically, a value of m = 7.5 has been used for random environments, but values
between 5 and 8 are commonly used. A value of 6 is commonly used for sinusoidal environments. This cumulative
damage assumption is based on the fatigue properties of metals. Paragraph 6.1, reference aa (chapter 35) recommends
that Miner’s cumulative damage theory not be used for composite materials. However, a “wearout model,” defined
as “the deterioration of a composite structure to the point where it can no longer fulfill its intended purpose,” is shown
as a power law model in the form of Equation (1) with variable exponents dependent upon the type of composite
system. It is recommended that test time compression for composite structures be treated on a case-by-case basis.
Since most vibration environments are expressed in terms of the auto spectral density function, Equation (1) can also
be formulated as:
m
2
t2  W ( f )1  Equation (4)
= 
t1 W ( f ) 2 

where:
t1 = equivalent test time
t = in-service time for specified condition
2

W(ƒ)1 = ASD at test condition, g2/Hz

W(ƒ)2 = ASD at in-service condition, g2/Hz
[The ratio W(ƒ)1 /W(ƒ)2 is commonly known as the exaggeration factor]
m = as stated in Equation (1)
In many instances these equations appear to offer a satisfactory solution. However, caution should always be exercised
in the application of the equations. Some methods of characterizing vibration severities, notably ASDs, do not
necessarily reproduce under laboratory testing the same strain responses as those experienced under in-service
conditions. Exaggeration factors for materials whose fatigue characteristics are unknown or for failure mechanisms
other than fatigue (such as loosening of threaded connections) cannot be calculated. Real time test levels and durations
should be used in these instances unless there is sufficient information about the particular application to allow for the
use of a reasonable exaggeration factor. It is recommended that the exaggeration factor be kept to a minimum value
consistent with the constraints of in-service time and desired test time, and should generally not exceed values of 2
(S1/S2) or 4 (W(f)1/W(f)2).

Note: Using material S-N curves results in different equivalencies for different parts in a given test item. A
decision will be required as to which equivalency to use to establish test criteria.

2.3 Vibration Characterization.

The majority of vibration experienced by materiel in operational service is broadband in spectral content. That is,
vibration is present at all frequencies over a relatively wide frequency range at varying intensities. Vibration
amplitudes may vary randomly, periodically, or as a combination of mixed random and periodic.

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the sinusoid(s) frequency(s) through bands representative of frequency variations in the environment and
resonant frequency variations in materiel (see paragraph 2.4.3 below).
2.3.4 Transient vibration.
Transient vibration is a time-varying "windowed" portion of a random vibration that is of comparatively short duration
(e.g., 0.5 second to 7.5 seconds). Currently, such a measured environment is replicated in the laboratory on a vibration
exciter under waveform control. Verification of the laboratory test is provided by (1) display of the laboratory
measured amplitude time history; (2) an optimally smooth estimate of the amplitude time history time-varying root-
mean-square, and (3) either an energy spectral density estimate, or a Shock Response Spectrum (SRS) estimate for
comparatively short environments (transient vibration duration less than the period of the first natural mode of the test
item), or a time-varying auto spectral density estimate of longer duration environments, e.g., 2.5 to 7.5 seconds. In
general, since the environment is being replicated in the laboratory under waveform control, if the impulse response
function of the system is correctly determined and correctly applied, the replication should be nearly identical to the
measured environment. The transient vibration environment is an important environment for stores resident in
platform weapon bays that may be exposed to such environments many times in the life of training missions. See
paragraph 6.1, references c and bb; Method 516.8; and Method 525.2 for procedures relative to transient vibration.
2.3.5 Random versus sinusoidal vibration equivalence.
In the past, most vibration was characterized in terms of sinusoids. Currently, most vibration is correctly understood
to be random in nature and is characterized as such. This results in a demand to determine equivalence between
random and sine vibration. This demand is generated by the need to use materiel that was developed to sine
requirements.
a. General equivalence. Sine and random characterizations of vibration are based on distinctly different sets
of mathematics. In order to compare the effects of given random and sine vibration on materiel, it is
necessary to know the details of materiel dynamic response. A general definition of equivalence is not
feasible.
b. G-rms. Often, attempts are made to compare the peak acceleration of sine to the rms acceleration of
random. The only similarity between these measures is the dimensional units that are typically acceleration
in standard gravity units (g). Peak sine acceleration is the maximum acceleration at one frequency (see
paragraph 2.3.2). Random rms is the square root of the area under a spectral density curve (see paragraph
2.3.1). These are not equivalent.
2.3.6 Combination of test spectra
When combining test spectra to develop an envelope or weighted average of multiple vibration profiles, refer to the
discussion and techniques presented in Annex F of this method.
2.4 Platform/Materiel and Fixture/Test Item Interaction.
Generally, it is assumed that the vibration environment of the materiel is not affected by the materiel itself. That is,
the vibration of the platform at the materiel attachment point would be the same whether or not the materiel is attached.
Since the entire platform, including all materiel, vibrates as a system, this is not strictly correct. However, when the
materiel does not add significantly to the mass or stiffness of the platform, the assumption is correct within reasonable
accuracy. The following paragraphs discuss the limitations of this assumption. These effects also apply to sub-
elements within materiel and to the interactions of materiel with vibration excitation devices (shakers, slip tables,
fixtures, etc.).
2.4.1 Mechanical impedance.
a. Large mass items. At platform natural frequencies where structural response of the platform is high, the
materiel will load the supporting structures. That is, the mass of the materiel is added to the mass of the
structure, and it inertially resists structural motions. If the materiel mass is large compared to the platform
mass, it causes the entire system to vibrate differently by lowering natural frequencies and changing mode
shapes. If the materiel inertia is large compared to the stiffness of the local support structure, it causes the
local support to flex, introducing new low frequency local resonances. These new local resonances may
act as vibration isolators (see paragraph 2.4.2 below).

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b. Items acting as structural members. When materiel is installed such that it acts as a structural member of
the platform, it will affect vibrations and it will be structurally loaded. This is particularly important for
relatively large materiel items, but it applies to materiel of any size. In these cases, the materiel structure
adds to the stiffness of the platform and may significantly affect vibration modes and frequencies. Further,
the materiel will be subjected to structural loads for which it may not have been designed. An example is
a beam tied down to the cargo deck of a truck, aircraft, or ship. If the tie-downs are not designed to slip at
appropriate points, the beam becomes a structural part of the deck. When the deck bends or twists, the
beam is loaded and it changes the load paths of the platform structure. This may be catastrophic for the
beam, the platform, or both. Be careful in the design of structural attachments to assure that the materiel
does not act as a structural member.
c. Large item mass relative to supporting structures. When materiel items are small relative to the overall
platform, but large relative to supporting structures, account for the change in local vibration levels, if
practical. This effect is discussed in Annex D, paragraph 2.1 for materiel mounted in jet aircraft. Due to
differences in environments, relative sizes, and structural methods, the factor defined in Annex C, Table
514.8C-X is not applicable to materiel mounted in small, unmanned aircraft.
d. Large item size/mass relative to platform. When materiel is large in size or mass relative to the platform,
always consider the potential of damage to the platform as a result of materiel vibration. It is imperative
to consider these effects in the design of vibration test fixtures. Otherwise, the vibration transmitted to the
test item may be greatly different than intended.
2.4.2 Vibration isolation.
Vibration isolators (shock mounts), isolated shelves, and other vibration isolation devices add low-frequency
resonances to the dynamic system that attenuate high-frequency vibration inputs to materiel. Vibration inputs at the
isolation frequencies (materiel six degree-of-freedom rigid body modes) are amplified, resulting in substantial rigid
body motions of the isolated materiel. Effective performance of these devices depends on adequate frequency
separation (minimum factor of two) between materiel resonant frequencies and isolation frequencies, and on adequate
sway space (clearance around isolated materiel) to avoid impacts of the isolated materiel with surrounding materiel
(possibly also vibration isolated and moving) and structure.
a. Sway space. Include sway amplitude and isolation characteristics (transmissibility versus frequency) in
all design analyses and measure them in all vibration tests. Isolation devices are nonlinear with amplitude.
Evaluate these parameters at vibration levels ranging from minimum to maximum. These comments also
apply to isolated sub-elements within materiel items.
b. Minimum ruggedness. All materiel should have a minimum level of ruggedness, even if protected by
isolation in service use and shipping. Thus, when materiel development does not include all shipping and
handling environments of the materiel’s life cycle, include the appropriate minimum integrity exposures
in materiel (Annex E, paragraph 2.1.1).
2.4.3 Materiel resonant frequency variation.
The installed resonant frequencies of materiel may vary from those of the laboratory test. One cause is the small
variations between serial items from an assembly process. Tightness of joints, slight differences in dimensions of
parts and subassemblies, and similar differences affect both the resonant frequencies and the damping of the various
modes of the item. A second cause is the interaction between the materiel and the mounting. As installed for field
use, a materiel item is tied to mounting points that have an undefined local flexibility, and that move relative to each
other in six degrees of freedom as the platform structure vibrates in its modes. In a typical laboratory test, the test
item is tied to a massive, very stiff fixture intended to transmit single axis vibration uniformly to each mounting point.
In each case, the mounting participates in the vibration modes of the materiel item and, in each case, the influence is
different. When defining test criteria, consider these influences. Both in the cases of measured data and arbitrary
criteria, add an allowance to narrow band spectral elements.
2.5 Modal Test and Analysis.
Modal test and analysis is a technique for determining the structural dynamic characteristics of materiel and test
fixtures. Modal tests (paragraph 6.1, reference cc), also known as ground vibration tests (GVT) and ground vibration
surveys (GVS), apply a known dynamic input to the test item, and the resulting responses are measured and stored.
Modal analysis methods are applied to the measured data to extract modal parameters (resonant frequencies, mode

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shapes, modal damping, etc.). Modal parameters are used to confirm or generate analytical models, investigate
problems, determine appropriate instrumentation locations, evaluate measured vibration data, design test fixtures, etc.
Modal analysis methods range from frequency domain, single degree of freedom methods, to time domain, multi-
degree of freedom methods (paragraph 6.1, references dd and ee).
2.5.1 Modal test techniques.
Experimental modal tests involve excitation of a structure with a measured force while measuring the acceleration
response and computing the frequency response functions (FRF) at location(s) of interest for subsequent modal
analysis. Excitation of the structure for modal test may be accomplished in various ways. The simplest method, a
modal impact test, consists of excitation with a modally tuned impact hammer instrumented with a force gage to
produce a low force impact on the structure that approximates an impulse function. This technique is commonly used
as a quick check of resonant frequencies for fixtures and installed components. A more sophisticated approach would
use burst random excitation with small vibration exciter(s) attached to a structure that is instrumented with an array
of accelerometers. Modal tests with vibration exciters is more commonly used for high channel count modal tests of
complex structures with more precise measurements required for the development of mode shapes and verification of
analytical models. Sinusoidal and broadband random vibration excitation of a test fixture/item mounted on large
vibration exciters are also options to check resonant frequencies for laboratory vibration test setups. Select
methodology that will result in well-understood, usable data, and that will provide the level or detail needed for the
specific test goals.
2.5.2 Material non-linear behavior.
Dynamic inputs should be at as realistic levels as possible, and at as many levels as practical because materiel response
is generally nonlinear with amplitude. Modal parameters determined through modal test and analysis techniques are
typically based on assumption of structural linearity. Linearity checks can be conducted during modal tests by
collecting and analyzing data at various force levels and identifying frequency shifts, if any, in the resonant
frequencies. For structures that exhibit highly non-linear behavior, additional analysis will be required to extrapolate
modal test results to the expected life cycle vibration environments.
2.6 Aerodynamic Effects.
A primary source of vibration in aircraft and aircraft stores is the aerodynamic flow over the vehicle. Oscillating
pressures (turbulence) within the flow drive vibration of the airframe surfaces. These pressures and, thus, the vibration
are a linear function of dynamic pressure, and a non-linear function of Mach number. When a flow becomes
supersonic, it smooths out and turbulence drops off. Then, as speed increases, further turbulence builds up again.
This phenomenon is well illustrated in the vibration data contained in paragraph 6.1, reference k. The Mach
corrections given in Annex D, Table 514.8D-IV are based on an average of this data. The following definitions and
the values and the formulas of Annex D, Table 514.8D-V are provided for use in calculating airspeeds and dynamic
pressures. The source of the formulas is paragraph 6.1, reference ff, and the source of the atmospheric values is
paragraph 6.1, reference kk.
2.6.1 Dynamic pressure.
The total pressure of a gas acting on an object moving through it is made up of static pressure plus dynamic pressure
(q). The proportions vary with speed of the body through the gas. Dynamic pressure is related to speed by
q = 1/2 ρ V2 where ρ is the density of the gas, and V is the velocity of the object through the gas.
2.6.2 Airspeed.
The speed of an aircraft moving through the atmosphere is measured in terms of airspeed or Mach number. There are
several forms of airspeed designation that are discussed below. At sea level these are equal, but as altitude increases
they diverge. Equations and data required for airspeed and dynamic pressure calculations are provided in Annex D,
Table 514.8D-V. These are based on paragraph 6.1, references ff and kk.
a. Calibrated airspeed. Airspeed is usually specified and measured in calibrated airspeed. Calibrated airspeed
is typically expressed in nautical miles per hour (knots) and designated knots calibrated air speed (Kcas).
Kcas is not true airspeed. It is derived from quantities that are directly measurable in flight. Since it is not
true airspeed, it cannot be used in the simple formula for q given above.

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METHOD 514.8 ANNEX A

b. Indicated airspeed. Another form of airspeed measurement is indicated airspeed. Calibrated airspeed is
indicated airspeed when empirical corrections are added to account for factors in the specific aircraft
installation. Indicated airspeed is expressed in various units (kilometers per hour, miles per hour, and
knots), but in military aircraft it is normally in knots indicated airspeed (Kias).
c. Equivalent airspeed. Equivalent airspeed is a form directly related to dynamic pressure. It is sometimes
used in engineering calculations since other forces (lift, drag, and structural air-loads) acting on an airframe
are also proportional to dynamic pressure. However, it is not used in airspeed measurement systems or
flight handbooks. Equivalent airspeed may be expressed in various units, but it is usually seen as knots
equivalent airspeed (Keas).
d. True airspeed. This is the actual airspeed. To calculate true airspeed with an aircraft air data system, local
atmospheric properties must be accurately known. This was not practical until recent years and aircraft
generally do not use true airspeed in handbooks or to navigate. True airspeed may be expressed in various
units but it is usually seen as knots true airspeed (Ktas).
e. Mach number. Mach number is the ratio of true airspeed to the speed of sound. When Mach number is
measured by an aircraft air data system, it is true Mach number.
2.6.3 Altitude.
Aircraft air data systems measure local atmospheric pressure and convert this value to pressure altitude through a
standard atmosphere model that relates pressure, temperature, and density. Pressure altitude is used in the equations
relating airspeeds and dynamic pressure. Care must be exercised to assure that altitudes are pressure altitudes. Often,
low altitude values for modern military aircraft are given as absolute height above local terrain. These values should
be changed to pressure altitude values. Guidance from engineers familiar with mission profile development is required
to make this adjustment.
2.7 Similarity.
It is often desirable to use materiel in an application other than that for which it was developed. Also, changes are
made to existing materiel or the environmental exposures because of an application change. The question arises as to
how to verify that the materiel is suitable for the application? This is usually accomplished through a process called
"qualification by similarity." Unfortunately, this process has never had a generally accepted definition. In practice it
sometimes devolves to a paper exercise that provides traceability but has no engineering content. The following
paragraphs are an adaptation of a set of criterion that was provided to an Air Force avionics program. It is suggested
as a basis for vibration similarity criteria. Tailor the criteria for materiel type, platform environments, and program
restraints. Change the emphasis from circuit cards to the particular critical elements when the materiel is not an
electronic box. Also, change the fatigue equation exponents as appropriate.
2.7.1 Unmodified materiel.
Qualify unmodified materiel by documented evidence that one of the following is met:
a. The materiel was successfully qualified by test to vibration criteria that equals or exceeds the vibration
requirements of the application.
b. The materiel has demonstrated acceptable reliability in an application where vibration environments and
exposure durations are equal to, or more stringent than the vibration requirements of the application.
c. The materiel was successfully qualified by test to vibration criteria that falls short of the application ASD
requirements in very narrow bands of energy (<5 percent of the test bandwidth) by no more than 3 dB,
contingent that the materiel under test has no resonant frequencies within the subject narrow band, and that
the G-rms falls within a minimum of 90 percent of the application and subsequently the materiel
demonstrated acceptable reliability.
2.7.2 Modified materiel.
Qualify modified materiel by documented evidence that the unmodified materiel meets the vibration requirements for
the application supplemented by analyses and/or test data demonstrating that the modified materiel is dynamically
similar to the unmodified materiel.

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METHOD 514.8 ANNEX A

2.7.3 Equal vibration environment.

Previous tests or other vibration exposures are considered to equal the application requirement when ALL of the
following conditions are met:
a. Previous exposures were the same type of vibration as the application requirement. That is, random
vibration must be compared to random criteria, and sine must be compared to sine criteria.
b. The exposure frequency range encompasses the application frequency range. Use a low frequency limit
of the range that is the low frequency limit of the application requirement, or 1/2 of the lowest materiel
resonant frequency, whichever is higher. The high frequency limit of the range is the high frequency limit
of the application requirement.
c. The exposure level (acceleration spectral density level or peak sinusoidal acceleration as applicable) was
no more than 3.0 dB below the application requirement at any frequency, and was at or above the
requirement for at least 80 percent of the total bandwidth.
d. The fatigue damage potential of the exposure(s) is not less than 50 percent of the application fatigue
damage potential at each frequency, and the fatigue damage potential of the exposure(s) equals or exceeds
the application fatigue damage potential over 80 percent of the frequency range. State fatigue damage
potentials as totaled equivalent exposure times at maximum application levels. Base summations and
equivalencies on the relationships shown in paragraph 2.2 of this Annex. These relationships should be
used with metal structures only.
2.7.4 Reliability data.
Use field reliability data that meets all of the following criteria:
a. The numbers of fielded materiel from which the data were taken are sufficient to statistically represent the
specific materiel item.
b. The field service seen by the materiel from which the data were taken is representative of the design
environmental life cycle.
c. The field reliability data satisfies maintainability, mission readiness, mission completion, and safety
requirements.
2.7.5 Critical resonant response.
Evaluate the first three natural frequencies of the chassis, and the first natural frequency of each sub assembly with
the following procedure:
a. Determine the required set (first set) of natural frequencies by test.
b. Compare maximum levels at which the materiel is required to operate for the original qualification and for
the application environment. Define the set (second set) of frequencies at which the application
environment exceeds the original levels.
c. Determine which resonances of the first set coincide with the frequencies of the second set. Show by test
or analysis that the materiel will function as required when these resonances are exposed to the application
environment maximum levels.
d. Use the procedure of paragraph 2.2 above to compare the fatigue damage potential of the original
qualification and the application environment. Define the set (third set) of frequencies at which the
application fatigue damage potential exceeds the fatigue damage potential of the original criteria.
e. Determine which resonances of the first set coincide with the frequencies of the third set. Show by test or
analysis that the required materiel life will be obtained when these resonances are exposed to the
application fatigue damage potential.
2.7.6 Dynamic similarity.
Consider modified materiel as dynamically similar to baseline materiel when all of the following apply (circuit card
used as an example):

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METHOD 514.8 ANNEX A

a. The total change in mass of the unit and of each subassembly is within ±10 percent.
b. The unit center of gravity is within ±10 percent of the original location in any direction.
c. The mounting configuration is unchanged.
d. The mounting configuration of circuit cards is unchanged.
e. The first three natural frequencies of the chassis and the first natural frequency of each subassembly are
within ±5 percent of the original frequencies.
f. The first natural frequency of each circuit board is within ±10 percent of the original frequency.
g. Each modified circuit card is vibrated for one hour in the axis perpendicular to the plane of the board. Use
a test exposure that is 0.04 g2/Hz from 15 to 1000 Hz rolled off at 6 dB per octave to 2000 Hz. Maintain
electrical continuity throughout the card during and after the test. (Where vibration levels and durations at
board level are known, these may be substituted for the stated exposure.)
h. Changes to mounts, chassis, internal support structures, and circuit card materials are to materials with
equal or greater high cycle fatigue strength.

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