BASIC CONCEPTS OF TESTING
Philosophy of testing
1.Technical people want to test to obtain
knowledge
2.Commercial people will test only when there
is some pressure to do so.
BASIC CONCEPTS
why test?.
The emphasis is on
automation,
high production,
cost reduction.
high-tolerance parts.
Consumer awareness,
a subject totally ignored by the
manufactures once upon a time, is now
a major area of concern.
SPECIFICATION AND STANDARDS
A specication description of requirements,
dimensions, materials, and so on.
A standard is something established for use as a
rule or a basis of comparison in measuring or
judging capacity, quantity, content, extent, value,
and quality.
Purpose
The specication also relates standard test methods
to be used to determine properties.
Thus, standard methods of test and evaluation
commonly provide the bases of measurement
required in the specie cation for needed or desired
properties .
the ultimate purpose of a standard is to develop a
common language, so that there can be no confusion
or communication problems among developers,
designers, fabricators, end-users, and other
concerned parties
BENEFIT OF STANADRD
1. Improved efficiency,
2. mass production,
3. superior quality goods through
uniformity,
4. and new challenges.
Standardization has opened the door
international trade,
technical exchanges,
establishment of common markets.
Origin of standard
Standards originate from a variety of
sources. The majority of standards originate
from industry. The industry standards are
generally established by voluntary
organizations that make every effort to see
that the standards are freely adopted and
represent a general agreement
PURPOSE OF SPECIFICATIONS
the major reason is to help the purchasing
department in
purchase equipment,
materials,
and products on an equal basis.
The speci cations, generally written by the
engineering department, allow the purchasing agent
to meet his requirements and ensure that the
material received at different times is within the
speci ed limits .
The specications is intended to ensure
batch-to-batch uniformity, as well as
remove confusion between the purchaser
and supplierwe all know that more often
than not what is provided by the supplier is
not what is expected by the purchaser.
PROFESSIONAL AND TESTING ORGANIZAT
1. AMERICAN NATIONAL STANDARDS INSTITUTE (ANSI)
In 1918, when ANSI was founded, standardization activities
were just beginning in the United States.ANSI is a
federation of standards competent from commerce and
industry, professional, trade, consumer, and labor
organizations, and government. ANSI, in cooperation with
these federation participants,
1. Identies the needs for standards and sets priorities for
their completion.
2. Assigns development work to competent and willing
organizations.
3. Sees to it that public interests, including those of the
consumer, are protected and represented.
4.Supplies standards writing organizations with
effective procedures and management services to
ensure efcient use of their manpower and
nancial resources and timely development of
standards.
5. Follows up to assure that needed standards are
developed on time.
ASTM INTERNATIONAL
ASTM International, originally known as the
American Society for Testing and Materials
(ASTM), was founded in 1898.
Membership in ASTM is open to all concerned with
the
elds in which ASTM is active. An ASTM standard
represents a common viewpoint of those parties
concerned with its provisions, namely, producers,
users, and general interest groups. It is intended
to aid industry, government agencies, and the
general public
FOOD AND DRUG ADMINISTRATION (F
The Food and Drug Administration, rst
established in 1931, is an American government
agency of the U.S. Department of Health and
Human Services. The FDAs activities are directed
toward protecting the health of the nation against
impure and unsafe foods, drugs, cosmetics, and
other potential hazards. The plastics industry is
mainly concerned with the Bureau of Foods,
which conducts research and develops standards
on the composition, quality, nutrition, and safety
of foods, food additives, colors, and cosmetics,
and conducts research designed to improve the
detection, prevention, and control of
contamination
NATIONAL INSTITUTE OF
STANDARDS AND TECHNOLOGY
(NIST)
The National Bureau of Standards was
established by an act of Congress in March
1901. The NBS was renamed the National
Institute of Standard and Technology in
1988. The bureaus overall goal is to
strengthen and advance the nations
science and technology and to facilitate
their effective application for public benet.
NATIONAL ELECTRICAL
MANUFACTURERS ASSOCIATION
(NEMA)
The National Electrical Manufacturers Association
was founded in 1926. This 600member association
consists of manufacturers of equipment and
apparatus for the generation, transmission,
distribution, and utilization of electric power. The
membership is limited to corporations, rms, and
individuals actively engaged in the manufacture of
products included within the product scope of NEMA
product subdivisions.
SOCIETY OF PLASTICS
ENGINEERS (SPE)
The Society of Plastics Engineers was founded in
1942 with the objective of promoting scienti c
and engineering knowledge relating to plastics.
SPE is a professional society of plastics scientists,
engineers, educators, students, and others
interested in the design, development,
production, and utilization of plastics materials,
products, and equipment.
NATIONAL FIRE PROTECTION
ASSOCIATION (NFPA)
The National Fire Protection Association was
founded in 1896 with the objective of developing,
publishing, and disseminating standards intended
to minimize the possibility and effect of re and
explosion. The NFPAs membership consists of
individuals from business and industry, re
service, health care, insurance, and educational
and government institutions. The NFPA conducts
re safety education programs for the general public
and provides information on re protection and
prevention. Also provided by the association is
eld service by specialists on ammable liquids,
SOCIETY OF PLASTICS INDUSTRY
(SPI)
The Society of Plastics Industry is a major society,
whose membership consists of manufacturers and
processors of plastics materials and equipment.
The society has four major operating units
consisting of the Eastern Section, the Midwest
Section. the New England Section, and the
Western Section. SPIs Public Affairs Committee
concentrates on coordinating and managing the
response of the plastics industry to issues like
toxicology, combustibility, solid waste, and
energy.
INTERNATIONAL ORGANIZATION FOR
STANDERDIZATION (ISO)
ISO is a network of the national standards institutes
of 148 countries, on the basis of one member per
country, with a Central Secretariat in Geneva,
Switzerland, that coordinates the system. ISO is a
nongovernmental organization: Its members are
not, as is the case in the United Nations system,
delegations of national governments. Nevertheless,
ISO occupies a special position between the public
and private sectors
UNDERWRITERS LABORATORIES
(UL)
Underwriters Laboratories, founded in 1894, is
chartered as a not-for-pro t organization to
establish, maintain, and operate laboratories
for the investigation of materials, devices,
products, equipment, constructions, methods,
and systems with respect to hazards affecting
life and property.
major reasons for testing:
past experience and quality of workmanship is
simply not enough. The following are some of the
major reasons for testing:
1. To prove design concepts
2. To provide a basis for reliability
3. Safety
4. Protection against product liability suits
5. Quality control
6. To meet standards and specications
7. To verify the manufacturing process
8. To evaluate competitors products
9. To establish a history for new materials
need to develop standard test
methods
1. The need to develop standard test methods
specically designed for plastic materials originated
for two main reasons. Initially, the properties of
plastic materials were determined by duplicating
the test methods developed for testing metals and
other similar materials
2.The standardization of test methods
acceptable to everyone solved the problem of
communication between developers, designers,
and end users, allowing them to speak a
common language when comparing the test
data and results
3.we still face the problem of comprehension and
interpretation of test data by an average person in the
plastics industry. This is due to the complex nature of
the test procedures and the number of tests and
testing organizations. The key in overcoming this
problem is to develop a thorough understanding of
what the various tests mean and the signi cance of
the result to the application being considered
Acceptable error
As a general rule, the error of testing should be
considered 5 percent. Some tests are more
precise than others. Such testing errors occur
from three major areas: (1) the basic test itself,
(2) the operators conducting the tests, and
(3) variations in the test specimens.
determination of necessary
manufacturing condition
Any analysis and interpretation must ensure that
the tested did not them selves contribute any
variation. Sample tested were prepared with
consistent present or precondition properties, no
meaning full interpretation of these of their test
can be made.
Careful and consistence sample preparation for
polymer and their composite is important because
both physical and mechanical properties of almost
all the polymer vary signicantly depend on the
ways they are prepared.
Variation factor
1.Different heating /cooling rate
2.Applied pressure,
3. Different type of atmosphere (RH etc. )
Care should be taken to ensure that the
variation of physical properties within the
same sample should be minimized if not
eliminate.
Preparation of plastic samples
The three important variation to be
avoided in sample preparation of
polymer
1.Degree of crystallization
2.Glass transition temperature
3.Void content
Degree of crystallization
Its depend on
1. Thermal and pressure history of sample
2. The prole
3. Surface smoothness of mold cavity(rough
surface induce high crystallization )
4. Composition of mold (copper have high
cooling rate than aluminium.
Glass transition temperature
1.Final tg will depend on thermal and
pressure history of polymer
2. The moisture during curing convert to
voids. Lower the Tg.
Void content
All the polymer either from liquid base or
melted from granules.
Moisture,
voltaile content
can induce a large and signicant amount
of voids due to high partial pressure of
water..
These can be minimize.
Rule: volume fraction of 5 % voids would
affet the properties.
It can be avoided by the use of vacuum
Specication for processing samples
Several standard and specication exit for the
processing the test sample.
1. The american stanadrd for testing material
(ASTM) probably provide the most
comprehensive series of standard.
2. International organization for standarzaation
(ISO)-293,294,295and 3167
3. British stanadard (BS 2782 part 9)
Technique for making test
sample
1.Injection molding
2.Compression molding
3. Transfer molding
4.Vacuum injection molding etc.
Storage
Immediately after its formation a polymer is most
likely to nd its properties changing at their rapid
ate, in absence of specically aggressive
environment.
Avoid leaving test material for too long before it is
tested if thisis to represent unaged material. The
longer the material is left before testing. The
greater the chance of deterioration through
accidential exposure to damage enviroment such
as heat, light , ozne etc. For commercial reason for
not leaving material too long before havig it tested.
To knoww theeleength of tie that elasped between
manufacturee and testing is diffcult. As ISO 471 , 4
week maximum for non product testig and three
Cutting specimen
The sample/specimen are cut from rolled
sheet or cutting from a molded piece. By
surgical knife or scissor., die cut,rotatry
cutter shear cutter
Care should be taken for cutting
conductive carbon lled composite
because it will short circuit if they are
allowed to be air born.
Variation that occur
1.Due to different edge cutting nish
(sanded off edege)
2.Due to lubrication (do not use any liquid
Conditioning
Plastic material properties are more
affted by variation in temperature, type
of material, relative humidity at the
time of test. So it important to mention
the condition at the time of testing.
Pretest conditioning
Conditioning is dened as the process of
subjecting a material to a stipulated inuence
or combination of inuences for a stipulated
period of time .
Three basic reasons for conditioning specimens
are:
1. To bring the material into equilibrium with
normal or average room conditions
2. To obtain reproducible results regardless of
previous history or exposure
3. To subject the material to abnormal
conditions of temperature and humidity in
order to predict its service behavior
1. ISO ( 291,558)method for plastic material : 23
C ( 2 C) and 50 %RH ( 5 % RH tolerance) for
4hour to 96 hour
2.ISO (554 and471)method for rubber material :
27 C ( 2 C) and 65 %RH ( 5 % RH ) for 3 hour
96 hour
3. ASTM D 618 : 23 C ( 2 C) and 50 %RH ( 5 %
RH tolerance)
Test Atmosphere
It should be carried out at 23 C. providing
testing is performed reasonably quickly after
removal from the controlled humidity
enviroment
DESIGNATION FOR CONDITIONING
Conditioning of a test specimen is designated as
A/B/C
where
A= a number indicating duration of conditioning
(hr);
B= a number indicating conditioning temperature
(C);
C = a number indicating relative humidity
(percent or a word
Example. 40/23/50 indicates conditioning for 40
hr at 23C at 50 percent RH
Assessment of properties of
nished products in relation to
service requirements
How
long will it last? An answer to this
question is wanted by both suppliers and
users. This is scarcity of denitive data.
What is Failure
Failure occurs when the component ceases to
perform its required function
Strictly, the useful life of a product can only
be measured directly by
service trials or
tests on the complete product.
Most assessments of lifetime of plastics are
made by considering some measure of
performance and specifying some limit or
threshold value for the property, which is
taken as the end point corresponding to
where the material is no longer usabl
Typical threshold parameters include:
mechanical strength
elongation at break
toughness
hardness
reduction in prestress
electrical breakdown strength
dielectric loss factor
electrical resistivity
colour,
gloss
surface texture
vapour permeability
adhesion
optical quality
dimensional stability:
warping.
The extension of polymers to long life
applications has been due to the
development of new polymers,
1. better understanding of the physical and
chemical processes by which they degrade.
2. the development of stabilising additives
which arrest or retard degradation and
extend polymer.
3.
Manufacturers are being asked increasingly for
assurance of product lifetime, particularly for
components which, because of their location in
service, cannot be easily inspected or replaced.
Examples are components for electrical
generation and distribution equipment where
outage time is costly, in areas of nuclear plant
where access is restricted because of the
safety of personnel, in underground uses such
as cables, gas pipes or geosynthetics, in
automatic lighthouses, in space, or as
prostheses in the
The Problems for assessment in service lif
Two of the fundamental hurdles in assessing the
service life of a product are denition of the
service conditions
uncertainty and
variation - and establishing the time scales for
expected lifetime.
The implication are that uncertainty may mean
designing for the worst case (or being
unexpectedly caught out) and the variation
potentially calls for testing (or making
extrapolations) under many conditions.
Prediction Techniques
An indirect indication of service life is
obtained simply by
1. comparison of the performance of
materials under given test conditions,
the one which shows the smaller change
being deemed to perform better.
2. If one material is a standard with known
service performance an estimate can be
made of the other materials expected
performance.
There are then two stages to modeling the
degradation process:
(1)obtaining a function for the rate of change
of the parameter(s) of interest with time.
(2) obtaining a function for the rate of change
of the parameter(s) with the level of the
degrading agent(temperature, vapor etc.).
Any Query Please
THE END
