[ULTRASONIC TESTING] Ultrasonic Testing 01
ULTRASONIC TESTING
Experimental Manual
By: Engr. M I Minhas
Department of Materials Engineering
School of Chemical and Materials Engineering
National University of Science and Technology (NUST)
H - 12, Islamabad
Ultrasonic Testing 01
Experiment No. 01
Title:
Demonstration, calibration of ultrasonic flaw detector and thickness
measurement of different given samples by using ultrasonic flaw detector.
Objective:
To familiarize the students with,the ultrasonic flaw detector, its calibration, and
how to measure the thickness of different materials.
Introduction:
Of all the applications of industrial ultrasonic testing, flaw detection is the oldest
and the most common. Since the 1940s, the laws of physics that govern the propagation
of sound waves through solid materials have been used to detect hidden cracks, voids,
porosity, and other internal discontinuities in metals, composites, plastics, and ceramics.
High frequency sound waves reflect from flaws in predictable ways, producing distinctive
echo patterns that can be displayed and recorded by portable instruments. Ultrasonic
testing is completely nondestructive and safe, and it is a well established test method in
many basic manufacturing, process, and service industries, especially in applications
involving welds and structural metals.
The ultrasonic principle is based on the fact that solid materials are good
conductors of sound waves. Whereby the waves are not only reflected at the interfaces
but also by internal flaws (material separations, inclusions etc.). The interaction effect of
sound waves with the material is stronger. The smaller the wavelength; this means the
higher the frequency of the wave.
𝑉 V = Sound velocity [km/s]
𝜆= f = Frequency [MHz]
𝑓
λ = Wave length [mm]
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Ultrasonic Testing 01
This means that ultrasonic waves must be used in a frequency range between about
0.5 MHz and 25 MHz and that the resulting wave length is in mm. With lower frequencies,
the interaction effect of the waves with internal flaws would be so small that detection
becomes questionable. Both test methods, radiography and ultrasonic testing, are the
most frequently used methods of testing different test pieces for internal flaws, partly
covering the application range and partly extending it. This means that today many
volume tests are possible with the more economical and non-risk ultrasonic test method,
on the other hand special test problems are solved, the same as before, using
radiography. In cases where the highest safety requirements are demanded (e.g. nuclear
power plants, aerospace industry) both methods are used. If we limit ourselves to testing
objects for possible material flaws then the classification of tasks assigned to the
ultrasonic operator is as follows:
1. Detection ofdiscontinuity
2. Location of reflectorsdiscontinuity
3. Evaluation of discontinuity
4. Diagnosis of discontinuity
In ultrasonic testing the proper handling and operation is very important to get reliable
and reproducible results. So it is essential for the operator to know about the functions
of a particular ultrasonic flaw detector
Calibration:
Calibration means to set the delay and range controls so that a specific known
depth range in a test specimen can be formed linearly. Calibration refers to the act of
evaluating and adjusting the precision and accuracy of measurement equipment. In
ultrasonic testing, there is also a need for reference standards. Reference standards are
used to establish a general level of consistency in measurements and to help, interpret
and quantify the information contained in the received signal. Reference standards are
used to validate that the equipment and the set-up provide similar results from one day
to the next and that similar results are produced by different systems. Reference
standards also help the inspector to estimate the size of flaws. In a pulse-echo type set-
up, signal strength depends on both the size of the flaw and the distance between the
flaw and the transducer. The inspector can use a reference standard with an artificially
induced flaw of known size and at approximately the same distance away for the
transducer to produce a signal. By comparing the signal from the reference standard to
that received from the actual flaw, the inspector can estimate the flaw size.
Calibration and reference standards for ultrasonic testing come in many shapes and
sizes. The type of standard used is dependent on the NDE application and the form and
shape of the object being evaluated. The material of the reference standard should be
the same as the material being inspected and the artificially induced flaw should closely
resemble that of the actual flaw. This second requirement is a major limitation of most
standard reference samples. Most use drilled holes and notches that do not closely
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Ultrasonic Testing 01
represent real flaws. In most cases the artificially induced defects in reference standards
are better reflectors of sound energy (due to their flatter and smoother surfaces) and
produce indications that are larger than those that a similar sized flaw would produce.
Producing more "realistic" defects is cost prohibitive in most cases and, therefore, the
inspector can only make an estimate of the flaw size. In order to make an exact range
calibration a reference block is necessary which must meet with the following
requirements:
i. The exact size of the reference path must be known.
ii. The reference block and the test object must be made from the same material
(the same sound velocity).
iii. The calibration blocks are to be plane-parallel and smooth.
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Ultrasonic Testing 01
Title:
Demonstration, calibration of ultrasonic flaw detector with straight beam and
thickness measurement of different given samples by using ultrasonic flaw detector.
Equipment:
Ultrasonic Flaw Detector, Connecting wires, Probes, Vernier caliper
Materials:
Given metallic sample, Couplant, calibration block
Procedure:
1. Switch on the equipment EPOCH LT and it will go through a “Self-Test” on Power up.
This assures that the instrument is functioning properly.
2. Select the transducer of 5.0MHz frequency and connect it with equipment.
3. Adjust the following parameters,
a. GAIN 30 dB
b. Zero OFFSET 0.000 us
c. VELOCITY 5734 m/s
d. RANGE 50mmFull Screen
4. Adjust the pulser settings,
a. RECTIFICATION: Fullwave, RF, Halfwave +, Halfwave–
b. PULSER ENERGY: Low (100V), Med (200V), High (300V), Max (400V)
c. PULSER DAMPING: 50, 63, 150, 400 ohms
d. PULSER MODE: Pulse Echo, Dual, Through-Transmission
5. Step # 1
a. Couple the transducer to the THIN reference sample.
b. Position Gate 1 over the FIRST backwall echo.
c. Adjust the Gain so the signal amplitude is ~ 80%
d. Press “Calibration” button
e. Wait for a steady reading, then press “Zero Offset” button
f. Uncouple the transducer.
g. Enter the known thickness of the THIN reference sample
6. Step # 2
a. Press “Calibration” button
b. Couple the transducer to the THICK reference sample.
c. Position Gate 1 over the FIRST backwall echo.
d. Wait for a steady reading, then press
e. Uncouple the transducer.
f. Enter the known thickness of the THICK reference sample.
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7. Press “Enter” key to complete the calibration.
8. Now apply couplant and couple the transducer to the given steel sample for thickness
measurement.
9. Position Gate 1 over the FIRST backwall echo
10. Note down the value display on the screen
11. Take three values from different places for each sample
Safety precaution:
Must apply the couplant between the test block and the probe
Handle the probe carefully
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Student Name: Session:
Ultrasonic Testing 01
Reg. # Group:
WORKSHEET
(DEMONSTRATION, CALIBRATION OF ULTRASONIC FLAW DETECTOR
&
THICKNESS MEASUREMENT OF GIVEN STEEL SAMPLES)
Apparatus/Machine used:
Sample’s material:
Procedure:
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Ultrasonic Testing 01
Calculation/Observation:
Sketch the calibration block along with the dimensions?
1. Why ultrasonic flaw detector is Fill the following table?
Test material
Test Range
Velocity of sound in given material
Thickness measurement by UT
Thickness measurement by Vernier Caliper
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Ultrasonic Testing 01
2. Which essential elements are contained in an ultrasonic testing system?
1-
2-
3-
4-
3. Which wave lengths result from a 4 MHz sound pulse in
(a) Plexiglas (V long = 2700m/sec)
λ=
(b) Steel (Vlong= 4400 m/sec)
λ=
4. Which frequencies have to be chosen in order to obtain
(a) In steel a transverse wave of 3 mm wave length (Vtrans, steel = 3250m/sec)
f=
(b) In water a longitudinal wave of 6 mm wavelength (Vlong, water = 1480m/sec)
f=
