L31 transmission and pulse echo method

1. M.KARTHIKEYAN
ASSISTANT PROFESSOR
DEPARTMENT OF MECHANICAL ENGINEERING
AAA COLLEGE OF ENGINEERING & TECHNOLOGY, SIVAKASI
karthikeyan@aaacet.ac.in
ME8097 NON DESTRUCTIVE
TESTING AND EVALUATION

2. UNIT IV ULTRASONIC TESTING (UT) AND ACOUSTIC
EMISSION (AE)
1. Ultrasonic Testing-Principle,
2. Transducers,
3. Transmission and pulse-echo method,
4. Straight beam and angle beam,
5. Instrumentation,
6. Data representation, A/Scan, B-scan, C-scan.
7. Phased Array Ultrasound, Time of Flight Diffraction.
8. Acoustic Emission Technique – Principle,
9. AE parameters, Applications

3. INSPECTION METHODS
1. PULSE ECHO METHOD
2. THROUGH TRANSMISSION METHOD
3. ANGLE BEAM ULTRASONIC TESTING
4. IMMERSION ULTRASONIC TESTING

4. PULSE ECHO METHOD

6.  A typical UT inspection system consists of several functional
units, such as the pulser/receiver, transducer, and display
devices.
 A pulser/receiver is an electronic device that can produce high
voltage electrical pulses.
 Driven by the pulser, the transducer generates high frequency
ultrasonic energy.
 The sound energy is introduced and propagates through the
materials in the form of waves.
 When there is a discontinuity (such as a crack) in the wave path,
part of the energy will be reflected back from the flaw surface.

7.  The reflected wave signal is transformed into an electrical signal
by the transducer and is displayed on a screen.
 In the applet below, the reflected signal strength is displayed
versus the time from signal generation to when a echo was
received.
 Signal travel time can be directly related to the distance that
the signal traveled.
 From the signal, information about the reflector location, size,
orientation and other features can sometimes be gained.

8. 2. THROUGH TRANSMISSION METHOD

9.  Through-transmission ultrasonic testing (UT) is used for
detection, verification, sizing, and growth rate monitoring of
cracks in piping, vessels, cylindrical shapes, and sometimes
noncylindrical shapes.
 Through-transmission UT is most widely known as a method of
inspection in automated immersion testing for detection of
laminars in steel or disbonding in composite materials where
two opposite and parallel surfaces can be used for scanning
 Through-transmission UT is a two transducer technique in a
pitch-catch arrangement.
 While there are many types of UT techniques, because of the
wide variety of component shapes, sizes, and orientations it is
sometimes valuable to have an alternative technique for
verification, such as through-transmission

10. The advantages of through transmission are:
 Less attenuation of sound energy
 No probe ringing
 No dead zone on the screen
 The orientation of a defect does not matter in the way that it
does on the pulse echo display.
The disadvantages are:
 The defect cannot be located
 The defect cannot be identified
 The component surfaces must be parallel
 Vertical defects do not show
 The process must be automated
 There must be access to both sides of the component.

11. In an A scan presentation, the amplitude of vertical
indications on the screen represents the:
(a) Amount of ultrasonic sound energy returning to the
search unit
(b) Distance travelled by the search unit
(c) Thickness of material being tested
(d) Elapsed time since the ultrasonic pulse was generated
MCQ - 1

12. An instrument display in which the horizontal base line
represents elapsed time and the vertical deflection
represents signal amplitudes is called:
(a) A scan
(b) B scan
(c) C scan
(d) A time line display
MCQ - 2

13. A cross section view of a test piece is produced by which of
the following?
(a) A scan
(b) B scan
(c) C scan
(d) A time line display
MCQ - 3

14. The process of comparing an instrument or device with a
standard is called:
(a) Angulation
(b) Calibration
(c) Attenuation
(d) Correlation
MCQ - 4

15. Which technique would most likely be used to examine a
weld, with the weld cap still in place?
(a) Through transmission testing
(b) Angle beam testing
(c) Straight beam testing
(d) None of the above
MCQ - 5