L35 phased array ultrasound & time of flight diffraction

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. PHASED ARRAY ULTRASOUND

5.  Phased array ultrasonic testing (PAUT) probes are composed of
several piezoelectric crystals that can transmit/receive
independently at different times.
 This technique can be used to inspect more complex geometries
that are difficult and much slower to inspect with single probes.

7. ADVANTAGES
 PAUT can be conducted more quickly than other forms of UT,
often within a fraction of a second.
 It can easily be used for repeat scans because it has a high
degree of repeatability.
 By emitting beams of multiple different angles sequentially,
PAUT is able to create detailed and accurate cross-sections of a
part.
 It is able to sweep the beam without moving the probe.

8. APPLICATIONS
 Phased array is widely used for nondestructive testing (NDT) in
several industrial sectors, such as
 construction,
 pipelines, and
 power generation.
 Phased arrays are used to detect and image defects including
 cracks,
 voids, and
 pits caused by corrosion.

9.  They are used to measure material and coating thickness
and to detect changes in material properties.
 Another common application is to assess the quality of
welds and rivets.
 Phased arrays are also used to inspect joints and
interfaces

10. TIME OF FLIGHT DIFFRACTION

12.  A pair of ultrasonic probes is placed on opposite sides of the
weld or tested item.
 One of the probes acts as a transmitter and sends out an
ultrasonic pulse that is picked up by the other probe which is
the receiver.
 With an undamaged item, the signals picked up by the receiver
probe are from two waves – one wave that travels along the
surface (lateral wave) and one that reflects off the far wall (back
wall reflection).
 If there is a flaw, such as crack, there is a diffraction of the
ultrasound pulse from the tips of the crack.
 By measuring the time of flight of the pulse, the depth of the
crack can be calculated by trigonometry.

13.  Time of flight diffraction is an advanced non-destructive testing
method used for weld inspection.
 Time of flight diffraction (TOFD) is one of the most reliable non-
destructive testing methods.
 This ultrasonic method is used in a diverse range of industries
including petrochemical, chemical, oil and gas, power
generation and fabrication.

14. ADVANTAGES
 Can take place during production work
 No radiation with this method
 Inspection data is recorded and can be stored digitally for future
reference
 Inspection results are immediately available
 Quick inspection method
 Sensitivity to all weld flaw types including cracks, slag and lack
of fusion
 Accurate sizing of defects

15. Polymer probes are compared to conventional ceramic
probes are:
a) more noisy
b) less noisy
MCQ - 1

16. Ultrasonic NDT at elevated temperatures is
a) only possible when the probe is cooled down to less than
60 �C with water or air
b) not possible
c) possible with special probes up to 800 �C surface
temperature
MCQ - 2

17. The most efficient sound receiver of the piezoelectric material
listed is:
1. lithium sulfate,
2. quartz,
3. barium titanate,
4. silver oxide)
MCQ - 3

18. The most efficient sound transmitter of the piezoelectric material
is:
1. lithium sulfate,
2. quartz,
3. barium titanate,
4. silver oxide
MCQ - 4

19. Acoustic impedance is a material's:
(a) (Density)/(velocity)
(b) (Density) × (velocity)
(c) Refractive index
(d) (Density)/(refractive index)
MCQ - 5