Chapter 11 Ultrasonic Inspection

Question 1

1. If an ultrasonic wave in a block of steel has a wavelength of 1.3 mm and travels at a velocity of 5.85 x 10° m/s, what is the frequency?

Answer 1

5.85/1.3 = 4.5Mhz

Question 2

2. Do transverse waves in a solid travel faster or slower than longitudinal waves?

Answer 2

Slower

Question 3

3. If the amplitude of a wave is reduced to 2596, what is the corresponding drop in dB? (Hint: you can figure it out from the information in Section 2.5 but you could also use logarithm tables or a calculator).

Answer 3

12dB

Question 4

4. Name one piezoelectric material.

Answer 4

Quartz and lead metaniobate

Question 5

5. Why is good acoustic contact between the transducer and the test specimen needed?

Answer 5

Ultrasonic waves of the frequency used in inspection do not travel far in air, so good coupling between the transducer and the specimen is needed

Question 6

6. Draw a block diagram of the basic pulse-echo equipment from memory, then compare your sketch with Figure 217 in Section 3.1.

Answer 6

Question 7

7. In what unit is the gain control (or attenuator) marked?

Answer 7

dB (Decibels)

Question 8

8. Which type of display gives a cross-sectional view showing the length and depth of discontinuities?

Answer 8

B-Scan

Question 9

9. Give an example of a system where the entire specimen is immersed in water, which acts as the couplant.

Answer 9

On-line examination of plate for defects such as laminations in a steel mill

Question 10

10. Acoustic emission relies on detecting very small amounts of mechanical energy released from such things as growing cracks or structural discontinuities under load.

a. True
b. False

Answer 10

a. True

Question 11

11. Why should most ultrasonic examinations of welds begin with a search of the plate with a normal probe?

Answer 11

To identify plate defects such as laminations that could interfere with examination of the weld with an angle probe.

Question 12

12. When using an angle probe, when would it be necessary to bounce the beam off the back wall?

Answer 12

Allows inspection of upper part of weld

Question 13

13. Difficulties with UT can arise when welds have backing bars due to reflections from corners, internal reflections in the bars, etc.

a. True
b. False

Answer 13

a. True

Question 14

14. When working to CSA W59, to what must the ultrasonic operator be certified?

Answer 14

CAN/CGSB-48.9712, Certification of Nondestructive Testing Personnel

Question 15

15. What two features of an angle probe can be calibrated or checked using the IIW block?

Answer 15

Exit point (index point) and angle

Question 16

16. Distance calibration using an IIW block for a normal (longitudinal mode) probe requires the probe to be placed on the:

a. top of the block such that the beam reflects from the 1.5 mm hole.
b. other edge to reflect off the curved end.
c. side to reflect off the back wall.

Answer 16

c. side to reflect off the back wall.

Question 17

17. For the transverse mode, what reflector in the IIW block is used to calibrate sensitivity according to CSA W59?

Answer 17

1.5 mm side hole

Question 18

18. As the direction of approach of the beam is changed, the amplitude of the wave reflected from a spherical pore can be expected to:

a. rise to a maximum then decrease.
b. rise to a peak only if the probe were moved in the plane of the plate.
c. not vary significantly.

Answer 18

c. not vary significantly.

Question 19

19. In most codes and standards the acceptance or rejection of a discontinuity is based on whether it is shown that it will cause failure.

a. True
b. False

Answer 19

b. False

Question 20

20. For imperfections interpreted as incomplete fusion, the maximum acceptable length according to ASME Section VIII, Div. 1 is:

a. 20 mm.
b. 1/3 T (where T is weld thickness).
c. neither of the above. Incomplete fusion imperfections are unacceptable regardless of length.

Answer 20

c. neither of the above. Incomplete fusion imperfections are unacceptable regardless of length.

Question 21

21. To reduce the height of an indication on the screen by 50%, you would turn the gain control (or attenuator) through:

a. 2 dB.
b. 50 dB.
c. 60 dB.
d. 20 dB.
e. 6 dB.

Answer 21

e. 6 dB.

Question 22

22. If you are examining a groove weld in a plate from one surface with an angle probe, you would examine the upper portion of the weld by:

a. placing the probe on the weld reinforcement.
b. moving the probe as close as possible to the weld.
c. using a normal probe close to the edge of the weld.
d. moving the probe away from the weld so the beam bounces off the lower surface to strike the upper portion of the weld.
e. none of the above. The upper portion cannot be examined.

Answer 22

d. moving the probe away from the weld so the beam bounces off the lower surface to strike the upper portion of the weld.

Question 23

23. The frequency of a sound passing through a material with an ultrasonic velocity of 4.65 x 10° m/s and a wavelength of 1.8 mm is:

a. 26 MHz.
b. 2,600 km/s.
c. 2.6 kHz.
d. 2.6 MHz.

Answer 23

d. 2.6 MHz.

Question 24

24. Can we say that the action of a hammer pounding onto the surface of a metal is just about the same as the action exerted by ultrasonic probe?

a Yes
b. No

Answer 24

a Yes

Question 25

25. Sound wave is a mechanical vibration.

a. No, it is a radiation vibration
b. No, it is like gamma radiation
c. Yes, it is like spiritual vibration
d. Yes, it is vibration that has characteristic frequency, that is, a number of vibrations per second

Answer 25

d. Yes, it is vibration that has characteristic frequency, that is, a number of vibrations per second

Question 26

26. Can shear waves operate in similar ways to longitudinal waves in the water?

a. No, because its not enough force of attraction between the atoms of water
b. Yes, because there are a lot of attraction between the atoms
c. Yes, they certainly can operate in similar ways
d. Yes, because shear waves cause more vibration than longitudinal waves

Answer 26

a. No, because its not enough force of attraction between the atoms of water

Question 27

27. In UT probe of the transverse wave mode, is the angle of incidence always equal to the angle of refraction?

a. Yes
b. The angle of refraction is always more
c. The angle of incidence is always more
d. Both angles are regulated by frequency

Answer 27

b. The angle of refraction is always more

Question 28

28. The amplifier in the ultrasonic testing circuit performs the following task:

a. It regulates the vertical beam deflection
b. It regulates the horizontal time-base
c. It regulates the gate’s size
d. It regulates the frequency

Answer 28

a. It regulates the vertical beam deflection

Question 29

29. Other display methods used for UT inspection are B-scan, C-scan and P-scan. Which one of these scans provide a permanent record of the test when automatic testing is used?

a. The B-scan
b. The P-scan
c. None of them
d. The C-scan

Answer 29

d. The C-scan

Question 30

30. Is it possible to use acoustic emission method for global monitoring of the structure service life?

Answer 30

Yes