PCN

Question 1

1)

Theoretically, what would the size of the smallest detectable defect be in a steel, when using a 0 degree 4 MHz probe?

a) 1.5 mm
b) 0.75 mm
c) 0.4 mm
d) 0.375 mm

Answer 1

b) 0.75 mm

Question 2

2)

**How much gain in dB is required to bring an echo from 25% screen height up to 80% screen height?

a) 18
b) 12
c) 10
d) 8

Answer 2

c) 10

Question 3

3)

What major advantage does a twin crystal probe have over a single crystal angle probe?

a) greater sound penetration into the specimen
b) good near surface resolution
c) narrow beam spread
d) all of the above

Answer 3

b) good near surface resolution

Question 4

4)

The pulse width of a transducer is controlled by?

a) Low and high pass filtering
b) Mechanical damping
c) Amplifier settings
d) the probe shoe design

Answer 4

b) Mechanical damping

Question 5

5)

Compensation for the natural reductions in signal height caused by variations in the material path length is termed:

a) Supplementary gain
b) Distance size gain (DCG)
c) Distance amplitude correction (DAC)
d) Suppression

Answer 5

c) Distance amplitude correction (DAC)

Question 6

6)

The velocity of compression waves in copper is 0.383 cm/us and the wavelength is 1.9 mm. What is the probe frequency?

a) 7.2 kHz
b) 7.3 MHz
c) 2.02 kHz
d) 2.02 MHz

Answer 6

d) 2.02 MHz

Question 7

7)

The causes of all energy losses to a wave of ultrasound travelling through a test material are collectively called?

a) attenuation
b) scatter
c) absorption
d) deflection

Answer 7

a) attenuation

Question 8

9)

Calculate the second critical angle in aluminium for a standard perspex wedge angle probe incorporating a single 5 MHz 12.5 mm o/ transducer?

a) 26.8 degree
b) 59.6 degree
c) 63.2 degree
d) 90.0 degree

Answer 8

b) 59.6 degree

Question 9

10)

When the distance to a small reflector is doubled in the far field, the signal amplitude would be expected to decrease by?

a) one quarter
b) 12 dB
c) 6 dB
d) either B or C depending on the area of the reflector with respect to that of the incident ultrasonic wave front

Answer 9

b) 12 dB

Question 9

8)

What incident angle is required to generate a 45 degree beam angle in steel, using a standard perspex wedge shoe probe?

a) 35.7 degree
b) 36.6 degree
c) 37.7 degree
d) 38.6 degree

Answer 9

d) 38.6 degree

Question 10

11)

Which of the following ultrasonic transducers would be most suitable for testing large castings with a very coarse grain structure?

a) high frequency and small diameter
b) high frequency and large diameter
c) low frequency and small diameter
d) low frequency and large diameter

Answer 10

d) low frequency and large diameter

Question 11

12)

The ultrasonic velocity of a material is determined by its?

a) acoustic impedance
b) electrical resistance and density
c) density and elasticity
d) coefficient of attenuation

Answer 11

c) density and elasticity

Question 12

13)

Refraction will occur when a beam of ultrasound passes through an interface between?

a) materials with different ultrasonic velocities
b) water and steel
c) materials with different acoustic impedances
d) both A and B

Answer 12

d) both A and B

Question 13

14)

At what position in the ultrasonic beam can divergence be accurately predicted?

a) in the near field
b) in the crystal surface
c) at the point of refraction
d) in the far field

Answer 13

d) in the far field

Question 14

15)

As the frequency of a fixed diameter transducer increases its beam divergence will?

a) decrease
b) vary according to the material characteristics
c) remain unchanged
d) increase

Answer 14

a) decrease

Question 15

16)

The incident angle at which a 90 degree refraction of the shear wave mode occurs is called the?

a) first critical angle
b) third critical angle
c) second critical angle
d) angle of refraction

Answer 15

c) second critical angle

Question 16

17)

When the particle motion of the test material is paralell to hat of ultrasonic wave propagation, the wave mode is?

a) lamb wave
b) compression
c) surface
d) shear

Answer 16

b) compression

Question 16

18)

On an A-scan presentation generated by a pulse echo technique, signal amplitude represents?

a) elapsed time from when the ultrasonic pulse first entered the test piece
b) thickness of the test piece
c) gain setting
d) amount of reflected ultrasonic energy received by the probe

Answer 16

d) amount of reflected ultrasonic energy received by the probe

Question 17

19)

A piezoelectric transducer?

a) converts electrical energy into mechanical energy
b) converts mechanical energy to electrical energy
c) vibrates naturally
d) both a and b

Answer 17

d) both a and b

Question 18

20)

A test method incorporating two angle probes, the first transmitting ultrasound into the material from one surface and the other receiving i from a second so that a signal is always present on the screen of the flaw detector, is termed?

a) through-transmission testing
b) delta scanning
c) tandem scanning
d) both a and b

Answer 18

a) through-transmission testing

Question 19

21)

**If a shear wave probe generates a 45 degree beam angle in steel, what beam angle will it generate in aluminium?

VSts= 0.323 cm VAIs= 0.313 cm

a) 45 degree
b) less than 45 degree
c) greater than 45 degree
d) it will depend on the acoustic impedance of aluminium

Answer 19

b) less than 45 degree

Question 20

22)

As the impedance ratio between two materials rises, the amount of ultrasonic energy transmitted through the interface between them will?

a) increase
b) remain the same
c) decrease
d) be dependant on the wave mode

Answer 20

c) decrease

Question 21

23)

In ultrasonic testing, the maximum scanning speed is governed by?

a) probe frequency
b) amplifier response time
c) pulse repetition frequency
d) both b and c

Answer 21

d) both b and c

Question 22

24)

Which of the following ultrasonic wave modes can be generated in water?

a) suface waves
b) shear waves
c) longitudinal waves
d) both a and b

Answer 22

d) both a and b

Question 23

25

The formula for calculating the fundamental resonant frequency of a crystal transducer, where t = thickness and v = velocity is?

a) f = t/v
b) f = vt
c) f = v/2t
d) f = v/t

Answer 23

c) f = v/2t

Question 24

26)

When contact testing, excessively high pulse repetition frequencies can cause which of the following?

a) screen blanking
b) distortion of the time base
c) flickerig of the time base
d) ghost or phantom echoes on the timebase

Answer 24

d) ghost or phantom echoes on the timebase

Question 25

27)

What is the product of ultrasonic wave velocity multiplied by density?

a) reflection coefficient
b) index of refraction
c) Acoustic impedance
d) velocity-density ratio

Answer 25

c) Acoustic impedance

Question 26

28)

All other factors being equal, which of the following transducers would have the greatest beam spread?

a) a smaller diamater transducer
b) a larger diameter transducer
c) a high frequency transducer
d) none of the above

Answer 26

a) a smaller diamater transducer

Question 27

29)

The amount of energy reflected from a discontinuity will be dependant on its?

a) size
b) orientation
c) type
d) all of the above

Answer 27

d) all of the above

Question 28

30)

If the velocity of a 2.5 MHz compression wave in steel is 0.59 cm/usec, what will the wavelength be?

a) 4.35mm
b) 3.26mm
c) 2.36 mm
d) 1.97 mm

Answer 28

c) 2.36 mm

Question 29

31)

The fresnel region of an ultrasonic beam is also called the?

a) far field
b) dead zone
c) near zone
d) beam spread

Answer 29

c) near zone

Question 30

32)

Lamb (plate) waves are used mainly for the detection of?

a) porosity
b) laminations
c) inclusions
d) all of the above

Answer 30

b) laminations

Question 31

33)

When ultrasound is transmitted into a steel test piece at a refracted angle of 65 degrees, the predominant wave modes would be?

a) shear waves and compression waves
b) shear wave and surface waves
c) compression waves and surface waves
d) lamb waves and shear waves

Answer 31

b) shear wave and surface waves

Question 32

34)

Which wave mode will n theory be more sensitive in terms of defect detection?

a) shear wave
b) compression wave
c) surface wave
d) all of the above

Answer 32

c) surface wave

Question 33

35)

A materials resistance to the passage of soundwaves is termed:

a) echo response
b) acoustic impedance
c) Snell’s law
d) Youngs modulus

Answer 33

b) acoustic impedance

Question 34

36)

Ultrasonic vibrations in liquid are transmitted as:

a) compression waves
b) shear waves
c) surface waves
d) lamb waves

Answer 34

a) compression waves

Question 35

37)

The distance an ultrasonic wave travels in one complete cycle is termed:

a) pulse envelope
b) frequency
c) wavelength
d) wave velocity

Answer 35

c) wavelength

Question 36

38)

**In an immersion test the incident angle of the ultrasonic beam at water steel interface is 15 degree. what is the angle of the refracted shear wave?

VWa = 0.1480 metres VSts = 0.3250 metres**

a) 15
b) 27
c) 35
d) 42

Answer 36

c) 35

Question 37

39)

The signal to noise ratio is a comparisson of amplitudes between:

a) any two signals on the time base
b) a signal from an unknown reflector to the transmission pulse
c) a signal from a known reflector and background signals (grass) on the timebase
d) two successive backwall signals

Answer 37

c) a signal from a known reflector and background signals (grass) on the timebase

Question 37

40)

Calculate the length fo the near zone (N) in aluminium for a 0 degreeprobe incorporating a single 0.5cm, 5 MHz barium titanate crystal transducer:

VAIc = 0.635 cm

a) N = 0.025 CM
b) N = 0.49cm
c) N = 2.0cm
d) N = 1.25 cm

Answer 37

b) N = 0.49cm