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UT L1 > Level 2 > Flashcards

Level 2 Flashcards

1
Q

Which frequency will produce the shortest wavelength?
1 MHz
25 MHz
10 MHz
5 MHz

A

25 MHz

(The higher the frequency, the shorter the wavelength.)

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2
Q

In UT, the frequency of the sound wave refers to what?
A) amplitude of the particle vibrations
B) direction of the particle vibrations
C) number of vibrations in a given period of time
D) the velocity of the particle vibrations

A

C) the NUMBER OF VIBRATIONS in a given period of time

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3
Q

In UT, the higher the frequency of transducer:
A) longer the wavelength
B) longer the pulse length
C) shorter the wavelength
D) shorter the pulse length

A

C) shorter the wavelength

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4
Q

Most commercial UT is accomplished by using frequencies between:
A) 1-25 KHz
B) 1-25 MHz
C) 1-1000 KHz
D) 15-100 MHz

A

B) 1-25 MHz

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5
Q

The term used to describe the BENDING of sound waves around and past reflectors, that are small when compared to a wavelength is:
A) refraction
B) mode conversion
C) reflection
D) diffraction

A

D) diffraction

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6
Q

The wavelength of an ultrasonic sound wave can be calculated using what formula?

A

Lambda (A) = V / f

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7
Q

A term used in UT to express the speed at which the sound wave passes through a substance is:
A) frequency
B) velocity
C) wavelength
D) none of the above

A

B) velocity

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8
Q

The piezoelectric material in a search unit or probe which vibrates to produce ultrasonic waves is commonly referred to as what?

A

A crystal

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9
Q

The frequency 25 million cycles per second can also be stated as what?

A

25 MHz

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10
Q

Sound waves of frequency beyond the hearing range of human ears are referred to as ultrasonic waves or vibrations; the term embraces all vibrational waves of a frequency greater than approximately:
A) 20,000 hertz
B) 2 megahertz
C) 2 kilohertz
D) 200 kilohertz

A

À) 20,000 Hz

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11
Q

The number of complete waves of which pass a given point in a GIVEN PERIOD of time (usually a second) is referred to as the:
A) amplitude of wave motion
B) pulse length of wave motion
C) frequency of wave motion
D) wavelength of wave motion

A

C) frequency of wave motion

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12
Q

Primarily the velocity of sound waves is dependant on:
A) the pulse length
B) the frequency
C) the material in which the sound is transmitted
D) none of the above

A

C) the material in which the sound is transmitted

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13
Q

The piezoelectric material in the search unit:
A) converts electrical energy to mechanical energy
B) converts mechanical energy to electrical energy
C) both a & b
D) neither a or b

A

C) BOTH A & B

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14
Q

In which medium listed below would the velocity of sound be lowest?
A) air
B) water
C) aluminum
D) stainless steel

A

À) air

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15
Q

Which would contain the thickest crystal?
A) 1 MHz
B) 5 MHz
C) 10 MHz
D) 15 MHz

A

À) 1 MHz

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16
Q

How much does the near field increase when put in water?

A

4x

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17
Q

UT used what frequency range?

A

.5 to 15 MHz

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18
Q

Lead zirconate titanate is the best what?

A

Generator

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19
Q

Barium titanate is the best what?

A

Best generator that is MOST COMMONLY USED

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20
Q

When you heat a crystal above its curie point, what happens?

A

Loses its piezoelectric qualities

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21
Q

Lowest acoustic impedance means what for transmitting/receiving?

A

Best receiver

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22
Q

Highest acoustic impedance means what for transmitting/receiving?

A

Best generator

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23
Q

How many volts does it take to excite a crystal?

A

100-400 volts

24
Q

Highly damped is what length of pulse and what are the characteristics?

A

Short pulse: low pen, sensitivity, Q value but good resolution.

25
Q

What length is the pulse for low level dampening and what are the characteristics?

A

Long pulse: high pen, sensitivity, Q value and poor resolution.

26
Q

Which of the following has the longest near zone:
A) 12.5 mm diameter 1 MHz
B) 12.5 mm diameter 2-1/2 MHz
C) 25 mm diameter 1 MHz
D) 25 mm diameter 2-1/2 MHz

A

D) 25 mm diameter 2-1/2 MHz

27
Q

Which of the following has the longest near zone:
A) 12.5 mm diameter 1 MHz
B) 12.5 mm diameter 2-1/2 MHz
C) 25 mm diameter 1 MHz
D) 25 mm diameter 2-1/2 MHz

A

D) 25 mm diameter 2-1/2 MHz

28
Q

As frequency increases, the angle of beam divergence of a given diameter crystal:
A) decreases
B) remains unchanged
C) increases
D) varies uniformly through each wavelength

A

À) decreases

29
Q

The amount of beam divergence from a crystal is primarily dependant on the:
A) type of test
B) tightness of backing material
C) frequency and crystal size
D) pulse length

A

C) frequency and crystal size

30
Q

A disadvantage of using quartz crystals in a search unit is:
A) it will dissolve in water
B) it is the least efficient generator of ultrasonic energy of all commonly used materials
C) it is subject to the aging process
D) it easily loses its operating characteristics as it ages

A

B) it is the least efficient generator of ultrasonic energy of all commonly used materials

31
Q

Which commonly used crystal has a tendency to age?

A

Barium titanate (polarized ceramic)

32
Q

Which commonly used crystal can withstand high heat?

A

Quartz

33
Q

Which commonly used crystal is soluble in water?

A

Lithium sulphate

34
Q

If a crystal has a high acoustic impedance, what does that mean for transmitting/receiving?

A

Best generator

35
Q

An advantage of using ceramics in search units is:
A) it is one of the most efficient generators of ultrasonic energy
B) it is one of the most efficient receivers of ultrasonic energy
C) it has a very low mechanical impedance
D) it can withstand temperatures as high as 700•C

A

À) it is one of the most efficient generators of ultrasonic energy (barium titanate)

36
Q

An advantage of using lithium sulphate in search units is:
A) one of the most efficient generators
B) one of the most efficient receivers
C) it is insoluble
D) it can withstand temps as high as 700•C

A

B) one of the most efficient receivers

37
Q

The backing material in a probe is designed to:
A) control ringing time
B) prevent crosstalk
C) control near zone length
D) none

A

À) control ringing time

38
Q

Under most circumstances, which of the following would results in the best resolving power?

À) 1 MHz
B) 5 MHz
C) 10 MHz
D) 25 MHz

A

D) 25 MHz

39
Q

The gradual spread of the sound beam in the far zone is referred to as:
A) attenuation
B) rare fraction
C) dead zone
D) divergence

A

D) divergence

40
Q

A materials density multiplied by its velocity is known as its:
A) conductivity
B) resistance
C) impedance
D) amplitude

A

C) impedance

41
Q

Define pulse repetition rate:

A

The rate at which the pulses are sent to the receiver

42
Q

What happens to the near zone with the smaller the diameter of the near zone?

A

Smaller the diameter = shorter the near zone

43
Q

As the frequency increases and the wavelength decreases, what happens to the near zone?

A

It lengthens

44
Q

Whats another name for a lamb wave?

A

Plate wave

45
Q

Lamb waves can be classified into two different types, what are they?

A

Symmetrical and asymmetrical

46
Q

Symmetrical waves are sometimes referred to as what?

A

Dilatational waves

47
Q

Asymmetrical waves are sometimes referred to as what?

A

Bending waves

48
Q

The symmetrical wave is characterized by the motion of the centre fibres of the plate being what type of oscillations?

A

Purely longitudinal

49
Q

The asymmetrical lamb waves are characterized by the motion of the centre fibres of the plate being what?

A

Purely transverse

50
Q

The combination of symmetrical and asymmetrical waves generated are dispersive waves which means what?

A

The velocity of the wave will change as it progresses through the materials.

51
Q

How are dispersive waves caused?

A

When the wavelength is greater than the thickness of the material

52
Q

What are guided waves used for today?

A

Inspecting piping, specifically corrosion/wear locations

53
Q

When will a phase shift occur?

A

If the sound wave transmitted goes from an acoustically ‘hard’ material to an acoustically ‘soft’ one

54
Q

The reflected angle is equal to what?

A

The incident angle

55
Q

Refracted angles can be calculated by what law?

A

Snells law

56
Q

What is known as the index of refraction?

A

The velocity ratio is (V1/V2)

UT L1 (9 decks)

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