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.)
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
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
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
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
6
Q
The wavelength of an ultrasonic sound wave can be calculated using what formula?
A
Lambda (A) = V / f
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
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
9
Q
The frequency 25 million cycles per second can also be stated as what?
A
25 MHz
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
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
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
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
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
15
Q
Which would contain the thickest crystal?
A) 1 MHz
B) 5 MHz
C) 10 MHz
D) 15 MHz
A
À) 1 MHz
16
Q
How much does the near field increase when put in water?
A
4x
17
Q
UT used what frequency range?
A
.5 to 15 MHz
18
Q
Lead zirconate titanate is the best what?
A
Generator
19
Q
Barium titanate is the best what?
A
Best generator that is MOST COMMONLY USED
20
Q
When you heat a crystal above its curie point, what happens?
A
Loses its piezoelectric qualities
21
Q
Lowest acoustic impedance means what for transmitting/receiving?
A
Best receiver
22
Q
Highest acoustic impedance means what for transmitting/receiving?
A
Best generator
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
What length is the pulse for low level dampening and what are the characteristics?
Long pulse: high pen, sensitivity, Q value and poor resolution.
26
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
D) 25 mm diameter 2-1/2 MHz
27
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
D) 25 mm diameter 2-1/2 MHz
28
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
À) decreases
29
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
C) frequency and crystal size
30
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
B) it is the least efficient generator of ultrasonic energy of all commonly used materials
31
Which commonly used crystal has a tendency to age?
Barium titanate (polarized ceramic)
32
Which commonly used crystal can withstand high heat?
Quartz
33
Which commonly used crystal is soluble in water?
Lithium sulphate
34
If a crystal has a high acoustic impedance, what does that mean for transmitting/receiving?
Best generator
35
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
À) it is one of the most efficient generators of ultrasonic energy (barium titanate)
36
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
B) one of the most efficient receivers
37
The backing material in a probe is designed to:
A) control ringing time
B) prevent crosstalk
C) control near zone length
D) none
À) control ringing time
38
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
D) 25 MHz
39
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
D) divergence
40
A materials density multiplied by its velocity is known as its:
A) conductivity
B) resistance
C) impedance
D) amplitude
C) impedance
41
Define pulse repetition rate:
The rate at which the pulses are sent to the receiver
42
What happens to the near zone with the smaller the diameter of the probe?
Smaller the diameter = shorter the near zone
43
As the frequency increases and the wavelength decreases, what happens to the near zone?
It lengthens
44
Whats another name for a lamb wave?
Plate wave
45
Lamb waves can be classified into two different types, what are they?
Symmetrical and asymmetrical
46
Symmetrical waves are sometimes referred to as what?
Dilatational waves
47
Asymmetrical waves are sometimes referred to as what?
Bending waves
48
The symmetrical wave is characterized by the motion of the centre fibres of the plate being what type of oscillations?
Purely longitudinal
49
The asymmetrical lamb waves are characterized by the motion of the centre fibres of the plate being what?
Purely transverse
50
The combination of symmetrical and asymmetrical waves generated are dispersive waves which means what?
The velocity of the wave will change as it progresses through the materials.
51
How are dispersive waves caused?
When the wavelength is greater than the thickness of the material
52
What are guided waves used for today?
Inspecting piping, specifically corrosion/wear locations
53
When will a phase shift occur?
If the sound wave transmitted goes from an acoustically ‘hard’ material to an acoustically ‘soft’ one
54
The reflected angle is equal to what?
The incident angle
55
Refracted angles can be calculated by what law?
Snells law
56
What is known as the index of refraction?
The velocity ratio is (V1/V2)
57
The ultrasonic testing of a material where the search unit or probe is in direct contact with the material being tested is called:
A) straight beam contact testing
B) surface wave testing
C) angle beam testing
D) may be a, b or c
D) may be a, b, c
58
A test method in which the ultrasonic sound is emitted by transmitting search unit, transmitted through the test part, and picked up by a second receiving search unit on the opposite boundary is called:
A) surface wave testing
B) angle beam testing
C) through transmission testing
D) straight beam testing
C) through transmission testing
59
The amount of energy reflected from a discontinuity will be dependant on:
A) the size of the discontinuity
B) the orientation of the discontinuity
C) the type of discontinuity
D) all of the above
D) all of the above
60
The crystal thickness and transducer frequency are related. The thinner the crystal:
A) the lower the frequency
B) the higher the frequency
C) there is no appreciable affect
D) none of the above
B) the higher the frequency
61
The total energy losses occurring in all materials is called:
A) attenuation
B) scatter
C) beam spread
D) interface
À) atténuation
62
The transducer most commonly found in ultrasonic search units (probes) used for discontinuity testing utilize:
A) magnétostriction principles
B) piezoelectric principles
C) mode conversion principles
D) none of the above
B) piezoelectric principles
63
Which of the following frequencies would probably result in the greatest ultrasonic attenuation losses?
A) 1 MHz
B) 2.25 MHz
C) 10 MHz
D) 25 MHz
D) 25 MHz
64
The product of the sound velocity and the density of a material is known as the:
A) refraction value of the material
B) acoustic impedance of the material
C) elastic constant of the material
D) poisson’s ratio of the material
B) acoustic impedance of the material
65
The pulse applied to the electrodes of the ultrasonic search unit is:
A) electrical
B) mechanical
C) electro-mechanical
D) piezoelectric
À) electrical
66
Snells law sin01/sin02 = v1/v2 is used to determine:
A) angular relationships
B) phase velocities
C) amount of reflected sound energy
D) acoustic impedance
À) angular relationships
67
When using the through transmission techniques, best results would be obtained with:
A) a quartz transmitter with a lithium sulphate receiver
B) a barium titanate transmitter with a quartz receiver
C) a barium titanate transmitter with a lithium sulphate receiver
D) a lithium sulphate transmitter with a barium titanate receiver
C) a barium titanate transmitter with a lithium sulphate receiver
68
Which calibration blocks are used to determine the signal to noise ratio?
AREA Amplitude Blocks
69
Which calibration blocks are used to determine the minimum size flat bottom hole that can be detected with the system?
DISTANCE Amplitude Blocks
70
Bandwidth is the frequency measured between which two frequencies?
Upper and lower frequency
71
Bandwidth may be expressed as a percentage of which frequency?
Peak frequency
72
As a rule of thumb, the water path distance should be at least what?
1/4 the thickness of the part PLUS 1/4’’
73
What are the two basic types of focus used in UT?
Spherical and cylindrical
74
What’s the difference in the focal zone between spherical and cylindrical lenses?
Spherical have a SINGLE point focal zone and cylindrical lenses have a LINE focal zone
75
Which of the following would be considered applications of ultrasonic testing?
A) determination of a materials elastic modulus
B) study of a materials metallurgical structure
C) measurement of a materials thickness
D) all of the above
D) all of the above
76
The acoustic impedance of a material is to:
A) determine the angle of refraction at an interface
B) determine the attenuation within the material
C) determine the relative amounts of sound energy coupled through and reflected at an interface
D) determine the beam spread within the material
C) determine the relative amounts of sound energy coupled through and reflected at an interface
77
The crystal thickness and transducer frequency are related: the thinner the crystal….
The higher the frequency
78
As the radius of curvature of a curved lens is increased, the focal length of the lens will:
A) increase
B) decrease
C) remain the same
D) be indeterminate unless the frequency is known
À) increase
79
A primary purpose of a reference standard is:
A) to provide a guide for adjusting instrument controls to reveal discontinuities that are considered harmful to the end end of the product
B) to give the technician a tool for determining exact discontinuity size
C) to provide assurance that all discontinuities smaller than a certain specified reference reflector are capable of being detected by the test
D) to provide a standard reflector which exactly simulates natural discontinuities of a critical size
À) to provide a guide for adjusting instrument controls to reveal discontinuities that are considered harmful to the end use of the product
80
Mechanical and electrical stability, insolubility in liquids and resistance to aging are three advantages of search unites containing transducers made of:
A) lithium sulfate
B) barium titanate
C) quartz
D) Rochelle salts
C) quartz
81
Which ultrasonic test frequency would probably provide the best penetration in a 12’’ thick specimen if coarse grained steel:
A) 2.25 MHz
B) 1 MHz
C) 5 MHz
D) 10 MHz
B) 1 MHz
82
Significant efforts in ultrasonic thickness measurement can occur if:
A) the test frequency is varying at a constant rate
B) the velocity of propagation deviates substantially from an assumed constant value for a given material
C) water is employed as a coupling between the transducer and part being measured
D) non of the above should cause errors
B) the velocity of propagation deviates substantially from an assumed constant value for a given material
83
When material grain size is on the order of _______ wavelength or larger, excessive scattering of the ultrasonic beam may affect test results.
A) 1
B) 1/2
C) 1/10
D) 1/100
C) 1/10
84
When maximum sensitivity is required from a transducer:
A) a straight-beam unit should be used
B) large diameter crystals are required
C) the piezoelectric element should be driven at its fundamental resonant frequency
D) the bandwidth of the transducer should be as large as possible
C) the piezoelectric element should be driven at its fundamental resonant frequency
85
What is the formula for finding the fundamental resonant frequency?
t = t1 / f
86
The velocity of lamb waves is dependent upon:
A) the frequency of the waves
B) the plate thickness
C) the test material
D) all the above
D) All the above
87
Two basic types of plate (lamb) waves exist. They are:
A) symmetrical and dilational
B) symmetrical and asymmetrical
C) asymmetrical and rotational
D) perpendicular and normal
B) symmetrical and asymmetrical
88
The impedance of the backing member in a search unit:
A) is a factor controlling transducer bandwidth
B) is a factor controlling the Q of a transducer
C) is a factor controlling the ringing time of the crystal
D) all of the above
D) all of the above
89
The angle of reflection of an ultrasonic beam at an aluminum-water interface is:
A) approximately 1/2 the angle of incidence
B) approximately 4x the angle of incidence
C) equal to the angle of incidence
D) .256 times the angle of incidence
C) equal to the angle of incidence
90
The index of refraction may be expressed in terms of the following ratio:
A) velocity in first medium/velocity in second medium
B) wavelength in first medium/wavelength in second medium
C) tan01/tan02
D) none of the above
À) velocity in first medium/velocity in second medium
91
When an incident ultrasonic wave impinges upon an interface of two materials with difference impedance values at an angle other than normal to the surface, the wave may be:
A) reflected
B) refracted
C) mode converted
D) all of the above
D) all of the above
92
When the angle of incidence for shear waves exceeds the critical angle, we have:
A) only the surface wave mode entering the specimen
B) maximum amplitude of shear wave mode entering the specimen
C) only longitudinal wave mode entering specimen
D) total reflection of both longitudinal and shear wave modes
D) total reflection of both longitudinal and shear wave modes
93
Heat conduction, viscous friction and especially scattering are three different mechanisms which lead to:
A) attenuation
B) refraction
C) beam spreading
D) saturation
À) atténuation
94
Atténuation of ultrasonic energy in metals occurs by:
A) conversion of mechanical energy into heat
B) energy being scattered at grain boundaries
C) both A and B
D) conversion of mechanical energy into electrical
C) both A and B
95
Which of the following would produce the shortest near field?
A) a large crystal and a short wavelength
B) a small crystal and a short wavelength
C) a large crystal and low frequency
D) a small crystal and a long wavelength
D) a small crystal and a long wavelength
96
Which of the following reflects the relation between the band width and the ‘Q’ of a search unit?
A) the band width is directly proportional to the Q
B) the bandwidth is inversely proportional to the Q
C) the Q always has a value twice the value of the band width
D) the relation between the band width and the Q is logarithmic
B) the band width is inversely proportional to the Q
97
For maximum sensitivity in pulse echo testing, transducer elements (crystals) are electrically driven:
A) at their fundamental resonant frequency
B) at the variable frequencies to prevent resonance
C) at a frequency of at least 10 MHz
D) at one of their harmonic frequencies
À) at their fundamental resonant frequency
98
In general, shear waves are more sensitive to small discontinuities than longitudinal waves for a given frequency and in a given material because:
A) a wavelength of shear waves is shorter than the wavelength of longitudinal waves
B) shear waves are not easily dispersed in the material
C) the direction of particle vibration for shear waves is more sensitive to discontinuities
D) the wavelength of shear waves is longer than the wavelength of longitudinal waves
À) a wavelength of shear waves is shorter than the wavelength of longitudinal waves
99
The angle formed by an ultrasonic wave as it enters a medium of different characteristics than the one from which it came and a line drawn perpendicular to the interface between the two media is called:
A) angle of incidence
B) angle of refraction
C) angle of raréfaction
D) angle of reflection
B) angle of refraction
100
A grouping of a number of crystals in one search unit, with all contact surfaces in the same plane, and vibrating in phase with each other to act as a single transducer is called:
A) a focusing crystal
B) a crystal mosaic
C) a scrubber
D) a single plane manipulator
B) A crystal mosaic
101
The scattering of the rays of an ultrasonic beam due to reflection from a highly irregular surface is called:
A) angulation
B) dispersion
C) refraction
D) raréfaction
B) dispersion
102
In UT, the time duration of the transmitted pulse is referred to as:
A) the pulse length or pulse width
B) the pulse amplitude
C) the pulse shape
D) none of the above
À) the pulse length or pulse width
103
A form of thickness measurement testing in which ultrasonic vibrations of varying frequency are introduced into the material being measured by means of a suitable transducer is called:
A) angle beam testing
B) magnetostrictive testing
C) resonance testing
D) through-transmission
C) resonance testing
104
In resonance testing, fundamental resonance occurs when the thickness of the material is:
A) 1/2 wave length of transmitted ultrasound
B) 1 wave length of the transmitted ultrasound
C) 1/4 wave length of the transmitted ultrasound
D) 2 wave lengths of the transmitted ultrasound
À) 1/2 wave length of the transmitted ultrasound
105
The coated inside surface of the large end of a cathode ray tube which becomes luminous when struck by an electron beam is called:
A) an electron gun
B) an electron amplifier
C) a CRT screen
D) an electron counter
C) a CRT screen
106
If an ultrasonic wave is transmitted through an interface of two materials in which the first material has a higher acoustic impedance value but the same velocity value as the second material, the angle of refraction will:
A) be greater than the angle of incidence
B) be less than the angle of incidence
C) be the same as the angle of incidence
D) be beyond the critical angle
C) be the same as the angle of incidence
107
Which of the following may result if the beam divergence results in a reflection from a side of the test piece before the sound wave reaches the back surface?
A) multiple back surface reflections
B) multiple front surface reflections
C) conversion from the longitudinal mode to the shear mode
D( loss of front surface indications
C) conversion from the longitudinal mode to the shear mode
108
When testing large forgings, it is normal practice to employ:
A) an axial test
B) a radial test
C) both a and b above
D) both a low and high frequency test
C) both a and b above
109
The amplifier range over which the unsaturated signal response increases in amplitude in proportion to the discontinuity surface area is:
A) sensitivity range
B) linearity range
C) selectivity range
D) resolution range
B) linearity range
110
When inspecting a rolled or forged surface with a thin scale that is generally tightly adhering to the part, it is necessary to _____________ before testing the part.
A) clean the surface of loose scale
B) have all scale removed
C) rough machine the surface
D) caustic etch the surface
A clean the surface of loose scale
111
An instrument that operates on the resonance principle can be used to measure the thickness of metallic parts. Such an instrument usually employs:
A) surface waves
B) shear waves
C) longitudinal waves
D) lamb waves
C) longitudinal waves
112
Another name for resonance testing is:
A) pulse echo testing
B) through transmission testing
C) continuous wave testing
D) surface wave testing
C) continuous wave testing
113
In liquid, the only mode of vibration that can exist is:
A) longitudinal
B) shear
C) both A and B
D) surface waves
À) longitudinal
114
In a basic pulse echo ultrasonic instrument, the component that produces the voltage that activates the search unit is called:
A) an amplifier
B) a receiver
C) a pulser
D) a synchronizer
C) a pulser
115
In a basic pulse echo ultrasonic instrument, the component to that produces visible signals on the CRT which are used to measure distance is called a:
A) sweep circuit
B) marker circuit
C) receiver circuit
D) synchronizer
B) marker circuit
116
The angle at which 90• refraction of the particle mode is reached is called:
A) the normal angle of incidence
B) the critical angle
C) the angle of maximum reflection
D) none of the above
B) the critical angle
117
In immersion testing of aluminum using water as a couplant, the critical angle of incidence for the longitudinal mode is approximately:
A) 8•
B) 14•
C) 26•
D) 32•
B) 14•
118
The refraction angle of longitudinal ultrasonic waves passing from water into a metallic material at angles other than normal to the interface is primarily a function of:
A) the impedance ratio of water to metal
B) the relative velocities of sound in water and metal
C) the frequency of the ultrasonic beam
D) the density ratio of water to metal
B) the relative velocities of sound in water and metal
119
As frequency increases in UT, the angle of beam divergence in a given diameter crystal:
A) decreases
B) remains unchanged
C) increases
D) varies uniformly through each wavelength
À) decreases
120
A longitudinal ultrasonic wave is transmitted from water in steel at an angle of 5• from the normal. In such a case, the refracted angle of the transverse wave is:
A) less than the refracted angle of the longitudinal wave
B) equal to the refracted angle of the longitudinal wave
C) greater than the refracted angle of the longitudinal wave
D) not present at all
À) less than the refracted angle of the longitudinal wave
121
The velocity of sound travel will be highest in?
A) water
B) air
C) aluminum
D) stainless steel
C) aluminum
122
A quartz crystal used in a 10 MHz straight beam longitudinal wave search unit has a thickness of approximately:
A) 12 mm
B) 1.2 mm
C) 0.30 mm
D) variable depending on crystal grain structure
C) 0.3 mm
123
The thickness of an aluminum sheet is one centimetre and the velocity of longitudinal wave in aluminum is 6.35 x 10^5 cm/s. The fundamental resonant ultrasonic frequency is nearest:
A) 3.2 x 10^5 Hz
B) 4.3 X 10^5 Hz
C) 8.6 X 10^5 Hz
D) 6.4 X 10^5 Hz
À) 3.2 X 10^5 Hz
124
Ultrasonic resonance testing is used to determine:
A) part thickness with a taper of 12• or more
B) to measure wall thinning
C) case hardness depth
D) none of the above
B) to measure wall thinning
125
The acoustic impedance is:
A) used to calculate the angle of reflection
B) the product of the density of the element and the velocity of sound in the element
C) found by Snell’s law
D) used to determine resonance values
B) the product of density of the element and the velocity of sound in the element
126
A diagram in which entire circuit stages or sections are shown by geometric figures and the path of the signal or energy by lines and/or arrows is called a:
A) schematic diagram
B) blueprint
C) block diagram
D) none of the above
C) block diagram
127
The ratio between the wave speed in one material and the wave speed in a second material is called:
A) the acoustic impedance of the interface
B) Young’s modulus
C) Poissons’s ratio
D) index of refraction
D) index refraction
128
A point, line, or surface of a vibrating body marked by absolute or relative freedom from vibratory motion is referred to as:
A) a node
B) an antibody
C) raréfaction
D) compression
À) a node
129
A quartz crystal so cut that it’s major faces are parallel to the Z and Y axes and perpendicular to the X axis is called:
A) a Y-cut crystal
B) an X-cut crystal
C) a Z-cut crystal
D) a XY-cut crystal
B) an X-cut crystal
130
The propagation of surface waves on a part which is immersed in water is limited to approximately:
A) 25 mm
B) 250 mm
C) 500 mm
D) 1 m
À) 25 mm
131
Measurement of thickness by the ultrasonic resonance technique is possible because the velocity of propagation of ultrasonic waves in a given material can be considered constant and:
A) a reinforcement of ultrasonic energy occurs when the thickness of the material equals one half the wavelength of the ultrasound
B) a significant loss of ultrasonic energy occur when the thickness of the material is less than one quarter of the wavelength of the ultrasonic
C) a mode conversion causes shear waves to be developed when the thickness of the material equals the wavelength of the ultrasound
D) none of the above
À) a reinforcement of ultrasonic energy occurs when the thickness of the material equals one half the wavelength
132
The cathode ray tube screen of an instrument used for ultrasonic resonance thickness measurement displays:
A) indications representing reflections from discontinuities as a function of time and metal distance
B) indication representing the resonance condition when testing at a fixed frequency
C) indications representing resonance conditions that occur as a function of a continuously varying frequency
D) none of the above
C) indications representing the resonance condition when testing at a continuously varying frequnecy
133
Beam divergence is a function of the dimensions of the crystal and the wavelength of the beam transmitted through a medium and:
A) increases if frequency or crystal diameter is decreased
B) decreases if frequency or crystal diameter is decreased
C) increases if frequency is increased and crystal diameter is decreased
D) decreases if frequency is increased and crystal diameter decreased
À) increases if frequency or crystal diameter is decreased
134
The acoustic impedance of a material is:
A) directly proportional to density and inversely proportional to velocity
B) directly proportional to velocity and inversely proportional to density
C) inversely proportional to density and velocity
D) equal to the product of density and velocity
D) equal to the product of density and velocity
135
Lamb waves may be used to inspect:
A) forgings
B) bar stock
C) ingots
D) thin sheet
D) thin sheet
136
The thickness range of ultrasonic resonance thickness gauges can be increased by:
A) using large transducers
B) operating at the fundamental frequency
C) operating at the harmonic frequencies
D) increasing the AC voltage
C) operating at the harmonic frequencies
137
The resolving power of a search unit is directly proportional to its:
A) diameter
B) bandwidth
C) pulse rep rate
D) thickness
B) bandwidth
138
Since the velocity of sound in aluminum is approximately 622,300 cm/s, it takes _________ for sound to travel through 1 cm of aluminum.
A) 0.2 s
B) 1.6 micro seconds
C) 16 ms
D) 4 x 10^3 s
B) 1.6 micro seconds
139
In general, __________ will travel around gradual curves with little or no reflection from the curve.
A) transverse
B) surface
C) shear waves
D) longitudinal
B) surface
140
When contact testing by the straight beam method, refraction caused by _________ may generate a surface wave that might lead to spurious indications.
A) irregularly-shaped discontinuities
B) the couplant
C) machining marks
D) none if the above could cause a surface wave
C) machining marks
141
To evaluate and accurately locate discontinuities after scanning a part with a paint-brush transducer,it is generally necessary to use a:
A) search unit with a smaller crystal
B) scrubber
C) grid map
D) crystal collimator
À) search unit with a smaller crystal
142
An ultrasonic instrument has vern calibrated to obtain a 50 mm indication from a 2 mm diameter flat-bottomed hole located 75 mm from the front surface of an aluminum reference block. When testing an aluminum forging, a 59 mm indication is obtained from a discontinuity located 75 mm from the entry surface. The cross-sectional ares of this discontinuity is probably:
A) the same as the area of the 2 mm flat bottomed hole
B) greater than the area of the 2 mm flat bottomed hole
C) slightly less than the area of the 2 mm flat bottomed hole
D) about 1/2 the area of the 2 mm flat bottomed hole
B) greater than the area of the 2 mm flat bottomed hole
143
Which of the following would be the best conductor of ultrasonic energy?
A) an aluminum forging
B) a steel ingot
C) an aluminum casting
D) an aluminum ingot
À) an aluminum forging
144
Slotted ultrasonic reference blocks can be used:
A) to determine the depth of a discontinuity
B) to evaluate surface defects
C) as a standard when evaluating stringer-type discontinuities
D) when correcting for distance amplitude variations
C) as a standard when evaluating stringer type discontinuities
145
In general, discontinuities in wrought products tend to be oriented:
A) randomly
B) in the direction of grain flow
C) at right angles to the entry surface
D) at right angles to the grain flow
B) in the direction of grain flow
146
An easily detectable discontinuity would be at least:
A) one half the wavelength in width
B) one wavelength in width
C) one quarter wavelength in width
D) several wavelengths in width
À) one half the a wavelength in width
147
Irrelevant or false indications caused by contoured surfaces are likely to result in a:
A) broad based indication
B) peaked indication
C) ‘hashy’ signal
D) narrow based indication
À) broad based indication
148
The _______________ is frequently displayed by a facsimile recording instead of a CRT presentation.
A) A-Scan
B) B-Scan
C) C-Scan
D) none of the above are adaptable for facsimile recordings
C) C-Scan
149
A notch type reference standard for tubing should be machined on:
A) both the inner and outer surfaces
B) the inner surface only
C) the outer surface only
D) the inner surface to a depth of 1/2 times the wall thickness
À) both the inner and outer surfaces
150
Surface waves are reduced to an energy level of approximately 1/25 of the original power at a depth of:
A) 25 mm
B) 100 mm
C) one wavelength
D) four wavelengths
C) one wavelength
151
Increasing the length of the pulse used to activate the search unit will:
A) increase the strength of the ultrasound but decrease the resolving power of the instrument
B) increase the resolving power of the instrument
C) have no effect on the test
D) will decrease the penetration of the sound wave
À) increase the strength of the ultrasound but decrease the resolving power of the interment
152
Angle beam testing of plate will often miss:
A) cracks that are perpendicular to the sound wave
B) inclusions that are randomly orientated
C) cracks that are parallel to the front surface
D) a series of small discontinuities
C) cracks that are parallel to the front surface
153
With reference to pulse-echo testing, through transmission testing has better:
A) near surface resolution
B) specimen penetration power
C) resolution at all depths
D) sensitivity at all depths
B) specimen penetration power
154
Which of the following characteristics applies to the wheel-transducer technique?
A) it is a variation of the contact method
B) the wheel may be mounted on a mobile apparatus or a stationary fixture
C) it is used only to project straight beam
D) oil is usually used a couplant
B) the wheel may be mounted on a mobile apparatus or a stationary fixture
155
In ultrasonic resonance testing for thickness:
A) the search unit crystal is vibrated at its resonant frequency
B) the search unit crystal is vibrated at its fundamental or harmonic frequency
C) both A and B
D) the material being inspected is caused to vibrate at least two harmonic frequencies before thickness can be measured
D) the material being inspected is caused to vibrate at least two harmonic frequencies before thickness can be measured
156
What type of waves are usually used to excite resonance within a specimen?
A) pulsed longitudinal waves
B) pulsed shear waves
C) continuous longitudinal waves
D) continuous shear waves
C) continuous longitudinal waves
157
During inspection, a small discontinuity indication appears on the CRT screen with a correspondence great loss of back reflection. This means:
A) the defect has a surface smaller than the diameter of the probe
B) the discontinuity is probably turned at an angle to the test surface
C) the surface of the defect is larger than the diameter of the probe
D) the defect is very near the surface
B) the discontinuity is probably turned at an angle to the test surface
158
Which of the following is a true statement related to crystalline materials?
À) crystalline materials cannot be tested using shear waves
B) the acoustic impedance and the velocity are the same everywhere in the material
C) both A and B
D) in materials of randomly orientated crystals, the values of velocity and impedance are average values
159
What material property is needed for shear waves to exist?
Shear strength
160
What is the lowest acoustic pressure that a human is capable of hearing?
20 microPascsals (0 dB)
161
What dB range is known as the pain threshold?
120-130 dB
162
How is the length of the near field related to the diameter and frequency of transducer?
DIRECTLY proportional.
Increase the diameter or frequency = increase in length of near field
163
What is the wave called when it has transitioned from the near to the far zone, the sound pressure builds and the wave front has become uniform?
PLANE wave
164
In which zone does beam spread/divergence occur?
FAR zone
165
How is the angle of divergence related to the diameter and frequency of the transducer?
INVERSELY proportional.
Increase in diameter or frequency = smaller angle of divergence
166
When talking about standing waves, what are the points called of maximum amplitude between two waves?
Antinodes
167
When standing waves are formed, it results in a phenomenon called what?
Résonance
168
Low level damping means what length of waveform?
Longer waveform = Low Level damping
169
What type of transducer does not require couplant?
EMATs (electromagnetic acoustic transducer)
170
The distance and area each increase by a factor of what in the far zone?
Distance increases by a factor of 2,
Area increases by a factor of 4
171
What is the difference between pulse frequency and pulse repetition frequency?
Pulse frequency is the natural frequency of crystalline vibration (probe) while Pulse Repetition Frequency is the # of electrical pulses to a crystal per unit time (1 sec)
172
How much more sensitive is shear waves compared to compression waves?
2x more sensitive
173
Where do shear waves not travel?
Liquids or gases
174
What size of grain boundary may cause scattering or reflection?
1/10th a wavelength
175
The reflection of surface waves is caused by the radius being less than what?
One wavelength
176
Guided waves take two different types of waves to generate, what are they?
Dispersive (longitudinal) vs plane/bulk (transverse)
177
The 1ST CRITICAL ANGLE is the incident angle at which the longitudinal wave is refracted to ______• and mode converted to a ___________ wave.
90• and mode converted to a creeping wave
178
The velocity of a creeping wave is about what compared to a longitudinal wave?
0.9
179
What happens if you exceed the first critical angle?
All longitudinal wave will be reflected, ONLY shear waves will enter.
180
The 2ND CRITICAL ANGLE is the incident angle at which the transverse wave is refracted to ____• and mode converted to a ___________ wave.
90• and mode converted to a Rayleigh/surface wave
181
What happens if you exceed the 2ND critical angle?
TOTAL REFLECTION
182
What is rarefraction?
The low pressure side of a wave
183
How does the bandwidth affect the Q?
Broad bandwidth = LOW Q
Narrow bandwidth = HIGH Q
184
What is the fall time of the probe?
-14 dB
185
How far from the stated angle should a shoe be thrown away at?
+/- 2•
186
What type of damping is more sensitive to small reflectors?
LOW
187
Beyond the near zone, sound pressure reduces to what 3 things?
1) beam spread
2) generation of heat
3) grain boundary scatter
188
What does Huygens Principle explain?
The ability of sound to move around an object and refraction/mode conversion at the interface of 2 mediums
189
What are the two rules of thumbs for the near field?
Keep NF under 100 mm and half angle at 17•
190
For the DISTANCE Amplitude Blocks, the flat bottom of the hole is ALWAYS how far from the bottom?
0.750’’
191
The AREA Amplitude Blocks have the same metal travel distance of what?
3’’
192
What is a code?
A systematic collection of laws and regulations
