WorldSpec Final Exam Practice Flashcards
1
Q
Direct current saturation coils would most likely be used when testing:
a. steel
b. aluminum
c. copper
d. brass
A
a. steel
2
Q
An important, property of metals is the ease with which electrons can flow within them, commonly referred to as:
a. permeability
b. coercive force
c. conductivity
d. resistivity
A
c. conductivity
3
Q
Demagnetization is generally needed when the residual field in a specimen:
a. may affect the operation or accuracy of instruments when the specimen is placed in service
b. may interfere with the proper functioning of the part
c. might cause particles to be attracted and held to the surface of moving parts
d. any of the above reasons could make demagnetization necessary
A
d. any of the above reasons could make demagnetization necessary
4
Q
Eddy current testing is more sensitive to dimensional changes when the material is:
a. thick
b. thin
A
b. thin
5
Q
In eddy current test systems, where encircling coils are used, coupling efficiency is referred to as:
a. lift-off
b. edge effect
c. fill factor
d. phased differentiation
A
c. fill factor
6
Q
A secondary magnetic field produced by eddy currents induced in a nonmagnetic conductor close to the inducing coils:
a. induces a magnetic field parallel to the surface
b. aids the coil’s magnetic field
c. opposes the coil’s magnetic field
d. decreases the frequency of the current
A
c. opposes the coil’s magnetic field
7
Q
Electromagnetic induction is the principle by which an alternating current is induced in a coil by:
a. eddy currents
b. the sine wave
c. a changing magnetic field
d. changes in permeability
A
c. a changing magnetic field
8
Q
The conductivity of a material can be altered by changing the:
a. alloy of the specimen
b. heat treatment of the specimen
c. temperature of the specimen
d. all of the above
A
d. all of the above
9
Q
Which of the following test frequencies would produce eddy currents with the largest depth penetration?
a. 100 Hz
b. 10 kHz
c. 1 MHz
d. 10 MHz
A
a. 100 Hz
10
Q
A test coil’s opposition to the flow of alternating current, causing the current to lag behind the voltage, is called:
a. resistance
b. inductive reactance
c. impedance
d. capacitive reactance
A
b. inductive reactance
11
Q
An alternating current flowing in a conductor will set up:
a. an alternating current field around the conductor
b. a periodically changing voltage tangent to the conductor
c. an alternating magnetic field around the conductor
d. none of the above
A
c. an alternating magnetic field around the conductor
12
Q
A coil’s magnetic field may be viewed as a distribution of lines of flux around the coil. The number of lines in a unit area is defined as:
a. magnetic density
b. flux density
c. magnetic coupling
d. hysteresis density
A
b. flux density
13
Q
In the feedback controlled method special feedback circuits are used that eliminate one component of the coil’s impedance. The eliminated component might be either:
a. frequency or phase angle
b. conductivity or dimension
c. inductive reactance or resistance
d. lift-off or fill factor
A
c. inductive reactance or resistance
14
Q
In a feedthrough encircling coil eddy current system, a calibration standard may be used to:
a. ensure repeatability and reliability of the setup
b. determine the circumferential extent of a discontinuity
c. reduce sensitivity to vibration
d. measure the test frequency
A
a. ensure repeatability and reliability of the setup
15
Q
A term used to define one or more turns or loops of a conductor wound in such a manner as to produce an axial magnetic field when current passes through the conductor is:
a. a coil
b. a resistor
c. a capacitor
d. an oscillator
A
a. a coil
16
Q
Permeability in an article affects eddy current tests by introducing inconsistencies in:
a. conductivity
b. the depth of penetration
c. the test results
d. dimension
A
c. the test results
17
Q
Data from the external-reference differential channels of ID bobbin probe data can be used to detect:
a. long, gradually tapering discontinuities
b. one-sided erosion
c. temperature differences
d. all of the above
A
d. all of the above
18
Q
When attempting to determine the exact point location of a discontinuity, the test system should include:
a. a phase shifter
b. a probe coil
c. an impedance bridge
d. a differential coil
A
b. a probe coil
19
Q
In the reflection method of eddy current testing the exciting coil and the receiving coil are on:
a. the same side of the material
b. opposite sides of the material
A
a. the same side of the material
20
Q
Changes in a material’s chemical composition will affect the flow of eddy currents.
a. True
b. False
A
a. True
21
Q
Large diameter surface scanning coils would most likely be used for the detection of:
a. pitting
b. small inclusions
c. changes in conductivity
d. porosity
A
c. changes in conductivity
22
Q
Which of the following products would be most applicable to a test using an inside coil?
a. sheet
b. rod
c. bolt hole
d. coating thicknesses
A
c. bolt hole
23
Q
Which of the following is NOT true about an eddy current test?
a. it can be used for high-speed testing
b. it can accurately measure conductivity
c. it can be set up to provide high sensitivity to small discontinuities
d. it can penetrate up to 152 mm (6 in.) in a test part
A
d. it can penetrate up to 152 mm (6 in.) in a test part
24
Q
In a feedthrough encircling coil eddy current system, DC saturation would probably be most helpful in testing:
a. copper water tubing
b. titanium tubing
c. ferromagnetic steel tubing
d. brass rivet wire
A
c. ferromagnetic steel tubing
25
In multifrequency tubing inspection applications, signal analysis is most often performed using:
a. phase angle analysis only
b. signal amplitude analysis only
c. a careful correlation of both amplitude and phase information
d. the ellipse method
c. a careful correlation of both amplitude and phase information
26
When testing tubing with a bobbin coil, most of the eddy currents:
a. flow in a longitudinal direction down the tubing
b. flow radially in the tube
c. flow around only the outside diameter
d. flow around the inside diameter of the tubing
d. flow around the inside diameter of the tubing
27
The Greek letter alpha (?) usually denotes:
a. impedance
b. inductive reactance
c. phase angle
d. resistance
c. phase angle
28
An increase in the impedance of a test coil will:
a. produce an increase in the voltage through the test coil
b. cause a decrease in the measured voltage across the test coil
c. not affect the voltage in the test coil
d. decrease the voltage applied to the coil
a. produce an increase in the voltage through the test coil
29
The method used to generate eddy currents in a test specimen by means of a coil can most closely be compared with the action of a:
a. transformer
b. capacitor
c. storage battery
d. generator
a. transformer
30
Which of the following is NOT a primary purpose for using an eddy current standard?
a. to determine if the eddy current test system is capable of performing the test properly
b. to determine if a discontinuity is a cause for rejection
c. to determine the instrument control settings needed to pass the highest percentage of test specimens run
d. to determine if the sensitivity of a test system has drifted with time
c. to determine the instrument control settings needed to pass the highest percentage of test specimens run
31
Self-comparison differential channels would be best for the detection of:
a. long tapered discontinuities
b. short abrupt discontinuities
c. temperature differences
d. all of the above
b. short abrupt discontinuities
32
The most serious type of flaw found in metals is:
a. porosity
b. cracks
c. inclusions
d. laminations
b. cracks
33
Which of the following is NOT a nondestructive testing method?
a. ultrasonic testing
b. fatigue testing
c. eddy current testing
d. radiographic testing
b. fatigue testing
34
One method of reducing nonrelevant indications when eddy current testing ferromagnetic materials is to:
a. decrease the pressure on the hold-down rollers
b. use a direct current saturation coil to magnetically saturate the test specimen
c. readjust the gain control
d. increase the rate of feedthrough in the coil
b. use a direct current saturation coil to magnetically saturate the test specimen
35
Which of the following options would NOT have the potential to improve the displayed signal-to-noise ratio of a test?
a. change to a test frequency that will decrease the noise
b. increase the amplification of the test instrument
c. improve the fill factor
d. enable filter functions in the instrument
b. increase the amplification of the test instrument
36
Which of the following are common applications for eddy current testing?
a. measurement of conductivity or a combination of conductivity and permeability
b. measurement of the thickness of thin metal sections, cladding or coating
c. detection of surface and subsurface discontinuities
d. all of the above
d. all of the above
37
When testing ferromagnetic materials, the depth to which eddy currents are induced in the material will be determined by:
a. the conductivity of the material
b. the permeability of the material
c. the geometrical shape of the material
d. all of the above
d. all of the above
38
When eddy current testing a nonferrous specimen, a discontinuity will:
a. increase the effective conductivity of the specimen
b. increase the effective permeability of the specimen
c. decrease the effective conductivity of the specimen
d. none of the above
c. decrease the effective conductivity of the specimen
39
One principal advantage of spinning probe eddy current testing is:
a. the ability to locate the exact position of discontinuities
b. its relative insensitivity to permeability variations
c. the variety of internal and surface discontinuities that may be detected
d. all of the above
a. the ability to locate the exact position of discontinuities
40
When testing tubes with an ID bobbin probe:
a. low voltage signals indicate insignificant discontinuity depths
b. high voltage signals are always from rejectable discontinuities
c. signals from support plates always hide discontinuity signals
d. none of the above is true
d. none of the above is true
41
Grinding cracks can be caused by:
a. lack of poor coolant
b. dull or improper grinding wheel
c. a too heavy cut
d. all of the above
d. all of the above
42
Which of the following affects the characteristics of the primary coil in an eddy current system?
a. the presence of a crack
b. the presence of an edge
c. change in material properties
d. all of the above
d. all of the above
43
As the temperature of a metal increases, the conductivity:
a. increases
b. decreases
c. does not change
d. any of the above may occur depending on the type of metal
b. decreases
44
Eddy currents generate a magnetic field.
a. True
b. False
a. True
45
Nondestructive tests are commonly conducted to:
a. determine the quality of finished products
b. locate defective materials before excessive fabrication is performed on the material
c. monitor material production techniques and processes
d. all of the above
d. all of the above
46
The impedance of a test coil will increase if the:
a. test frequency increases
b. inductive reactance of the coil decreases
c. inductance of the coil decreases
d. resistance of the coil decreases
a. test frequency increases
47
The impedance of a test coil never changes.
a. true
b. false
b. false
48
A sudden, momentary deflection of the needle on a meter as the inspection coil is moved over the surface of the material under test probably indicates the presence of:
a. a discontinuity
b. a change in dimension
c. a change in direction
d. all of the above
a. a discontinuity
49
The impedance of an eddy current test coil will increase if:
a. the test frequency increases
b. the inductive reactance of the coil decreases
c. the inductance of the coil decreases
d. the resistance of the coil decreases
a. the test frequency increases
50
In an electromagnetic test system, the test frequency is controlled by the:
a. oscilloscope
b. sensitivity setting
c. oscillator circuit
d. modulation analysis setting
c. oscillator circuit
51
In eddy current test systems where encircling coils are used, coupling efficiency is referred to as:
a. lift-off
b. edge effect
c. fill factor
d. phase differentiation
c. fill factor
52
IACS is a recognized abbreviation for:
a. Induced Alternating Current System
b. Inductively-Activated Comparison System
c. Internal Applied Current System
d. International Annealed Copper Standard
d. International Annealed Copper Standard
53
The entire cross-sectional area of a tube can be evaluated at one time when using:
a. an encircling coil
b. a probe coil
c. a secondary winding
d. none of the above
a. an encircling coil
54
Steel is basically an alloy of:
a. iron and silicon
b. iron and carbon
c. iron and nickel
d. none of the above
b. iron and carbon
55
It is often possible to sort various nonferromagnetic alloys of a metal by means of an eddy current test when:
a. there is a unique range of permeability values for each alloy
b. there is a unique range of conductivity values for each alloy
c. the direction of induced eddy currents varies for each alloy
d. the magnetic domains for each alloy are different
b. there is a unique range of conductivity values for each alloy
56
The read-out mechanism used when testing by the ellipse method is a:
a. meter
b. strip-chart recorder
c. cathode ray tube
d. any of the above
c. cathode ray tube
57
The lag of the current behind the voltage through a coil is caused by a factor of the coil called:
a. permeability
b. conductivity
c. inductive reactance
d. impedance
c. inductive reactance
58
Which of the following characteristics do NOT apply to magnetic materials?
a. high permeability value
b. no hysteresis loop
c. definite saturation point on hysteresis loop
d. appreciable residual magnetism
b. no hysteresis loop
59
Ferromagnetic materials that have been magnetically saturated to suppress permeability variations may retain a certain amount of the magnetization. This is called:
a. coercive force
b. residual magnetism
c. hysteresis loop
d. hysteresis loss
b. residual magnetism
60
When conducting an eddy current test using a differential comparison coil arrangement that compares an external reference standard with the test specimen, the system should be nulled or balanced:
a. with only the reference standard in one coil
b. with the reference standard in one coil and an acceptable test specimen in the other coil
c. with the reference standard in one coil and an unacceptable test specimen in the other coil
d. with only the test specimen in one coil
b. with the reference standard in one coil and an acceptable test specimen in the other coil
61
When testing plate with a probe coil, it is noted that the eddy current output indication varies as the distance from the coil to the surface of the test part varies. The term used to describe this action is:
a. fill factor
b. lift-off
c. phase differentiation
d. edge effect
b. lift-off
62
Eddy current test coils which are wound to form a narrow coil would normally be used to detect:
a. slow changes in dimensions
b. gradual changes in conductivity
c. variation in heat treatment
d. small surface defects
d. small surface defects
63
An inclusion in a material will NOT affect the flow of eddy currents.
True
False
False
64
Small diameter probe coils would typically be used for the detection of:
a. slow changes in dimensions
b. gradual changes in conductivity
c. variation in heat treatment
d. small surface discontinuities
d. small surface discontinuities
65
For most eddy current test, the minimum acceptable signal-to-noise ratio is usually considered to be:
a. 1:2
b. 1:1
c. 3:1
d. 6:1
c. 3:1
66
A service defect that appears as a series of small micro-openings with no definite pattern and extend in any direction following the grain boundaries is:
a. a fatigue crack
b. a fillet crack
c. hydrogen embrittlement
d. intergranular corrosion
d. intergranular corrosion
67
An eddy current coil arrangement that does NOT make a comparison with either two sections of the test specimen or one section of the test part and a reference standard is called:
a. an absolute coil arrangement
b. a self-comparison differential coil arrangement
c. an external reference differential coil arrangement
d. none of the above
a. an absolute coil arrangement
68
A test coil's magnetic field will not pass through a nonconductive material.
a. True
b. False
b. False
69
When inspecting products with a uniform cross section, an eddy current signal is produced when the leading end or trailing end of the product approaches the test coil. This phenomenon is referred to as:
a. lift-off
b. end effect
c. fill factor
d. phase discrimination
b. end effect
70
When using an eddy current test system for sorting, it is generally recommended that:
a. all parts other than the part being tested be kept at least 300 mm from the test coil
b. the test coil be kept away from large motors and transformers the table on which the parts are placed be equipped with a nonmagnetic top
c. all of the above may be important
d. none of the above are important
c. all of the above may be important
71
Eddy currents are evenly distributed throughout an article being inspected.
a. true
b. false
b. false
72
Eddy currents cannot be induced in:
a. latex paint
b. aluminum
c. steel
d. copper
a. latex paint
73
When using an encircling coil with both primary and secondary windings, the excitation alternating current is applied to:
a. the secondary winding
b. the primary winding
c. either the primary or secondary winding depending on the setting of an instrument control
d. both the primary and secondary coils
b. the primary winding
74
A length of tubing containing a notch of uniform width and depth running from end to end, when tested with an encircling self-reference differential coil system, will produce:
a. erratic signals
b. a continuous, sustained signal
c. no signal change
d. excessive signals
c. no signal change
75
The maximum response from a discontinuity is obtained when the eddy currents:
a. are parallel to the discontinuity
b. are perpendicular to the discontinuity
c. encircle the discontinuity
b. are perpendicular to the discontinuity
76
The principal advantage of spinning probe eddy current instruments is:
a. relative accuracy to depth of defects
b. relative insensitivity to vibration
c. the variety of internal and surface defects which may be detected
d. all of the above
a. relative accuracy to depth of defects
77
Which of the following eddy current test coil arrangements uses one area of the test specimen as a reference standard against which another area on the same specimen is simultaneously compared?
a. single absolute coil
b. double absolute coil
c. DC saturation coil
d. differential coil
d. differential coil
78
Which of the following expresses the primary purpose(s) of the secondary winding(s) in an eddy current coil?
a. induce eddy currents in the test specimen
b. detect changes in the eddy current flow
c. induce eddy currents in the test specimen and detect changes in the eddy current flow
d. provide DC saturation
b. detect changes in the eddy current flow
79
In a feedthrough encircling coil discontinuity detection eddy current system, what would be the purpose of running a calibration discontinuity several times but in various positions (such as top,bottom,left and right)?
a. to check the phase selectivity
b. to ensure proper centering of the material in the test coil
c. to select the modulation analysis setting
d. to select the proper operating speed
b. to ensure proper centering of the material in the test coil
80
Which of the following is applicable to eddy current testing?
a. it can be used to provide high sensitivity to small discontinuities
b. it can be used for high-speed testing
c. it can be used for measure coating thicknesses
d. all of the above
d. all of the above
81
When an alternating current source is connected to a test coil, the coil's magnetic field is:
a. constantly varying
b. parallel to the face of the coil
c. constant
d. inducing eddy current
a. constantly varying
82
Variations in the chemical composition of a nonferromagnetic alloy would likely affect its:
a. permeability
b. conductivity
c. diameter
d. frequency
b. conductivity
83
Which of the following frequencies will provide the greatest eddy current penetration in aluminum?
a. 1 kHz
b. 10 kHz
c. 3 kHz
d. 300 Hz
d. 300 Hz
84
Which of the following could NOT be tested by the eddy current testing method?
a. a 102 mm (4 in.) thick plate to be tested for small discontinuities throughout the plate
b. tubing to be tested for surface cracks
c. rod to be tested for laps and seams
d. tubing to be tested for variations in outside diameter
a. a 102 mm (4 in.) thick plate to be tested for small discontinuities throughout the plate
85
A coil's magnetic field may be viewed as a distribution of lines of flux around the coil. The number of lines in a unit area is defined as:
a. magnetic density
b. flux density
c. magnetic coupling
d. hysteresis density
b. flux density
86
Lift-off is utilized in:
a. measuring permeability changes
b. measuring conductivity changes
c. measuring thickness of nonconductive coatings
d. determining proper test frequency
c. measuring thickness of nonconductive coatings
87
In which of the following welding processes is filler metal never added?
a. Spot welding
b. Arc welding
c. Soldering
d. Brazing
a. Spot welding
88
When sorting a known mix of two alloys with a comparator having a quantitative read-out device, it is desirable to hold all indications with the bounds of the read-out device to:
a. eliminate overloading
b. detect the possible existence of a third alloy
c. make proper balancing possible
d. phase the readings correctly
b. detect the possible existence of a third alloy
89
A magnetic material may be demagnetized by:
a. heating to above the curie temperature
b. cold working
c. passing the material through an AC coil
d. all of the above
d. all of the above
90
The main purpose for spring-loaded eddy current probe coils is:
a. to minimize lift-off variations
b. to minimize wear on the probe
c. to reduce operator fatigue
d. to eliminate edge effect
a. to minimize lift-off variations
91
The depth to which eddy currents are induced in the material will be determined by the:
a. conductivity of the material
b. permeability of the material
c. geometrical shape of the material
d. all of the above
d. all of the above
92
Which of the following is NOT an eddy current testing method?
a. pulse-echo testing
b. impedance testing
c. phase analysis testing
d. modulation analysis testing
a. pulse-echo testing
93
When a test coil consists of a double winding arrangement and one winding is referred to as a primary winding, the other winding is referred to as the:
a. absolute winding
b. secondary winding
c. phase winding
d. none of the above
b. secondary winding
94
Which of the following would you normally be considered the best fill factor when testing straight tubing with an encircling or feedthrough coil?
a. 1.75 (175%)
b. 0.95 (95%)
c. 0.50 (50%)
d. 0.25 (25%)
b. 0.95 (95%)
95
An eddy current system will measure variations caused by differences in:
a. size or shape
b. grade or chemistry of the material
c. the way in which the material has been processed
d. all of the above
d. all of the above
96
A non-magnetic stainless steel has:
a. a ferritic structure
b. an austenitic structure
c. a martensitic structure
d. a random grain structure
b. an austenitic structure
97
An eddy current or 60 Hz comparator will measure variations caused by:
a. differences in size or shape
b. differences in grade or chemistry of the material
c. differences in the way in which the material has been processed
d. all of the above
d. all of the above
98
Eddy currents prefer to travel:
a. in nonconductive materials
b. radially when testing rod with an encircling coil
c. in closed paths
d. in a gas
c. in closed paths
99
Spinning probe type eddy current instruments are most useful in:
a. detection of surface and subsurface inclusions
b. detection of longitudinally oriented surface defects
c. detection of internal piping or burst
d. all of the above
b. detection of longitudinally oriented surface defects
100
What causes phase shift in an eddy current test coil?
a. a change in the ratio of inductive reactance (XL) to resistance (R)
b. a change in the sensitivity setting of the instrument
c. use of modulation analysis
d. none of the above
a. a change in the ratio of inductive reactance (XL) to resistance (R)
101
A multicoil array probe used in a surface scanning application:
a. should improve detection of localized discontinuities
b. can cover a large surface area in one pass
c. might increase the complexity of signal detection and interpretation
d. all of the above
d. all of the above
102
Once an eddy current instrument is calibrated, the controls are not to be touched during ensuing tests.
a. true
b. false
a. true
103
When conducting an eddy current test on tubing, the magnitude of the indication caused by a discontinuity is dependent on:
a. the depth of the discontinuity
b. the width of the discontinuity
c. the length of the discontinuity
d. all of the above
d. all of the above
104
A joining process which occurs without fusion of the base metal is:
a. arc welding
b. brazing
c. spot welding
d. gas welding
b. brazing
105
The method used to generate eddy currents in a test specimen by means of a coil can most closely be compared with the action of a:
a. transformer
b. capacitor
c. storage battery
d. generator
a. transformer
106
Some of the products commonly tested using encircling coils are:
a. rods, tubes and wires
b. plate when volumetrically inspected
c. sheets and metalized foil
d. all of the above
a. rods, tubes and wires
107
The region around a magnet that attracts other pieces of iron or steel is called:
a. a maxwell
b. retentivity
c. the magnetic field
d. alternating current
c. the magnetic field
108
A spinning probe eddy current instrument would be most useful in:
a. measuring the hardness of ferromagnetic steel products
b. discontinuity detection in hexagonal and shaped material
c. detecting and precisely locating surface discontinuities
d. inspection of copper bus bars for electrical conductivity
c. detecting and precisely locating surface discontinuities
109
Reference standards for thickness gaging are made from the same type of material as the material being tested.
a. true
b. false
a. true
110
Which of the following is NOT a readout system used to present eddy current test information?
a. alarms
b. litmus paper
c. cathode ray tubes
d. digital data storage
b. litmus paper
111
A test specimen is used as a basis for calibrating test equipment or as a comparison when evaluating test results is referred to as a:
a. null-balancer
b. phase shifter
c. reference standard
d. high pass filter
c. reference standard
112
In encircling coil eddy current testing, optimum sensitivity to a known discontinuity placed at random on the surface of a nonferrous length of tubing is obtained by:
a. proper choice of frequency
b. centering the tubing in the coil
c. proper adjustment of phase
d. all of the above
d. all of the above
113
When eddy current testing rod for discontinuities, which of the following conditions could produce extraneous indications?
a. improper adjustment of the hold-down rollers used to center the rod in the coil
b. feeding rod through the coil at an excessive speed
c. changes in dimension
d. all of the above
e. none of the above
d. all of the above
114
An eddy current is a circulating electrical current induced in a conducting article by:
a. gamma rays
b. an alternating magnetic field
c. a piezoelectric force
d. any of the above
b. an alternating magnetic field
115
An important, property of metals is the ease with which electrons can flow within them, commonly referred to as:
a. permeability
b. coercive force
c. conductivity
d. resistivity
c. conductivity
116
An eddy current can be defined as a circulating alternating current induced into an isolated conductor by an alternating magnetic field.
a. True
b. False
a. True
117
In the reactance testing method, conductivity variables and dimension variables:
a. can be separated
b. cannot be separated
b. cannot be separated
118
A factor which affects the conductivity of a material is:
a. a temperature change
b. a change in residual stresses
c. a change in composition
d. all of the above
d. all of the above
119
An eddy current test coil's opposition to the flow of alternating current is called:
a. resistance
b. inductive reactance
c. impedance
d. capacitive reactance
c. impedance
120
A forging defect caused by the metal being folded over and forced into the surface but
not welded to form a single piece is called:
a. a hot tear
b. a forging lap
c. a burst
d. a forging crack
b. a forging lap
121
When a metal part is placed in an eddy current test coil, the impedance of the coil will be changed by which of the following properties of the part?
a. conductivity
b. dimensions
c. permeability
d. all of the above
d. all of the above
122
Eddy currents always travel:
a. in circular paths
b. in nonconductive materials
c. radially when testing rod with an encircling coil
d. in a gas
a. in circular paths
123
Which of the following statements is NOT true of ferromagnetic materials?
a. they have permeability values much greater than 1
b. they do not exhibit any magnetic hysteresis characteristics
c. they will have a definite saturation point on a B/H curve
d. they will exhibit some degree of residual magnetism
b. they do not exhibit any magnetic hysteresis characteristics
124
A length of tubing containing a notch running from end to end and having uniform width and depth, when tested with an encircling self-reference differential coil system, will produce:
a. erratic signals
b. a continuous, sustained signal
c. no signal
d. excessive signals
c. no signal
125
The coercive force of a soft iron electromagnetic core would be ___________ the coercive force of a permanent magnet:
a. greater than
b. less than
c. twice
d. equal to
b. less than
126
Differential coils are exactly alike except:
a. one is a surface coil and the other is an encircling coil
b. for their impedances
c. they are wound in opposite directions
d. one is energized with DC while the other is energized with AC
c. they are wound in opposite directions
127
Metals which do not react or only slightly react to magnetic fields are called:
a. diamagnetic metals
b. paramagnetic metals
c. nonmagnetic metals
d. any of the above may be used
d. any of the above may be used
128
A material which is considered ferromagnetic is:
a. nickel
b. cobalt
c. iron
d. all of the above
d. all of the above
129
Eddy current testing is more sensitive to dimensional changes when the material is:
a. thick
b. thin
b. thin
130
The depth of penetration would _________ if the localized permeability of a material is increased.
a. increase the conductivity
b. remain constant
c. decrease
d. increase
c. decrease
131
A term used to define a unit of flux density is:
a. a weber
b. a tesla
c. an ohm
d. a siemens
b. a tesla
132
At any given instant, a spinning probe eddy current instrument should be inspecting:
a. one complete circumference of the product
b. an area defined by the size of the probe coil
c. one longitudinal line the length of the product
d. none of the above
b. an area defined by the size of the probe coil
133
The conductivity of a material can be altered by changing the:
a. alloy of the specimen
b. heat treatment of the specimen
c. temperature of the specimen
d. all of the above
d. all of the above
134
A term used to describe holes, grooves, notches, etc. that are introduced into a reference standard to provide accurately reproducible quality levels is:
a. a natural discontinuity
b. an artificial discontinuity
c. an ellipse
d. none of the above
b. an artificial discontinuity
135
When attempting to determine the exact circumferential location of a discontinuity in a tube, the test system should include:
a. a phase shifter
b. a probe coil
c. an attenuator
d. a penetrameter
b. a probe coil
136
Which of the following statements best describes the selection of eddy current test frequency?
a. the frequency must equal the f/fc ratio to give an accurate test
b. the frequency must be within +/-3% of the f/fc ratio to give an accurate test
c. there is a range of suitable frequencies centered around the optimum frequency
d. the frequency should be within +/-25% of the characteristic frequency
c. there is a range of suitable frequencies centered around the optimum frequency
137
A term used to define a standardized condition in a device or system which results in zero output is:
a. high frequency standardization
b. integration
c. null or balance
d. differentiation
c. null or balance
138
Eddy current test coils which are wound to form a wide coil would normally be used to detect:
a. pitting
b. small inclusions
c. changes in conductivity
d. porosity
c. changes in conductivity
139
Eddy currents generate a magnetic field that:
a. opposes the coil's magnetic field
b. aids the coil's magnetic field
a. opposes the coil's magnetic field
140
An absolute coil arrangement can be used in:
a. encircling coils only
b. probe coils only
c. probe and encircling coils
d. probe, encircling, and inside diameter coils
d. probe, encircling, and inside diameter coils
141
When using a surface coil the best resolution is obtained with:
a. larger diameter coils
b. smaller diameter coils
b. smaller diameter coils
142
An increase in the impedance of an eddy current test coil will:
a. cause an increase in the current flow through the test coil
b. cause a decrease in the current flow through the test coil
c. not affect current flow in the test coil
d. decrease the voltage applied to the coil
b. cause a decrease in the current flow through the test coil
143
Which of the following will affect the impedance of a test probe?
a. conductivity of a test specimen in the coil
b. permeability of a test specimen in the coil
c. fill factor
d. all of the above
d. all of the above
144
Material must be reasonably centered in an encircling test coil of a discontinuity detection system because, even with an acceptable fill factor ratio:
a. the coil would otherwise be out of balance
b. parts of the material farthest away from the coil, radially, may receive a less sensitive inspection
c. the flow of eddy currents around the product will be disturbed, resulting in improper penetration
d. lack of proper centering may change the phase adjustment of the instrument
b. parts of the material farthest away from the coil, radially, may receive a less sensitive inspection
145
A reference standard used to ensure that the amplitude and phase characteristics of a test system do not drift during continuous testing is called a:
a. DGS standard
b. calibration standard
c. reference block
d. none of the above
b. calibration standard
146
The ratio of the response or amplitude from signals of interest to the response or amplitude of indications that contain no useful information for the test being conducted is referred to as:
a. Poisson's ratio
b. signal-to-noise ratio
c. the conductivity-to-permeability ratio
d. the reactance-to-resistance ratio
b. signal-to-noise ratio
147
Reference standards used for electromagnetic testing:
a. must contain artificial discontinuities such as notches and drilled holes
b. must contain natural discontinuities such as cracks and inclusions
c. must be free of measurable discontinuities
d. may contain artificial or natural discontinuities or be free of discontinuities depending on the test system and the type of test being conducted
d. may contain artificial or natural discontinuities or be free of discontinuities depending on the test system and the type of test being conducted
