Ginzel Question Bank Flashcards
NRCAN prep
1)Degree of cold working of which material can be determined by eddy current methods monitoring for permeability changes instead of resistivity changes? a) austenitic stainless steel b) titanium c) tungsten d) annealed aluminum
a) austenitic stainless steel
2) Three main reason as eddy current coil can detect support plates in heat exchangers when testing tubes from the inside diameter is a) support plates are always ferro- magnetic b) support plates are always the same material as the tube c) magnetic flux is not restricted by the tube wall d) support plates act as resonance amplifiers in the circuit
c) magnetic flux is not restricted by the tube wall
3) Another term for voltage is a) electromotive force b) magnetomotive force c) potential drop d) both a and c
d) both a and c
4) Separation of diameter and conductivity effects is better carried out at frequency ratios greater than 4 because a) greater penetration afforded permits better determination of bulk properties b) the angle between diameter and conductivity locii is greater c) the angle between diameter and conductivity locii is 90 deg d) none of the above, frequency ratio should be less than 4 for such work
b) the angle between diameter and conductivity locii is greater
5) Resistivity measurements made on bull material and without reference standards a) cannot be made by any methods known b) use very high frequency eddy current probes c) do not use eddy current methods d) use magnetostrictive effects
c) do not use eddy current methods
6) What conditions can be “eliminated” using multifrequency eddy current techniques? a) denting and pilgering b) magnetic deposits c) support plates d) all of the above
d) all of the above
7) A circuit block that accepts a binary number and translates it to an analogue or current proportional to the boundary number is a(n) a) CPU b) analogue-to-digital converter c) digital-to-analogue converter d) retro-virus
c) digital-to-analogue converter
8) What is the f90 for am encircling chill used to aluminum tubing, p = 5.1 uohm-cm, equal thickness 5mm, diameter 40mm? a) 612 Hz b) 3.1 kHz c) 14.7 kHz d) 6.12 kHz
a) 612 Hz
9) Lenz’s law states a) an alternating magnetic field includes am alternating voltage b) the magnitude of induced current is a function of magnetic flux through a circuit c) the induced EMF is opposite to the change causing it d) I=BA cos p where B= flux density, A = circuit area and p = the angle between B and the circuit area A
c) the induced EMF is opposite to the change causing it
10) When does material thickness affect the results of a conductivity test? a) when eddy current penetration is greater than material thickness b) when conductivity is very high c) when the material is backed by a higher conductivity material d) when liftoff is a result of a surface roughness
a) when eddy current penetration is greater than material thickness
11) The impedance of probes used inn eddy current testing can vary over a range. instruments must be able to balance over this range. Most instruments cam handle probe impedances between a) 50 to 75 ohms b) 0.1 to 100 kohms c) 10 to 200 ohms d) 5 to 500 ohmd
c) 10 to 200 ohms
12) The time required for a test system to return to it’s original state after it had received a signal is the a) dead time b) recovery time c) recoil time d) system delay
b) recovery time
13) Eddy Current flow in a test sample is accomplished indirectly by monitoring a) current changes in the sample b) resistivity changes in the sample c) impedance changes in the coil d) coil resonance
c) impedance changes in the coil
14) The f90 frequency has been found empirically from the radio of thickness and skin depth. For testing this ratio is a) 0.08 b) 0.9 c) 1.1 d) 3
c) 1.1
15) Relative permeability is measured in which units? a) no units (dimensionless ratio) b) Webers/Ampere-meter c) Webers/meter squared d) amperes/ meter
a) no units (dimensionless ratio)
16) Test levels used in ECT that establish the group into which a ma material under test belongs are termed a) acceptance limits b) reject level c) test criteria d) group level options
a) acceptance limits
17) The result of using a longer encircling test coil to test a spherical object as compared to a short or hemispherical coil would be a) increased sensitivity b) reduced fill factor c) improved phase discrimination of cracks and conductivity changes d) ask if the above
b) reduced fill factor
18) The purpose of curved wear pieces (shoes) to guide surface probe assemblies is to a) maintain constant lift - off b) ensure the coil axis is perpendicular to the rest surface c) prevent the probe from scratching the test piece d) shape the magnetizing field
b) ensure the coil axis is perpendicular to the rest surface
19) What test frequency has a standard depth of penetration of 1mm for a plate material with resistivity of 130 uohm-cm and relative magnetic permeability of 500? a) 650 Hz b) 1.20 kHz c) 240 kHz d) 1 MHz
a) 650 Hz
20) Differential coils are, in some areas, also called a) ID coils b) bucking coils c) annular coils d) tandem coils
b) bucking coils
21) What is the purpose of calibration reference standard? a) establish acceptance criteria b) verify accuracy of a test c) provide traceability back to the national standard d) all if the above
b) verify accuracy of a test
22) Measuring the thickness of conductive layer over another conductor (neither being magnetic) requires a) two frequencies be used b) a difference in resistivity between the 2 materials c) the use of a ferrite cup d) a gap probe be used
b) a difference in resistivity between the 2 materials
23) Instrument frequency rest response is limited by a) probe size b) operating frequency of the probe c) probe motion (inspection speed) d) none of the above
d) none of the above
24) The purpose of multifrequency ECT techniques is a) to increase frequency response to instruments b) elimination of the effects of undesirable parameters c) increase sensitivity to non- surface breaking defects d) to allow inspection with phased array probes
b) elimination of the effects of undesirable parameters
25) Ferromagnetic inclusions on or in normally non magnetic aluminium will arise due to a) tooling or handling equipment b) impurities in the melt c) working below the currie temperature
a) tooling or handling equipmen
26) An increase in electrical resistivity of a sample will move the operating point on the impedance curve a) upward b) downward c) to a point inside the curve d) to a point outside the curve
a) upward
27) Which of the following noise sources can be filtered with the appropriate electronics in an eddy current instrument? a) external, stray magnetic and electric fields b) electrical noise generated within the EC instrument c) mechanical vibrations of test coil or material d) all of the above
d) all of the above
28) The best method of measuring the effects of a specific discontinuity totally within a test specimen but different depths and orientations is by using a) suitably shaped insulators inside a mercury filled tube b) suitably shaped conductors inside a water filled tube c) saw cuts in the material to be tested d) EDM notches in the material to be tested
a) suitably shaped insulators inside a mercury filled tube
29) An increase in tube wall or plate thickness will move the operating pint on the impedance curve a) up b) down c) inside the curve d) outside the curve
b) down
30) What is the biggest advantage eddy current test methods have that make them the most frequently used NDT method in the automotive industry? a) both surface and subsurface defects are found b) even automotive engineers can perform the tests c) the speed at which tests can be performed d) the application to determine heart treatment quality
c) the speed at which tests can be performed
31) Which of the following is the direct cause of eddy currents in a test piece placed in an encircling transducer? a) induced voltages form the AC magnetic field b) back emf within the transducer c) resistivity of the test piece d) three magnetic field opposing the transducer’s fields
a) induced voltages form the AC magnetic field
32) When eddy currents are used for sorting techniques it is usual to establish impedance values from a) probe characteristics b) samples of known materials c) published information d) trial and error methods
b) samples of known materials
33) Voltage and current will bee in phase for ____________ in an AC circuit. a) pure inductance b) pure resistance c) all conditions d) no conditions
b) pure resistance
34) Vectorial addition of signals auth conductivity non - magnetic support plates is not usually viable because a) signals are too large making small defects hard to see b) no magnetic occurs to use as a reference c) elimination frequency are too high d) elimination frequencies are too small
a) signals are too large making small defects hard to see
35) The phase angle between applied voltage and resultant current in an AC circuit of pure inductance is a) 0 deg b) 45 deg c) 90 deg d) 180 deg
c) 90 deg
36) The equation 1/2pifC = a) inductive reactance b) capacitance c) capacitive reactance d) total impedance (electrical)
c) capacitive reactance
37) Multifrequency instruments have the same controls and functions as general purpose ECT instruments with th he addition of a) mixing modules b) filters c) phasors d) frequency selectors
a) mixing modules
38) What are skip rings used for in eddy current inspection system? a) electrical contacts in rotating heads b) clutch mechanisms in probe pushers c) to allow ease of motion by encircling probes d) to allow ease of motion by bobbin probes
a) electrical contacts in rotating heads
39) Low frequency eddy current ( 100 Hz to 5kHz) is commonly used in aircraft inspections for a) paint thickness determinations b) subsurface corrosion detection in multilayer structures c) conductivity determination for alloy sorting d) all of the above
b) subsurface corrosion detection in multilayer structures
40) Th he slope of the induction curve at zero magnetizing force as the test piece is being taken from it’s demagnetized state is the a) virgin permeability b) initial permeability c) maximum permeability d) effective permeability
b) initial permeability
41) Tesla or Webbers per square meter (Wb/m^2) are units of a) eddy current b) impedance c) reluctance d) magnetic flux density
d) magnetic flux density
42) Which of the following is not an advantage of the eddy current test method? a) 100% volumetric inspection is possible (within limits) b) speed c) clean smooth surfaced not required d) no coolant required
c) clean smooth surfaced not required
43) Small eddy current sensors is the vicinity of cracks could be used for a) precise crack length determinations b) crack extension rate determination c) crack width determination d) both a and b
d) both a and b
44) Surface coil eddy current transducers are a) always used in the absolute mode b) always flat c) always used on fist surfaces d) none is the above
d) none is the above
45) Instrumentation for systems using hall detectors instead of pickup coils are different in what respect? a) stabilized DC supplies are needed b) excitation AC current must be constant for all frequencies c) both a and b d) none of the above, Hall detectors can be used on an EC I instrument
c) both a and b
46) During evaluation of an induction id’s a great exchanger tube, the probe is moved back and forth over the defect. It is noted that the indication had changed position along the length of the tube. What is the likely source? a) a magnetic departure b) a spiral fret c) active cracking d) a probe write has loosened at the connector
a) a magnetic departure
47) At 2 standard depths of penetration, eddy current density is about ______ that it is at the surface a) 66% b) 37% c) 14% d) 9%
c) 14%
48) Phase lag of eddy currents is a sample is dependant on a) depth into the smoke b) resistivity of the test piece c) relative magnetic permeability of the sample d) all of the above
d) all of the above
49) When tube testing at f90 (internal absolute probe), if ID wall loss moves the operating point for an absolute c cool in a negative X direction, a shallow OD defect would move the operating point a) +X b) -Y c) +Y d) both -X and -Y in equal proportions
c) +Y
