Ginzel Question Bank

Question 1

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

Answer 1

a) austenitic stainless steel

Question 2

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

Answer 2

c) magnetic flux is not restricted by the tube wall

Question 3

3) Another term for voltage is a) electromotive force b) magnetomotive force c) potential drop d) both a and c

Answer 3

d) both a and c

Question 4

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

Answer 4

b) the angle between diameter and conductivity locii is greater

Question 5

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

Answer 5

c) do not use eddy current methods

Question 6

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

Answer 6

d) all of the above

Question 7

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

Answer 7

c) digital-to-analogue converter

Question 8

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

Answer 8

a) 612 Hz

Question 9

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

Answer 9

c) the induced EMF is opposite to the change causing it

Question 10

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

Answer 10

a) when eddy current penetration is greater than material thickness

Question 11

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

Answer 11

c) 10 to 200 ohms

Question 12

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

Answer 12

b) recovery time

Question 13

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

Answer 13

c) impedance changes in the coil

Question 14

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

Answer 14

c) 1.1

Question 15

15) Relative permeability is measured in which units? a) no units (dimensionless ratio) b) Webers/Ampere-meter c) Webers/meter squared d) amperes/ meter

Answer 15

a) no units (dimensionless ratio)

Question 16

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

Answer 16

a) acceptance limits

Question 17

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

Answer 17

b) reduced fill factor

Question 18

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

Answer 18

b) ensure the coil axis is perpendicular to the rest surface

Question 19

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

Answer 19

a) 650 Hz

Question 20

20) Differential coils are, in some areas, also called a) ID coils b) bucking coils c) annular coils d) tandem coils

Answer 20

b) bucking coils

Question 21

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

Answer 21

b) verify accuracy of a test

Question 22

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

Answer 22

b) a difference in resistivity between the 2 materials

Question 23

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

Answer 23

d) none of the above

Question 24

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

Answer 24

b) elimination of the effects of undesirable parameters

Question 25

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

Answer 25

a) tooling or handling equipmen

Question 26

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

Answer 26

a) upward

Question 27

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

Answer 27

d) all of the above

Question 28

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

Answer 28

a) suitably shaped insulators inside a mercury filled tube

Question 29

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

Answer 29

b) down

Question 30

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

Answer 30

c) the speed at which tests can be performed

Question 31

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

Answer 31

a) induced voltages form the AC magnetic field

Question 32

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

Answer 32

b) samples of known materials

Question 33

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

Answer 33

b) pure resistance

Question 34

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

Answer 34

a) signals are too large making small defects hard to see

Question 35

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

Answer 35

c) 90 deg

Question 36

36) The equation 1/2pifC = a) inductive reactance b) capacitance c) capacitive reactance d) total impedance (electrical)

Answer 36

c) capacitive reactance

Question 37

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

Answer 37

a) mixing modules

Question 38

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

Answer 38

a) electrical contacts in rotating heads

Question 39

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

Answer 39

b) subsurface corrosion detection in multilayer structures

Question 40

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

Answer 40

b) initial permeability

Question 41

41) Tesla or Webbers per square meter (Wb/m^2) are units of a) eddy current b) impedance c) reluctance d) magnetic flux density

Answer 41

d) magnetic flux density

Question 42

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

Answer 42

c) clean smooth surfaced not required

Question 43

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

Answer 43

d) both a and b

Question 44

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

Answer 44

d) none is the above

Question 45

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

Answer 45

c) both a and b

Question 46

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

Answer 46

a) a magnetic departure

Question 47

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%

Answer 47

c) 14%

Question 48

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

Answer 48

d) all of the above

Question 49

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

Answer 49

c) +Y