Questions for Magnetic Particle Testing – General

Questions for Magnetic Particle Testing – General

1) The area of maximum induced field strength using a yoke is:

(a)       At the north pole of the yoke

(b)       At the south pole of the yoke

(c)       The area directly between the poles

(d)       On the outside of the pole pieces

2) Magnetic lines of flux which are parallel to a discontinuity produce:

(a)       Strong indications

(b)       Weak indications

(c)       No indications

(d)       Fuzzy indications

3) An advantage of AC equipment over DC is:

(a)       AC is more penetrating

(b)       AC is less hazardous

(c)       AC makes the magnetic particles more mobile on the test surface

(d)       AC equipment is heavier than DC

4) When the orientation of likely discontinuities is unknown, what is the minimum number of magnetizing operations required to perform an adequate test?

(a)       1

(b)       2

(c)       3

(d)       None of the above

5) Wet magnetic particle bath strength is checked by which of the following?

(a)       Specific gravity

(b)       Optical density

(c)       Settling test

(d)       None of the above

6) Which of the following might cause non-relevant indications?

(a)       Over magnetization

(b)       Indications at the edges of a braze joint

(c)       A joint between hard and soft steels

(d)       All of the above

7) An indication which is formed when two pieces of magnetized steel come in contact with each other is called:

(a)       A metallurgical discontinuity

(b)       Magnetic writing

(c)       Magnetic transfer

(d)       A ferromagnetic notch

8) MPI use for ……………………..defects of weld and body but with this method we cannot find the …………….. in volume.

(a)     Surface, scratch

(b)     Subsurface, dent

(c)     Volumetric, lamination

(d)     Surface/subsurface, volumetric defect

9)  The most common method of demagnetizing small test pieces is:

(a)       Heat treatment

(b)       Shot peening

(c)       Passing through an AC coil

(d)       Direct contact with AC current

10) Demagnetization with reversing DC is more effective than AC because:

(a)       DC is more penetrating

(b)       Demagnetization is assisted by the skin effect

(c)       DC is more direct

(d)       Not true – AC is more effective

11) The type of discontinuity which magnetic particle testing most effectively locates is:

(a)       Slag inclusions

(b)       Magnetic writing

(c)       Porosity

(d)       Surface cracks

12) The temperature above which steels become nonmagnetic is called the:

(a)       Melting point

(b)       Curie point

(c)       Demagnetization temperature

(d)       Random polar point

13) The temperature above which most soft steels become nonmagnetic is about:

(a)       440ºC (770oF)

(b)       523ºC (975ºF)

(c)       626ºC (1160ºF)

(d)       754ºC (1390ºF)

14) The unit usually used to denote flux density is the:

(a)       Gauss

(b)       henry

(c)       farad

(d)     ampere

15) Which of the following can be magnetized?

(a)       cobalt

(b)       nickel

(c)       iron

(d)       all of the above

16) The permeability (µ) can be defined as:

(a) B/H

(b) H/B

(c) Penetrating ability

(d) None of the above

17) How many turns of a coil will be needed to establish a longitudinal field in a steel shaft that is 22.86 cm (9 inches) long and 7.62 cm (3 inches) in diameter? 3000 amperes magnetizing current is available, it is desired to magnetize the part in accordance with the formula NI = 45,000/(L/D):

(a)       1

(b)       3

(c)       5

(d)       7

18) The strength of wet suspension should be maintained at a given level because:

(a) a low level might give a weak indication

(b) a high level might give a heavy background

(c) both a and b

(d) none of the above

19) Demagnetization:

(a) may be easy or difficult depending on the type of material

(b) is easy for material having a high coercive force

(c) is always most difficult in materials retaining a high residual field

(d) all of the above

20) Half-wave rectified AC (HWDC) is used for detection of:

(a)       surface defects only

(b)       subsurface defects only

(c)       surface and subsurface defects

(d)       all defects

21) The general term used to refer to break the metallic continuity of the part being tested is:

(a)       defect

(b)       discontinuity

(c)       crack

(d)       indication

22) In order to detect the defect of any directions in a material by magnetic particle inspection, it is best to use:

(a)       two or more field on different directions

(b)      high current required

(c)       only one field

(d)       All of the above

23) The magnetic line of flux from magnet bar, leave the …………………..pole and entered in ………………..pole.

(a)       north, south

(b)       south, north

(c)       cannot define

(d)       none of the above

24) Any imperfection that above the acceptance limit of procedure that followed, is called:

(a)       discontinuity

(b)       indication

(c)       irregularity

(d)       defect

25) The indications that should be consider:

(a)       relevant

(b)       nonrelevant

(c)       false

(d)       none of the above

36) Materials that are magnetically repelled are called:

(a)       ferromagnetic

(b)     Paramagnetic

(c)      diamagnetic

(d)      all of the above

27) In magnetic particle testing the indication form by:

(a)       current leakage

(b)       voltage leakage

(c)       water leakage

(d)       flux leakage

(e)       all of the above

28) Desire properties of magnetic particle used for the inspection medium for either the dry or wet method is that they:

(a)       are nontoxic

(b)       possess high permeability

(c)       possess low retentivity

(d)       all of the above

29) The formula, NI = 45000/(L/D), is used to calculate the proper magnetizing current for:

(a)       Prod magnetization

(b)       A head shot

(c)       A central conductor

(d)       Coil magnetization

30) What is the magnetic field strength at the surface of a 25 mm diameter bar as compared to that at the surface of a 50 mm diameter bar, each carrying 1000 amps of current?

(a)       Twice

(b)       One half

(c)       One quarter

(d)       Four times

31) The most common source of DC current for magnetic particle testing is:

(a)       Motor generators

(b)       Rectified AC

(c)       Storage batteries

(d)       None of the above

32) By which of the following fill-factor, the greater magnetization can occurred:

(a)       80%

(b)       85%

(c)       90%

(d)       95%

33) Some limitations of coil magnetization techniques are:

(a)       that the fill factor should be high

(b)       that the effective field is generally limited of either side of the coil

(c)       the small diameter part should be placed closed to the coil

(d)       all of the above

34) A leakage field is strongest when a discontinuity interrupts the magnetic flux lines at an angle of:

(a)       0°

(b)       45°

(c)       90°

(d)       180°

35) Opposition to establishment of a magnetic field in a test piece is called:

(a)       Reluctance

(b)       Retentivity

(c)       Permeability

(d)       Electromagnetism

36) How many techniques for magnetization:

(a)       direct and indirect

(b)       direct, indirect and headshot

(c)       headshot, central conductor and coil

(d)       none of the above

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