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NDT Methods > Magnetic Particle Inspection MT > Flashcards

Magnetic Particle Inspection MT Flashcards

1
Q

And inspection method in which an initial magnetizing force is applied to a part and then reduce to a lower continuous value was called

A

Surge method

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2
Q

The term used to refer to the total opposition to flow of current represented by the combined effect of resistance, inductance, and capacitance of a circuit is

A

Impedance

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3
Q

Discontinuities in plate , sheet or strip caused by internal fissures, inclusions, or blow holes in the original ingot which after rolling, are usually flat and parallel to the outside surface are called

A

Laminations

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4
Q

The cumulation of particles at a site on the part surface, collected at and held to the site by the magnetic leakage field, is called

A

An indication

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5
Q

The leakage field strength is controlled by

A

The materials permeability, the depth and width of the discontinuity and the relative strength of the applied magnetic flux

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6
Q

Primarily a qualitative inspection, detecting changes in volume

A

Magnetic flux leakage - tank floor scanning, in line inspection of pipelines, wire rope, coil tubing and rail inspections

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7
Q

Relatively thin coating of paint or plating on the surface can cause a surface crack to appear as

A

Broad and fuzzy

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8
Q

When matters is place within an external magnetic field, the magnetic moments of that material’s electrons maybe reorientated. When this occurs the material produces its own macroscopic magnetic field this is known as

A

Faraday’s Law of magnetic induction

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9
Q

Any material with a negative relative permeability that is slightly less than one is

A

Diamagnetic - Mercury gold bismuth and zinc

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10
Q

When the internal magnetic field of a material is aligned in the same direction as the applied external field, and the material has a small positive suspect ability and a positive relative permeability that is slightly more than one the material is called

A

Paramagnetic- aluminum platinum copper sulfate and wood

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11
Q

When the internal magnetic field of the material is aligned in the same direction as the applied external field, and the material has a high positive suspect ability and a high positive permeability that is much greater than one, the material is called

A

Ferromagnetic

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12
Q

When an electric current is passed through the part the part is the conductor of the electric current and a circling magnetic field is established both within the inside and outside the conductor

A

Direct magnetization

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13
Q

Magnetism that results when a ferromagnetic material is influenced by an external field. Devices such as central conductors, coil’s, and yokes

A

Indirect magnetization

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14
Q

Coil where the length is greater than the diameter

A

Solenoids

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15
Q

Term used to refer to the total opposition to flow of current represented by the combined effect of resistance, inductance, and capacitance of a circuit

A

Impedance

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16
Q

Lines of force that form a path around the crack in a ring magnet

A

Magnetic lines

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17
Q

Earths field this week, how week?

A

0.3 gauss

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18
Q

Particle sizes for wet method testing ranges from

A

1 to 25 µm (micrometer)

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19
Q

When magnetic material reaches its curie temperature, the material becomes

A

Paramagnetic

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20
Q

Which type of radiation can most damage human tissue?

A

UV-B

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21
Q

µ =

A

Permeability =B/H

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22
Q

B =

A

Flux density measured in gauss (SI units measured in tesla)

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23
Q

Best technique for testing of large flat area

A

Prods

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24
Q

H =

A

Magnetizing force measured in oersted

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25
Q

Most common wattage of mercury vapor bulbs florescent MT exams

A

100 W

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26
Q

Amp turns L/D, yoke, coil around part are all types of this field

A

Longitudinal

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27
Q

Prods, central conductor, headshot, passing current directly through part or all types of this field

A

Circular

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28
Q

The field established in a part when it is placed next to a conductor carrying a current, which should be avoided

A

Parallel magnetization

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29
Q

Useful when orientation of discontinuities are unknown (proper sequence) magnetize, apply particles, shut off current, and inspect

A

Multidirectional magnetization

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30
Q

Produced by simultaneously imposing two magnetizing forces in two directions where one is stronger than the other upon a magnetizable article

A

Vector field

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31
Q

N*I =

N= number of turns
I = current (amps)
A

45,000/(L/D)

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32
Q

Advantage to demagnetize a part

A

Position east to west

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33
Q

Check concentration of particles for wet method

A

Settling test

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34
Q

Unit of viscosity

A

Centistokes

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35
Q

MT machine is calibrated with

A

A shunt and a calibrated ammeter

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36
Q

Determines amperage being used

A

Ammeter

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37
Q

Fill factor equals

A

10% or 10 to 1

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38
Q

One line of flux per square centimeter is

A

Gauss (flux density)

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39
Q

Interruption or break in the normal physical structure

A

Discontinuity

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40
Q

Accumulation of particles

A

Indication

41
Q

Plated parts can be reliably tested at what thickness

A

.1 mm or.004

42
Q

To retain a magnetic field

A

Retentivity or remnant

43
Q

The ease which something can be magnetized

A

Permeability

44
Q

Best subsurface inspection

A

Dry continuous half wave DC with prods (Deepest Penetration)

45
Q

Best surface and subsurface

A

Half wave rectified AC with dry particles (most effective with greatest particle mobility)

46
Q

Best surface

A

Wet fluorescent continuous AC shallowest penetration

47
Q

Easiest to demagnetize

A

Longitudinal fields

48
Q

Harder to demagnetize

A

Circular fields

49
Q

Current for skin affect

A

AC

50
Q

Greater in hard materials than soft materials

A

Resistance to demagnetization

51
Q

When a magnetic field is at 90° to the defect, it will cause an abrupt change in this of the part

A

Permeability

52
Q

Sub microscopic regions inside of material

A

Magnetic domains

53
Q

Permeability less than one

A

Diamagnetic

54
Q

One or slightly more

A

Paramagnetic

55
Q

Many more times more than one

A

Ferromagnetic

56
Q

MT particles need to have

A

High permeability and low retentivity

57
Q

Human vision range is

A

380nm to 770 nm violet to red

58
Q

A nano meter equals

A

Billionth of a meter

59
Q

Black light is how far outside of the humans range

A

365 nm

60
Q

Fluorescent particles absorb at

A

365 nm or 3650 angstroms

61
Q

Fluorescent particles released at

A

550 nm or 5500 Å yellow green

62
Q

Required visible light for visible MT

A

100 foot candles

63
Q

Magnetic particle building from the discontinuity the strongest one the discontinuity is orientated

A

90° to the magnetic flux flow

64
Q

The number of lines of flux intercepting in area perpendicular to the flux

A

Flux density

65
Q

Prod spacing less than___________is usually not practical because the particles tend to band around the prize, making interpretation difficult

A

3 inches

66
Q

The source that supplies the most power for magnetizing is

A

Three phase alternating current, full wave rectified

67
Q

Half wave direct current is obtained from

A

Single phase alternating current power

68
Q

Full wave, three phase rectified alternating current produces

A

Low ripple direct current

69
Q

The timer on a bench should have an accuracy of

A

+/-.1 second

70
Q

Field that is easiest to detect, but hardest to demagnetize

A

Circular

71
Q

Field that is easier to demagnetize

A

Longitudinal

72
Q

Shuts off current at its maximum causing the collapsing magnetic field to produce eddy currents that compensate for decreased flux density at the ends of parts

A

Quick break

73
Q

Typical average output for mobile equipment is

A

1.5 KA to 4000 amperes

74
Q

Single phase equipment require how many more times then three phase unit

A

1.73

75
Q

Alternating current is available in voltages ranging from

A

120 to 440 V

76
Q

The level of fluorescent particles and suspension should be maintained consistently, from

A

.1 to .4 mL in 100 mL settling test

77
Q

Most military and commercial specifications require the test site to be darkened to

A

20 luxs or 2 ftc

78
Q

The settling rate is inversely proportional to the

A

Liquids viscosity

79
Q

Skin depth for 60 Hz alternating current fields is typically about

A

1 mm or .04 inch

80
Q

Detects field strength because the fields creates a voltage difference between two sides of the sensor in proportion to the field strength

A

Hall Effect Probe

81
Q

The hall effect probe sensitivity is increased using a ferrite ring because

A

Increased permeability and higher B value

82
Q

Most likely subsurface discontinuity detectable by Mt

A

Stringer

83
Q

Most difficult to detect by MT

A

Porosity

84
Q

Longer shots are required with magnetic rubber due to

A

Higher viscosity

85
Q

Provides information about particle concentration, magnetic properties of the particles, and the functioning of magnetizing machine

A

Ketos Ring Test

86
Q

The magnetization of a ferromagnetic substance by increasing magnetic field takes place in discontinuous steps rather than continuously

A

Barkhausen Effect

87
Q

A single shot magnetization method using discharge from the bank of capacitors. A means by which electrical current is built up and stored until a sufficient level is achieved to provide a predetermined magnetic field in a test object, usually saturation

A

Capacitor discharge method

88
Q

A potential difference developed across a conductor at right angles to the direction of both the magnetic field and the electric current. Produce when a current flows along the rectangular conductor subjected to a transverse magnetic field. The magnitude of the voltage is proportional to the applied field.

A

Hall Effect

89
Q

Radiant energy generated to the 400 to 700 nm or 4000 to 7000 angstroms wave range

A

Visible light

90
Q

Yokes produce either alternating current or alternating current half wave direct current output from

A

120 V or 240 V alternating current single phase

91
Q

The shot timer is typically adjustable from

A

.5 seconds to 1 second

92
Q

Why is the shot timer usually set between .6 seconds and .9 seconds?

A

Because the timing device used to calibrate the timer has an accuracy of plus or minus .1 second

93
Q

Mobile power supply normally operate on

A

240 V or 480 V

94
Q

Mobile power supplies provide both alternating current and half wave direct current output up to

A

6000 A

95
Q

Amps per 1 inch diameter of cross-section with alternating current

A

500 to 600 A

96
Q

Amps per 1 inch of diameter or cross section with direct current or rectified alternating current

A

800 to 1000 A

97
Q

The level of visible particles and suspension should be maintained consistently, from

A

1.2 to 2.4 100 mL

98
Q

The most visible indications generally result when the depth exceeds

A

Five times the width

NDT Methods (9 decks)

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