Magnetic Particle Inspection MT Flashcards Preview

NDT Methods > Magnetic Particle Inspection MT > Flashcards

Flashcards in Magnetic Particle Inspection MT Deck (98):
1

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

Surge method

2

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

Impedance

3

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

Laminations

4

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

An indication

5

The leakage field strength is controlled by

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

6

Primarily a qualitative inspection, detecting changes in volume

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

7

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

Broad and fuzzy

8

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

Faraday's Law of magnetic induction

9

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

Diamagnetic - Mercury gold bismuth and zinc

10

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

Paramagnetic- aluminum platinum copper sulfate and wood

11

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

Ferromagnetic

12

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

Direct magnetization

13

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

Indirect magnetization

14

Coil where the length is greater than the diameter

Solenoids

15

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

Impedance

16

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

Magnetic lines

17

Earths field this week, how week?

0.3 gauss

18

Particle sizes for wet method testing ranges from

1 to 25 µm (micrometer)

19

When magnetic material reaches its curie temperature, the material becomes

Paramagnetic

20

Which type of radiation can most damage human tissue?

UV-B

21

µ =

Permeability =B/H

22

B =

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

23

Best technique for testing of large flat area

Prods

24

H =

Magnetizing force measured in oersted

25

Most common wattage of mercury vapor bulbs florescent MT exams

100 W

26

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

Longitudinal

27

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

Circular

28

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

Parallel magnetization

29

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

Multidirectional magnetization

30

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

Vector field

31

N*I =

N= number of turns
I = current (amps)

45,000/(L/D)

32

Advantage to demagnetize a part

Position east to west

33

Check concentration of particles for wet method

Settling test

34

Unit of viscosity

Centistokes

35

MT machine is calibrated with

A shunt and a calibrated ammeter

36

Determines amperage being used

Ammeter

37

Fill factor equals

10% or 10 to 1

38

One line of flux per square centimeter is

Gauss (flux density)

39

Interruption or break in the normal physical structure

Discontinuity

40

Accumulation of particles

Indication

41

Plated parts can be reliably tested at what thickness

.1 mm or.004

42

To retain a magnetic field

Retentivity or remnant

43

The ease which something can be magnetized

Permeability

44

Best subsurface inspection

Dry continuous half wave DC with prods (Deepest Penetration)

45

Best surface and subsurface

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

46

Best surface

Wet fluorescent continuous AC shallowest penetration

47

Easiest to demagnetize

Longitudinal fields

48

Harder to demagnetize

Circular fields

49

Current for skin affect

AC

50

Greater in hard materials than soft materials

Resistance to demagnetization

51

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

Permeability

52

Sub microscopic regions inside of material

Magnetic domains

53

Permeability less than one

Diamagnetic

54

One or slightly more

Paramagnetic

55

Many more times more than one

Ferromagnetic

56

MT particles need to have

High permeability and low retentivity

57

Human vision range is

380nm to 770 nm violet to red

58

A nano meter equals

Billionth of a meter

59

Black light is how far outside of the humans range

365 nm

60

Fluorescent particles absorb at

365 nm or 3650 angstroms

61

Fluorescent particles released at

550 nm or 5500 Å yellow green

62

Required visible light for visible MT

100 foot candles

63

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

90° to the magnetic flux flow

64

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

Flux density

65

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

3 inches

66

The source that supplies the most power for magnetizing is

Three phase alternating current, full wave rectified

67

Half wave direct current is obtained from

Single phase alternating current power

68

Full wave, three phase rectified alternating current produces

Low ripple direct current

69

The timer on a bench should have an accuracy of

+/-.1 second

70

Field that is easiest to detect, but hardest to demagnetize

Circular

71

Field that is easier to demagnetize

Longitudinal

72

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

Quick break

73

Typical average output for mobile equipment is

1.5 KA to 4000 amperes

74

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

1.73

75

Alternating current is available in voltages ranging from

120 to 440 V

76

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

.1 to .4 mL in 100 mL settling test

77

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

20 luxs or 2 ftc

78

The settling rate is inversely proportional to the

Liquids viscosity

79

Skin depth for 60 Hz alternating current fields is typically about

1 mm or .04 inch

80

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

Hall Effect Probe

81

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

Increased permeability and higher B value

82

Most likely subsurface discontinuity detectable by Mt

Stringer

83

Most difficult to detect by MT

Porosity

84

Longer shots are required with magnetic rubber due to

Higher viscosity

85

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

Ketos Ring Test

86

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

Barkhausen Effect

87

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

Capacitor discharge method

88

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.

Hall Effect

89

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

Visible light

90

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

120 V or 240 V alternating current single phase

91

The shot timer is typically adjustable from

.5 seconds to 1 second

92

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

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

93

Mobile power supply normally operate on

240 V or 480 V

94

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

6000 A

95

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

500 to 600 A

96

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

800 to 1000 A

97

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

1.2 to 2.4 100 mL

98

The most visible indications generally result when the depth exceeds

Five times the width