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EC L1 > Random Q's > Flashcards

Random Q's Flashcards

1
Q

Who discovered Eddy Currents?

A

Leon Foucault

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2
Q

What symbol is commonly used to express conductivity?

A

DELTA “fancy o”

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3
Q

What symbol is commonly used to express permeability?

A

MU “micro symbol”

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4
Q

What is the term used to define a material that has a permeability larger than 1?

A

Ferromagnetic

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5
Q

What symbol is commonly used to signify inductance?

A

L

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6
Q

What supplies the AC required for Eddy Current testing?

A

Sine wave oscillator

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7
Q

All materials have a characteristic resistance to the flow of electricity. What are materials with low resistance called?

A

Conductors

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8
Q

Pure annealed copper has a resistivity of 1.7241 micro ohms per cm at 20 degrees Celsius. How do you convert this value to 100% IACS value?

A

Divide by 0.017241

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9
Q

What discontinuity is most likely to be found in a rolled bar stock?

A

Seams

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10
Q

A fatigue crack would be defined as what type of defect?

A

Service defect

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11
Q

Eddy Current testing is generally used to inspect what type of materials?

A

Conductors

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12
Q

How do Eddy Currents travel?

A

In closed paths

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13
Q

At any given moment, a spring loaded internal probe can inspect how much of the material?

A

An area roughly defined by the size of the probe coil

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14
Q

What are some products commonly tested with an encircling probe?

A

Rods, tubes and wire

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15
Q

Who discovered electromagnetic induction?

A

Michael faraday

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16
Q

What type of materials are easiest to test with Eddy Current?

A

Paramagnetic and diamagnetic

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17
Q

What type of wave is used in Eddy Current as opposed to UT?

A

Electromagnetic wave instead of a mechanical wave

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18
Q

What is the most common use of ECT?

A
  1. Crack and corrosion detecting**
  2. Material sorting
  3. Coating thickness testing
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19
Q

What is a limitation of Eddy Current?

A

Only can be conducted in electrically conductive materials

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20
Q

The depth for subsurface flaws will be limited to what?

A

10 mm or less

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21
Q

What type of method is ET?

A

Comparative

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22
Q

What is magnetic flux? And what units is it expressed in?

A

Totally number of lines of force existing in a magnetic circuit.

Units: Weber and maxwell

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23
Q

What is magnetic flux density?

A

Strength of magnetic field expressed in number of flux lines passing traversal through a unit area

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24
Q

What are the two basic types of solids?

A
  1. Crystalline (typical metals)

2. Amorphous (mainly viscous liquids)

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25
Q

How are north and south polls determined?

A

By the way the electrons are spinning

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26
Q

A high carbon content means what did permeability?

A

Low permeability

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27
Q

The flow of electrons is measured in what unit?

A

Amperes

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28
Q

Electromotive Force (EMF) is measured in what units?

A

Volts

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29
Q

What is the definition of resistance?

A

The OPPOSITION to the flow of electrons within an electric circuit

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30
Q

Electricity always takes the path of….

A

Least resistance

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31
Q

What does the number of electrons in the valence shell of an atom say about its conductivity?

A

The least number of electrons means a great conductor

Full valence shell = non-conductive

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32
Q

The symbol for resistance is what?

A

OMEGA “ohm”

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33
Q

What leads and what lags?

A

Voltage leads and current (amperage) lags

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34
Q

What type of couplant is used in ECT?

A

Magnetic couplant

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35
Q

What is an ammeter used for?

A

To indicate how many AMPS of current are flowing in an electrical circuit

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36
Q

What does a voltmeter measure?

A

EMF/volts in a circuit

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37
Q

What is an Ohm meter used to measure?

A

Electrical resistance in a circuit

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38
Q

What is electromagnetic induction?

A

Inducing an electrical current in a conductor by bringing conductor in proximity with a magnetic field

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39
Q

What is induction measured in?

A

Henries

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40
Q

What is self inductance?

A

Inductance occurring with a current containing a coil or solenoid

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41
Q

What would be the worst core material to use?

A

Diamagnetic (copper)

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42
Q

What is mutual inductance?

A

Electrical relationship that occurs between 2 electrical circuits coupled by moving magnetic fields

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43
Q

What is impedance?**

A

The TOTAL OPPOSITION to primary current flow

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44
Q

Hertz is used instead of…

A

Cycles per second

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45
Q

What is inductive reactance?

A

Effect that causes the current to lag behind the voltage

46
Q

What is the best and worst conductive?

A

Silver is the best and titanium is the worst

47
Q

What does Ohm’s Law state?

A

The resistance in a circuit is equal to the voltage divided by current

48
Q

Why can’t resistance and inductive reactance be added directly?

A

Their effect on voltage is out of phase

49
Q

What is the easiest way to combine resistance and inductive reactance?

A

Vector addition

50
Q

What does the vector direction and length represent?

A

Length represents a value and direction represents its phase relationship

51
Q

What is alpha?

A

The phase angle of the impedance vector

52
Q

As resistance decreases, what happens to impedance and phase angle?

A

Impedance value increases and phase angle decreases

53
Q

What happens to the phase angle as inductive reactance increases?

A

Phase angle increases

54
Q

Change in voltage or frequency does NOT affect what?

A

Resistance

Inductive reactance is affect by frequency changes

55
Q

Inductance value is determined by what?

A

Size, shape and number of coil turns

56
Q

Currents and magnetic fields involved are constantly changing but __________ always stays the same.

A

Phase relationship between each

57
Q

Lift off is considered what type of factor?

A

Dimensional factor

58
Q

What is the resistivity symbol and what is it expressed in?

A

Symbol is RHO (p) and it’s expressed in micro ohm centimetres

59
Q

What are the 3 basic coils?

A
  1. Probe coils (surface, flat or pancake)
  2. Bobbin
  3. Encircling
60
Q

The spring mechanism in a probe coil is used to…

A

Minimize lift off

61
Q

The coil is secured with what to prevent electrical shorts?

A

Epoxy

62
Q

What is an advantage of shielding?

A

Can perform inspection near edge of sample

63
Q

What 3 main factors cause resistance?

A
  1. Cross sectional area
  2. Length
  3. Resistivity (composition) of material
64
Q

Lift off is utilized in what?

A

Fill factor

65
Q

What happens to impedance as frequency increases?

A

Increases

66
Q

What types of defects are easiest to see when using an encircling coil?

A

Longitudinal defects

67
Q

What are the 2 types of differential coils?

A
  1. Self comparison differential

2. External reference differential

68
Q

What are 4 factors that the absolute coil method measures?

A
  1. Conductivity
  2. Permeability
  3. Dimensions
  4. Hardness
69
Q

What do hybrid coils consist of?

A

Excitation AND receiving coil

70
Q

What are 3 other names for a hybrid coil?

A
  1. Driver/pickup
  2. Through transmission
  3. Primary-secondary coil
71
Q

Phase discrimination uses angles to differentiate between what?

A

XL and R

72
Q

What are the 5 basic components?

A
  1. Excitation
  2. Modulation
  3. Signal Prep
  4. Demodulation & Analysis Control
  5. Signal Display
73
Q

Where do changes in brightness, contrast, phase rotation and screen persist happen?

A

Signal display

74
Q

Which component occurs at the primary and secondary magnetic field interface?

A

Modulation circuitry

75
Q

What component operates the power generator/oscillator?

A

Excitation

76
Q

In which component involves sampling and speed of inspection?

A

Demodulation & Analysis Control

77
Q

In what component do you balance networks and gain & dB control?

A

Signal Prep

78
Q

What is the sixth optional component?

A

Alarms & Data Recorders

79
Q

What are 4 types of displays and something brief about each?

A
  1. Flying dot - most current
  2. Needle/Meter - most basic
  3. Elliptical - CRT screen
  4. Digital/Numeric - conductivity
80
Q

Hand heat can change what variable of the the coil?

A

Resistance

81
Q

What does a armiture wear face entail?

A

Coated with a resin

82
Q

What type of probe has an adjacent collar to maintain position when the probe has been inserted inside test piece?

A

Manual rotating bore probe

83
Q

Why is a spot probe good for conductivity measuring?

A

It can’t wobble

84
Q

What does a collar help to minimize?

A

Edge effect and keeps probe at a specific height

85
Q

At what orientation are the eddy currents to the coil and magnetic field?

A

Parallel to the coil and 90 degrees to the magnetic field

86
Q

How do eddy currents flow in an encircling coil?

A

Circumferentially

87
Q

What are the 2 major differences in conductivity models?

A
  1. Signal generation:
    a) fixed OR
    b) variable
  2. Output style
    a) analog (meter) OR
    b) digital (LCD)
88
Q

With a “fixed” frequency device, what do you know?

A

The material thickness that should be inspected because you also know the depth of penetration

89
Q

How do you change the frequency in a “variable” device?

A

You can’t, it changes internally during calibration

90
Q

What is assigned a relative permeability of one?

A

Aluminum

91
Q

The phase is?

A

The direction the change occurred in

92
Q

Older versions of CRT test instruments relied on what?

A

Focused beams of electrons being emitted by a “gun”

93
Q

What is a primary advantage of a single frequency device?

A

Very portable and don’t need direct access to AC power supply

94
Q

What can you set channels for in a multi frequency device?

A

Only detects changes to a certain depth

95
Q

Multi frequency can help reduce signal loss due to what?

A

“Ganging” several coils on the same circuit

96
Q

What degree “out of phase” is a good ratio to mix a new channel on a multi-parameter device?

A

90 degrees

97
Q

What are the two options that systems can be?

A
  1. Multitasked

2. Dedicated

98
Q

What are the 3 main categories of test equipment?

A
  1. Conductivity testers
  2. Crack detectors
  3. Multi purpose
99
Q

Phase Angle Discrimination Module circuitry is used in what type of detector?

A

Multi purpose

100
Q

What did Phase Angle Discrimination Module circuitry allow CRT’s to do?

A

Detect conductivity, cracks PLUS measure thickness, hardness and heat treatment

(Old elliptical signals displays were then replaced with flying vector dot displays)

101
Q

A hybrid coil is not suited for what type of discontinuities and testing?

A

Not suitable for small surface inspections or conductivity testing

102
Q

An increase in magnetic permeability will do what to the noise?

A

Increase it

103
Q

Why would you choose an automatic bolt hole scanner over a manual one?

A

It’s spinning so fast that you won’t see deviation between layers of material (which reduces sensitivity)

104
Q

What are the 2 other names that a “flying vector dot” can be called?

A

Multipurpose or phase analysis

105
Q

What is the biggest disadvantage of a crack detector?

A

Can’t measure variables independently

106
Q

Frequencies for surface inspection is generally is what range?

A

100 kHz - 2 MHz

107
Q

What frequencies are generally used for subsurface inspections?

A

500 Hz - 10 kHz

108
Q

We want no less than what percentage of fill factor?

A

80%

109
Q

How do you calculate fill factor?

A

Diameter of part divided by diameter of coil

110
Q

How many standard depths of penetration can you see on an EC machine?

A

Five

111
Q

Which coil is the most sensitive?

A

Hybrid/Reflection coil

EC L1 (3 decks)

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