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27 Cards in this Set
- Front
- Back
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What eight conditions affect interpretation?
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1. acceptance/rejection criteria 2. surface damage
3. edge effect 4. layered materials 5. rate of deflection/ response 6. probe wobble 7. crack size 8. scanning speed |
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What cannot be directly measured in most cases by eddy current inspections?
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depth of flaws detected
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What must the signal of the flaw be compared to?
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the signal of the standard
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What must be establish prior to any test?
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the relationship between response of a standard and the maximum allowable flaw size
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Inspection for cracks can often be complicated by what?
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the presence of various types of damage like scratches, gouges, pitting and metal smearing
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What three thing may be required if there is severe damage?
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1. refinishing the before inspection
2. lower sensitivity must be used 3. alternate method |
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What is metal smearing?
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the flowing of surface metal
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How is metal smearing caused?
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from machining, abrasion, during service, or by deformation during assembly or dis-assembly
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If deep enough what may result in signals similar to cracks?
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scratches gouges and pitting
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How are edge of a part crack represented?
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as an infinitely large crack and consequently produce strong signals
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what problem is encounters when inspecting edges for cracks?
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the separation of crack response from the strong edge signal
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what are the two approaches to inspect part edge for cracks?
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1. null the instrument with the probe at the edge of the part. Then scan maintaining probe distance for the edge.
2. utilize a shielded probe which minimizes edge effect |
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rapidity of response is a means of what?
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evaluating indications
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what kind of deflection /response do cracks give?
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quick rapid deflection/response
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what causes slow gradual change in meters reading or an etching effect?
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variations in conductivity, gradual thickness changes, out of round holes, variations in surface to probe spacing
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What is probe wobble?
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when using a surface/pencil probe with a meter type unit it is difficult to maintain the same angle with respect to the inspection surface
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the degree of defection depends on what?
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shape and diameter of the probe
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what can be used to minimize probe wobble?
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guide blocks
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crack are considered to have what?
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three dimensions: length, width and depth
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The length of the flaw can be related to what?
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the distance over which a signal above specified levels is obtained
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width also influences what?
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the magnitude of an indication
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depth can only be what?
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approximately determined
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what is the greatest interest of crack dimension?
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depth and is the most difficult to measure
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estimation of crack size should only be applied when?
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situations where crack geometry is similar and considered data has been developed relating crack size to eddy current response
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because of variable difficult to measure estimation of crack size can only be performed when
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1. extensive preparation
2. the same individual test system |
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scanning speeds should not exceed what
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1/4" to 1/2" per second
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As scanning speed is increased what happens to the crack response?
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the damping effect reduces the magnitude
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