Electromagnetic Testing - Eddy Current Testing Applications Chapter 5 & 6

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Sliding probes give a signal as they pass over a fastener, but if a crack or corrosion is present, a characteristically different and more complex signal is produced. For multilayered structures, characteristically different signals are given for cracks extending along the row of fasteners and for cracks extending normal to the row. In addition, the signals are different for cracks in each layer. Interpretation is therefore done by recognition of the characteristic pattern of the signal from each condition, rather than by analysis of the signal. An appropriate reference sample is essential so the operator can become familiar with the signal patterns. An experienced operator can test a row of fasteners much more rapidly than when using a ring or other type of probe. Multi-frequency testing can be used to eliminate signals from fasteners, so that the only signals displayed will be flaw signals. The use of multi-frequency inspection for the detection of subsurface cracks and corrosion is becoming more common in use. Two applications of multi-frequency is to, separate the variables due to skin separation and corrosion at similar depths into the material, and to inspect beneath installed fasteners for cracks where the variables caused by the fastener can be eliminated. Charlie Chong/ Fion Zhang
5.1.4.4 Reference samples Reference samples should be as far as possible identical to the parts to be tested. They should be of the same material (or material of the same conductivity) and thickness as the parts to be tested, and, if a multilayered part is to be tested, each layer should have the same material (or conductivity), thickness, and separation as the test parts. In addition, they should have real or artificial flaws simulating the type sought and at the locations and orientations at which flaws are required to be detected. Corrosion may be simulated by drilling shallow poles, using either a standard or flat-bottom drill bit. Alternatively, milled slots may be used. Cracks may be simulated by spark-eroded slots, or by narrow saw cuts. 5.1.4.5 Test procedure The test procedures are generally similar to those for detecting surface flaws. Charlie Chong/ Fion Zhang
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Electromagnetic Testing - Eddy Curr
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http://igor113.livejournal.com/5121
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Charlie Chong/ Fion Zhang
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同桌的你 Charlie Chong/ Fion
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Fion Zhang at Shanghai 2014/Novembe
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5.0 APPLICATIONS 5.1. Surface testi
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FIG. 5.1. Schematic diagram showing
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Eddy current field extends laterall
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Depth of Penetration & Current Dens
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Please also comment on this illustr
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FIG. 5.2 Directional properties of
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The depth of surface flaws (the dis
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Case Discussion: The corresponding
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5.1.2.2 Types of standard surface t
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(b) Spot probes Spot probes are pro
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FIG. 5.6. A spring loaded probe. Ch
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FIG. 5.5. (a) The core and coil of
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Although it is usually evident by i
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FIG. 5.7. Effects of cores and shie
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5.1.2.3 Other types of surface prob
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FIG. 5.8. A tangential probe showin
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Compare vertical probe with the FIG
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Discussion Topic- Why in the tangen
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FIG. 5.9. A gap (horseshoe) probe.
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Horseshoe probe - maximum sensitivi
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A gap (horseshoe) probe - Magnetic
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5.1.3 Testing for surface-breaking
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Eddy Current Testing over painted s
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Testing Frequency: • 200 kHz to 5
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If the fastener is not removed, cra
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Following are some examples of spec
Page 63 and 64: Threaded Probe Charlie Chong/ Fion
Page 65 and 66: Eddy Current Testing- Hole fatigue
Page 67 and 68: Hand operated or manual hole probes
Page 69 and 70: If motor driven probes are to be us
Page 71 and 72: FIG. 5.12. Typical rotating hole pr
Page 73 and 74: Bolt hole probes Charlie Chong/ Fio
Page 75 and 76: (c) Aircraft wheels: Aircraft wheel
Page 77 and 78: Aircraft wheels Charlie Chong/ Fion
Page 79 and 80: Automated equipment which will perf
Page 81 and 82: Tangential probe - used in electron
Page 83 and 84: FIG. 5.3 Charlie Chong/ Fion Zhang
Page 85 and 86: Although these blocks can be used f
Page 87 and 88: (f) Scan over the appropriate disco
Page 89 and 90: 4.1.3.5 Testing in-service welds in
Page 91 and 92: FIG. 5.14 a. Typical weld testing p
Page 93 and 94: Since the eddy currents produced at
Page 95 and 96: For testing, the instrument should
Page 97 and 98: Charlie Chong/ Fion Zhang
Page 101 and 102: Keywords: Typically, the magnetic f
Page 103 and 104: Multilayer structures - of flaws in
Page 105 and 106: 5.1.4.2 Probe and frequency selecti
Page 107 and 108: An acceptable compromise which give
Page 109 and 110: FIG. 5.15. Eddy current signals fro
Page 111 and 112: FIG. 5.16. Spot probes testing a la
Page 113: ) Sliding probes Sliding probes are
Page 117 and 118: 5.1.5 Conductivity testing and mate
Page 119 and 120: 5.1.5.3 Factors which affect conduc
Page 121 and 122: (b) Alloying. Dissolving any elemen
Page 123 and 124: (d) Cold work Plastic deformation o
Page 125 and 126: (b) Test part thickness The conduct
Page 127 and 128: (c) Edge effect Probes dedicated to
Page 129 and 130: 5.1.5.6 Frequency selection The fre
Page 131 and 132: FIG. 5.19. Impedance diagrams and t
Page 135 and 136: The Characteristic Parameter (PC) i
Page 137 and 138: Example: Calculate the optimum freq
Page 139 and 140: When eddy current conductivity mete
Page 141 and 142: (d) Perform conductivity measuremen
Page 143 and 144: 5.1.5.9 Heat treatment of aluminium
Page 145 and 146: 5.1.5.10 Sorting materials by magne
Page 147 and 148: 5.1.6 Thickness measurement of non-
Page 149 and 150: FIG. 5.22. Methods of obtaining sta
Page 151 and 152: Non-conducting coating thickness me
Page 153 and 154: A typical operating frequency to me
Page 155 and 156: 5.1.6.4 Measurement procedure (a) C
Page 157 and 158: (k) (l) Alternatively, if the measu
Page 159 and 160: 5.1.7 Thickness measurement of cond
Page 161 and 162: 5.1.7.2 Probe and frequency selecti
Page 163 and 164: 5.1.7.3 Signals from variations in
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FIG. 5.26. Part of the display show
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5.1.7.5 Measurement procedure (a) C
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(j) (k) Alternatively, if the measu
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5.1.8 Thickness measurement of cond
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FIG. 5.28 shows the impedance curve
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5.2.1.1 Tube testing probes and the
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The coil(s) in bobbin probes produc
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Bobbin probe eddy current the orien
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To obtain adequate sensitivity to f
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As for surface testing, the test se
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5.2.1.2 Selection of test frequency
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The basis for the selection of test
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FIG. 5.32. Impedance diagram showin
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5.2.1.4 Flaw signals from absolute
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At f 90 , all flaw signals appear i
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5.2.1.5 Absolute probe signals from
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Wobble - A-go-go Charlie Chong/ Fio
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Discussion Topic- Discuss on the fo
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(c) Ferromagnetic conditions at the
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A signal from a ferromagnetic condi
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FIG. 5.36 shows the signal from a f
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Tube Sheet: Baffle Plate Charlie Ch
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Tube Sheet: Baffle Plate Charlie Ch
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(e) Non-ferromagnetic support or ba
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This signal will be modified by any
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(f) Ferromagnetic support or baffle
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FIG. 5.37. The signals from a carbo
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FIG. 5.38. Absolute and differentia
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5.2.1.7 Correlating flaw depth and
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FIG. 5.39. Graph showing the correl
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5.2.1.8 Correlating flaw depth and
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5.2.2 Bar and tube testing using en
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Discussion Topic: This means that p
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FIG. 5.41. The eddy current intensi
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5.2.2.2 Selection of frequency For
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Associated with the f/f g concept i
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The optimum operating point depends
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5.2.2.3 Specific test applications
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(c) Flaw detection Surface flaw ind
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5.2.2.4 Testing ferromagnetic bars
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Ferromagnetic material can be teste
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5.3.2 Equipment Most modern eddy cu
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These standards cover such topics a
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The following example is taken from
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The content of written procedures d
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Charlie Chong/ Fion Zhang
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6.5. Records and reports 6.5.1 Test
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6.5.2 Test reports A formal test re
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Records Charlie Chong/ Fion Zhang
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Calibration Standard A test standar
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Coil, probe A small coil or coil as
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Discontinuity Artificial Reference
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Electromagnetic Testing That non de
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IACS σ IACS . International Anneal
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Material, Diamagnetic A material ha
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Parameter A material property or in
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Phase Lag β (beta), radians or deg
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Resistivity ρ (ro), microhm centim
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Signal A change in eddy current ins
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Space Station Charlie Chong/ Fion Z
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Charlie https://www.yumpu.com/en/br
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Good Luck! Charlie Chong/ Fion Zhan
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