Electromagnetic Testing - Eddy Current Testing Applications Chapter 5 & 6

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<strong>Eddy</strong> currents (I, red) induced in a conductive metal plate (C) as it moves to right under a magnet (N). The magnetic field (B, green) is directed down through the plate. From Lenz's law the increasing field at the leading edge of the magnet (left) induces a counterclockwise current, which creates its own magnetic field (left blue arrow) directed up, which opposes the magnet's field, producing a retarding force. Similarly, at the trailing edge of the magnet (right), a clockwise current and downward counterfield is created (right blue arrow) also producing a retarding force. Charlie Chong/ Fion Zhang http://en.wikipedia.org/wiki/<strong>Eddy</strong>_current
Horseshoe probe - maximum sensitivity to surface flaws occurs if the flaw is parallel to magnetic line of force. Charlie Chong/ Fion Zhang
Page 1 and 2: Electromagnetic Testing - Eddy Curr
Page 3 and 4: http://igor113.livejournal.com/5121
Page 5 and 6: Charlie Chong/ Fion Zhang
Page 7 and 8: 同桌的你 Charlie Chong/ Fion
Page 9 and 10: Fion Zhang at Shanghai 2014/Novembe
Page 11 and 12: 5.0 APPLICATIONS 5.1. Surface testi
Page 13 and 14: FIG. 5.1. Schematic diagram showing
Page 15 and 16: Eddy current field extends laterall
Page 17 and 18: Depth of Penetration & Current Dens
Page 19 and 20: Please also comment on this illustr
Page 21 and 22: FIG. 5.2 Directional properties of
Page 23 and 24: The depth of surface flaws (the dis
Page 25 and 26: Case Discussion: The corresponding
Page 27 and 28: 5.1.2.2 Types of standard surface t
Page 29 and 30: (b) Spot probes Spot probes are pro
Page 31 and 32: FIG. 5.6. A spring loaded probe. Ch
Page 33 and 34: FIG. 5.5. (a) The core and coil of
Page 35 and 36: Although it is usually evident by i
Page 37 and 38: FIG. 5.7. Effects of cores and shie
Page 39 and 40: 5.1.2.3 Other types of surface prob
Page 41 and 42: FIG. 5.8. A tangential probe showin
Page 43 and 44: Compare vertical probe with the FIG
Page 45 and 46: Discussion Topic- Why in the tangen
Page 47: FIG. 5.9. A gap (horseshoe) probe.
Page 51 and 52: A gap (horseshoe) probe - Magnetic
Page 53 and 54: 5.1.3 Testing for surface-breaking
Page 55 and 56: Eddy Current Testing over painted s
Page 57 and 58: Testing Frequency: • 200 kHz to 5
Page 59 and 60: If the fastener is not removed, cra
Page 61 and 62: 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
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Charlie Chong/ Fion Zhang
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Keywords: Typically, the magnetic f
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Multilayer structures - of flaws in
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5.1.4.2 Probe and frequency selecti
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An acceptable compromise which give
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FIG. 5.15. Eddy current signals fro
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FIG. 5.16. Spot probes testing a la
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) Sliding probes Sliding probes are
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5.1.4.4 Reference samples Reference
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5.1.5 Conductivity testing and mate
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5.1.5.3 Factors which affect conduc
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(b) Alloying. Dissolving any elemen
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(d) Cold work Plastic deformation o
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(b) Test part thickness The conduct
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(c) Edge effect Probes dedicated to
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5.1.5.6 Frequency selection The fre
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FIG. 5.19. Impedance diagrams and t
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The Characteristic Parameter (PC) i
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Example: Calculate the optimum freq
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When eddy current conductivity mete
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(d) Perform conductivity measuremen
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5.1.5.9 Heat treatment of aluminium
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5.1.5.10 Sorting materials by magne
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5.1.6 Thickness measurement of non-
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FIG. 5.22. Methods of obtaining sta
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Non-conducting coating thickness me
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A typical operating frequency to me
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5.1.6.4 Measurement procedure (a) C
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(k) (l) Alternatively, if the measu
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5.1.7 Thickness measurement of cond
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5.1.7.2 Probe and frequency selecti
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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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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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Electromagnetic Testing - Eddy Current Testing Applications Chapter 5 & 6

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