Electromagnetic Testing - Eddy Current Testing Applications Chapter 5 & 6

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The eddy current intensity is maximum immediately below the coil windings, and decreases linearly to zero at the centre of the coil. In addition, except for shielded probes (discussed below), the eddy current field extends laterally for some distance away from the coil, the distance increasing as the coil diameter increases and as the depth of penetration increases. Therefore, large diameter, low frequency coils, which show the greatest depth of penetration, also show the greatest lateral eddy current field. Flaws can be detected only if they distort the flow of eddy currents. This means that cracks and similar flaws normal to the test surface in any direction can be detected, but flaws parallel to the test surface, like laminations, cannot be detected. flaws normal maximum detectability flaws parallel minimum detectability Charlie Chong/ Fion Zhang
<strong>Eddy</strong> current field extends laterally for some distance away from the coil, the distance increasing as the coil diameter increases and as the depth of penetration increases. <strong>Eddy</strong> current field extends laterally 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: FIG. 5.1. Schematic diagram showing
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 and 48: FIG. 5.9. A gap (horseshoe) probe.
Page 49 and 50: Horseshoe probe - maximum sensitivi
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
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Eddy Current Testing- Hole fatigue
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Hand operated or manual hole probes
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If motor driven probes are to be us
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FIG. 5.12. Typical rotating hole pr
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Bolt hole probes Charlie Chong/ Fio
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(c) Aircraft wheels: Aircraft wheel
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Aircraft wheels Charlie Chong/ Fion
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Automated equipment which will perf
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Tangential probe - used in electron
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FIG. 5.3 Charlie Chong/ Fion Zhang
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Although these blocks can be used f
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(f) Scan over the appropriate disco
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4.1.3.5 Testing in-service welds in
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FIG. 5.14 a. Typical weld testing p
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Since the eddy currents produced at
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For testing, the instrument should
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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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