Electromagnetic Testing - Eddy Current Testing Applications Chapter 5 & 6

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These are invariably differential because absolute probes would show excessive lift-off noise. In addition differential probes will eliminate signals from the end and interfaces within the hole. Differential probes are essentially cylinders with the two coils near one end, side by side circumferentially with their axis at right angles to the probe axis (similarly to manual probes). The probe diameter is normally slightly smaller than the hole diameter (commonly 0.2 mm) to allow ease of rotation. Alternatively, split, differential, probes similar to manual probes are sometimes used to allow for variations in hole size. Charlie Chong/ Fion Zhang
If motor driven probes are to be used, the eddy current instrument must support this facility. The displays are the normal vector point display, and also a time base display which shows the vertical amplitude of the signals against time, the period of time displayed by the screen being automatically adjusted to correspond to a complete rotation of the probe. The position of a flaw signal along the time base display then represents the angular position of the flaw around the hole with respect to a reference mark on the probe motor housing. When setting up, a signal is obtained on the vector spot display from a discontinuity in a hole in a test block, the material and hole diameter being the same as those being tested. This signal is rotated until it is vertical and the amplitude set, typically 80% full screen height, the signal is then rotated to 30° from vertical, clockwise for ferromagnetic material and anticlockwise for non ferrous materials (FIG. 5.12a). A tight fatigue crack will then appear vertical as in FIG. 5.12b. Keywords: ■ Normal vector display ■ Time based display 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
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
Page 65 and 66: Eddy Current Testing- Hole fatigue
Page 67: Hand operated or manual hole probes
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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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 and 114: ) Sliding probes Sliding probes are
Page 115 and 116: 5.1.4.4 Reference samples Reference
Page 117 and 118: 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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