Electromagnetic Testing - Eddy Current Testing Applications Chapter 5 & 6

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Note that this is similar to surface testing except that, for tubes, the tube diameter is the relevant parameter, not the coil diameter as for surface testing. The reason for this is that it is actually the diameter of the eddy currents that is the significant parameter. For surface testing with standard probes, the strongest eddy currents flow immediately beneath the coil, so the diameter of the eddy currents is essentially the same as the coil diameter. For tubes, the eddy currents flow in the tube and so their diameter is essentially that of the tube. Charlie Chong/ Fion Zhang
The basis for the selection of test frequency is the same as that for the selection of frequency for surface testing for subsurface flaws or thickness measurement. The frequency should be low enough so that the eddy current intensity at the outside surface is relatively high, but low enough to give a relatively high degree of phase separation between signals from different thicknesses. Therefore, the normal operating frequency should be the frequency which gives a f 90 separation between the signals from a shallow inside surface flaw and a shallow outside surface flaw. However, because of the difference in configuration between surface testing and tube testing, this frequency is that at which the tube wall thickness equals approximately 1.1 standard depths of penetration. f 90 =530/(t 2 σ) (5.4) Where: f 90 = the operating frequency (kHz), t = the tube wall thickness (mm) , and σ = the conductivity of the test material (% IACS) 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
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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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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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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
Page 165 and 166: FIG. 5.26. Part of the display show
Page 167 and 168: 5.1.7.5 Measurement procedure (a) C
Page 169 and 170: (j) (k) Alternatively, if the measu
Page 171 and 172: 5.1.8 Thickness measurement of cond
Page 173 and 174: FIG. 5.28 shows the impedance curve
Page 175 and 176: 5.2.1.1 Tube testing probes and the
Page 177 and 178: The coil(s) in bobbin probes produc
Page 179 and 180: Bobbin probe eddy current the orien
Page 181 and 182: To obtain adequate sensitivity to f
Page 183 and 184: As for surface testing, the test se
Page 185: 5.2.1.2 Selection of test frequency
Page 189 and 190: FIG. 5.32. Impedance diagram showin
Page 191 and 192: 5.2.1.4 Flaw signals from absolute
Page 193 and 194: At f 90 , all flaw signals appear i
Page 195 and 196: 5.2.1.5 Absolute probe signals from
Page 197 and 198: Wobble - A-go-go Charlie Chong/ Fio
Page 199 and 200: Discussion Topic- Discuss on the fo
Page 201 and 202: (c) Ferromagnetic conditions at the
Page 203 and 204: A signal from a ferromagnetic condi
Page 205 and 206: FIG. 5.36 shows the signal from a f
Page 207 and 208: Tube Sheet: Baffle Plate Charlie Ch
Page 209 and 210: Tube Sheet: Baffle Plate Charlie Ch
Page 211 and 212: (e) Non-ferromagnetic support or ba
Page 213 and 214: This signal will be modified by any
Page 215 and 216: (f) Ferromagnetic support or baffle
Page 217 and 218: FIG. 5.37. The signals from a carbo
Page 219 and 220: FIG. 5.38. Absolute and differentia
Page 221 and 222: 5.2.1.7 Correlating flaw depth and
Page 223 and 224: FIG. 5.39. Graph showing the correl
Page 225 and 226: 5.2.1.8 Correlating flaw depth and
Page 227 and 228: 5.2.2 Bar and tube testing using en
Page 229 and 230: Discussion Topic: This means that p
Page 231 and 232: FIG. 5.41. The eddy current intensi
Page 233 and 234: 5.2.2.2 Selection of frequency For
Page 235 and 236: 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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