Electromagnetic Testing - Eddy Current Testing Applications Chapter 5 & 6

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This leads to the possibility of the support signal being rotated sufficiently clockwise to appear above the horizontal, at an angle similar to that for an inside surface flaw. One condition when this is possible is the deposition of copper on the outside surface of a tube. Copper can be leached out of copper alloys and re-deposited on tube surfaces, particularly adjacent to tube supports. Even very thin copper deposits give a strong signal because of the high conductivity of copper. If this condition is suspected, retesting at a lower frequency, for example ½f 90 , should be carried out. This will reduce the phase shift of the signal so that it appears in the lower left quadrant, easily distinguishable from inside surface flaws. Charlie Chong/ Fion Zhang
(f) Ferromagnetic support or baffle plates The signal from ferromagnetic support or baffle plates is complex because it combines an increase of thickness, a phase shifted change of conductivity, and a phase shifted increase in permeability. The first two effects give a signal similar to that of a non-ferromagnetic baffle plate, and move the spot downwards and to the left. In fact, the signal from a ferromagnetic baffle plate commences in much the same way, because there is little magnetic response to the very weak magnetic field produced initially in the baffle plate. However, as the probe gets closer to the baffle plate, the magnetic effect increases, and the spot moves sideways to the right, as was the case for a ferromagnetic condition at the outside surface. The signal therefore usually has a distinct bend in it, giving rise to a characteristic hooked or curved signal (see FIG. 5.36). 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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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
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 and 186: 5.2.1.2 Selection of test frequency
Page 187 and 188: The basis for the selection of test
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: This signal will be modified by any
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
Page 237 and 238: The optimum operating point depends
Page 239 and 240: 5.2.2.3 Specific test applications
Page 241 and 242: (c) Flaw detection Surface flaw ind
Page 243 and 244: 5.2.2.4 Testing ferromagnetic bars
Page 245 and 246: Ferromagnetic material can be teste
Page 247 and 248: 5.3.2 Equipment Most modern eddy cu
Page 249 and 250: These standards cover such topics a
Page 251 and 252: The following example is taken from
Page 253 and 254: The content of written procedures d
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Page 257 and 258: 6.5. Records and reports 6.5.1 Test
Page 259 and 260: 6.5.2 Test reports A formal test re
Page 261 and 262: Records Charlie Chong/ Fion Zhang
Page 263 and 264: 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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