Electromagnetic Testing - Eddy Current Testing Applications Chapter 5 & 6

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The limit frequency is not the test frequency, nor in itself does it have any practical significance for eddy current testing. Its importance lies in the ratio of the test frequency (f) to f g , which allows determination of the position of the operating point on the impedance curve. This ratio, f/f g , is therefore the equivalent to the Characteristic Parameter, and is used in the same way by referring to an impedance curve showing values of f/f g (FIG. 5.42). It should be noted, however, that the value of f/f g at a particular point on the impedance curve does not equal the value of PC at the corresponding location (compare FIG. 5.42 with FIG. 5.20). The value of f/f g may be calculated for nonferromagnetic materials using the following formula, which is derived from Forster's but with more practical units. f/f g = (fdσ)/873 (5.8) Where: f = the operating frequency (kHz), d = bar diameter (mm), and σ = conductivity (% IACS). Charlie Chong/ Fion Zhang
Associated with the f/f g concept is the law of similarity. This may be stated that, if two test bars are tested at the same f/f g ratio, the geometrical distribution and the eddy current density are the same. Thus, for instance, if two bars, which may differ in diameter, conductivity, and permeability, both have flaws of the same depth and width measured as a percentage of the bar diameter, the eddy current signals will be identical. This law can be helpful in that experience with bars of one material or diameter can assist in setting up to test and to interpret signals from bars of a different material or diameter. The law of similarity also applies to surface testing, using the Characteristic Parameter, but it is more commonly used to test bars and tubes during manufacture. 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
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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
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 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: 5.2.2.2 Selection of frequency For
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
Page 265 and 266: Coil, probe A small coil or coil as
Page 267 and 268: Discontinuity Artificial Reference
Page 269 and 270: Electromagnetic Testing That non de
Page 271 and 272: IACS σ IACS . International Anneal
Page 273 and 274: Material, Diamagnetic A material ha
Page 275 and 276: Parameter A material property or in
Page 277 and 278: Phase Lag β (beta), radians or deg
Page 279 and 280: Resistivity ρ (ro), microhm centim
Page 281 and 282: Signal A change in eddy current ins
Page 283 and 284: 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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