Electromagnetic Testing - Eddy Current Testing Applications Chapter 5 & 6

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Eddy Currents A closed loop alternating current flow induced in a conductor by a varying magnetic field. Eddy Current Method An electromagnetic NDT method based on the process of inducing electrical currents into a conductive material and observing the interaction between the currents and the material. Eddy-current Testing A non destructive testing method in which eddy-current flow is induced in the test object. Changes in the flow caused by variations in the specimen are reflected into a nearby coil or coils for subsequent analysis by suitable instrumentation and techniques. Edge Effect Signal obtained when a surface probe approaches the sample’s edge or geometric boundaries that makes it impractical to apply electromagnetic test methods to the associated regions of the sample.. Effective Depth of Penetration EDP Depth at which eddy current density drops off to 5% of the surface density. Charlie Chong/ Fion Zhang
Electromagnetic Testing That non destructive test method for engineering materials, including magnetic materials, which use electromagnetic energy having frequencies less than those of visible light to yield information regarding the quality of the tested material. End Effect Signal obtained when an internal or encircling probe approaches the end of a tube or rod (similar to edge effect). Encircling probe (Coil) Also referred to as a feed through coil. A probe which completely surrounds test material; can be absolute or differential. Feed Through Coil see encircling probe. Ferrite Ferromagnetic oxide material. Used for cores in high frequency transformers. Flaw A defect. Ferromagnetic A material with a relative magnetic permeability greater than 1.0 Fill Factor η (eta), dimensionless. The ratio of the square of the diameter of a cylindrical test specimen to the square of the average diameter of the encircling coil. It is a measure of coupling between the coil and test object. Fraction of the test coil area filled by the test specimen. 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
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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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Page 221 and 222: 5.2.1.7 Correlating flaw depth and
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Page 227 and 228: 5.2.2 Bar and tube testing using en
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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: Discontinuity Artificial Reference
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
Page 285 and 286: Charlie https://www.yumpu.com/en/br
Page 287: Good Luck! Charlie Chong/ Fion Zhan
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Electromagnetic Testing - Eddy Current Testing Applications Chapter 5 & 6

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