1、Designation: E 1004 02Standard Practice forDetermining Electrical Conductivity Using theElectromagnetic (Eddy-Current) Method1This standard is issued under the fixed designation E 1004; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revisio
2、n, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This practice covers a procedure for determining theelectrical conductivity of nonmagnetic metals usin
3、g the elec-tromagnetic (eddy-current) method. The procedure has beenwritten primarily for use with commercially available directreading electrical conductivity instruments. General purposeeddy-current instruments may also be used for electricalconductivity measurements but will not be addressed in t
4、hispractice.1.2 This practice is applicable to metals that have either aflat or slightly curved surface and includes metals with orwithout a thin nonconductive coating.1.3 Eddy-current determinations of electrical conductivitymay be used in the sorting of metals with respect to variablessuch as type
5、 of alloy, aging, cold deformation, heat treatment,effects associated with non-uniform heating or overheating,and effects of corrosion. The usefulness of the examinations ofthese properties is dependent on the amount of electricalconductivity change caused by a change in the specificvariable.1.4 Ele
6、ctrical conductivity, when evaluated with eddy-current instruments, is usually expressed as a percentage of theconductivity of the International Annealed Copper Standard(IACS). The conductivity of the Annealed Copper Standard isdefined to be 0.583108S/m (100 % IACS) at 20C.1.5 The values stated in S
7、I units are regarded as standard.1.6 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitat
8、ions prior to use.2. Referenced Documents2.1 ASTM Standards:B 193 Test Method for Resistivity of Electrical ConductorMaterials2E 105 Practice for Probability Sampling of Materials3E 122 Practice for Calculating Sample Size to Estimate,with a Specified Tolerable Error, the Average for Charac-teristic
9、 of a Lot or Process3E 543 Practice for Agencies Performing NondestructiveTesting4E 1316 Terminology for Nondestructive Examinations42.2 ASNT Documents:Recommended Practice SNT-TC-1A for Personnel Qualifi-cation and Certification In Nondestructive Testing5ANSI/ASNT-CP-189 Standard for Qualification
10、and Certi-fication of NDT Personnel52.3 AIA Document:NAS410 Certification and Qualification of NondestructiveTesting Personnel63. Terminology3.1 DefinitionsDefinitions of terms relating to eddy-current examination are given in Terminology E 1316.3.2 Definitions of Terms Specific to This Standard:3.2
11、.1 temperature coeffcientthe fractional or percentagechange in electrical conductivity per degree Celsius change intemperature.4. Significance and Use4.1 Absolute probe coil methods, when used in conjunctionwith reference standards of known value, provide a means fordetermining the electrical conduc
12、tivity of nonmagnetic mate-rials.4.2 Electrical conductivity of a sample can be used as ameans of determining: (1) type of metal or alloy, (2) type ofheat treatment (for aluminum this evaluation should be used inconjunction with a hardness examination), (3) aging of thealloy, (4) effects of corrosio
13、n, and (5) heat damage.1This practice is under the jurisdiction of ASTM Committee E07 on Nonde-structive Testing and is the direct responsibility of Subcommittee E07.07 onElectromagnetic Method.Current edition approved July 10, 2002. Published September 2002. Originallypublished as E 1004 91. Last p
14、revious edition E 1004 99.2Annual Book of ASTM Standards, Vol 02.03.3Annual Book of ASTM Standards, Vol 14.02.4Annual Book of ASTM Standards, Vol 03.03.5Available from American Society for Nondestructive Testing 1711 ArlingatePlaza, PO Box 28518, Columbus, OH 4322805186Available from Aerospace Indus
15、tries Association of America, Inc., 1250 Eye St.NW, Washington, D.C. 20005.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.5. Limitations5.1 The ability to accomplish the examinations included in4.2 is dependent on the conductivity c
16、hange caused by thevariable of interest. If the conductivity is a strong function ofthe variable of interest, these examinations can be veryaccurate. In some cases, however, changes in conductivity dueto changes in the variable of interest may be too small to detect.The ability to isolate the variab
17、le of interest from othervariables is also important. For example, if the alloy is notknown, the heat treatment cannot be determined from conduc-tivity alone.5.2 The curve relating temper and conductivity of an alu-minum alloy should be known before attempting to interpretconductivity measurements.
18、For example, knowing alloy andheat treatment, the adequacy of the heat treatment can beestimated.6. Basis of Application6.1 Personnel Qualification:6.1.1 If specified by the contractual agreement, personnelperforming examinations to this standard shall be qualified inaccordance with a nationally or
19、internationally recognizedNDT personnel qualification standard such as ANSI/ASNT-CP-189, SNT-TC-1A, NAS-410, or a similar document andcertified by the employer or certifying agency, as applicable.The practice of the standard used and its applicable revisionshall be specified in the contractual agree
20、ment between theusing parties.6.1.2 Qualification and certification for personnel may bereduced when the following conditions are met:6.1.2.1 The examination will be limited to operating equip-ment, which displays the results in percent IACS.6.1.2.2 A specific procedure is used that is approved by a
21、certified Level III in accordance with 6.1.1.6.1.2.3 Documentation of training and examination is per-formed to ensure that personnel are qualified. Qualified per-sonnel are those who have demonstrated, by passing writtenand practical proficiency tests, that they possess the skills andjob knowledge
22、necessary to ensure acceptable workmanship.6.2 Qualification of Nondestructive AgenciesIf specifiedin the contractual agreement, NDT agencies shall be qualifiedand evaluated as described in Practice E 543. The applicableedition of Practice E 543 shall be specified in the contractualagreement.6.3 The
23、 following additional items are subject to contractualagreement between the parties using or referencing this stan-dard.6.3.1 Timing of Examination6.3.2 Extent of Examination6.3.3 Reporting Criteria/Acceptance Criteria6.3.4 Reexamination of Repaired/Reworked Items7. Variables Influencing Accuracy7.1
24、 Consider the influence of the following variables toensure an accurate evaluation of electrical conductivity.7.1.1 TemperatureThe instrument, probe, reference stan-dards, and parts being examined shall be stabilized as ambienttemperature prior to conductivity evaluation. When possible,examinations
25、should be performed at room temperature (typi-cally 70 6 15F).7.1.2 Probe Coil to Metal CouplingVariations in theseparation between the probe coil and the surface of the sample(lift-off) can cause large changes in the instrument outputsignal. Instruments vary widely in sensitivity due to lift-off,an
26、d some have adjustments for minimizing it. Standardize theinstrument with values at least as large as the known lift-off.Surface curvature may also affect the coupling. (Consult themanufacturers manual for limitations on lift-off and surfacecurvature).7.1.3 Edge EffectExaminations should not be perf
27、ormedwithin two coil diameters of any discontinuity, such as an edge,hole, or notch. Use a shielded probe if examinations closer tothe geometric features are required.7.1.4 Uniformity of SampleVariations in material proper-ties are common and can be quite large. Discontinuities orinhomogeneities in
28、the metal near the position of the probe coilwill change the value of the measured conductivity.7.1.5 Surface ConditionsSurface treatments and rough-ness can affect the measured conductivity value of a material.Cladding also has a pronounced effect on conductivity readingsas compared to the base met
29、al values. Procedures for deter-mining the electrical conductivity of clad materials are notaddressed in this practice. The sample surface should be cleanand free of grease.7.1.6 Instrument StabilityInstrument drift, noise, and non-linearities can cause inaccuracies in the measurement.7.1.7 Nonuniqu
30、e Conductivity ValuesIt should be notedthat two different alloys can have the same conductivity. Thus,in some cases, a measurement of conductivity may notuniquely characterize an alloy. Overheated parts and someheat-treated aluminum alloys are examples of materials thatmay have identical conductivit
31、y values for different heattreatments or tempers.7.1.8 Sample ThicknessEddy-current density decreasesexponentially with depth (that is, distance from the metalsurface). The depth at which the density is approximately 37 %(1/e) of its value at the surface is called the standard depth ofpenetration d.
32、 Calculate the standard depth of penetration fornonmagnetic materials using one of the following formulas:d5503.3=fsm!, s51/r (1)d5K=1/r! frcm!, K.50, r51 (2)d51=psfm!, 5or, o54p31027, r51 (3)where:s = electrical conductivity of the sample in S/m,r = electrical conductivity in Vm, andf = examination
33、 frequency in Hz.These formulas are for nonmagnetic materials when therelative permeability, rel=1. If the thickness of the sample andthe reference standards is at least 2.6d, the effect of thicknessE1004022is negligible. Smaller depths of penetration (higher frequen-cies) may be desirable for measu
34、ring surface effects. Depth ofpenetration is also a function of coil diameter. The change dueto coil diameter variation is not considered in the aboveequation. Consult the instrument manufacturer if penetrationdepth appears to be a source of error in the measurement.8. Apparatus8.1 Electronic Appara
35、tusThe electronic apparatus shallbe capable of energizing the probe coil with alternatingcurrents of suitable frequencies and power levels and shall becapable of sensing changes in the measured impedance of thecoil. Equipment may include any suitable signal-processingdevice (phase discriminator, fil
36、ter circuits, and so forth). Theoutput may be displayed in either analog or digital readouts.Readout is normally in percent IACS although it may be scaledfor readings in other units. Additional apparatus, such ascomputers, plotters, or printers, or combination thereof, may beused in the recording of
37、 data.8.2 ProbeProbe coil designs combine empirical andmathematical design methods to choose appropriate combina-tions of characteristics. Many instruments use one probe coil.In instruments with several coils, the difference between coilsis the coil geometry. For most conductivity instruments, theca
38、ble connecting the coil to the instrument is an integral part ofthe measuring circuit and the cable length should not bemodified without consulting the instrument manufacturer ormanual.8.2.1 The probe coil should be designed to minimize theeffect of heat transfer from hand to coil.8.2.2 Some probe c
39、oils are designed to permit measure-ments closer than two coil diameters from an edge or discon-tinuity.8.3 Mechanical handling apparatus for feeding the samplesor moving the probe coil, or both, may be used to automate aspecific measurement.9. Standardization and Calibration9.1 StandardizationTurn
40、the instrument on and allow itsufficient time to stabilize in accordance with the manufactur-ers instructions. Adjust, balance, and standardize the conduc-tivity meter against the instruments operational standards, andcompensate the conductivity meter for surface roughness andlift-off in accordance
41、with the manufacturers instructions. If alift-off adjustment is not available, determine the acceptablerange of lift-off that will meet the accuracy requirements.Verify the standardization of the conductivity meter at periodicintervals (see Section 10).9.1.1 The instrument, probe, and reference stan
42、dards shallbe standardized while maintaining the temperature within 5Fof the ambient temperature. It is desirable to perform thestandardization at room temperature (typically 70 6 15F).9.1.2 Instruments with two standardization adjustmentsshall be adjusted so that the known value of conductivity iso
43、btained for both reference standards. The reference standardsused should have conductivities that bracket the conductivityvalue of the sample.9.1.3 Some instruments have only one standardization ad-justment. In these cases the instrument should be standardizedto a reference standard at one end of th
44、e range to be examined.A reference standard at the other end of the range should beexamined to verify that the error is within acceptable limitsover the entire range.9.2 Reference StandardsElectrical conductivity referencestandards are usually classified as primary, secondary, andoperational standar
45、ds.9.2.1 Primary Conductivity StandardsThese are referencestandards that have been verified in terms of the fundamentalunits. The primary standards are kept in a laboratory environ-ment and are used only to standardize secondary standards.9.2.2 Secondary Conductivity StandardsThese referencestandard
46、s have a value assigned through comparison withprimary standards. The primary standards used for assignmentof values to these secondary standards shall have been stan-dardized using Test Method B 193. The secondary standardsare kept in a laboratory environment and are used only tocalibrate operation
47、al or instrument standards.9.2.3 Operational Conductivity StandardsThese refer-ence standards are standardized by comparison with secondarystandards. These reference standards are used to standardizethe instrument during use.9.3 Reference standards should be examined with a rela-tively small coil to
48、 determine the uniformity of electricalconductivity over the surface of the standard. Both the frontand the back surface should be examined for any conductivitydifferences that may exist. If possible, scan the surfaces atseveral different input signal frequencies.9.4 Each time the reference standard
49、s are used, place theprobe coil at the same position within 66.35 mm (60.25 in.)of the center of the standard.9.5 Electrical conductivity reference standards are preciseelectrical standards and should be treated as such. Scratchingof the surface of the standard may introduce measurementerror. Avoid dropping or other rough handling of the standard.Keep the surface of the standard as clean as possible. Cleanwith a nonreactive liquid and a soft cloth or tissue. Storereference standards in a place where the temperature isrelatively constant. Avoi
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