1、Designation: A342/A342M 04 (Reapproved 2012)Standard Test Methods forPermeability of Feebly Magnetic Materials1This standard is issued under the fixed designation A342/A342M; the number immediately following the designation indicates the yearof original adoption or, in the case of revision, the year
2、 of last revision. A number in parentheses indicates the year of last reapproval.A superscript epsilon () indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the Department of Defense.1. Scope1.1 These test methods cover three pr
3、ocedures for determi-nation of the permeability relative permeability2of materialshaving a permeability not exceeding 4.0.1.2 The test methods covered are as follows:1.2.1 Test Method 1 is suitable for materials with perme-abilities between 1.0 and 4.0.1.2.2 Test Method 2 is suitable for measuring t
4、he permeabil-ity of paramagnetic materials having a permeability less than1.05.1.2.3 Test Method 3 is a suitable means of measuring thepermeability of a material as “less than” or “greater than” thatof calibrated standard inserts designated for use in a Low-MuPermeability Indicator.31.3 The values a
5、nd equations stated in customary (cgs-emuand inch-pound) or SI units are to be regarded separately asstandard. Within this standard, SI units are shown in bracketsexcept for the sections concerning calculations where there areseparate sections for the respective unit systems. The valuesstated in eac
6、h system may not be exact equivalents; therefore,each system shall be used independently of the other. Combin-ing values from the two systems may result in nonconformancewith this standard.1.4 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is
7、 theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:4A341/A341M Test Method for Direct Current MagneticProperties of Materials Using D-C
8、 Permeameters and theBallistic Test MethodsTEST METHOD NO. 1, FLUXMETRIC METHOD3. Significance and Use of Test Method 13.1 This test method is suitable for specification acceptance,design purposes, service evaluation, regulatory statutes, manu-facturing control, and research and development.3.2 Beca
9、use of the restrictions on the specimen shape andsize, this test method is most often used to evaluate semifin-ished product before fabrication of parts.4. Apparatus4.1 Power SupplyA source of dc current for the electricalcircuit shown in Fig. 1. Electronic power supplies are prefer-able although th
10、e use of storage batteries is permitted.4.2 Test FixtureA test fixture consisting of a magnetizingsolenoid with a set of test coils mounted midway between theends of the solenoid for measuring magnetic induction and anair flux balancing resistor, fluxmeter, and associated circuitryconforming to the
11、following requirements:4.2.1 Magnetizing Solenoid, C1, having a minimum lengthof 30 cm 300 mm and a ratio of length to equivalent diameterof four or more. The magnetizing winding shall be uniformlywound and be capable of producing a uniform field of at least300 Oe 24 kA/m over the length of the test
12、 specimen withoutoverheating.1These test methods are under the jurisdiction of ASTM Committee A06 onMagnetic Properties and are the direct responsibility of Subcommittee A06.01 onTest Methods.Current edition approved May 1, 2012. Published July 2012. Originally approvedin 1949. Last previous edition
13、 approved in 2004 as A342/A342M04. DOI:10.1520/A0342_A0342M-04R12.2Test Methods 1 and 2 actually measure magnetic susceptibility. The perme-ability () relative permeability ( r) is related to the susceptibility (k)bytheequations: =1+4pk (cgs-emu)r=1+k (SI)The term permeability has been retained in t
14、hese test methods because of itswidespread commercial and technological usage.3The sole source of supply of the apparatus known to the committee at this timeis Low-Mu Permeability Indicator, manufactured by Severn Engineering Co., Inc.,555 Stage Rd., Suite 1A, Auburn, AL 36830, http:/.(Indicators ca
15、n be returned for recalibration.) If you are aware of alternativesuppliers, please provide this information to ASTM International Headquarters.Your comments will receive careful consideration at a meeting of the responsibletechnical committee,1which you may attend.4For referenced ASTM standards, vis
16、it the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-29
17、59. United States14.2.2 Test Coil, B1, used for measuring induction, shall havea cross-sectional area not greater than ten times that of the testspecimen. The test coil should have sufficient turns (1000) toprovide adequate resolution and should be no longer than 20 %of the test specimen length.4.2.
18、3 Compensating Coil, B81, of the same length, cross-sectional area, and number of turns as coil B1and connected toit in series opposition.4.2.4 Air Flux Compensating Resistor, R8BThis resistor isused in conjunction with coil B81of Fig. 1 to help itcompensate for the air flux enclosed by coil B1in or
19、der that theintrinsic induction may be measured directly.4.2.5 Electronic Fluxmeter, Fused to measure magneticinduction. Alternatively, the magnetizing fixture may be con-nected to a dc hysteresigraph.4.2.6 Magnetic Field Strength Sensor (optional)If themagnetic field strength cannot be accurately d
20、etermined fromthe magnetizing current, then either a Hall effect sensor orH-coil connected to the fluxmeter shall be used.5. Test Specimens5.1 The test specimens shall consist of straight bars, rods,wires, or strips of uniform cross section. Multiple pieces of thesame test lot may be used to increas
21、e the specimen cross-sectional area when needed. The cross-sectional area shall benot less than 0.2 cm220 mm2. The length shall be not lessthan 10 cm 100 mm and the ratio of length to diameter orequivalent diameter (that is, the diameter of a circle having anarea equal to the cross-sectional area of
22、 the specimen) shall beas follows:Permeability Dimensional RatioUnder 1.5 10 or greater1.5 to 2.0, incl. 15 or greater2.0 to 4.0 30 or greater5.2 This test method can be used with smaller dimension-ratio test specimens when used for comparing to similarspecimens for quality control purposes.6. Proce
23、dure6.1 Measure the thickness and width or diameter of the testspecimens and calculate the cross-sectional area in squarecentimetres square millimetres.6.2 Before inserting the test specimen in the solenoid,obtain an exact balance to nullify the effect of air flux in coilB1by reversing the highest m
24、agnetizing current to be used inthe test and adjusting the compensating resistor to obtain theminimum output from the flux sensing coils.6.3 Place the test specimen in position in coil B1, adjust themagnetic field strength to the desired test value, then reversethe magnetizing current and record the
25、 fluxmeter reading.Optionally, the B versus H curve can be recorded on ahysteresigraph.7. Calculation (Customary Units)7.1 Convert the fluxmeter reading to intrinsic induction Biand calculate the permeability as follows: 5 11BiH(1)where: = permeability of the test specimen;Bi= intrinsic induction of
26、 the test specimen, G; andH = magnetic field strength, Oe.8. Calculation (SI Units)8.1 The output from the fluxmeter is the magnetic polariza-tion J. The relative permeability is calculated as follows:r5 11JGmH(2)where:r= relative permeability of the test specimen;J = magnetic polarization, T;FIG. 1
27、 Circuit Diagram for Method No. 1A342/A342M 04 (2012)2Gm=4p 107H/m; andH = magnetic field strength, A/m.9. Precision and Bias of Test Method 19.1 The precision and bias of this test method have not beenestablished by interlaboratory study.9.2 The measured permeabilities will be less than their truev
28、alues due to the demagnetizing field arising from the sampledimensional ratio. This leads not only to an overestimation ofthe magnetic field strength but also reduces the flux linkages inthe B-coil. Provided the sample and coil dimensional ratios areas specified in 4.2.2 and 5.1, the largest negativ
29、e error in 1as a result of demagnetizing effects5,6will be 3 % for 10.5.TEST METHOD NO. 2, PERMEABILITY OFPARAMAGNETIC MATERIALS10. Significance and Use of Test Method 210.1 This test method is suitable for specification accep-tance, design purposes, service evaluation, regulatory statutes,manufactu
30、ring control, and research and development.10.2 Because of the restrictions on the specimen shape, size,and permeability, this test method is most often used toevaluate semifinished product before fabrication of parts.11. Apparatus11.1 Power SupplyA source of steady dc power such as astorage battery
31、 or a suitably regulated dc power supply.11.2 PermeameterA permeameter as shown in Fig. 2,consisting of an electromagnet and a balance conforming to thefollowing requirements:11.2.1 ElectromagnetThe electromagnet shall have polefaces whose horizontal dimension is 3.8 cm 38 mm andwhose vertical dimen
32、sion is 1.9 cm 19 mm. The distancebetween the pole faces shall be 1.9 cm 19 mm. Themagnetizing winding shall be so wound as to produce amagnetic field strength of at least 1000 Oe 80 kA/m betweenthe pole pieces without overheating.11.2.2 BalanceA balance capable of weighing up to 50 gwith a sensitiv
33、ity of 0.1 mg. Any magnetic material in thebalance should be 12.7 cm 127 mm or more above theelectromagnet. The space surrounding the sample shall beclosed by a shield of nonmagnetic material to protect thesample from air currents during measurements.11.3 Miscellaneous Current Control Equipment, for
34、 themagnetizing circuit such as ammeter, rheostat, and reversingswitch.12. Test Specimens12.1 The test specimens shall consist of straight bars, rods,wires, strips, or tubing of uniform cross section. The length ofthe specimen shall be not less than 6.6 cm 66 mm and thewidth shall not exceed 1.27 cm
35、 12.7 mm. The minimumcross-sectional area shall be not less than 0.13 cm213 mm2.13. Procedure13.1 Measure the thickness and width or diameter of the testspecimens and calculate the cross-sectional area in squarecentimetres square millimetres.13.2 Suspend the specimen from the balance in such amanner
36、 that its lower end is within 60.16 cm 61.6 mm of thecenter line of the air gap (Fig. 2) and weigh it with themagnetizing current off.13.3 Turn on the magnetizing current and set it at such avalue as to give a magnetic field strength 500 Oe 40 kA/malong the center line of the air gap (Note 1). Rever
37、se thecurrent at least five times to nullify the effect of hysteresis inthe electromagnet core. Then weigh the specimen with thecurrent on.NOTE 1The field strength along the center line of the air gap may bedetermined by using a reference standard such as a saturated solution ofnickel chloride of kn
38、own permeability or a standard search coil andfluxmeter. If the coil is used its maximum diameter shall not exceed 0.32cm 3.2 mm and its axis shall be along the center line of the air gap whenmeasuring the field by means of reversing the magnetizing current.13.4 Repeat the procedure described in 13.
39、3 with themagnetizing current adjusted to give a magnetic field strengthof 1000 Oe 80 kA/m along the center line of the air gap.14. Calculations (Customary Units)14.1 Calculate the permeability as follows: 5 118pFAH2(3)5Chen, D.-X., and Li, B.-Z., “On the Error of Measurement of Feebly MagneticMater
40、ial in Regard to Demagnetizing Field,” Acta Metall. Sinica, Vol. 19, pp.217224, Oct. 1983 (in Chinese).6Chen, D.-X., Brug, J. A., and Goldfarb, R. B., “Demagnetizing Factors forCylinders,” IEEE Trans. Magn., Vol. 27, 1991, pp. 36013619.FIG. 2 Circuit Diagram for Method No. 2A342/A342M 04 (2012)3or:
41、5 1124.65D mAH2(4)where: = permeability of the test specimen;F = force acting on the specimen caused by the magneticfield, dynes;A = cross-sectional area of the specimen, cm2;H = magnetic field strength along the center line of the airgap at the time of weighing, Oe; and,Dm = apparent change in mass
42、, mg.15. Calculations (SI Units)15.1 Calculate the relative permeability as follows:r5 112FGmAH2(5)or:r5 111.561 3107D mAH2(6)where:r= relative permeability of the test specimen;F = force acting on the specimen caused by the magneticfield, N;Gm=4p 107H/m;A = cross-sectional area of the specimen, m2;
43、H = magnetic field strength along the center line of the airgap at the time of weighing, A/m; and,Dm = apparent change in mass, kg.16. Precision and Bias of Test Method 216.1 The precision and bias of this test method has not beenestablished by interlaboratory study. For specimens having asatisfacto
44、ry degree of magnetic uniformity along their length,and tested at a definite temperature, it is believed the quantity( 1) should be accurate within 68%or60.0001, whicheveris the greater.16.2 If the values of the permeability obtained from themeasurements prescribed in 13.3 and 13.4 do not agree with
45、inthe limits of error stated in 16.1, this test method of measuringthe permeability is not valid, because the permeability is notindependent of field.TEST METHOD NO. 3, LOW-MU PERMEABILITYINDICATOR METHOD OF TEST17. Significance and Use of Test Method 317.1 The Low-Mu Permeability Indicator, schemat
46、icallyshown in Fig. 3, is suitable for determining if the permeabilityof low permeability materials (relative of 3.0 or less) isgreater than or less than that of the standard insert employed atthe time of the test.17.2 The instrument is portable and suitable for use in theshop, field, and laboratory
47、.17.3 The instrument is suitable to test all forms and shapesincluding parts, provided a suitable flat surface is available onthe specimen. The material under test is that which is at thesurface and is against or is in immediate proximity to thepermanent bar magnet.17.4 This test method provides tes
48、t values (generally statedas “permeability is less than”) suitable for specification pur-poses.18. Apparatus18.1 Permanent Bar MagnetThe center of the permanentbar magnet is attached to an end of a movable arm having afulcrum in the center and a counterbalance at the opposite end,thus permitting the
49、 permanent magnet to move in one plane inboth directions.18.2 The standard inserts are feebly magnetic materials ofknown permeability values as calibrated by the manufacturerof the indicator against their established standards.19. Test Specimen19.1 The test specimen or material to be tested is recom-mended to have a minimum area of 1 cm2100 mm2 and aminimum thickness of 0.3 cm 3 mm (the specimen may belaminated). Test specimens having a volume in excess of theminimum val
