1、Designation: B896 10 (Reapproved 2015)Standard Test Methods forEvaluating Connectability Characteristics of ElectricalConductor Materials1This standard is issued under the fixed designation B896; the number immediately following the designation indicates the year oforiginal adoption or, in the case
2、of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 These test methods define procedures for the relativecharacterization of conductor material c
3、onnectability on thebasis of measurements of parameters important to the designand performance of electrical contacts and connections to andwith such conductors for both power and signal applications.1.2 The parameters measured are contact resistance as afunction of contact force, fretting sensitivi
4、ty, and compressiverelaxation.1.3 Provision is made for measurement of the connectabilityparameters at elevated temperature, or corrosive ambient, orboth, as may be required for evaluation for particular applica-tions.1.4 These test methods, using standardized specimen geom-etry and procedures, are
5、applicable to conductor materials asemployed in an electrical system and may be adapted forevaluation of connectability of materials in the form of actualconnection system components.1.5 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisst
6、andard.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 become familiarwith all hazards including those identified in the appropriateSafety Data Sheet (SDS) for this product/material as p
7、rovidedby the manufacturer, to establish appropriate safety and healthpractices, and determine the applicability of regulatory limi-tations prior to use.2. Referenced Documents2.1 ASTM Standards:2B539 Test Methods for Measuring Resistance of ElectricalConnections (Static Contacts)B542 Terminology Re
8、lating to Electrical Contacts and TheirUse3. Terminology3.1 DefinitionsDefinitions of terms used in this testmethod are in accordance with Terminology B542.3.2 Definitions of Terms Specific to This Standard:3.2.1 connectability, na combination of properties deter-mining the ability of a material to
9、establish and maintain stablelow resistance electrical contact under the influence of dete-riorating environmental and operational factors.3.2.2 fretting, naccelerated surface damage occurring atthe interface of contacting materials subjected to small oscil-latory displacements.4. Summary of Test Me
10、thod4.1 Contact ResistanceContact resistance is measured asforce is increased between conductors in a crossed-rod contactpair of the material(s) being tested. Held at the maximumspecified force, test contacts may be exposed to temperaturechanges or corrosive environments such as high humidity toobse
11、rve the effects of such conditions on electrical contactresistance.4.2 Fretting SensitivityContact resistance of a crossed-rodpair is measured at constant normal force while a microscopicoscillitory tangential motion is applied at the contact interface.The number of applied motion cycles required to
12、 inducecontact resistance instability is determined. The test may beperformed at elevated temperature or in corrosive environment.1These test methods are under the jurisdiction of ASTM Committee B02 onNonferrous Metals and Alloys and are the direct responsibility of SubcommitteeB02.11 on Electrical
13、Contact Test Methods.Current edition approved Oct. 1, 2015. Published October 2015. Originallyapproved in 1999. Last previous edition approved in 2010 as B896 101. DOI:10.1520/B0896-10R15.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at service
14、astm.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 19428-2959. United States14.3 Compressive RelaxationChange of applied contactforce wi
15、th time, at fixed engagement displacement of crossed-wire specimens, is measured. The test may be performed atelevated temperature.5. Significance and Use5.1 These test methods develop comparative informationuseful for the design of stationary contacts for wire, cable, andother conductors.5.2 These
16、test methods produce results, which are free of theinfluence of arbitrary connection systems.5.3 The influence of conductor surface pretreatments andplatings can be evaluated by these test methods.5.4 The influence of environmental factors, such as hightemperature and corrosive environment can be ev
17、aluated bythese test methods.5.5 The results obtained by these test methods provideguidance on connection system design parameters, such ascontact force and gas tightness requirements.6. Test Methods6.1 These test methods provide for standardization of speci-men geometry, contact loads, and other fa
18、ctors, which mayinfluence the results. Use of nonstandard specimens or proce-dures may influence the validity of relative connectabilitycomparisons based on the test results.CROSSED WIRE CONTACT RESISTANCEFIXEDLOAD6.2 The standard specimen shall be 2 mm (#12 AWG)diameter wire, at least 25 mm long, a
19、nd straight to within 1 %.Specimens of nonstandard diameter may be used. Resultingperformance data only is considered valid for comparison withresults on same-size specimens, however.6.3 The apparatus consists of a fixture capable of perform-ing as follows:6.3.1 Specimens are oriented perpendicular
20、to one another.Contact between the specimens occurs approximately at thecenter of each specimen (lengthwise).6.3.2 Specimens are supported by flat or vee-groove, orequivalent holders, so as to prevent bending due to appliedcontact load. Specimen support fixture shall support the speci-men for a leng
21、th of 4D 6 0.5D, where D = specimen diameterand shall be centered 60.5D with respect to the point at whichthe crossed specimens make contact. Beyond the load supportregion (at center of the specimens), the specimens shall beunsupported.6.3.3 Electrical connections to the ends of the specimensshall b
22、e made by flexible leads to fixed terminals mounted onthe fixture base.6.3.4 The specimens are brought into contact at a rate of 1mm/min or less until contact is made. After physical contact isestablished, the contact force is increased at a rate of 1 kg/minwith a maximum allowable lateral motion of
23、 0.025 mm.Contact force is increased until it reaches the lesser of thefollowing:6.3.4.1 120 % of the force required to achieve contactresistance of 1.0 m.6.3.4.2 2.0 kg (for standard specimen diameter).6.3.4.3 2.0 D/2 kg (for nonstandard specimen diameter)where D = diameter in mm.6.3.5 Instrumentat
24、ion is provided for measurement of con-tact force, contact current, and contact voltage. The maximumopen circuit voltage shall be 10 mV and the maximum currentshall be 100 mA.6.3.6 Constant load long-term testing at the maximum force(see 6.3.3) the specimen assembly may be fixed, maintainingthe cont
25、act force and the physical relationship between thespecimens so as to allow controlled evaluation of the effects oflong-term environmental variables, such as temperature,humidity, or gaseous ambient.6.3.7 Constant displacement long-term testing at the maxi-mum force (see 6.3.4), the specimen assembl
26、y may be fixed,maintaining the contact displacement and the physical relation-ship between the specimens so as to allow controlled evalua-tion of the effects of long-term environmental variables, suchas temperature, humidity, or gaseous ambient under conditionswhereby the contact load is influenced
27、by stress-relaxationeffects. Fixture design for constant displacement testing mustbe rigid and matched in thermal expansion characteristics tothe material being tested, such as to maintain displacementwithin 1 % of the initial value for the temperature range inwhich it is used for the duration of th
28、e test. The rigidityrequirement may be satisfied by a fixture whose spring constant(force/unit displacement) is calculated to be no less than 200larger than the elastic spring constant of the specimen pairwhen fully engaged. The specimen spring constant is deter-mined by measuring the displacement r
29、equired to decrease thecontact force to 1 kg from an initial 2 kg.6.3.8 For the purpose of environmental exposure in accor-dance with 6.3.6 and 6.3.7, the fixturing shall be designed tomaintain contact load within 62 % over the range of appliedtemperature for the duration of the test. Fixturing shal
30、l bedesigned symmetrically so as to preclude introduction of shearforces in the plane of the specimen contact interface astemperature is changed.6.3.9 The specific design of the apparatus may vary, pro-vided that the functional requirements are met.Arepresentativeembodiment of a constant load crosse
31、d-wire fixture is providedin Appendix X1. For constant displacement crossed-wiretesting, a variation of the stress relaxation fixture shown inAppendix X3 may be used.6.4 Specimen contact load, current, and potential drop shallbe recorded for each specimen pair as they are brought intoinitial contact
32、 and as the load increases. During subsequentlong-term testing at constant load or constant displacement,specimen current and potential drop shall be measured atappropriate intervals, no less frequent than110 of the durationof the test. For specimens exposed to elevated temperature, themeasurements
33、may be performed at room temperature ifrequired to achieve the specified accuracy.B896 10 (2015)2FRETTING SENSITIVITY6.5 Specimen size and fixturing for initial engagement shallbe in accordance with 6.1 6.3.5. Additional requirements areas follows:6.5.1 At a maximum force as determined in 6.3.4, the
34、specimen load shall be fixed, maintaining the contact force forthe balance of the test.6.5.2 A cyclic motion of 20 m amplitude at the contactinterface shall be imposed on one of the specimens in thedirection of its longitudinal axis. The other specimen shall beheld rigid. Fixture must be calibrated
35、to assure the correctdisplacement at the actual contact interface between thespecimens. Frequency of the applied motion shall be 1 cycle/min.6.5.3 For the purpose of environmental exposure during thefretting sensitivity test, the fixturing shall be sufficientlyresistant to the test environment so as
36、 to maintain the contactload and position (except for the applied cyclic motion) of thespecimens without change for the duration of the test.6.5.4 The specific design of the apparatus may vary, pro-vided that the functional requirements are met.Arepresentativeembodiment is provided in Appendix X2.6.
37、6 The cyclic motion shall be continued until the contactresistance becomes unstable.3COMPRESSIVE RELAXATION6.7 Specimen size and fixturing for initial engagement shallbe in accordance with 6.1 6.3.5. Additional requirements areas follows:6.7.1 The apparatus consists of a fixture capable of perform-i
38、ng the following functions:6.7.1.1 Specimens are supported fully by flat or vee-grooveor equivalent holders that will prevent bending due to theapplied contact load. To achieve this, the specimens shall becemented in place using a material that remains sufficientlyrigid and chemically stable under a
39、pplied conditions of the testto meet the requirements of 6.7.1.2. The specimen supportfixture shall support the specimen for a length of 4D 6 0.5D,where D = specimen diameter and shall be centered 60.5Dwith respect to the point at which the crossed specimens makecontact. Beyond the load support regi
40、on (at center of thespecimens) the specimens shall be unsupported.6.7.1.2 The compliance of the fixture, including the contactforce measuring means, shall be designed to be no more than5 % of the elastic spring constant of the fully loaded specimen.The specimen spring constant is determined by measu
41、ring thedisplacement required to decrease the contact force to 1 kgfrom the initial 2 kg.6.7.1.3 The test fixture may be maintained at normal roomtemperature, 23 6 3C, or exposed to elevated temperature, asappropriate for evaluating the materials of interest with respectto the requirements for propo
42、sed applications. The fixture shallbe designed to impart no more than 5 % change of contactforce when changing temperature from the loading condition tothe long-term dwell condition.6.7.1.4 The specimens are brought into contact at a rate of 1mm/min or less until contact is established. After physic
43、alcontact is established, the contact force is increased at a rate of1 kg/min until it reaches 2 kg.6.7.1.5 The mechanical position of the specimen holdersrelative to one another then is fixed. The fixture must accom-plish this without change in force or position. The loadingmechanism may be removed
44、 once the specimen holders arefixed.6.7.1.6 The specific design of the apparatus may varyprovided that the functional requirements are met. A represen-tative embodiment is provided in Appendix X3.6.7.2 Contact force is measured as a function of time,maintaining the fixed relationship between the spe
45、cimen hold-ers.7. Sampling7.1 Sample size for each conductor material evaluated andfor the reference material to which the performance is beingcompared, shall be as follows:7.1.1 Minimum sample size for contact resistance tests is 10specimens.7.1.2 Minimum sample size for fretting sensitivity tests
46、is10 specimens.7.1.3 Minimum sample size for compressive relaxation testsis 4 specimens.8. Specimen Preparation8.1 Specimens shall be cut from random points along alength of the conductor being evaluated.8.2 A basic set of specimens shall be tested withoutchemical, abrasive, or other surface cleanin
47、g or treatment. Theeffect of cleaning or other surface treatment may be evaluatedusing additional specimen sets. If electrical insulation must beremoved as part of the specimen preparation, this must beaccomplished without scraping the conductor surface at (whatwill become) the contact point.9. Repo
48、rt9.1 A report of connectability testing according to these testmethod, as a minimum, shall include the information defined inthis section. All nonstandard aspects of test procedure or testspecimen configuration shall be noted.9.1.1 Identification of person/organization performing thetests.9.1.2 Dat
49、e of test report.9.1.3 Identification of conductor materials (test materialsand reference materials).9.1.3.1 Sufficient detail shall be provided to allow procure-ment of materials essentially identical to that tested.9.1.4 Specimen configuration and preparation.9.1.5 Tests performed.9.1.5.1 Procedure.9.1.5.2 Sample size.9.1.5.3 Applied conditions.3Braunovic M., “Effect of Fretting on the Contact Resistance ofAluminum WithDifferent Contact Materials,” Proceedings of the Ninth International Conference onElectric Contact Phenomena and the 24th Annual Holm Conference
