1、Designation: B896 101Standard 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 of revision, the
2、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.1NOTEA Summary of Changes was added editorially in December 2010.1. Scope*1.1 These test methods define procedures for the
3、 relativecharacterization of conductor material connectability 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
4、as afunction of contact force, fretting sensitivity, 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 sta
5、ndardized specimen geom-etry and procedures, are 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
6、other units of measurement are included in thisstandard.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 appropriateMater
7、ial Safety Data Sheet (MSDS) for this product/materialas provided by the manufacturer, to establish appropriatesafety and health practices, and determine the applicability ofregulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2B539 Test Methods for Measuring Resistance of E
8、lectricalConnections (Static Contacts)B542 Terminology Relating to Electrical Contacts andTheir Use3. 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
9、 of properties deter-mining the ability of a material to 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
10、to small oscil-latory displacements.4. Summary of Test Method4.1 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 temperaturechang
11、es or corrosive environments such as high humidity toobserve 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
12、interface.The number of applied motion cycles required to 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 d
13、irect responsibility of SubcommitteeB02.11 on Electrical Contact Test Methods.Current edition approved Oct. 1, 2010. Published October 2010. Originallyapproved in 1999. Last previous edition approved in 2005 as B896 - 99 (2005).DOI: 10.1520/B0896-10E01.2For referenced ASTM standards, visit the ASTM
14、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.1*A Summary of Changes section appears at the end of this standard.Copyright ASTM International, 100 Barr Ha
15、rbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.4.3 Compressive RelaxationChange of applied contactforce with 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
16、 methods develop comparative informationuseful for the design of stationary contacts for wire, cable, andother conductors.5.2 These test methods produce results, which are free of theinfluence of arbitrary connection systems.5.3 The influence of conductor surface pretreatments andplatings can be eva
17、luated by these test methods.5.4 The influence of environmental factors, such as hightemperature and corrosive environment can be evaluated bythese test methods.5.5 The results obtained by these test methods provideguidance on connection system design parameters, such ascontact force and gas tightne
18、ss requirements.6. Test Methods6.1 These test methods provide for standardization of speci-men geometry, contact loads, and other factors, which mayinfluence the results. Use of nonstandard specimens or proce-dures may influence the validity of relative connectabilitycomparisons based on the test re
19、sults.CROSSED WIRE CONTACT RESISTANCEFIXEDLOAD6.2 The standard specimen shall be 2 mm (#12 AWG)diameter wire, at least 25 mm long, and straight to within 1 %.Specimens of nonstandard diameter may be used. Resultingperformance data only is considered valid for comparison withresults on same-size spec
20、imens, however.6.3 The apparatus consists of a fixture capable of perform-ing as follows:6.3.1 Specimens are oriented perpendicular 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, orequi
21、valent holders, so as to prevent bending due to appliedcontact load. Specimen support fixture shall support the speci-men for a length 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 supportreg
22、ion (at center of the specimens), the specimens shall beunsupported.6.3.3 Electrical connections to the ends of the specimensshall be 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.
23、After physical contact isestablished, the contact force is increased at a rate of 1 kg/minwith a maximum allowable lateral motion of 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 mV.6.3.4.2 2.0
24、kg (for standard specimen diameter).6.3.4.3 2.0 3 D/2 kg (for nonstandard specimen diameter)where D = diameter in mm.6.3.5 Instrumentation 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
25、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 contact force and the physical relationship between thespecimens so as to allow controlled evaluation of the effects oflong-term environmental variables, such as tempera
26、ture, hu-midity, or gaseous ambient.6.3.7 Constant displacement long-term testing at the maxi-mum force (see 6.3.4), the specimen assembly 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 lo
27、ng-term environmental variables, suchas temperature, humidity, or gaseous ambient under conditionswhereby the contact load is influenced by stress-relaxationeffects. Fixture design for constant displacement testing mustbe rigid and matched in thermal expansion characteristics tothe material being te
28、sted, such as to maintain displacementwithin 1 % of the initial value for the temperature range inwhich it is used for the duration of the test. The rigidityrequirement may be satisfied by a fixture whose spring constant(force/unit displacement) is calculated to be no less than 2003larger than the e
29、lastic spring constant of the specimen pairwhen fully engaged. The specimen spring constant is deter-mined by measuring the displacement required 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 fixturi
30、ng shall be designed tomaintain contact load within 62 % over the range of appliedtemperature for the duration of the test. Fixturing shall bedesigned symmetrically so as to preclude introduction of shearforces in the plane of the specimen contact interface astemperature is changed.6.3.9 The specifi
31、c design of the apparatus may vary, pro-vided that the functional requirements are met.Arepresentativeembodiment of a constant load crossed-wire fixture is providedin Appendix X1. For constant displacement crossed-wiretesting, a variation of the stress relaxation fixture shown inAppendix X3 may be u
32、sed.6.4 Specimen contact load, current, and potential drop shallbe recorded for each specimen pair as they are brought intoinitial contact and as the load increases. During subsequentlong-term testing at constant load or constant displacement,specimen current and potential drop shall be measured ata
33、ppropriate intervals, no less frequent than110 of the durationof the test. For specimens exposed to elevated temperature, themeasurements may be performed at room temperature ifrequired to achieve the specified accuracy.FRETTING SENSITIVITY6.5 Specimen size and fixturing for initial engagement shall
34、be in accordance with 6.1-6.3.5.Additional requirements are asfollows:B896 10126.5.1 At a maximum force as determined in 6.3.4, thespecimen 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 o
35、n one of the specimens in thedirection of its longitudinal axis. The other specimen shall beheld rigid. Fixture must be calibrated 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 env
36、ironmental exposure during thefretting sensitivity test, the fixturing shall be sufficientlyresistant to the test environment so as 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
37、 the apparatus may vary, pro-vided that the functional requirements are met.Arepresentativeembodiment is provided in Appendix X2.6.6 The cyclic motion shall be continued until the contactresistance becomes unstable.3COMPRESSIVE RELAXATION6.7 Specimen size and fixturing for initial engagement shallbe
38、 in accordance with 6.1-6.3.5.Additional requirements are asfollows:6.7.1 The apparatus consists of a fixture capable of perform-ing 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 a
39、chieve this, the specimens shall becemented in place using a material that remains sufficientlyrigid and chemically stable under applied 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 diam
40、eter and shall be centered 60.5Dwith respect to the point at which the crossed specimens makecontact. Beyond the load support region (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
41、be no more than5 % of the elastic spring constant of the fully loaded specimen.The specimen spring constant is determined by measuring 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
42、 exposed to elevated temperature, asappropriate for evaluating the materials of interest with respectto the requirements for proposed applications. The fixture shallbe designed to impart no more than 5 % change of contactforce when changing temperature from the loading condition tothe long-term dwel
43、l condition.6.7.1.4 The specimens are brought into contact at a rate of 1mm/min or less until contact is established. After physicalcontact 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
44、 another then is fixed. The fixture must accom-plish this without change in force or position. The loadingmechanism may be removed 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 i
45、s provided in Appendix X3.6.7.2 Contact force is measured as a function of time,maintaining the fixed relationship between the specimen 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 follo
46、ws:7.1.1 Minimum sample size for contact resistance tests is 10specimens.7.1.2 Minimum sample size for fretting sensitivity tests 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
47、 of the conductor being evaluated.8.2 A basic set of specimens shall be tested without chemi-cal, abrasive, or other surface cleaning or treatment. The effectof cleaning or other surface treatment may be evaluated usingadditional specimen sets. If electrical insulation must beremoved as part of the
48、specimen preparation, this must beaccomplished without scraping the conductor surface at (whatwill become) the contact point.9. Report9.1 A report of connectability testing according to these testmethod, as a minimum, shall include the information defined inthis section. All nonstandard aspects of t
49、est procedure or testspecimen configuration shall be noted.9.1.1 Identification of person/organization performing thetests.9.1.2 Date 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.9.1.5.4 Test ResultsRaw data plus (optional) plotted and(optional) statistical summaries compar
