1、Designation: B 896 99 (Reapproved 2005)Standard Test Methods forEvaluating Connectability Characteristics of ElectricalConductor Materials1This standard is issued under the fixed designation B 896; the number immediately following the designation indicates the year oforiginal adoption or, in the cas
2、e of revision, 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 These test methods define procedures for the relativecharacterization of conductor materia
3、l 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 as afunction of contact force, fretting sensit
4、ivity, 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, a
5、re applicable to conductor materials asemployed in an electrical connection system and may beadapted for evaluation of connectability of materials in theform of actual connection system components.1.5 The values stated in either SI units or inch-pound unitsare to be regarded separately as standard.
6、The values stated ineach system may not be exact equivalents; therefore, eachsystem shall be used independently of the other. Combiningvalues from the two systems may result in non-conformancewith the standard.1.6 This standard does not purport to address all of thesafety concerns, if any, associate
7、d with its use. It is theresponsibility of the user of this standard to become familiarwith all hazards including those identified in the appropriateMaterial Safety Data Sheet (MSDS) for this product/materialas provided by the manufacturer, to establish appropriatesafety and health practices, and de
8、termine the applicability ofregulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2B 539 Test Methods for Measuring Resistance of ElectricalConnections (Static Contacts)B 542 Terminology Relating to Electrical Contacts andTheir Use3. Terminology3.1 DefinitionsDefinitions of t
9、erms used in this testmethod are in accordance with Terminology B 542.3.2 Definitions of Terms Specific to This Standard:3.2.1 connectability, na combination of properties deter-mining the ability of a material to establish and maintain stablelow resistance electrical contact under the influence of
10、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 Method4.1 Contact ResistanceContact resistance is measured asforce is increased between
11、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 toobserve the effects of such changes on electrical contactresistance.4.2 Fretting Sensitivi
12、tyContact 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 inducecontact resistance instability is determined. The test may beperformed at elevated
13、 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 Contact Test Methods.Current edition approved Nov. 1, 2005. Published November 2005. Orig
14、inallyapproved in 1999. Last previous edition approved in 1999 as B 896 - 99.2For referenced ASTM standards, visit 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 ont
15、he ASTM website.1Copyright ASTM International, 100 Barr Harbor 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 at
16、elevated temperature.5. Significance and Use5.1 These test methods develop comparative informationuseful for the design of stationary contacts for wire conductors.5.2 These test methods produce results, which are free of theinfluence of arbitrary connection systems.5.3 The influence of conductor sur
17、face pretreatments andplatings can be evaluated 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 paramet
18、ers, 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 factors, which mayinfluence the results. Use of nonstandard specimens or proce-dures may influence the validity of relative conne
19、ctabilitycomparisons based on the test results.CROSSED WIRE CONTACT RESISTANCEFIXEDLOAD6.2 The standard specimen shall be 2 mm (#12 AWG, .081in.) diameter wire, at least 25 mm long, and straight to within1 %. Specimens of nonstandard diameter may be used. Result-ing performance data only is consider
20、ed valid for comparisonwith results 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 to one another.Contact between the specimens occurs approximately at thecenter of each specimen (lengthwise).6.3.2
21、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 length of 4D 6 0.5D, where D = specimen diameterand shall be centered 60.5D with respect to the point at whichthe cross
22、ed 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 be made by flexible leads to fixed terminals mounted onthe fixture base.6.3.4 The specimens are brought into contact
23、 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 0.001 mm.Contact force is increased until it reaches the lesser of thefollowing:6.3.4.1 120 % of the force require
24、d to achieve contactresistance of 1.0 mV.6.3.4.2 2.0 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
25、 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 contact force and the physical relationship between thespecimens so as to allow controlled evaluation of the effects
26、 oflong-term environmental variables, such as temperature, 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
27、 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 by stress-relaxationeffects. Fixture design for constant displacement testing mustbe rigid and matched in ther
28、mal 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 the test. The rigidityrequirement may be satisfied by a fixture whose spring constant(force/unit displacement) i
29、s calculated to be no less than 2003larger than the elastic 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 expo
30、sure accordingto 6.3.6 and 6.3.7, the fixturing shall be designed to maintaincontact load within 62 % over the range of applied tempera-ture for the duration of the test. Fixturing shall be designedsymmetrically so as to preclude introduction of shear forces inthe plane of the specimen contact inter
31、face as temperature ischanged.6.3.9 The specific 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
32、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 and as the load increases. During subsequentlong-term testing at constant load or constant displacement,specimen c
33、urrent and potential drop shall be measured atappropriate 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
34、size and fixturing for initial engagement shallbe in accordance with 6.1-6.3.5.Additional requirements are asfollows:B 896 99 (2005)26.5.1 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
35、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 to assure the correctdisplacement at the actual contact interface between thespecimens. Frequency of the applied mo
36、tion 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 to maintain the contactload and position (except for the applied cyclic motion) of thespecimens without change for
37、 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 X2.6.6 The cyclic motion shall be continued until the contactresistance becomes unstable.3COMPRESSIVE RELAXATION6.7 Spec
38、imen size and fixturing for initial engagement shallbe 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 wil
39、l 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 applied conditions of the testto meet the requirements of 6.7.1.2. The specimen supportfixture shall support the spec
40、imen for a length of 4D 6 0.5D,where D = specimen diameter and shall be centered 6 0.5Dwith 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
41、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 measuring thedisplacement required to decrease the contact force to 1 kgfrom the initial 2 kg.6.7.1.3 The test fixture m
42、ay 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 proposed applications. The fixture shallbe designed to impart no more than 5 % change of contactforce when changing temp
43、erature 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 physicalcontact is established, the contact force is increased at a rate of1 kg/min until it reaches 2 kg.6.7.1.5 The mec
44、hanical 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 once the specimen holders arefixed.6.7.1.6 The specific design of the apparatus may varyprovided that the function
45、al 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 specimen hold-ers.7. Sampling7.1 Sample size for each conductor material evaluated andfor the reference material to wh
46、ich 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 is10 specimens.7.1.3 Minimum sample size for compressive relaxation testsis 4 specimens.8. Specimen Preparation8.1
47、Specimens shall be cut from random points along alength 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.
48、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. Report9.1 A report of connectability testing according to these testmethod, as a minimum, shall include the informati
49、on 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 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)
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