ASTM B896-99(2005)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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Designation:B896–99(Reapproved2005)
Standard Test Methods for
Evaluating Connectability Characteristics of Electrical
Conductor Materials
This standard is issued under the fixed designation B896; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year 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.
1. Scope B539 Test Methods for Measuring Resistance of Electrical
Connections (Static Contacts)
1.1 These test methods define procedures for the relative
B542 Terminology Relating to Electrical Contacts and
characterization of conductor material connectability on the
Their Use
basis of measurements of parameters important to the design
and performance of electrical contacts and connections to and
3. Terminology
with such conductors for both power and signal applications.
3.1 Definitions—Definitions of terms used in this test
1.2 The parameters measured are contact resistance as a
method are in accordance with Terminology B542.
function of contact force, fretting sensitivity, and compressive
3.2 Definitions of Terms Specific to This Standard:
relaxation.
3.2.1 connectability, n—a combination of properties deter-
1.3 Provisionismadeformeasurementoftheconnectability
mining the ability of a material to establish and maintain stable
parameters at elevated temperature, or corrosive ambient, or
low resistance electrical contact under the influence of dete-
both, as may be required for evaluation for particular applica-
riorating environmental and operational factors.
tions.
3.2.2 fretting, n—accelerated surface damage occurring at
1.4 These test methods, using standardized specimen geom-
the interface of contacting materials subjected to small oscil-
etry and procedures, are applicable to conductor materials as
latory displacements.
employed in an electrical connection system and may be
adapted for evaluation of connectability of materials in the
4. Summary of Test Method
form of actual connection system components.
4.1 Contact Resistance—Contact resistance is measured as
1.5 The values stated in SI units are to be regarded as
force is increased between conductors in a crossed-rod contact
standard. No other units of measurement are included in this
pair of the material(s) being tested. Held at the maximum
standard.
specified force, test contacts may be exposed to temperature
1.6 This standard does not purport to address all of the
changes or corrosive environments such as high humidity to
safety concerns, if any, associated with its use. It is the
observe the effects of such changes on electrical contact
responsibility of the user of this standard to become familiar
resistance.
with all hazards including those identified in the appropriate
4.2 Fretting Sensitivity—Contactresistanceofacrossed-rod
Material Safety Data Sheet (MSDS) for this product/material
pair is measured at constant normal force while a microscopic
as provided by the manufacturer, to establish appropriate
oscillitory tangential motion is applied at the contact interface.
safety and health practices, and determine the applicability of
The number of applied motion cycles required to induce
regulatory limitations prior to use.
contact resistance instability is determined. The test may be
performedatelevatedtemperatureorincorrosiveenvironment.
2. Referenced Documents
4.3 Compressive Relaxation—Change of applied contact
2.1 ASTM Standards:
force with time, at fixed engagement displacement of crossed-
wire specimens, is measured. The test may be performed at
These test methods are under the jurisdiction of ASTM Committee B02 on
elevated temperature.
Nonferrous Metals and Alloys and are the direct responsibility of Subcommittee
B02.11 on Electrical Contact Test Methods.
5. Significance and Use
Current edition approved Nov. 1, 2005. Published November 2005. Originally
approved in 1999. Last previous edition approved in 1999 as B896 - 99. DOI: 5.1 These test methods develop comparative information
10.1520/B0896-99R05.
usefulforthedesignofstationarycontactsforwireconductors.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
5.2 Thesetestmethodsproduceresults,whicharefreeofthe
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
influence of arbitrary connection systems.
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
B896–99 (2005)
5.3 The influence of conductor surface pretreatments and long-term environmental variables, such as temperature, hu-
platings can be evaluated by these test methods. midity, or gaseous ambient.
5.4 The influence of environmental factors, such as high 6.3.7 Constant displacement long-term testing at the maxi-
temperature and corrosive environment can be evaluated by mum force (see 6.3.4), the specimen assembly may be fixed,
these test methods. maintainingthecontactdisplacementandthephysicalrelation-
5.5 The results obtained by these test methods provide ship between the specimens so as to allow controlled evalua-
tion of the effects of long-term environmental variables, such
guidance on connection system design parameters, such as
contact force and gas tightness requirements. as temperature, humidity, or gaseous ambient under conditions
whereby the contact load is influenced by stress-relaxation
6. Test Methods effects. Fixture design for constant displacement testing must
be rigid and matched in thermal expansion characteristics to
6.1 These test methods provide for standardization of speci-
the material being tested, such as to maintain displacement
men geometry, contact loads, and other factors, which may
within 1 % of the initial value for the temperature range in
influence the results. Use of nonstandard specimens or proce-
which it is used for the duration of the test. The rigidity
dures may influence the validity of relative connectability
requirementmaybesatisfiedbyafixturewhosespringconstant
comparisons based on the test results.
(force/unit displacement) is calculated to be no less than 2003
larger than the elastic spring constant of the specimen pair
CROSSED WIRE CONTACT RESISTANCE—FIXED
when fully engaged. The specimen spring constant is deter-
LOAD
mined by measuring the displacement required to decrease the
6.2 The standard specimen shall be 2 mm (#12 AWG, .081
contact force to 1 kg from an initial 2 kg.
in.) diameter wire, at least 25 mm long, and straight to within
6.3.8 For the purpose of environmental exposure according
1 %. Specimens of nonstandard diameter may be used. Result-
to 6.3.6 and 6.3.7, the fixturing shall be designed to maintain
ing performance data only is considered valid for comparison
contact load within 62 % over the range of applied tempera-
with results on same-size specimens, however.
ture for the duration of the test. Fixturing shall be designed
6.3 The apparatus consists of a fixture capable of perform-
symmetrically so as to preclude introduction of shear forces in
ing as follows:
the plane of the specimen contact interface as temperature is
6.3.1 Specimens are oriented perpendicular to one another.
changed.
Contact between the specimens occurs approximately at the
6.3.9 The specific design of the apparatus may vary, pro-
center of each specimen (lengthwise).
videdthatthefunctionalrequirementsaremet.Arepresentative
6.3.2 Specimens are supported by flat or vee-groove, or
embodiment of a constant load crossed-wire fixture is provided
equivalent holders, so as to prevent bending due to applied
in Appendix X1. For constant displacement crossed-wire
contact load. Specimen support fixture shall support the speci-
testing, a variation of the stress relaxation fixture shown in
men for a length of 4D 6 0.5D, where D = specimen diameter
Appendix X3 may be used.
and shall be centered 60.5D with respect to the point at which
6.4 Specimen contact load, current, and potential drop shall
the crossed specimens make contact. Beyond the load support
be recorded for each specimen pair as they are brought into
region (at center of the specimens), the specimens shall be
initial contact and as the load increases. During subsequent
unsupported.
long-term testing at constant load or constant displacement,
6.3.3 Electrical connections to the ends of the specimens
specimen current and potential drop shall be measured at
shall be made by flexible leads to fixed terminals mounted on
appropriate intervals, no less frequent than ⁄10 of the duration
the fixture base.
of the test. For specimens exposed to elevated temperature, the
6.3.4 The specimens are brought into contact at a rate of 1
measurements may be performed at room temperature if
mm/min or less until contact is made.After physical contact is
required to achieve the specified accuracy.
established, the contact force is increased at a rate of 1 kg/min
FRETTING SENSITIVITY
with a maximum allowable lateral motion of 0.001 mm.
Contact force is increased until it reaches the lesser of the
6.5 Specimen size and fixturing for initial engagement shall
following:
beinaccordancewith6.1-6.3.5.Additionalrequirementsareas
6.3.4.1 120 % of the force required to achieve contact follows:
resistance of 1.0 mV.
6.5.1 At a maximum force as determined in 6.3.4, the
6.3.4.2 2.0 kg (for standard specimen diameter). specimen load shall be fixed, maintaining the contact force for
6.3.4.3 2.0 3 D/2 kg (for nonstandard specimen diameter)
the balance of the test.
where D = diameter in mm. 6.5.2 A cyclic motion of 20 µm amplitude at the contact
6.3.5 Instrumentation is provided for measurement of con- interface shall be imposed on one of the specimens in the
tact force, contact current, and contact voltage. The maximum direction of its longitudinal axis. The other specimen shall be
open circuit voltage sha
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