1、Designation: B820 18Standard Test Method forBend Test for Determining the Formability of Copper andCopper Alloy Strip1This standard is issued under the fixed designation B820; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the yea
2、r 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. Scope*1.1 This test method describes the technique of bend testingcopper and copper alloy strip samples to determine produ
3、ctformability or the ability to resist cracking when forming abend around a specific radius. The criterion for failure is theoccurrence of cracks on the outer (convex) radius of curvature.1.2 This bend test is limited to strip from 0.003 to andincluding 0.031 in. (0.076 to and including 0.79 mm) thi
4、ck.1.3 The forming or punch radius for the bend test is to bedetermined by agreement between the producer and the cus-tomer.1.4 UnitsValues stated in inch-pound units are to beregarded as standard. The values given in parentheses aremathematical conversions to SI units which are provided forinformat
5、ion only and are not considered standard.1.5 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 establish appro-priate safety, health, and environmental practices and deter-mine the applicabili
6、ty of regulatory limitations prior to use.1.6 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recom-mendations issued by the Wor
7、ld Trade Organization TechnicalBarriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2B846 Terminology for Copper and Copper AlloysE6 Terminology Relating to Methods of Mechanical TestingE290 Test Methods for Bend Testing of Material for Ductil-ity3. Terminology3.1 For definiti
8、ons of terms related to copper and copperalloys, refer to Terminology B846.3.2 For definitions of terms related to mechanical testing,refer to Terminology E6.3.3 Definitions of Terms Specific to This Standard:3.3.1 bend, longitudinal (or good way bend)a bend withan axis perpendicular to the directio
9、n of rolling, drawing, orextrusion (see Fig. 1).3.3.2 bend, transverse (or bad way bend)a bend with anaxis on a plane parallel to the direction of rolling, drawing, orextrusion (see Fig. 1).NOTE 1The usage of these two terms is consistent with Test MethodsE290.4. Summary of Test Method4.1 The bend t
10、est is made by applying a force transverselyto the length of the specimen in the portion being bent, usuallyat mid-length. The 90 bending forces are applied through anarrangement illustrated in Fig. 2, while 180 bending forces areapplied through an arrangement illustrated in Fig. 3. Whencomplete fra
11、cture does not occur, the convex surface of thespecimen is examined for cracks. In general, the test using a180 bend angle is a more severe test than the test using a 90bend angle.5. Significance and Use5.1 This bend test provides information as to the formabilityor the ability of copper and copper
12、alloy strip to resist crackingwhen being formed.5.2 This test method can be used as a quality control tool todetermine if material will form to a given radius.5.3 This test method is also useful in research and develop-ment to provide data for use in selecting a spring material thatwill safely form
13、to the geometry of a given part.5.4 The results are suitable for direct application in designand manufacturing, only when all factors such as the geometry1This test method is under the jurisdiction of ASTM Committee B05 on Copperand Copper Alloys and is the direct responsibility of Subcommittee B05.
14、06 onMethods of Test.Current edition approved March 1, 2018. Published March 2018. Originallyapproved in 1992. Last previous edition approved in 2014 as B820 14a. DOI:10.1520/B0820-18.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm
15、.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.*A Summary of Changes section appears at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United State
16、sThis international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trad
17、e (TBT) Committee.1of the part, punch and die design, lubrication, stamping speed,and other material properties are known.6. Apparatus6.1 Various devices are suitable for 90 or 180 bendtesting. The apparatus shall provide these features:6.1.1 90 Bend Test FixtureAn illustration of this testfixture i
18、s shown in Fig. 2. A specimen rests on a pair of pins,rollers, or radiused flat supports; a pin, mandrel, or 90 V-blockpunch of a given bend radius for applying the bending forcedirectly at the mid-length.6.1.2 180 Bend Test FixtureAn illustration of this testfixture is shown in Fig. 3. A specimen r
19、ests on a pair of pins,rollers, or radiused flat supports; a pin, mandrel, or 180 punchof a given bend radius for applying the bending force directlyat the mid-length. Dial indicators with a precision of 0.0005 in.(0.013 mm) or better are necessary to accurately position thetwo supports.6.1.2.1 To p
20、revent breaking the punch, it is recommendednot to use a radius smaller than12 the thickness of the materialbeing tested.6.2 The radius of the single pin, mandrel, or punch applyingthe bend force at the mid-length shall differ not more than65 % from the nominal value of the radius.6.3 The length of
21、all pins, rolls, mandrels, and radius flatsmust exceed the width of the specimen; they must be strongenough and sufficiently rigid to resist significant deformation.7. Test Specimens7.1 Test Specimen Requirement:7.1.1 When the purchaser does not define a bending widthrequirement, the default width s
22、hall be12 6116 in. (12.7 61.57 mm).7.1.1.1 Four test specimens shall be required, two in thelongitudinal and two in the transverse directions for the 90and 180 test angles.7.1.2 When the purchaser defines a bending test at or below14 in. (6.35 mm), then the producer can optionally apply thenarrow wi
23、dth specimen as defined in 7.1.2.1 (see Fig. 4).7.1.2.1 The narrow width specimen consists of four beams:0.024 6 0.002 in. (0.6 6 0.05 mm), 0.047 6 0.003 in. (1.2 60.08 mm), 0.095 6 0.004 in. (2.4 6 0.1 mm), and 0.189 60.005 in. (4.8 6 0.13 mm). Four test specimens shall berequired, two in the longi
24、tudinal and two in the transversedirections, for the 90 and 180 angles.7.1.2.2 When the purchaser does not identify a specificwidth in the narrow width specimen, the default width shall be0.095 6 0.004 in. (2.4 6 0.1 mm).7.2 The test specimens may be prepared by cutting,shearing, or stamping.7.3 The
25、 test specimens shall have any convenient lengthgreater than12 in. (12.7 mm) unless specified otherwise by thepurchaser.7.4 Direction of Specimen:7.4.1 The bending characteristics of a metal vary with theorientation of the bends to the direction of rolling. A longitu-dinal bend will typically take a
26、 sharper bend radius than atransverse bend. This characteristic becomes more pronouncedas the metal thickness increases.7.4.2 In a longitudinal specimen, its length shall be parallelto the direction of rolling as indicated in Fig. 1.7.4.3 In a transverse bend specimen, its length shall beperpendicul
27、ar to the direction of rolling as indicated in Fig. 1.7.4.4 Unless stated otherwise, the length and width ofrectangular specimens shall be in the plane of the two majordimensions of the product.7.5 The specimen thickness shall be measured using amicrometer with a precision of 0.0001 in. (0.00254 mm)
28、.FIG. 1 Direction of BendingFIG. 2 V-Block and Punch for 90 Bend TestFIG. 3 Fixture for 180 Bend TestFIG. 4 Narrow Width Specimen Produced by StampingB820 1828. Procedure8.1 Direction of TestAll tests shall be performed with theaxis of the bend at 90 to the specimen length.8.2 90 Bend Test:8.2.1 Pla
29、ce the specimen between the supports and applythe bend force until the angle of bend reaches 90. Release theforce and examine the specimen.8.3 180 Bend Test:8.3.1 Adjust the specimen supports using the dial indicators.Move each support away from the test punch center-line (fullyclosed position) by a
30、 distance equal to the strip thickness plusthe punch radius, plus 0.0005 in. (0.013 mm).8.3.2 Place the specimen between the supports and applythe bend force until the angle of bend reaches 180. Release theforce and examine the specimen.8.4 Pass/Fail CriterionTo pass either the 90 or 180bend test, a
31、ll specimens for acceptance shall not exhibit anycracks when examined at a magnification of 30. (The appear-ance of orange peel or roughened surface does not constitute acrack. See Fig. 5.) Metallographic cross-section shall be usedas a referee method, examining at 150 magnification.9. Report9.1 The
32、 results shall be reported as a minimum bend ratio(smallest passing bend test radius/strip thickness). It shall bereferenced with the degree of bend (90 or 180) and testdirection (longitudinal or transverse).10. Retest10.1 If one test specimen fails, a retest is permitted. If morethan one specimen f
33、ails, no retesting is permitted.10.2 A retest requires that the original number of testspecimens, in the failed direction, pass the bend retest.11. Precision and Bias11.1 No information is presented about either precision orbias of Test Method B820 for measuring formability of copperand copper alloy
34、 strip since the test result is nonquantitative.12. Keywords12.1 bend radius; bend test; copper and copper alloy strip;formability test; fracture; longitudinal bend; mandrel; narrowwidth specimen; transverse bendAPPENDIX(Nonmandatory Information)X1. REPORTING OF NARROW SPECIMEN TEST RESULTS (R or th
35、rough the ASTM website(www.astm.org). Permission rights to photocopy the standard may also be secured from the Copyright Clearance Center, 222Rosewood Drive, Danvers, MA 01923, Tel: (978) 646-2600; http:/ X1.1 Example 1 Reporting TableDir, Good Way (GW)/Bad Way (BW)Degree 90/180Minimum Bend Radius (MBR)at R3 at 0.095 in.0.024 in. 0.047 in. 0.095 in. 0.189 in.12 in.longitudinal 90 MBR = 1.0 R1 R2 R3 R3 R4longitudinal 180 MBR = 1.5 R1 R2 R3 R3 R4transverse 90 MBR = 2.0 R2 R3 R3 R4 R4transverse 180 MBR = 3.0 R2 R3 R3 R5 R5B820 184
