ASTM B820-98

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Designation: B 820 – 98
Standard Test Method for
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Bend Test for Formability of Copper Alloy Spring Material
This standard is issued under the fixed designation B 820; 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 (e) indicates an editorial change since the last revision or reapproval.
1. Scope *
1.1 This test method covers the testing of thin copper alloy
strip to determine its formability or its ability to resist cracking
when forming around a specific radius. The criterion for failure
is the occurrence of cracks found on the outer radius of
curvature (convex).
1.2 This bend test is limited to strip 0.003 to 0.031 in. thick.
(0.076 to 0.79 mm).
1.3 The size of the forming radii used in this test shall be
FIG. 1 Illustration of Terminology
0.005 to 0.250 in. (0.127 to 6.35 mm).
1.4 The values stated in inch-pounds are to be regarded as
the standard. The values given in parentheses are for informa-
3.2.2 transverse bend (or bad way bend)—The axis of the
tion only.
bend is a plane parallel to the direction of rolling, drawing or
1.5 This standard does not purport to address all of the
extrusion as shown in Fig. 2.
safety concerns, if any, associated with its use. It is the
NOTE 1—The usage of these two terms is consistent with Test Method
responsibility of the user of this standard to establish appro-
E 290.
priate safety and health practices and determine the applica-
bility of regulatory limitations prior to use.
4. Summary of Test Method
4.1 The bend test is made by applying a force transversely
2. Referenced Documents
to the length of the specimen in the portion being bent, usually
2.1 The following documents in the current issue of the
at midlength. These 90° bending forces are applied through an
Annual Book of ASTM Standards form a part of this specifi-
arrangement illustrated in Fig. 3, while 180° bending forces are
cation to the extent referenced herein:
applied through an arrangement illustrated in Fig. 4. When
2.2 ASTM Standards:
complete fracture does not occur, the convex surface of the
E 6 Terminology Relating to Methods of Mechanical Test-
specimen is examined for cracks. In general, the test using a
2
ing
180° bend angle is a more severe test than the test using a 90°
E 290 Test Method for Semi-Guided Bend Test for Ductility
bend angle.
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of Metallic Materials
5. Significance and Use
3. Terminology
5.1 This bend test provides information as to the formability
3.1 The following terms are defined in Terminology E 6,
or the ability of copper alloy spring material to resist cracking
and are illustrated in Fig. 1.
when being formed.
3.1.1 angle of bend, and
5.2 This test method can be used as a quality control tool to
3.1.2 radius of bend.
determine if a spring material is capable of forming to a given
3.2 Description of Terms Specific to This Standard:
radius.
3.2.1 longitudinal bend (or good way bend)—The axis of
the bend is at an angle of 90° to the direction of rolling,
drawing or extrusion as shown in Fig. 2.
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This test method is under the jurisdiction of ASTM Committee B-5 on Copper
and Copper Alloys and is the direct responsibility of Subcommittee B05.06 on
Methods of Test.
Current edition approved March 10, 1998. Published February 1999. Originally
published as B 820 – 92. Last previous edition B 820 – 92.
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Annual Book of ASTM Standards, Vol 03.01. FIG. 2 Direction of Bending
*A Summary of Changes section appears at the end of this standard.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
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B 820
7.2 The test specimens may be prepared by cutting, shear-
ing, or stamping.
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7.3 The test specimens shall have a width of ⁄2 6 ⁄16 in.
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(12.7 6 1.57 mm) and of any convenient length greater than ⁄2
in. unless specified otherwise by purchaser.
7.4 Direction of Specimen:
FIG. 3 V-Block and Punch for 90° Bend Test 7.4.1 The bending characteristics of a metal vary with the
orientation of the bends to the direction of rolling. A longitu-
dinal or good way bend will take a sharper bend radius than a
transverse bend. This characteristic becomes more pronounced
as the metal thickness increases.
7.4.2 In a longitudinal or good way bend specimen, its
length shall be parallel to the direction of rolling as indicated
in Fig. 2.
7.4.3 In a transverse bend (or bad way bend) specimen, its
length shall be at an angle of 90° to the direction of rolling as
indicated in Fig. 2.
7.4.4 Unless stated otherwise, the length and width of
rectangular specimens shall be in the plane of the two major
dimensions of the product.
7.5 The specimen thickness shall be
...