ASTM E290-97a
(Test Method)Standard Test Method for Bend Testing of Material for Ductility
Standard Test Method for Bend Testing of Material for Ductility
SCOPE
1.1 These test methods cover bend testing for ductility of materials. Included in the procedures are four conditions of constraint on the bent portion of the specimen; a guided-bend test using a mandrel or plunger of defined dimensions to force the mid-length of the specimen between two supports separated by a defined space; a semi-guided-bend test in which the specimen is bent, while in contact with a mandrel, through a specified angle or to a specified inside radius (r) of curvature, measured while under the bending force; a free-bend test in which the ends of the specimen are brought toward each other, but in which no transverse force is applied to the bend itself and there is no contact of the concave inside surface of the bend with other material; a bend and flatten test, in which a transverse force is applied to the bend such that the legs make contact with each other over the length of the specimen.
1.2 After bending, the convex surface of the bend is examined for evidence of a crack or surface irregularity. If the specimen fractures, the material has failed the test. When complete fracture does not occur, the criterion for failure is the number and size of cracks or other surface irregularity visible to the unaided eye occurring on the convex surface of the specimen after bending, as specified by the product standard. Any cracks within one thickness of the edge of the specimen are not considered a bend test failure. Cracks occurring in the corners of the bent portion shall not be considered significant unless they exceed the size specified for corner cracks in the product standard.
1.3 The values stated in SI units are to be regarded as standard. Inch-pound values given in parentheses were used in establishing test parameters and are for information only.
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.
General Information
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Standards Content (Sample)
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Designation:E290–97a
Standard Test Methods for
Bend Testing of Material for Ductility
This standard is issued under the fixed designation E290; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
This specification has been approved for use by agencies of the Department of Defense.
1. Scope 2. Referenced Documents
1.1 These test methods cover bend testing for ductility of 2.1 ASTM Standards:
materials. Included in the procedures are four conditions of E6 Terminology Relating to Methods of Mechanical Test-
constraint on the bent portion of the specimen; a guided-bend ing
test using a mandrel or plunger of defined dimensions to force E8 TestMethodsforTensionTestingofMetallicMaterials
themid-lengthofthespecimenbetweentwosupportsseparated E8M Test Methods for Tension Testing of Metallic Mate-
by a defined space; a semi-guided-bend test in which the rials (Metric)
specimen is bent, while in contact with a mandrel, through a E18 Test Methods for Rockwell Hardness and Rockwell
specified angle or to a specified inside radius (r) of curvature, Superficial Hardness of Metallic Materials
measured while under the bending force; a free-bend test in E190 Test Method for Guided Bend Test for Ductility of
which the ends of the specimen are brought toward each other, Welds
but in which no transverse force is applied to the bend itself
3. Summary of Test Methods
and there is no contact of the concave inside surface of the
3.1 Four methods for ductility testing employing bending
bend with other material; a bend and flatten test, in which a
transverse force is applied to the bend such that the legs make are included in these test methods. Two methods have sub-
groups with specific procedures.
contact with each other over the length of the specimen.
1.2 After bending, the convex surface of the bend is 3.1.1 Guided-Bend
3.1.2 Semi-guided Bend:
examined for evidence of a crack or surface irregularity. If the
specimen fractures, the material has failed the test. When 3.1.2.1 Arrangement A, specimen held at one end.
3.1.2.2 Arrangement B, for thin material.
complete fracture does not occur, the criterion for failure is the
number and size of cracks or other surface irregularity visible 3.1.2.3 Arrangement C, mandrel contact force in the bend.
3.1.3 Free-Bend:
to the unaided eye occurring on the convex surface of the
specimen after bending, as specified by the product standard. 3.1.3.1 Type 1, 180° bend.
3.1.3.2 Type 2, bend flat on itself.
Any cracks within one thickness of the edge of the specimen
are not considered a bend test failure. Cracks occurring in the 3.1.4 Bend and Flatten:
3.2 Aguided bend test for ductility of welds is described in
corners of the bent portion shall not be considered significant
Method E190 and may be used for flat-rolled materials when
unless they exceed the size specified for corner cracks in the
product standard. specifiedbytheproductstandard.Theessentialfeaturesofthis
bending method are employed in Method 1 Guided-Bend
1.3 The values stated in SI units are to be regarded as
standard. Inch-pound values given in parentheses were used in (3.1.1).
3.3 Bend tests are made in one of two directions relative to
establishing test parameters and are for information only.
1.4 This standard does not purport to address all of the the principal working direction employed in production pro-
cessing of the material.
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro- 3.3.1 Longitudinaltestsuseaspecimenwithitslongdimen-
sion aligned with the processing direction such that the bend is
priate safety and health practices and determine the applica-
bility of regulatory limitations prior to use. formed across the processing direction, as shown in Fig. 1.
3.3.2 Transverse tests use a specimen with the long dimen-
sion perpendicular to the processing direction so that the bend
axis is aligned with the processing direction, as shown in Fig.
This test method is under the jurisdiction of ASTM Committee E-28 on
2. The axis of bend is the center of the bend radius.
Mechanical Testing and is the direct responsibility of Subcommittee E28.02 on
Ductility and Flexure.
Current edition approved May 10 and Dec. 10, 1997. Published February 1998.
Originally published as E290–66. Last previous edition E290–92. Annual Book of ASTM Standards, Vol 03.01.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
E290
NOTE 1—Arrow indicates direction of processing.
FIG. 1 Longitudinal Bend Test
NOTE 1—C=distance between lower supports,
r=radius of the end of the mandrel or plunger,
t=sheet specimen thickness,
d=round specimen diameter, and
w=sheet specimen width.
FIG. 3 Schematic Fixture for the Guided-Bend Test
one-half thickness, as shown in Fig. 3.
3.6.2 The surfaces of the supports and plunger shall be
NOTE 1—Arrow indicates direction of processing.
hardened to between 20 and 30 HRC. Refer to Method E18.
FIG. 2 Transverse Bend Test
3.6.3 The supports can be fixed or free to rotate.Alubricant
may be applied to the supports and plunger.
3.3.3 Thin sheet products are generally produced by reduc- 3.6.4 The width of the guided-bend fixture, including the
ingthethicknessofstockinrollingmillsandfromthistheterm supportsandplunger,shallbesuchthatthespecimenissubject
rolling direction is used to identify the principal processing to the bending force across its width (w) during bending.
direction. Similarly, a product produced in coil form may have 3.6.5 When the thickness or strength of the specimen, or
the processing direction referred to as the coiling direction. capacity of the guided-bend test fixture (shown in Fig. 3) does
3.4 The location of the force application to the specimen not produce the required amount of bending, the specimen can
relative to the bend itself and the amount of bending differen- be removed from the fixture and the bend completed by
tiate the four methods of bending covered in these test applying force against the ends of the specimen, as shown
methods. The two semi-guided-bend test procedures provide schematically in Fig. 4. A spacer with a thickness equal to
radiused surfaces over which the bend is formed. The results twice the required bend radius is inserted at the location of the
obtained by different test procedures may not be the same, bend. The edges at the ends shall be constrained so the
especially for material with a tendency to crack or fracture. specimencannotejectfromthefixtureunderthebendingforce.
3.5 The test is completed when the designated angle of 3.6.6 Surface cracks and imperfections resulting from the
bend, or other specified condition, has been reached. bend shall be evaluated and reported.
3.5.1 If a defined amount of cracking is permitted by the 3.7 Semi-guidedBend—Thesemi-guided-bendtestemploys
product standard, the convex surface of the bend region is a constraining force on the inside of the bend during the
examined for cracks and surface irregularities. initiation of the bending and continuing until the final bend
3.5.2 Surface irregularities, such as orange peel, loss of condition is achieved.
coating adherence, or imperfections resulting from the bend,
shall be noted as required by the product specification.
3.6 Guided-Bend—The guided-bend test is made by sup-
porting the specimen on pins, rollers, or radiused flats near
each end and applying a force through a pin, mandrel, or
plunger midway between two supports, as shown schemati-
cally in Fig. 3, until the desired bend is formed. No force is
applied directly to the outer face of the bend.
3.6.1 The radii of the plunger and of the two supports shall
be defined in the product specification as related to the
thickness (t) of the specimen being tested.Aclearance of three
thickness with a tolerance of one half thickness shall be
provided between the pins, plunger, and specimen in the initial
bend fixture.
3.6.1.1 The distance between supports (C) shall be three
FIG. 4 Schematic Fixture for Completing the Guided-Bend Test
thicknesses plus twice the plunger radius, with a tolerance of Started as Shown in Fig. 3
E290
3.7.1 Thesemi-guidedbendtestismadebyapplyingaforce
transversely to the specimen’s long axis in the portion that is
being bent.
3.7.2 The angle of bend in the semi-guided-bend test is
measuredwhilethespecimenisheldstationaryundertheforce
forming the bend.
3.7.3 The location of the bend along the length of the
specimen is unimportant. The specimen is clamped or sup-
portedbyoneofthemethodsshownschematicallyinFigs.5-7.
It is possible that different results will be obtained with the use
of different devices.The method used shall be described in the
test report on the ductility of the material being evaluated.
3.7.4 Arrangement A—One End Held—Arrangement A in-
volves holding one end of the semi-guided bend specimen and
FIG. 6 Arrangement B for Semi-Guided-Bend Test of Thin
applyingaforcetransverselynearthefreeendasinFig.5.The
Specimens—One End Held
bend is formed around a stationary pin, mandrel, or roller of a
specified radius. Bending is continued until failure occurs or
the specified angle of bend has been achieved.
3.7.5 Arrangement B—Thin Materials— Arrangement B is
for semi-guided bend tests of thin specimens, and includes a
support between the clamp and the bend radius, as shown
schematically in Fig. 6. No tension force is applied to the
specimen during the bending. The results should be the same
for tests using either Arrangement A, or Arrangement B.
3.7.6 Arrangement C—Mandrel Contact on Outer
FIG. 7 Schematic Fixture for Semi-Guided-Bend Test
Surface—ArrangementCemploysastationarypin,ormandrel,
Arrangement C—One End Held—Force Applied Near Mandrel
overwhichthesemi-guided-bendspecimenisbentbytheforce
of a roller, or mandrel, in contact with the outer surface of the
bend(asshownschematicallyinFig.7).Thismayexertasmall
tension force in the bend. The test is sometimes referred to as
a wrap, but it is distinct from the wrap around wire test
described in Method E6.
3.7.7 Surface cracks and irregularities resulting from the
bend shall be evaluated and reported.
3.8 Free-Bend—Thefree-bendtestismadewithnoexternal
force applied to the specimen in the immediate area of the
bend.
FIG. 8 Free-Bend Support and Force
3.8.1 The force to initiate bending for a free-bend test shall
beappliedat,orwithinonewidthdistancefrom,theendsofthe
specimen. This may be done by gripping the specimen. If the
measurement required for a free-bend test.
material is too stiff to respond to such force it shall be 3.8.3 Type 1-Free-Bend–180° Bend—The bending is initi-
supported at the mid-length (as shown schematically in Fig. 8)
ated as described in 3.8.1 and is then continued until a 180°
overaspanofatleastthespecimenwidthwhiletheinitialforce bend is developed by applying force to bring the legs of the
is applied near the two ends of the specimen.
specimen to a parallel position (as shown schematically in Fig.
3.8.2 The angle of a free-bend is measured once the 9).
specimen has been removed from the bending fixture and is
3.8.4 Type 2-Free Bend (Flat on Itself Bend)—The legs of
under no constraining force. There is no radius of bend the specimen are placed under flat platens and compressed to
FIG. 5 Schematic Fixture for Semi-Guided-Bend Test
Arrangement A—One End Held—Force Applied Near Free End FIG. 9 Type 1 180° Free-Bend
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E290
contactnocloserthanonewidthofspecimendistancefromthe
outer extension of the bend (as shown schematically in Fig.
10).
3.8.5 The bending force is more severe in a Type 2-Free-
Bend test than in a Type 1-Free-Bend test. For this reason, the
type of bending used shall be described in the report.
3.8.6 Materialsthatagehardenatroomtemperatureshallbe
tested within the allowed period of time, as defined in the
product standard.
FIG. 11 Bend and Flatten
3.8.7 After completing the free-bend, the surface is exam-
ined for cracks and imperfections.
in full section to evaluate their bend properties by using the
3.9 Bend and Flatten—For the bend and flatten test for
procedures outlined in these test methods, in which case
ductility,aninitial180° bendismadeasdescribedin3.8.1and
relative width and thickness requirements do not apply.
3.8.3. The specimen is then placed between two parallel
platens extending beyond the bent portion of the specimen and
5. Apparatus
wider than the specimen width.
5.1 Topreventtheintroductionofuncontrolledforceswhile
3.9.1 Force is exerted to clamp the specimen and cause the
accomplishing the bend, the following clamping and force
twolegstocontactatthebend,exclusiveoftheeyeofthebend
application devices shall be used.
(as shown schematically in Fig. 11).
5.2 Guided-Bend Test—The shape of the material during
3.9.2 Examinationforcracksintheoutersurfaceofthebend
bending is controlled by employing a pair of pins, rollers, or
is done after removing the specimen from the bending force
surfaces with end radiused flat to support the specimen while a
and allowing springback. The allowed number and size of
guided plunger bends the material at its mid-length, as shown
cracks on the outer surface of the bend shall be as specified in
schematicallyinFig.3.Amoredetaileddescriptionofafixture
the product standard.
used for this test is given in Method E190.
3.9.3 Anysurfaceimperfectionsresultingfromthebendtest
5.2.1 Whentheguided-bendtestistobefinishedbybending
shall be noted and reported.
through a 180° bend that cannot be achieved using the fixture
4. Significance and Use
shown in Fig. 3, a fixture shown schematically in Fig. 4 can be
4.1 Bendtestsforductilityprovideasimplewaytoevaluate
used to position the ends of the specimen and prevent it from
the quality of materials by their ability to resist cracking or
being ejected while a compression force is applied to bring the
other surface irregularities during one continuous bend. No
legs of the specimen together until they are parallel to each
reversal of the bend force shall be employed when conducting
other. A spacer with a thickness equal to twice the required
these tests.
radius is inserted at the bend to stop the force at the specified
4.2 Thetypeofbendtestuseddeterminesthelocationofthe
spacing.
forces and constraints on the bent portion of the specimen,
5.
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