1、Designation: E 290 97a (Reapproved 2004)Standard Test Methods forBend Testing of Material for Ductility1This standard is issued under the fixed designation E 290; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last rev
2、ision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the Department of Defense.1. Scope1.1 These test methods cover bend testing for du
3、ctility ofmaterials. Included in the procedures are four conditions ofconstraint on the bent portion of the specimen; a guided-bendtest using a mandrel or plunger of defined dimensions to forcethe mid-length of the specimen between two supports separatedby a defined space; a semi-guided-bend test in
4、 which thespecimen is bent, while in contact with a mandrel, through aspecified angle or to a specified inside radius (r) of curvature,measured while under the bending force; a free-bend test inwhich the ends of the specimen are brought toward each other,but in which no transverse force is applied t
5、o the bend itselfand there is no contact of the concave inside surface of thebend with other material; a bend and flatten test, in which atransverse force is applied to the bend such that the legs makecontact with each other over the length of the specimen.1.2 After bending, the convex surface of th
6、e bend isexamined for evidence of a crack or surface irregularity. If thespecimen fractures, the material has failed the test. Whencomplete fracture does not occur, the criterion for failure is thenumber and size of cracks or other surface irregularity visibleto the unaided eye occurring on the conv
7、ex surface of thespecimen after bending, as specified by the product standard.Any cracks within one thickness of the edge of the specimenare not considered a bend test failure. Cracks occurring in thecorners of the bent portion shall not be considered significantunless they exceed the size specified
8、 for corner cracks in theproduct standard.1.3 The values stated in SI units are to be regarded asstandard. Inch-pound values given in parentheses were used inestablishing test parameters and are for information only.1.4 This standard does not purport to address all of thesafety concerns, if any, ass
9、ociated with its use. It is theresponsibility 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.2. Referenced Documents2.1 ASTM Standards:2E6 Terminology Relating to Methods of Mechanical Test-in
10、gE8 Test Methods for Tension Testing of Metallic MaterialsE8M Test Methods for Tension Testing of Metallic Mate-rials (Metric)E18 Test Methods for Rockwell Hardness and RockwellSuperficial Hardness of Metallic MaterialsE 190 Test Method for Guided Bend Test for Ductility ofWelds3. Summary of Test Me
11、thods3.1 Four methods for ductility testing employing bendingare included in these test methods. Two methods have sub-groups with specific procedures.3.1.1 Guided-Bend3.1.2 Semi-guided Bend:3.1.2.1 Arrangement A, specimen held at one end.3.1.2.2 Arrangement B, for thin material.3.1.2.3 Arrangement C
12、, mandrel contact force in the bend.3.1.3 Free-Bend:3.1.3.1 Type 1, 180 bend.3.1.3.2 Type 2, bend flat on itself.3.1.4 Bend and Flatten:3.2 A guided bend test for ductility of welds is described inMethod E 190 and may be used for flat-rolled materials whenspecified by the product standard. The essen
13、tial features of thisbending method are employed in Method 1 Guided-Bend(3.1.1).3.3 Bend tests are made in one of two directions relative tothe principal working direction employed in production pro-cessing of the material.3.3.1 Longitudinal tests use a specimen with its long dimen-sion aligned with
14、 the processing direction such that the bend isformed across the processing direction, as shown in Fig. 1.1This test method is under the jurisdiction of ASTM Committee E28 onMechanical Testing and is the direct responsibility of Subcommittee E28.02 onDuctility and Flexure Testing.Current edition app
15、roved Oct. 1, 2004. Published October 2004. Originallyapproved in 1966. Last previous edition approved in 1997 as E 290 97a.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, r
16、efer to the standards Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.3.3.2 Transverse tests use a specimen with the long dimen-sion perpendicular to the processing direction so that the benda
17、xis is aligned with the processing direction, as shown in Fig.2. The axis of bend is the center of the bend radius.3.3.3 Thin sheet products are generally produced by reduc-ing the thickness of stock in rolling mills and from this the termrolling direction is used to identify the principal processin
18、gdirection. Similarly, a product produced in coil form may havethe processing direction referred to as the coiling direction.3.4 The location of the force application to the specimenrelative to the bend itself and the amount of bending differen-tiate the four methods of bending covered in these test
19、methods. The two semi-guided-bend test procedures provideradiused surfaces over which the bend is formed. The resultsobtained by different test procedures may not be the same,especially for material with a tendency to crack or fracture.3.5 The test is completed when the designated angle ofbend, or o
20、ther specified condition, has been reached.3.5.1 If a defined amount of cracking is permitted by theproduct standard, the convex surface of the bend region isexamined for cracks and surface irregularities.3.5.2 Surface irregularities, such as orange peel, loss ofcoating adherence, or imperfections r
21、esulting from the bend,shall be noted as required by the product specification.3.6 Guided-BendThe guided-bend test is made by sup-porting the specimen on pins, rollers, or radiused flats neareach end and applying a force through a pin, mandrel, orplunger midway between two supports, as shown schemat
22、i-cally in Fig. 3, until the desired bend is formed. No force isapplied directly to the outer face of the bend.3.6.1 The radii of the plunger and of the two supports shallbe defined in the product specification as related to thethickness (t) of the specimen being tested. A clearance of threethicknes
23、s with a tolerance of one half thickness shall beprovided between the pins, plunger, and specimen in the initialbend fixture.3.6.1.1 The distance between supports (C) shall be threethicknesses plus twice the plunger radius, with a tolerance ofone-half thickness, as shown in Fig. 3.3.6.2 The surfaces
24、 of the supports and plunger shall behardened to between 20 and 30 HRC. Refer to Method E18.3.6.3 The supports can be fixed or free to rotate. A lubricantmay be applied to the supports and plunger.3.6.4 The width of the guided-bend fixture, including thesupports and plunger, shall be such that the s
25、pecimen is subjectto the bending force across its width (w) during bending.3.6.5 When the thickness or strength of the specimen, orcapacity of the guided-bend test fixture (shown in Fig. 3) doesnot produce the required amount of bending, the specimen canbe removed from the fixture and the bend compl
26、eted byapplying force against the ends of the specimen, as shownschematically in Fig. 4. A spacer with a thickness equal totwice the required bend radius is inserted at the location of thebend. The edges at the ends shall be constrained so thespecimen cannot eject from the fixture under the bending
27、force.NOTE 1Arrow indicates direction of processing.FIG. 1 Longitudinal Bend TestNOTE 1Arrow indicates direction of processing.FIG. 2 Transverse Bend TestNOTE 1C = distance between lower supports,r = radius of the end of the mandrel or plunger,t = sheet specimen thickness,d = round specimen diameter
28、, andw = sheet specimen width.FIG. 3 Schematic Fixture for the Guided-Bend TestFIG. 4 Schematic Fixture for Completing the Guided-Bend TestStarted as Shown in Fig. 3E 290 97a (2004)23.6.6 Surface cracks and imperfections resulting from thebend shall be evaluated and reported.3.7 Semi-guided BendThe
29、semi-guided-bend test employsa constraining force on the inside of the bend during theinitiation of the bending and continuing until the final bendcondition is achieved.3.7.1 The semi-guided bend test is made by applying a forcetransversely to the specimens long axis in the portion that isbeing bent
30、.3.7.2 The angle of bend in the semi-guided-bend test ismeasured while the specimen is held stationary under the forceforming the bend.3.7.3 The location of the bend along the length of thespecimen is unimportant. The specimen is clamped or sup-ported by one of the methods shown schematically in Fig
31、s. 5-7.It is possible that different results will be obtained with the useof different devices. The method used shall be described in thetest report on the ductility of the material being evaluated.3.7.4 Arrangement AOne End HeldArrangement A in-volves holding one end of the semi-guided bend specime
32、n andapplying a force transversely near the free end as in Fig. 5. Thebend is formed around a stationary pin, mandrel, or roller of aspecified radius. Bending is continued until failure occurs orthe specified angle of bend has been achieved.3.7.5 Arrangement BThin Materials Arrangement B isfor semi-
33、guided bend tests of thin specimens, and includes asupport between the clamp and the bend radius, as shownschematically in Fig. 6. No tension force is applied to thespecimen during the bending. The results should be the samefor tests using either Arrangement A, or Arrangement B.3.7.6 Arrangement CMa
34、ndrel Contact on OuterSurfaceArrangement C employs a stationary pin, or mandrel,over which the semi-guided-bend specimen is bent by the forceof a roller, or mandrel, in contact with the outer surface of thebend (as shown schematically in Fig. 7). This may exert a smalltension force in the bend. The
35、test is sometimes referred to asa wrap, but it is distinct from the wrap around wire testdescribed in Method E6.3.7.7 Surface cracks and irregularities resulting from thebend shall be evaluated and reported.3.8 Free-BendThe free-bend test is made with no externalforce applied to the specimen in the
36、immediate area of thebend.3.8.1 The force to initiate bending for a free-bend test shallbe applied at, or within one width distance from, the ends of thespecimen. This may be done by gripping the specimen. If thematerial is too stiff to respond to such force it shall besupported at the mid-length (a
37、s shown schematically in Fig. 8)over a span of at least the specimen width while the initial forceis applied near the two ends of the specimen.3.8.2 The angle of a free-bend is measured once thespecimen has been removed from the bending fixture and isunder no constraining force. There is no radius o
38、f bendmeasurement required for a free-bend test.3.8.3 Type 1-Free-Bend180 BendThe bending is initi-ated as described in 3.8.1 and is then continued until a 180bend is developed by applying force to bring the legs of thespecimen to a parallel position (as shown schematically in Fig.9).3.8.4 Type 2-Fr
39、ee Bend (Flat on Itself Bend)The legs ofthe specimen are placed under flat platens and compressed tocontact no closer than one width of specimen distance from theouter 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
40、 Type 1-Free-Bend test. For this reason, thetype of bending used shall be described in the report.FIG. 5 Schematic Fixture for Semi-Guided-Bend TestArrangement AOne End HeldForce Applied Near Free EndFIG. 6 Arrangement B for Semi-Guided-Bend Test of ThinSpecimensOne End HeldFIG. 7 Schematic Fixture
41、for Semi-Guided-Bend TestArrangement COne End HeldForce Applied Near MandrelFIG. 8 Free-Bend Support and ForceE 290 97a (2004)33.8.6 Materials that age harden at room temperature shall betested within the allowed period of time, as defined in theproduct standard.3.8.7 After completing the free-bend,
42、 the surface is exam-ined for cracks and imperfections.3.9 Bend and FlattenFor the bend and flatten test forductility, an initial 180 bend is made as described in 3.8.1 and3.8.3. The specimen is then placed between two parallelplatens extending beyond the bent portion of the specimen andwider than t
43、he specimen width.3.9.1 Force is exerted to clamp the specimen and cause thetwo legs to contact at the bend, exclusive of the eye of the bend(as shown schematically in Fig. 11).3.9.2 Examination for cracks in the outer surface of the bendis done after removing the specimen from the bending forceand
44、allowing springback. The allowed number and size ofcracks on the outer surface of the bend shall be as specified inthe product standard.3.9.3 Any surface imperfections resulting from the bend testshall be noted and reported.4. Significance and Use4.1 Bend tests for ductility provide a simple way to
45、evaluatethe quality of materials by their ability to resist cracking orother surface irregularities during one continuous bend. Noreversal of the bend force shall be employed when conductingthese tests.4.2 The type of bend test used determines the location of theforces and constraints on the bent po
46、rtion of the specimen,ranging from no direct contact to continuous contact.4.3 The test can terminate at a given angle of bend over aspecified radius or continue until the specimen legs are incontact. The bend angle can be measured while the specimen isunder the bending force (usually when the semi-
47、guided bendtest is employed), or after removal of the force as whenperforming a free-bend test. Product requirements for thematerial being tested determine the method used.4.4 Materials with an as-fabricated cross section of rectan-gular, round, hexagonal, or similar defined shape can be testedin fu
48、ll section to evaluate their bend properties by using theprocedures outlined in these test methods, in which caserelative width and thickness requirements do not apply.5. Apparatus5.1 To prevent the introduction of uncontrolled forces whileaccomplishing the bend, the following clamping and forceappl
49、ication devices shall be used.5.2 Guided-Bend TestThe shape of the material duringbending is controlled by employing a pair of pins, rollers, orsurfaces with end radiused flat to support the specimen while aguided plunger bends the material at its mid-length, as shownschematically in Fig. 3.Amore detailed description of a fixtureused for this test is given in Method E 190.5.2.1 When the guided-bend test is to be finished by bendingthrough a 180 bend that cannot be achieved using the fixtureshown in Fig. 3, a fixture shown schematically in Fig. 4 can beus
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