1、Designation: E290 13Standard Test Methods forBend Testing of Material for Ductility1This standard is issued under the fixed designation E290; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number in pa
2、rentheses indicates the year of last reapproval. Asuperscript epsilon () 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 ductility ofmaterials. I
3、ncluded 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 which thespecimen is
4、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 to the bend itselfand t
5、here 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 the bend isexamined for
6、evidence of a crack or surface irregularities. Ifthe specimen fractures, the material has failed the test. Whencomplete fracture does not occur, the criterion for failure is thenumber and size of cracks or surface irregularities visible to theunaided eye occurring on the convex surface of the specim
7、enafter bending, as specified by the product standard. Any crackswithin one thickness of the edge of the specimen are notconsidered a bend test failure. Cracks occurring in the cornersof the bent portion shall not be considered significant unlessthey exceed the size specified for corner cracks in th
8、e productstandard.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, associated with its use. It
9、 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 TestingE8/E8M Test Methods for
10、Tension Testing of Metallic Ma-terialsE18 Test Methods for Rockwell Hardness of Metallic Ma-terialsE190 Test Method for Guided Bend Test for Ductility ofWelds3. Summary of Test Methods3.1 Four methods for ductility testing employing bendingare included in these test methods. Three methods havesubgro
11、ups with specific procedures.3.1.1 Guided Bend:3.1.1.1 Guided Bend, No Die,3.1.1.2 Guided Bend, U-Bend,3.1.1.3 Guided Bend, V-Bend,3.1.1.4 Guided Bend, V-Bend for cold rolled sheet,3.1.2 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
12、 Arrangement C, 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 E190 and may be used for flat-rolled materials whenspecified by the product standa
13、rd. The essential features of thisbending method are employed in 3.1.1.2, Guided Bend,U-Bend.3.3 Bend tests are made in one of two directions relative tothe principal working direction employed in production pro-cessing of the material.1This test method is under the jurisdiction of ASTM Committee E2
14、8 onPetroleum Products and Lubricants and is the direct responsibility of SubcommitteeE28.02 on Ductility and Formability.Current edition approved April 1, 2013. Published May 2013. Originallyapproved in 1966. Last previous edition approved in 2009 as E290 09. DOI:10.1520/E0290-13.2For referenced AS
15、TM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshoho
16、cken, PA 19428-2959. United States13.3.1 Longitudinal tests use a specimen with its long dimen-sion aligned with the processing direction such that the bend isformed across the processing direction, as shown in Fig. 1.3.3.2 Transverse tests use a specimen with the long dimen-sion perpendicular to th
17、e processing direction so that the bendaxis 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
18、used to identify the principal processingdirection. 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
19、methods of bending covered in these testmethods. 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 complete
20、d when the designated angle ofbend, or other 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
21、 ofcoating adherence, or imperfections resulting 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 near each end on pins, rollers, or flatsurfaces with appropriate end radii and applying a forcethrough a pin,
22、 mandrel, plunger, or male die midway betweentwo supports, as shown schematically in Fig. 3, Fig. 4, Fig. 5,and Fig. 6 until the desired bend is formed. No force is applieddirectly to the outer face of the bend when no female die isused (3.1.1.1). Some force may be applied by the female die tothe ou
23、ter face of the bend in the case of U-bend (3.1.1.2) andV-bends (3.1.1.3 and 3.1.1.4). In some cases, for U-bend andV-bends it may be necessary for the specimen to bottom out inthe female die to ensure the correct amount of bending.3.6.1 The radii of the plunger and of the two supports shallbe defin
24、ed in the product specification as related to thethickness (t) of the specimen being tested. A clearance of threethickness 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 thr
25、eethicknesses plus twice the plunger radius, with a tolerance ofone-half thickness, as shown in Fig. 3.3.6.1.2 When female dies are used for U-bend and V-bend,they shall conform approximately to the geometries shown inFig. 4, Fig. 5, and Fig. 6.3.6.2 The surfaces of the supports and plunger shall be
26、harder than the material tested. Refer to Test Methods 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 bend region of thespecimen is subj
27、ect to 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 completed byapplying
28、 force against the ends of the specimen, as shownschematically in Fig. 7. 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 force.3.6.6 Sur
29、face cracks and imperfections resulting from thebend shall be evaluated and reported.3.7 Semi-guided BendThe 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
30、bend test is made by applying a forcetransversely to the specimens long axis in the portion that isbeing bent.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 thesp
31、ecimen is unimportant. The specimen is clamped or sup-ported by one of the methods shown schematically in Figs.8-10. It is possible that different results will be obtained withthe use of different devices. The method used shall bedescribed in the test report on the ductility of the material beingeva
32、luated.3.7.4 Arrangement AOne End HeldArrangement A in-volves holding one end of the semi-guided bend specimen andapplying a force transversely near the free end as in Fig. 8. Thebend is formed around a stationary pin, mandrel, or roller of aNOTE 1Arrow indicates direction of processing.FIG. 1 Longi
33、tudinal Bend TestNOTE 1Arrow indicates direction of processing.FIG. 2 Transverse Bend TestE290 132NOTE 1C = distance between lower supports,r = radius of the end of the mandrel or plunger,t = sheet specimen thickness,d = round specimen diameter, andw = sheet specimen width.FIG. 3 Schematic Fixture f
34、or the Guided Bend, No Die TestFIG. 4 Schematic Fixture for the Guided Bend, U-bend TestE290 133specified 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-guided bend tests of thin specimens,
35、and includes asupport between the clamp and the bend radius, as shownschematically in Fig. 9. 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 CMandrel Contact on OuterSurfaceArrangem
36、ent 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. 10). This may exert asmall tension force in the bend. The test is sometimes referredto as a wr
37、ap, 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 immediate area of thebend.3.8.1 The
38、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 (as shown schematically in Fig. 11)FIG
39、. 5 Schematic Fixture for the Guided Bend, V- Bend TestE290 134over 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 constrain
40、ing force. There is no radius of bendmeasurement required for a free-bend test.FIG. 6 Schematic Fixture for the Guided Bend, V- Bend Test for Cold Rolled SheetFIG. 7 Schematic Fixture for Completing the Guided-Bend TestStarted as Shown in Fig. 3FIG. 8 Schematic Fixture for Semi-Guided Bend Test Arra
41、nge-ment AOne End HeldForce Applied Near Free EndE290 1353.8.3 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.12).3.8.4
42、 Type 2-Free 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.13).3.8.5 The bending force is more severe in a Type 2-Free-Bend test
43、 than in a Type 1-Free-Bend test. For this reason, thetype of bending used shall be described in the report.3.8.6 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, the surface is exa
44、m-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 the specimen width.3
45、.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. 14).3.9.2 Examination for cracks in the outer surface of the bendis done after removing the specimen from the bending forceand allowing springback
46、. 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 evaluatethe quality
47、 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 portion of the specim
48、en,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-guided bendtest is
49、employed), or after removal of the force as whenFIG. 9 Arrangement B for Semi-Guided Bend Test of ThinSpecimensOne End HeldFIG. 10 Schematic Fixture for Semi-Guided Bend Test Arrange-ment COne End HeldForce Applied Near MandrelFIG. 11 Free Bend Support and ForceFIG. 12 Type 1 180 Free BendNOTE 1The distance from the clamping platens to the outer bend shallnot be less than the width (w) of the bend specimen.FIG. 13 Type 2 Flat-on-Itself Free BendE290 136performing a free-bend test. Product requirements for thematerial being tested determine the met
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