1、Designation: E290 13E290 14Standard 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 numbe
2、r in parentheses 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 U.S. Department of Defense.1. Scope Scope*1.1 These test methods cover bend testing for ducti
3、lity of materials. Included in the procedures are four conditions of constrainton the bent portion of the specimen; a guided-bend test using a mandrel or plunger of defined dimensions to force the mid-lengthof the specimen between two supports separated by a defined space; a semi-guided bend test in
4、 which the specimen is bent, whilein contact with a mandrel, through a specified angle or to a specified inside radius (r) of curvature, measured while under thebending force; a free-bend test in which the ends of the specimen are brought toward each other, but in which no transverse forceis applied
5、 to the bend itself and there is no contact of the concave inside surface of the bend with other material; a bend and flattentest, in which a transverse force is applied to the bend such that the legs make contact with each other over the length of thespecimen.1.2 After bending, the convex surface o
6、f the bend is examined for evidence of a crack or surface irregularities. If the specimenfractures, the material has failed the test. When complete fracture does not occur, the criterion for failure is the number and sizeof cracks or surface irregularities visible to the unaided eye occurring on the
7、 convex surface of the specimen after bending, asspecified by the product standard. Any cracks within one thickness of the edge of the specimen are not considered a bend testfailure. Cracks occurring in the corners of the bent portion shall not be considered significant unless they exceed the size s
8、pecifiedfor 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 inestablishing test parameters and are for information only.1.4 This standard does not purport to address all of the safety concerns, i
9、f any, associated with its use. It is the responsibilityof the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatorylimitations prior to use.2. Referenced Documents2.1 ASTM Standards:2E6 Terminology Relating to Methods of Mechanical
10、TestingE8/E8M Test Methods for Tension Testing of Metallic MaterialsE18 Test Methods for Rockwell Hardness of Metallic MaterialsE190 Test Method for Guided Bend Test for Ductility of Welds3. Summary of Test Methods3.1 Four methods for ductility testing employing bending are included in these test me
11、thods. Three methods have subgroupswith 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,1 This test method is under the jurisdiction of ASTM Committee E28 on Mechanical Testing
12、 and is the direct responsibility of Subcommittee E28.02 on Ductility andFormability.Current edition approved April 1, 2013May 1, 2014. Published May 2013September 2014. Originally approved in 1966. Last previous edition approved in 20092013 asE290 09.E290 13. DOI: 10.1520/E0290-13.10.1520/E0290-14.
13、2 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.This document is not an ASTM standard and is intended only to
14、 provide the user of an ASTM standard an indication of what changes have been made to the previous version. Becauseit may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current versionof
15、 the standard as published by ASTM is to be considered the official document.*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 States13.1.2 Semi-guided Bend:3.1.2.1 Arrangement A
16、, specimen held at one end.3.1.2.2 Arrangement B, for thin material.3.1.2.3 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 in Method E190 a
17、nd may be used for flat-rolled materials whenspecified by the product standard. The essential features of this bending method are employed in 3.1.1.2, Guided Bend, U-Bend.3.3 Bend tests are made in one of two directions relative to the principal working direction employed in production processingof
18、the material.3.3.1 Longitudinal tests use a specimen with its long dimension 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 dimension perpendicular to the processing direction s
19、o that the bend axisis 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 reducing the thickness of stock in rolling mills and from this the termrolling direction is used to identify the pri
20、ncipal processing direction. Similarly, a product produced in coil form may have theprocessing direction referred to as the coiling direction.3.4 The location of the force application to the specimen relative to the bend itself and the amount of bending differentiate thefour methods of bending cover
21、ed in these test methods. The two semi-guided bend test procedures provide radiused surfaces overwhich the bend is formed. The results obtained by different test procedures may not be the same, especially for material with atendency to crack or fracture.3.5 The test is completed when the designated
22、angle of bend, or other specified condition, has been reached.3.5.1 If a defined amount of cracking is permitted by the product standard, the convex surface of the bend region is examinedfor cracks and surface irregularities.3.5.2 Surface irregularities, such as orange peel, loss of coating adherenc
23、e, or imperfections resulting from the bend, shall benoted as required by the product specification.3.6 Guided BendThe guided-bend test is made by supporting the specimen near each end on pins, rollers, or flat surfaces withappropriate end radii and applying a force through a pin, mandrel, plunger,
24、or male die midway between two supports, as shownschematically in Fig. 3, Fig. 4, Fig. 5, and Fig. 6 until the desired bend is formed. No force is applied directly to the outer faceof the bend when no female die is used (3.1.1.1). Some force may be applied by the female die to the outer face of the
25、bend inthe case of U-bend (3.1.1.2) and V-bends (3.1.1.3 and 3.1.1.4). In some cases, for U-bend and V-bends it may be necessary forthe specimen to bottom out in the female die to ensure the correct amount of bending.3.6.1 The radii of the plunger and of the two supports shall be defined in the prod
26、uct specification as related to the thickness(t) of the specimen being tested. A clearance of three thickness with a tolerance of one half thickness shall be provided betweenthe pins, plunger, and specimen in the initial bend fixture.3.6.1.1 The distance between supports (C) shall be three thickness
27、es plus twice the plunger radius, with a tolerance of one-halfthickness, 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 in Fig.4, Fig. 5, and Fig. 6.3.6.2 The surfaces of the supports and plunger shall be harder th
28、an the material tested. Refer to Test Methodshard enough toresist plastic deformation and wear that can be observed after the test. If visible flattening, wear, or E18.other permanentdeformation of the test fixtures does occur, the test is invalid.NOTE 1Arrow indicates direction of processing.FIG. 1
29、 Longitudinal Bend TestE290 142NOTE 1Supports and plungers hardened to at least 20 HRC have been found to be generally suitable for this test. It is recommended that checkingby the unaided eye for flattening, wear, or other deformation of the test fixtures take place after testing different and pote
30、ntially harder materials than usual.3.6.3 The supports can be fixed or free to rotate. A lubricant may be applied to the supports and plunger.3.6.4 The width of the guided-bend fixture, including the supports and plunger, shall be such that the bend region of thespecimen is subject to the bending fo
31、rce across its width (w) during bending.3.6.5 When the thickness or strength of the specimen, or capacity of the guided-bend test fixture (shown in Fig. 3) does notproduce the required amount of bending, the specimen can be removed from the fixture and the bend completed by applying forceagainst the
32、 ends of the specimen, as shown schematically in Fig. 7. A spacer with a thickness equal to twice the required bendradius is inserted at the location of the bend. The edges at the ends shall be constrained so the specimen cannot eject from thefixture under the bending force.3.6.6 Surface cracks and
33、imperfections resulting from the bend shall be evaluated and reported.3.7 Semi-guided BendThe semi-guided bend test employs a constraining force on the inside of the bend during the initiationof the bending and continuing until the final bend condition is achieved.3.7.1 The semi-guided bend test is
34、made by applying a force transversely to the specimens long axis in the portion that is beingbent.3.7.2 The angle of bend in the semi-guided bend test is measured while the specimen is held stationary under the force formingthe bend.3.7.3 The location of the bend along the length of the specimen is
35、unimportant. The specimen is clamped or supported by oneof the methods shown schematically in Figs. 8-10. It is possible that different results will be obtained with the use of differentdevices. The method used shall be described in the test report on the ductility of the material being evaluated.3.
36、7.4 Arrangement AOne End HeldArrangement A involves holding one end of the semi-guided bend specimen andapplying a force transversely near the free end as in Fig. 8. The bend is formed around a stationary pin, mandrel, or roller of aspecified radius. Bending is continued until failure occurs or the
37、specified angle of bend has been achieved.3.7.5 Arrangement BThin MaterialsArrangement B is for semi-guided bend tests of thin specimens, and includes a supportbetween the clamp and the bend radius, as shown schematically in Fig. 9. No tension force is applied to the specimen during thebending. The
38、results should be the same for tests using either Arrangement A, or Arrangement B.3.7.6 Arrangement CMandrel Contact on Outer SurfaceArrangement C employs a stationary pin, or mandrel, over whichthe semi-guided bend specimen is bent by the force of a roller, or mandrel, in contact with the outer sur
39、face of the bend (as shownschematically in Fig. 10). This may exert a small tension force in the bend. The test is sometimes referred to as a wrap, but it isdistinct from the wrap around wire test described in Method E6.3.7.7 Surface cracks and irregularities resulting from the bend shall be evaluat
40、ed and reported.3.8 Free-BendThe free-bend test is made with no external force applied to the specimen in the immediate area of the bend.3.8.1 The force to initiate bending for a free-bend test shall be applied at, or within one width distance from, the ends of thespecimen. This may be done by gripp
41、ing the specimen. If the material is too stiff to respond to such force it shall be supportedat the mid-length (as shown schematically in Fig. 11) over a span of at least the specimen width while the initial force is appliednear the two ends of the specimen.3.8.2 The angle of a free-bend is measured
42、 once the specimen has been removed from the bending fixture and is under noconstraining force. There is no radius of bend measurement required for a free-bend test.3.8.3 Type 1-Free-Bend180 BendThe bending is initiated as described in 3.8.1 and is then continued until a 180 bend isdeveloped by appl
43、ying force to bring the legs of the specimen to a parallel position (as shown schematically in Fig. 12).3.8.4 Type 2-Free Bend (Flat on Itself Bend)The legs of the specimen are placed under flat platens and compressed to contactno closer than one width of specimen distance from the outer extension o
44、f the bend (as shown schematically in Fig. 13).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 typeof bending used shall be described in the report.3.8.6 Materials that age harden at room temperature shall be tested within the a
45、llowed period of time, as defined in the productstandard.NOTE 1Arrow indicates direction of processing.FIG. 2 Transverse Bend TestE290 143NOTE 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 s
46、pecimen width.FIG. 3 Schematic Fixture for the Guided Bend, No Die TestFIG. 4 Schematic Fixture for the Guided Bend, U-bend TestE290 1443.8.7 After completing the free-bend, the surface is examined for cracks and imperfections.3.9 Bend and FlattenFor the bend and flatten test for ductility, an initi
47、al 180 bend is made as described in 3.8.1 and 3.8.3.The specimen is then placed between two parallel platens extending beyond the bent portion of the specimen and wider than thespecimen width.3.9.1 Force is exerted to clamp the specimen and cause the two legs to contact at the bend, exclusive of the
48、 eye of the bend(as shown schematically in Fig. 14).3.9.2 Examination for cracks in the outer surface of the bend is done after removing the specimen from the bending force andallowing springback. The allowed number and size of cracks on the outer surface of the bend shall be as specified in the pro
49、ductstandard.3.9.3 Any surface imperfections resulting from the bend test shall be noted and reported.4. Significance and Use4.1 Bend tests for ductility provide a simple way to evaluate the quality of materials by their ability to resist cracking or othersurface irregularities during one continuous bend. No reversal of the bend force shall be employed when conducting these tests.FIG. 5 Schematic Fixture for the Guided Bend, V- Bend TestE290 1454.2 The type of bend test used determines the location of the forces and constraints on the bent portion of
