1、BSI Standards PublicationBS EN ISO 7438:2016Metallic materials Bend testBS EN ISO 7438:2016 BRITISH STANDARDNational forewordThis British Standard is the UK implementation of EN ISO 7438:2016.It supersedes BS EN ISO 7438:2005 which is withdrawn.The UK participation in its preparation was entrusted t
2、o TechnicalCommittee ISE/101/2, Ductility testing.A list of organizations represented on this committee can beobtained on request to its secretary.This publication does not purport to include all the necessaryprovisions of a contract. Users are responsible for its correctapplication. The British Sta
3、ndards Institution 2016.Published by BSI Standards Limited 2016ISBN 978 0 580 88921 9ICS 77.040.10Compliance with a British Standard cannot confer immunity fromlegal obligations.This British Standard was published under the authority of theStandards Policy and Strategy Committee on 31 January 2016.A
4、mendments/corrigenda issued since publicationDate T e x t a f f e c t e dEUROPEAN STANDARD NORME EUROPENNE EUROPISCHE NORM EN ISO 7438 January 2016 ICS 77.040.10 Supersedes EN ISO 7438:2005English Version Metallic materials - Bend test (ISO 7438:2016) Matriaux mtalliques - Essai de pliage (ISO 7438:
5、2016) Metallische Werkstoffe - Biegeversuch (ISO 7438:2016) This European Standard was approved by CEN on 21 November 2015. CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard wit
6、hout any alteration. Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN member. This European Standard exists in three official versions (English, French, German). A version in any other
7、 language made by translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management Centre has the same status as the official versions. CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, D
8、enmark, Estonia, Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey andUnited Kingdom. EUROPEAN COMMITT
9、EE FOR STANDARDIZATION COMIT EUROPEN DE NORMALISATION EUROPISCHES KOMITEE FR NORMUNG CEN-CENELEC Management Centre: Avenue Marnix 17, B-1000 Brussels 2016 CEN All rights of exploitation in any form and by any means reserved worldwide for CEN national Members. Ref. No. EN ISO 7438:2016 EBS EN ISO 743
10、8:2016EN ISO 7438:2016 (E) 3 European foreword This document (EN ISO 7438:2016) has been prepared by Technical Committee ISO/TC 164 “Mechanical testing of metals” in collaboration with Technical Committee ECISS/TC 101 “Test methods for steel (other than chemical analysis)” the secretariat of which i
11、s held by AFNOR. This European Standard shall be given the status of a national standard, either by publication of an identical text or by endorsement, at the latest by July 2016, and conflicting national standards shall be withdrawn at the latest by July 2016. Attention is drawn to the possibility
12、that some of the elements of this document may be the subject of patent rights. CEN and/or CENELEC shall not be held responsible for identifying any or all such patent rights. This document supersedes EN ISO 7438:2005. According to the CEN-CENELEC Internal Regulations, the national standards organiz
13、ations of the following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Ma
14、lta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the United Kingdom. Endorsement notice The text of ISO 7438:2016 has been approved by CEN as EN ISO 7438:2016 without any modification. BS EN ISO 7438:2016ISO 7438:2016(E)Foreword iv1 Scop
15、e . 12 Symbols and designations 13 Principle 14 Test equipment. 24.1 General . 24.2 Bending device with supports and a former . 34.3 Bending device with a V-block. 34.4 Bending device with a clamp 45 Test piece 45.1 General . 45.2 Edges of rectangular test pieces. 45.3 Width of the test piece 45.4 T
16、hickness of the test piece 45.5 Test pieces from forgings, castings and semi-finished products . 55.6 Agreement for test pieces of greater thickness and width . 55.7 Length of the test piece 56 Procedure. 57 Interpretation of results . 78 Test report . 7Annex A (informative) Determination of the ben
17、d angle from the measurement of the displacement of the former . 8 ISO 2016 All rights reserved iiiContents PageBS EN ISO 7438:2016ISO 7438:2016(E)ForewordISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of
18、preparing International Standards is normally carried out through ISO technical committees. Each member body interested in a subject for which a technical committee has been established has the right to be represented on that committee. International organizations, governmental and non-governmental,
19、 in liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.The procedures used to develop this document and those intended for its further maintenance are described in the ISO/
20、IEC Directives, Part 1. In particular the different approval criteria needed for the different types of ISO documents should be noted. This document was drafted in accordance with the editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).Attention is drawn to the possibility
21、 that some of the elements of this document may be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of any patent rights identified during the development of the document will be in the Introduction and/or on the ISO list of paten
22、t declarations received (see www.iso.org/patents).Any trade name used in this document is information given for the convenience of users and does not constitute an endorsement.For an explanation on the meaning of ISO specific terms and expressions related to conformity assessment, as well as informa
23、tion about ISOs adherence to the WTO principles in the Technical Barriers to Trade (TBT) see the following URL: Foreword - Supplementary informationThe committee responsible for this document is ISO/TC 164, Mechanical testing of metals, Subcommittee SC 2, Ductility testing.This third edition cancels
24、 and replaces the second edition (ISO 7438:2005), which has been technically revised. The following changes have been made: Figure 3 has been revised; a note has been added in 4.2.2; Formula (A.4) and Figure A.1 have been revised.iv ISO 2016 All rights reservedBS EN ISO 7438:2016INTERNATIONAL STANDA
25、RD ISO 7438:2016(E)Metallic materials Bend test1 ScopeThis International Standard specifies a method for determining the ability of metallic materials to undergo plastic deformation in bending.This International Standard applies to test pieces taken from metallic products, as specified in the releva
26、nt product standard. It is not applicable to certain materials or products, for example tubes in full section or welded joints, for which other standards exist.2 Symbols and designationsSymbols and designations used in the bend test are shown in Figures 1 and 2 and specified in Table 1.Table 1 Symbo
27、ls and designationsSymbol Designation Unita Thickness or diameter of test piece (or diameter of the inscribed circle for pieces of polygonal cross-section)mmb Width of the test piece mmL Length of the test piece mml Distance between supports mmD Diameter of the former mm Angle of bend degreesr Inter
28、nal radius of bend portion of test piece after bending mmf Displacement of the former mmc Distance between the plane including the horizontal axis of sup-ports and the central axis of the rounded portion of the former before testmmp Distance between the vertical planes including the central axis of
29、each support and the vertical plane including the central axis of the formermmR Radius of the supports mm3 PrincipleThe bend test consists of submitting a test piece of round, square, rectangular or polygonal cross-section to plastic deformation by bending, without changing the direction of loading,
30、 until a specified angle of bend is reached.The axes of two legs of the test piece remain in a plane perpendicular to the axis of bending. In the case of a 180 bend, the two lateral surfaces may, depending on the requirements of the product standard, lie flat against each other or may be parallel at
31、 a specified distance, an insert being used to control this distance. ISO 2016 All rights reserved 1BS EN ISO 7438:2016ISO 7438:2016(E)4 Test equipment4.1 GeneralThe bend test shall be carried out in testing machines or presses equipped with the following devices:a) bending device with two supports
32、and a former as shown in Figure 1;b) bending device with a V-block and a former as shown in Figure 2;c) bending device with a clamp as shown in Figure 3.Figure 1 Bending device with two supports and a formerFigure 2 Bending device with a V-block and a former2 ISO 2016 All rights reservedBS EN ISO 74
33、38:2016ISO 7438:2016(E)Key1 clamp2 formerFigure 3 Bending device with a clamp4.2 Bending device with supports and a former4.2.1 The length of the supports and the width of the former shall be greater than the width or diameter of the test piece. The diameter of the former is determined by the produc
34、t standard. The test piece supports and the former shall be of sufficient hardness (see Figure 1).4.2.2 Unless otherwise specified, the distance between the supports, l, shall be:la=+ ()Da32(1)and shall not change during the bend test.NOTE When the distance between the supports (l) is specified smal
35、ler than or equal to D + 2a, it can result in clamping during the test and stretch forming of the test piece.4.3 Bending device with a V-blockThe tapered surfaces of the V-block shall form an angle of 180 (see Figure 2). The angle is specified in the relevant standard. ISO 2016 All rights reserved 3
36、BS EN ISO 7438:2016ISO 7438:2016(E)The edges of the V-block shall have a radius between 1 to 10 times the thickness of the test piece and shall be of sufficient hardness.4.4 Bending device with a clampThe device consists of a clamp and a former of sufficient hardness; it may be equipped with a lever
37、 for applying force to the test piece (see Figure 3).Because the position of the left face of the clamp could influence the test results, the left face of the clamp (as shown in Figure 3) should not reach up to or beyond the vertical line through the centre of the circular former shape.5 Test piece5
38、.1 GeneralRound, square, rectangular, or polygonal cross-section test pieces shall be used in the test. Any areas of the material affected by shearing or flame cutting and similar operations during sampling of test pieces shall be removed. However, testing a test piece, the affected parts of which h
39、ave not been removed, is acceptable, provided the result is satisfactory.5.2 Edges of rectangular test piecesThe edges of rectangular test pieces shall be rounded to a radius not exceeding the following values: 3 mm, when the thickness of the test pieces is 50 mm or greater; 1,5 mm, when the thickne
40、ss of the test pieces is less than 50 mm and more than or equal to 10 mm (inclusive); 1 mm when the thickness is less than 10 mm.The rounding shall be made so that no transverse burrs, scratches or marks are formed which might adversely affect the test results. However, testing a test piece, the edg
41、es of which have not been rounded, is acceptable, provided that the result is satisfactory.5.3 Width of the test pieceUnless otherwise specified in the relevant standard, the width of the test piece shall be as follows:a) the same as the product width, if the latter is equal to or less than 20 mm;b)
42、 when the width of a product is more than 20 mm:1) (20 5) mm for products of thickness less than 3 mm,2) between 20 mm and 50 mm for products of thickness equal to or greater than 3 mm.5.4 Thickness of the test piece5.4.1 The thickness of test pieces from sheets, strips and sections shall be equal t
43、o the thickness of the product to be tested. If the thickness of the product is greater than 25 mm, it may be reduced by machining one surface to attain a thickness not less than 25 mm. During bending, the unmachined side shall be on the tension-side surface of the test piece.5.4.2 Test pieces of ro
44、und or polygonal cross-section shall have a cross-section equal to that of the product, if the diameter (for a round cross-section) or inscribed circle diameter (for a polygonal cross-section) does not exceed 30 mm. When the diameter, or the inscribed circle diameter, of the test piece 4 ISO 2016 Al
45、l rights reservedBS EN ISO 7438:2016ISO 7438:2016(E)exceeds 30 mm up to and including 50 mm, it may be reduced to not less than 25 mm. When the diameter, or inscribed circle diameter, exceeds 50 mm it shall be reduced to not less than 25 mm (see Figure 4). During bending, the unmachined side shall b
46、e on the tension-side surface of the test piece.Dimensions in millimetresFigure 4 Diameter and the inscribed circle diameter of the test piece5.5 Test pieces from forgings, castings and semi-finished productsIn the case of forgings, castings and semi-finished products, the dimensions of the test pie
47、ce and sampling shall be as defined in the general delivery requirements, or by agreement.5.6 Agreement for test pieces of greater thickness and widthBy agreement, test pieces of a greater width and thickness than those specified in 5.3 and 5.4 may be subjected to the bend test.5.7 Length of the tes
48、t pieceThe length of the test piece depends on the thickness of the test piece and the test equipment used.6 ProcedureWARNING During the test, adequate safety measures and guarding equipment shall be provided.6.1 In general, tests are carried out at ambient temperature between 10 C and 35 C. Tests c
49、arried out under controlled conditions, where required, shall be made at a temperature of (23 5) C.6.2 The bend test shall be carried out using one of the following methods as specified in the relevant standard:a) a specified angle of bend is achieved under an appropriate force and for the given conditions (see Figures 1, 2 and 3);b) the legs of the test piece are parallel to each other at a specified distance apart while under an appropriate force (see Figure 6);c) the legs of the test piece are in direct contact while u
