1、BSI Standards PublicationBS ISO 16842:2014Metallic materials Sheet andstrip Biaxial tensile testingmethod using a cruciform testpieceBS ISO 16842:2014 BRITISH STANDARDNational forewordThis British Standard is the UK implementation of ISO 16842:2014.The UK participation in its preparation was entrust
2、ed to 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
3、 Standards Institution 2014. Published by BSI StandardsLimited 2014ISBN 978 0 580 75438 8ICS 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 October 20
4、14.Amendments issued since publicationDate Text affectedBS ISO 16842:2014 ISO 2014Metallic materials Sheet and strip Biaxial tensile testing method using a cruciform test pieceMatriaux mtalliques Tles et bandes Mthode dessai de traction biaxiale sur prouvette cruciformeINTERNATIONAL STANDARDISO16842
5、First edition2014-10-01Reference numberISO 16842:2014(E)BS ISO 16842:2014ISO 16842:2014(E)ii ISO 2014 All rights reservedCOPYRIGHT PROTECTED DOCUMENT ISO 2014All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form or by any mea
6、ns, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below or ISOs member body in the country of the requester.ISO copyright officeCase postale 56 CH-1211 Geneva 2
7、0Tel. + 41 22 749 01 11Fax + 41 22 749 09 47E-mail copyrightiso.orgWeb www.iso.orgPublished in SwitzerlandBS ISO 16842:2014ISO 16842:2014(E) ISO 2014 All rights reserved iiiContents PageForeword ivIntroduction v1 Scope . 12 Normative references 13 Terms and definitions . 14 Principle 25 Test piece 2
8、5.1 Shape and dimensions 25.2 Preparation of the test pieces. 26 Testing method . 46.1 Testing machine . 46.2 Measurement method of force and strain . 46.3 Installation of the test piece to a biaxial tensile testing machine 66.4 Testing methods . 77 Determination of biaxial stress-strain curves . 77
9、.1 General . 77.2 Determination of the original cross-sectional area of the test piece 77.3 Determination of true stress . 77.4 Determination of true strain . 87.5 Determination of true plastic strain . 88 Test report 108.1 Information in the report 108.2 Additional note 11Annex A (informative) Meth
10、od for measuring a yield surface 12Annex B (informative) Factors affecting the maximum equivalent plastic strain applicable to the gauge area of the test piece 17Annex C (informative) Biaxial tensile testing machine 19Bibliography .23BS ISO 16842:2014ISO 16842:2014(E)ForewordISO (the International O
11、rganization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of 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 estab
12、lished has the right to be represented on that committee. International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardizat
13、ion.The procedures used to develop this document and those intended for its further maintenance are described in the ISO/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
14、 the editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).Attention is drawn to the possibility 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 pa
15、tent rights identified during the development of the document will be in the Introduction and/or on the ISO list of patent 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
16、 an explanation on the meaning of ISO specific terms and expressions related to conformity assessment, as well as information about ISOs adherence to the WTO principles in the Technical Barriers to Trade (TBT) see the following URL: Foreword - Supplementary informationThe committee responsible for t
17、his document is ISO/TC 164, Mechanical testing of metals, Subcommittee 2, Ductility testing.iv ISO 2014 All rights reservedBS ISO 16842:2014ISO 16842:2014(E)IntroductionThis International Standard specifies the testing method for measuring the biaxial stress-strain curves of sheet metals subject to
18、biaxial tension at an arbitrary stress ratio using a cruciform test piece made of flat sheet metals. The International Standard applies to the shape and strain measurement position for the cruciform test piece. The biaxial tensile testing machine is described in Annex C, only in terms of the typical
19、 example of the machine and the requirements that the machine should comply with.The cruciform test piece recommended in this International Standard has the following features:a) the gauge area of the test piece ensures superior homogeneity of stress, enabling measurement of biaxial stress with sati
20、sfactory accuracy;b) capability of measuring the elasto-plastic deformation behaviour of sheet metals at arbitrary stress or strain rate ratios;c) free from the out-of-plane deformation as is encountered in the hydrostatic bulge testing method;d) easy to fabricate from a flat metal sheet by laser cu
21、tting, water jet cutting, or other alternative manufacturing methods. ISO 2014 All rights reserved vBS ISO 16842:2014BS ISO 16842:2014Metallic materials Sheet and strip Biaxial tensile testing method using a cruciform test piece1 ScopeThis International Standard specifies the method for measuring th
22、e stress-strain curves of sheet metals subject to biaxial tension using a cruciform test piece fabricated from a sheet metal sample. The applicable thickness of the sheet shall be 0,1 mm or more and 0,08 times or less of the arm width of the cruciform test piece (see Figure 1). The test temperature
23、shall range from 10 C to 35 C. The amount of plastic strain applicable to the gauge area of the cruciform test piece depends on the force ratio, slit width of the arms, work hardening exponent (n-value) (see Annex B), and anisotropy of a test material.2 Normative referencesThe following documents, i
24、n whole or in part, are normatively referenced in this document and are indispensable for its application. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.ISO 10275, Metallic materials Shee
25、t and strip Determination of tensile strain hardening exponentISO 80000-1, Quantities and units Part 1: General3 Terms and definitionsFor the purpose of this document, the following terms and definitions apply.3.1cruciform test piecetest piece which is recommended in the biaxial tensile test and who
26、se geometry is specified in this International Standard (see Figure 1)3.2gauge areasquare area which is located in the middle of the cruciform test piece and is enclosed by the four arms of the cruciform test piece (see Figure 1)3.3armgeneric name for all areas other than the gauge area in the cruci
27、form test piece. The arms play a role of transmitting tensile forces in two orthogonal directions to the gauge area of the cruciform test piece (see Figure 1)3.4biaxial tensile testing machinetesting machine for applying biaxial tensile forces to a cruciform test piece in the orthogonal directions p
28、arallel to the arms of the test piece (see Annex C)3.5yield surfacea group of stress determined in a stress space, at which a metal starts plastic deformation when probing from the elastic region into the plastic range1(see Annex A)INTERNATIONAL STANDARD ISO 16842:2014(E) ISO 2014 All rights reserve
29、d 1BS ISO 16842:2014ISO 16842:2014(E)3.6yield functionmathematical function used to generate the conditional equation (yield criterion) which the stress components should comply with when the material subject to the stress is in the plastic deformation state (see Annex A)3.7contour of plastic workgr
30、aphic figure derived by subjecting the material to plastic deformation along various linear stress paths and plotting the stress points in stress space at the instance when the plastic work consumed per unit volume along each stress path becomes identical; and the plotted stress points are approxima
31、ted into either a smooth curve or curved surface (see Annex A)4 PrincipleMeasurement is made at room temperature, on the yield stress and the stress-strain curves of sheet metals under biaxial tensile stresses by measuring simultaneously and continuously the biaxial tensile forces and strain compone
32、nts applied to the gauge area of a cruciform test piece while applying biaxial tensile forces in the orthogonal directions parallel to the arms of the test piece. The test piece is made of a flat sheet metal and has a uniform thickness. The measured biaxial stress-strain curves are used to determine
33、 contours of plastic work of the sheet samples (see Annex A). According to the finite element analyses of the cruciform test piece as recommended in Clause 5 and the strain measurement position as specified in Clause 6.2.4, the stress calculation error is estimated to be less than 2,0 %.235 Test pie
34、ce5.1 Shape and dimensionsFigure 1 shows the shape and dimensions of the cruciform test piece recommended in this International Standard. The test piece shall be as described below.a) In principle, the thickness of a test piece, a, shall be the same as that of the as-received sheet sample, without a
35、ny work done in the thickness direction. See 5.1 b) for an exception to the rule.b) The arm width, B, should be 30 mm or more, except that it can be determined according to the agreement between parties involved in transaction. It shall satisfy a 0,08B and should be accurate to within 0,1 mm for all
36、 four arms. The sheet thickness can be reduced to satisfy a 0,08B according to the agreement between parties involved in transaction.c) Seven slits per one arm shall be made. Specifically, one slit shall be made on the centerline (x-axis or y-axis) of the test piece with a positional accuracy of 0,1
37、 mm, and three slits shall be made at an interval of B/8 with an positional accuracy of 0,1 mm on each side of the centerline. All slits shall have the same length, L, and should be accurate to within 0,1 mm. The relationship of B L 2B should be established. The opposing slit ends shall be made at a
38、n equal distance, BSx/2 and BSy/2, from the centerline with a positional accuracy of B/2 0,1 mm.d) The slit width, wS, should be made as small as possible (see Figure B.2), preferably less than 0,3 mm.e) The grip length, C, is considered to be enough if it can secure the test piece to the grips of t
39、he biaxial tensile testing machine and can transmit the necessary tensile force to the test piece. The standard grip length would be B/2 C B, but can be determined arbitrarily according to the agreement between parties involved in transaction.f) An alternative test piece geometry can be used. In the
40、 use of the alternative cruciform test pieces, the evidence of the stress measurement accuracy has to be clarified between the contractual partners.5.2 Preparation of the test pieces2 ISO 2014 All rights reservedBS ISO 16842:2014ISO 16842:2014(E)a) The permitted variations in thickness and the permi
41、tted variations from a flat surface of the sheet metal sample from which the cruciform test pieces are taken shall be in accordance with relevant product standards or national standards.b) The standard sampling direction of the test piece shall be such that the directions of arms are parallel to the
42、 rolling (x) and transverse (y) directions of the sheet sample, respectively. The test piece sampling direction can be determined according to the agreement between parties involved in transaction.c) For the fabrication of the test piece (including making of slits), any method, e.g. laser cutting, w
43、ater jet cutting, or other alternative manufacturing methods, demonstrated to work satisfactorily can be used if agreed upon by the parties.d) Unless otherwise specified and except for the sampling work, unnecessary deformation or heating to the test piece shall be avoided.xyBB/8LBC1432Lt0Cornerradi
44、us : RSlit width : wsSwRR=(0,00340,1)BaBSyBSxKey1 gauge area2 arm3 grip4 slita thickness of a test pieceB arm widthBSxdistance between opposing slit ends in the x directionBSydistance between opposing slit ends in the y directionC grip lengthL slit lengthR corner radius at the junctions of arms to t
45、he gauge areawSslit widthFigure 1 Standard shape and dimensions of the recommended cruciform test piece23 ISO 2014 All rights reserved 3BS ISO 16842:2014ISO 16842:2014(E)6 Testing method6.1 Testing machineThe specifications required for the biaxial tensile testing machine (hereinafter referred to as
46、 testing machine) are as follows (for examples of typical testing machines, see Annex C).a) It shall have sufficient functions and durability to hold four grips of a cruciform test piece (hereinafter referred to as test piece) in one single plane with a tolerance of 0,1 mm during testing.b) Two oppo
47、sing grips shall move along a single straight line (hereinafter referred to as x-axis and y-axis), and the x- and y-axes shall intersect at an angle of 90 0,1 (The plane that contains the x- and y-axes is referred to as the reference plane, while the intersection of x- and y-axes as the centre of te
48、sting machine).c) It shall have a function for adjusting the two opposing grips to the position at an equal distance from the centre of the testing machine with a tolerance of 0,1 mm before the installation of a test piece to the grips.d) It shall have a function for enabling the installation of a t
49、est piece to the grips while aligning the centre of the test piece to the centre of the testing machine.e) It shall have a function for enabling equal displacement of two opposing grips or the maintenance of the centre of the test piece always on the centre of the testing machine with a tolerance of 0,1 mm during biaxial tensile test (for example, the testing machines shown in Figures C.1 and C.2 use a link mechanism to ensure equivalent displacement of two opposing grips).f) It shall have a
