ISO 10275 2007

Reference numberISO 10275:2007(E)©ISO 2007INTERNATIONAL STANDARD ISO10275Second edition2007-06-01Metallic materials — Sheet and strip — Determination of tensile strain hardening exponent Matériaux métalliques — Tôles et bandes — Détermination du coefficient d écrouissage en traction Copyright International Organization for Standardization Provided by IHS under license with ISO Not for ResaleNo reproduction or networking permitted without license from IHS--`,,```,,,,````-`-`,,`,,`,`,,`---ISO 10275:2007(E) PDF disclaimer This PDF file may contain embedded typefaces. In accordance with Adobe s licensing policy, this file may be printed or viewed but shall not be edited unless the typefaces which are embedded are licensed to and installed on the computer performing the editing. In downloading this file, parties accept therein the responsibility of not infringing Adobe s licensing policy. The ISO Central Secretariat accepts no liability in this area. Adobe is a trademark of Adobe Systems Incorporated. Details of the software products used to create this PDF file can be found in the General Info relative to the file; the PDF-creation parameters were optimized for printing. Every care has been taken to ensure that the file is suitable for use by ISO member bodies. In the unlikely event that a problem relating to it is found, please inform the Central Secretariat at the address given below. COPYRIGHT PROTECTED DOCUMENT © ISO 2007 All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from either ISO at the address below or ISO s member body in the country of the requester. ISO copyright office Case postale 56 • CH-1211 Geneva 20 Tel. + 41 22 749 01 11 Fax + 41 22 749 09 47 E-mail copyright@iso.org Web www.iso.org Published in Switzerland ii © ISO 2007 – All rights reservedCopyright International Organization for Standardization Provided by IHS under license with ISO Not for ResaleNo reproduction or networking permitted without license from IHS--`,,```,,,,````-`-`,,`,,`,`,,`---ISO 10275:2007(E) © ISO 2007 – All rights reserved iiiContents Page Foreword iv Introduction v 1 Scope . 1 2 Normative references . 1 3 Symbols and designations 1 4 Principle. 3 5 Test equipment . 3 6 Test pieces 3 7 Procedure 3 8 Test report . 8 Annex A (informative) International comparison of symbols used in the determination of the tensile strain hardening exponent . 9 Bibliography . 10 Copyright International Organization for Standardization Provided by IHS under license with ISO Not for ResaleNo reproduction or networking permitted without license from IHS--`,,```,,,,````-`-`,,`,,`,`,,`---ISO 10275:2007(E) iv © ISO 2007 – All rights reservedForeword ISO (the International Organization 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 established 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 standardization. International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2. The main task of technical committees is to prepare International Standards. Draft International Standards adopted by the technical committees are circulated to the member bodies for voting. Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote. 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. ISO 10275 was prepared by Technical Committee ISO/TC 164, Mechanical testing of metals, Subcommittee SC 2, Ductility testing. This second edition cancels and replaces the first edition (ISO 10275:1993), which has been technically revised. Copyright International Organization for Standardization Provided by IHS under license with ISO Not for ResaleNo reproduction or networking permitted without license from IHS--`,,```,,,,````-`-`,,`,,`,`,,`---ISO 10275:2007(E) © ISO 2007 – All rights reserved vIntroduction In the former version of this International Standard, for the calculation of the true strain, the elastic strain did not need to be subtracted from the total strain if it was lower than 10 % of the total strain. In this new International Standard, the elastic strain is subtracted from the total strain for calculation of the true strain, which is now referred to as “true plastic strain”. Copyright International Organization for Standardization Provided by IHS under license with ISO Not for ResaleNo reproduction or networking permitted without license from IHS--`,,```,,,,````-`-`,,`,,`,`,,`---Copyright International Organization for Standardization Provided by IHS under license with ISO Not for ResaleNo reproduction or networking permitted without license from IHS--`,,```,,,,````-`-`,,`,,`,`,,`---INTERNATIONAL STANDARD ISO 10275:2007(E)© ISO 2007 – All rights reserved 1Metallic materials — Sheet and strip — Determination of tensile strain hardening exponent 1 Scope This International Standard specifies a method for determining the tensile strain hardening exponent n of flat products (sheet and strip) made of metallic materials. The method is valid only for that part of the stress-strain curve in the plastic range where the curve is continuous and monotonic (see 7.4). In the case of materials with a serrated stress-strain curve in the work hardening range (materials which show the Portevin-Le Chatelier effect, e.g. AlMg-alloys) the automatic determination (linear regression of the logarithm true stress vs. the logarithm true plastic strain, see 7.7) should be used to give reproducible results. 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. ISO 6892:1998, Metallic materials — Tensile testing at ambient temperature ISO 7500-1:2004, Metallic materials — Verification of static uniaxial testing machines — Part 1: Tension/compression testing machines — Verification and calibration of the force-measuring system ISO 9513:1999, Metallic materials — Calibration of extensometers used in uniaxial testing ISO 10113, Metallic materials — Sheet and strip — Determination of plastic strain ratio 3 Symbols and designations The symbols and corresponding designations used in determining the tensile strain hardening exponent are given in Table 1. Copyright International Organization for Standardization Provided by IHS under license with ISO Not for ResaleNo reproduction or networking permitted without license from IHS--`,,```,,,,````-`-`,,`,,`,`,,`---ISO 10275:2007(E) 2 © ISO 2007 – All rights reservedTable 1 — Symbols and designations Symbol Designation Units LeExtensometer gauge length (Le) mm ∆L Instantaneous extension of the measurement base mm L Instantaneous length of the extensometer gauge length L = Le+ ∆L mm epSpecified plastic (engineering) strain at which the tensile strain hardening exponent should be determined (single data point method) % epα− epβSpecified plastic (engineering) strain range at which the tensile strain hardening exponent should be determined (linear regression method, epα= lower limit of the plastic strain in percent, epβ= upper limit of the plastic strain in percent) % SoOriginal cross-sectional area of the parallel length mm2S True cross-sectional area mm2F Instantaneous force applied to the test piece N R Stress MPa σ True stress MPa ε True plastic strain — mESlope of the elastic part of the stress/percentage extension-curve MPa n Tensile strain hardening exponent — C Strength coefficient MPa N Number of measurements made in determining the tensile strain hardening exponent — r Plastic strain ratio — RmTensile strength MPa AePercentage yield point extension % AgPercentage plastic extension at maximum force % A, B, x, y Variables used for the evaluation of n by the manual method NOTE 1 In the literature the readers may encounter other symbols. For an international comparison of symbols, see Annex A. NOTE 2 1 MPa = 1 N/mm2. 3.2 The tensile strain hardening exponent n is defined as the exponent of the true plastic strain in the mathematical equation relating the true stress to the true plastic strain (during uniaxial application of a force). This equation can be taken as follows: nCσ ε=× (1) 3.3 This equation can be transformed into a logarithmic one as follows: ln ln lnCnσ ε=+ (2) The strain hardening exponent in the logarithmic system of coordinates is defined as the slope of the corresponding straight line. Copyright International Organization for Standardization Provided by IHS under license with ISO Not for ResaleNo reproduction or networking permitted without license from IHS--`,,```,,,,````-`-`,,`,,`,`,,`---ISO 10275:2007(E) © ISO 2007 – All rights reserved 34 Principle A test piece is subjected to uniaxial tensile strain at a prescribed constant rate within the region of uniform plastic strain. The tensile strain hardening exponent n is calculated either by considering a portion of the stress-strain curve in the plastic region, or by considering the whole uniform plastic strain region. 5 Test equipment 5.1 Tensile testing machine, verified and calibrated in accordance with ISO 7500-1:2004 and of class 1 or better. The method of gripping the test piece shall conform to the requirements of ISO 6892. 5.2 Extensometer, of class 2 or better (class 1 in the event of determination of the plastic strain ratio r, see ISO 10113) in accordance with ISO 9513:1999, for measuring changes in the gauge length. 5.3 Dimension-measuring equipment, capable of measuring the width and thickness of the parallel-sided section of the test piece to within the tolerances specified for these dimensions in ISO 6892. 6 Test pieces 6.1 Sampling to obtain test pieces shall be in accordance with the requirements of the relevant product standard or, if not specified therein, by agreement. Machining tolerances, tolerances on shape, and the marking shall be as specified in ISO 6892. 6.2 In the event of the plastic strain ratio r and the tensile strain hardening exponent n being determined simultaneously, the conditions of ISO 10113 shall apply. 6.3 The thickness of the test piece shall be that of the full sheet, unless otherwise specified. 6.4 The surface of the test piece shall not be damaged (by scratches, etc.). 7 Procedure 7.1 In general, the test shall be carried out at ambient temperature, i.e. between 10 °C and 35 °C. Tests carried out under controlled conditions, where required, shall be made at a temperature of (23 ± 5)°C. 7.2 The test piece shall be mounted in the tensile testing machine (see 5.1) so that the force can be applied axially in accordance with ISO 6892. 7.3 In the plastic range, the strain rate of parallel length shall not exceed 0,008 s−1, unless otherwise specified in the relevant standard. This rate shall be kept constant during the time interval over which the tensile strain hardening exponent is determined. If a proof strength or the yield strength is determined during the same tensile test, the strain rate for this determination shall be as defined in ISO 6892. 7.4 When n is determined over the whole uniform plastic strain range, the upper limit for these data points shall be immediately prior to the strain at which the maximum force occurs. For materials with homogenous deformation behaviour (i.e. materials without upper and/or lower yield strength), the lower limit of the range over which n is determined shall not be lower than a point after which the final testing rate used for determining Rmhas been achieved (see Figure 1). For the materials exhibiting yield point phenomena (upper and/or lower yield strengths), the lower limit shall not be lower than the start of uniform work hardening and after which the final testing rate used for determining Rmhas been achieved (see Figures 2 and 3). Copyright International Organization for Standardization Provided by IHS under license with ISO Not for ResaleNo reproduction or networking permitted without license from IHS--`,,```,,,,````-`-`,,`,,`,`,,`---ISO 10275:2007(E) 4 © ISO 2007 – All rights reservedThe lower limit and the upper limit shall be reported. Key X strain % Y stress 1 lower limit 2 upper limit Figure 1 — Range for n2−20/Agor n2−AgCopyright International Organization for Standardization Provided by IHS under license with ISO Not for ResaleNo reproduction or networking permitted without license from IHS--`,,```,,,,````-`-`,,`,,`,`,,`---ISO 10275:2007(E) © ISO 2007 – All rights reserved 5Key X strain % Y stress 1 lower limit 2 upper limit Figure 2 — Range for n4−20/Ago