EN ISO 10275-2014 en Metallic materials - Sheet and strip - Determination of tensile strain hardening exponent《金属材料 薄板和薄带拉伸应变硬化指数(ISO 10275 2007)》.pdf

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1、BSI Standards PublicationBS EN ISO 10275:2014Metallic materials Sheetand strip Determinationof tensile strain hardeningexponent (ISO 10275:2007)BS EN ISO 10275:2014National forewordThis British Standard is the UK implementation of EN ISO 10275:2014. It is identical to ISO 10275:2007. It supersedes B

2、S ISO 10275:2007, which is withdrawn.The UK participation in its preparation was entrusted by Technical Committee ISE/101, Test methods for metals, to Subcommittee ISE/101/2, Ductility testing.A list of organizations represented on this subcommittee can be obtained on request to its secretary.This p

3、ublication does not purport to include all the necessary provisions of a contract. Users are responsible for its correct application. The British Standards Institution 2014. Published by BSI Standards Limited 2014ISBN 978 0 580 84473 7ICS 77.040.10Compliance with a British Standard cannot confer imm

4、unity fromlegal obligations.This British Standard was published under the authority of the Standards Policy and Strategy Committee on 29 June 2007.Amendments/corrigenda issued since publicationDate Text affected31 July 2014 This corrigendum renumbers BS ISO 10275:2007 as BS EN ISO 10275:2014BRITISH

5、STANDARDEUROPEAN STANDARD NORME EUROPENNE EUROPISCHE NORM EN ISO 10275 June 2014 ICS 77.040.10 English Version Metallic materials - Sheet and strip - Determination of tensile strain hardening exponent (ISO 10275:2007) Matriaux mtalliques - Tles et bandes - Dtermination du coefficient dcrouissage en

6、traction (ISO 10275:2007) Metallische Werkstoffe - Blech und Band - Bestimmung des Verfestigungsexponenten im Zugversuch (ISO 10275:2007)This European Standard was approved by CEN on 6 June 2014. CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions

7、 for giving this European Standard the status of a national standard without 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 t

8、hree official versions (English, French, German). A version in any other 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

9、bodies of 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, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia

10、, Spain, Sweden, Switzerland, Turkey and United Kingdom. EUROPEAN COMMITTEE FOR STANDARDIZATION COMIT EUROPEN DE NORMALISATION EUROPISCHES KOMITEE FR NORMUNG CEN-CENELEC Management Centre: Avenue Marnix 17, B-1000 Brussels 2014 CEN All rights of exploitation in any form and by any means reserved wor

11、ldwide for CEN national Members. Ref. No. EN ISO 10275:2014 EBS EN ISO 10275:2014EN ISO 10275:2014 (E) 3 Foreword The text of ISO 10275:2007 has been prepared by Technical Committee ISO/TC 164 “Mechanical testing of metals” of the International Organization for Standardization (ISO) and has been tak

12、en over as EN ISO 10275:2014 by Technical Committee ECISS/TC 101 “Test methods for steel (other than chemical analysis)” the secretariat of which is 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, a

13、t the latest by December 2014, and conflicting national standards shall be withdrawn at the latest by December 2014. Attention is drawn to the possibility 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

14、any or all such patent rights. According to the CEN-CENELEC Internal Regulations, the national standards organizations of the following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, Former Yugoslav Rep

15、ublic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the United Kingdom. Endorsement notice The text of ISO 10275:2007 has been a

16、pproved by CEN as EN ISO 10275:2014 without any modification. ii ISO 2007 All rights reserved BS EN ISO 10275:2014ISO 10275:2007(E) ISO 2007 All rights reserved iiiContents PageForeword iLIntroduction.1Scope. 12Normative references. 13Symbols and designations 14Principle. 35Test equipment . 36Test p

17、ieces 37Procedure 38Test report.8AnnexA (informative) International comparison of symbols used in the determination of the tensile strain hardening exponent . 9Bibliography. 10iv.BS EN ISO 10275:2014ISO 10275:2007(E)iv ISO 2007 All rights reservedIntroduction In the former version of this Internatio

18、nal Standard, for the calculation of the true strain, the elastic strain didnot 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 truestrain, whi

19、ch is now referred to as “true plastic strain”.BS EN ISO 10275:2014INTERNATIONAL STANDA RD ISO 10275:2007(E) ISO 2007 All rights reserved 1Metallic materials Sheet and strip Determination of tensilestrain hardening exponent 1 Scope This International Standard specifies a method for determining the t

20、ensile strain hardening exponent n of flatproducts (sheet and strip)made ofm etallic materials.The method is valid onlyfor that part of the stress-strain curve in the plastic range where the curve iscontinuous and monotonic (see 7.4). In the case of materials with a serrated stress-strain curve in t

21、he work hardening range (materials which showthe 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 NormativereferencesThe following

22、referenced documents are indispensable for the application of this document. For datedreferences, onlyedition cited applies. For undated references, the latest edition of the referenced document(including anyamendments) applies.ISO 6892:1998, Metallic materials Tensile testing at ambient temperature

23、ISO 7500-1:2004, Metallic materials Verification of static uniaxial testing machines Part1: Tension/compression testing machines Verification and calibration of the force-measuring systemISO 9513:1999, Metallic materials Calibration of extensometers used in uniaxial testingISO 10113, Metallic materi

24、als Sheet and strip Determination of plastic strain ratio3 Symbols and designations The symbols and corresponding designations used in determining the tensile strain hardening exponent aregiven in Table 1. BS EN ISO 10275:2014ISO 10275:2007(E)2 ISO 2007 All rights reservedTable 1 Symbols and designa

25、tionsSymbol Designation Units L e Extensometer gauge length (L e ) mm L Instantaneous extension of the measurement base mm L Instantaneous length of the extensometer gauge length L = L e + L mm e p Specified plastic (engineering) strain at w hich the tensile strain hardeningexponent should be determ

26、ined (single data point method) % e p e p Specified plastic (engineering) strain range at which the tensile strainhardening exponent should be determined (linear regression method, e p =lower limit of the plastic strain in percent, e p = upper limit of the plasticstrain in percent) % S o Original cr

27、oss-sectional area of the parallel length mm2S True cross-sectional area mm2F Instantaneous force applied to the test piece NR Stress MPa True stressMPa True plastic strain m E Slope of the elastic part of the stress/percentage extension-curve MPa n Tensile strain hardening exponent C Strength coeff

28、icient MPa N Number of measurements made in determining the tensile strain hardening exponent r Plastic strain ratio R m Tensile strength MPa A e Percentage yield point extension % A g Percentage plastic extension at maximum force % A , B , x , y Variables used for the evaluation of n by the manual

29、methodNOTE 1 In the literature the readersmay encounter other symbols. For an international comparison ofsymbols, 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 strainin the mathematical equation relating the true stres

30、s to the true plastic strain (during uniaxial application of a force). This equation can be taken as follows: nC = (1) 3.3 This equation can be transformed into a logarithmic one as follows:ln ln lnCn =+ (2) The strain hardening exponent in the logarithmic system of coordinates is defined as the slo

31、pe of the corresponding straight line.BS EN ISO 10275:2014ISO 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 uniformplastic strain. The tensile strain hardening exponent n is calculated e

32、ither byconsidering a portion of the stress-strain curve in the plastic region, or by considering the whole uniform plastic strain reg ion. 5 Test equipment5.1 Tensile testing machine, verified a nd calibrated in accordance with ISO7500-1:2004 and of class1 orbetter. The method of gripping the test

33、piece shall conform to the requirements ofISO 6892. 5.2 Extensometer, of class2 or better (class1 in the event of determination of the plastic strain ratio r , seeISO 10113) in accordance with ISO 9513:1999, for measuring changes in the gauge length. 5.3 Dimension-measuring equipment, capable of mea

34、suring thewidth and thickness of the parallel-sidedsection of the testpiece 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 productstandard or, if not specified therein,

35、 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 determinedsimultaneously, the conditions of ISO 10113 shall apply. 6.3 The thickness of the te

36、st 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 10C and 35 C. Tests carried out under controlled conditions

37、,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 appliedaxially in accordancewith ISO 6892. 7.3 In the plastic range, the strain rate of parallel length shall not exceed 0,008 s 1 , unles

38、s otherwisespecified in the relevant standard. This rate shall be kept constant during the time interval over which thetensile strain hardening exponent is determined. If a proof strength or the yield strength is determined during the same tensile test, the strain rate for thisdetermination shall be

39、 as defined in ISO 6892. 7.4 When n is determined over the whole uniform plastic strain range, the upper limit for these data pointsshall be immediately prior to the strain at which the maximumforce occurs. For materials with homogenous deformation behaviour (i.e. materials without upper and/or lowe

40、r yieldstrength), the lower limit of the range overwhich n is determined shall not belower than a point after which thefinal testing rate used for determining R m has been achieved (see Figure 1). For the materials exhibitingyield point phenomena (upper and/or lower yield strengths), the lower limit

41、 shall not be lower than the start of uniform work hardening and after which the final testing rate used fordetermining R m has been achieved (see Figures 2 and 3). BS EN ISO 10275:2014ISO 10275:2007(E)4 ISO 2007 All rights reservedThe lowerlimit and the upper limit shall be reported. KeyX strain% Y

42、 stress1 lower limit 2 upper limit Figure 1 Range for n 2 20/A g or n 2 A gBS EN ISO 10275:2014ISO 10275:2007(E) ISO 2007 All rights reserved 5KeyX strain% Y stress1 lower limit 2 upper limit Figure 2 Range for n 4 20/A g or n 4 20BS EN ISO 10275:2014ISO 10275:2007(E)6 ISO 2007 All rights reservedKe

43、yX strain% Y stress1 lower limit 2 upper limit Figure 3 Range for n 4 20/A g or n 4 A g7.5 From the values of the force and corresponding strain, calculate the true stress using the equation = (F / S o ) (L e + L )/L e (3) Calculate the true plastic strain using the equation = ln( L e + L )/L e F /(

44、S o m E ) (4) NOTE From the physical view, in Equation (4) the true cross-sectional area S according to Equation(5) should beused instead of the original cross-sectional area S o to calculate the true plastic strain . The code of practice has provedthat the results obtained with S o or S are not sig

45、nificantly different. With respect to thisand the lower complexity of the calculation, the original cross-sectional area S o should be used in Equation (4): S = S o L e /(L e + L ) (5) 7.6 If the measurements are evaluated manually, calculate the tensile strain hardening exponent at aminimum of five

46、 points distributedin a geometric progression (see Figure 1), from Equation (2) given in 3.3using the method of least squares. For this purpose, Equation (2) may be rewritten in the formy = Ax + B (6) BS EN ISO 10275:2014ISO 10275:2007(E) ISO 2007 All rights reserved 7where y = In x = In A = nB = In

47、 CFrom this equation, the following relationship can be derived for the tensile strain hardening exponent: 1112211NNNii iiiiiNNiiiiNxyxynNx x=(7) 7.7 In the case of automatic determination, the tensile strain hardening exponent is obtained directlyusingan automatic tensile testing machine and data p

48、rocessing programme. The n -value is determined from a linear regression of the logarithm of true stress vs. the logarithm of true plastic strain. The interval for the regression shall be expressed as plastic strains, with a minimum range of 2 %. It is possible to determine n -values over different

49、intervals based on the same test. EXAMPLES: n 4 6 : linear regression lg( ) = n lg( ) + lg C , between 4 % and 6 % plastic strain; n 10 15:linear regression lg( ) = n lg( ) + lg C , between 10 % and 15 % plastic strain; n 10-20/A g :linear regression lg( ) = n lg( ) + lg C , between 10 % and 20 % plastic strain resp. A g if A g 20 %