1、BSI Standards PublicationBS ISO 6892-4:2015Metallic materials TensiletestingPart 4: Method of test in liquid heliumBS ISO 6892-4:2015 BRITISH STANDARDNational forewordThis British Standard is the UK implementation of ISO 6892-4:2015. It supersedes BS ISO 19819:2004 which is withdrawn.The UK particip
2、ation in its preparation was entrusted to TechnicalCommittee ISE/101/1, Uniaxial 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
3、its correctapplication. The British Standards Institution 2015.Published by BSI Standards Limited 2015ISBN 978 0 580 84558 1ICS 77.040.10Compliance with a British Standard cannot confer immunity fromlegal obligations.This British Standard was published under the authority of theStandards Policy and
4、Strategy Committee on 31 October 2015.Amendments issued since publicationDate T e x t a f f e c t e dBS ISO 6892-4:2015 ISO 2015Metallic materials Tensile testing Part 4: Method of test in liquid heliumMatriaux mtalliques Essai de traction Partie 4: Mthode dessai dans lhlium liquideINTERNATIONAL STA
5、NDARDISO6892-4First edition2015-10-01Reference numberISO 6892-4:2015(E)BS ISO 6892-4:2015ISO 6892-4:2015(E)ii ISO 2015 All rights reservedCOPYRIGHT PROTECTED DOCUMENT ISO 2015, Published in SwitzerlandAll rights reserved. Unless otherwise specified, no part of this publication may be reproduced or u
6、tilized otherwise in any form or by any means, 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 copyr
7、ight officeCh. de Blandonnet 8 CP 401CH-1214 Vernier, Geneva, SwitzerlandTel. +41 22 749 01 11Fax +41 22 749 09 47copyrightiso.orgwww.iso.orgBS ISO 6892-4:2015ISO 6892-4:2015(E)Foreword ivIntroduction v1 Scope . 12 Normative references 13 Terms and definitions . 14 Symbols and designations 45 Princi
8、ple 46 Apparatus . 47 Test piece 77.1 General . 77.2 Standard round bar test piece . 77.3 Alternatives 77.4 Sub-size test pieces . 77.5 Sampling . 78 Testing conditions . 88.1 Test piece installation . 88.2 Cooling procedure 88.3 Rate of testing 88.3.1 Rate limit. 88.3.2 Rate selection 89 Procedure.
9、 99.1 Determination of original cross-sectional area (So) . 99.2 Marking of the original gauge length (Lo) . 99.3 Determination of percentage elongation after fracture (A) . 99.4 Determination of the 0,2 % proof-strength, plastic extension (Rp0,2) 99.5 Discontinuous yielding strength (Ri) 109.6 Tens
10、ile strength (Rm) 109.7 Reduction of area (Z) 1010 Test report 1011 Measurement uncertainty .10Annex A (informative) Examples of test pieces for tensile testing in liquid helium 11Bibliography .13 ISO 2015 All rights reserved iiiContents PageBS ISO 6892-4:2015ISO 6892-4:2015(E)ForewordISO (the Inter
11、national 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
12、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 st
13、andardization.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 accor
14、dance with 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
15、 of any patent 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 endor
16、sement.For 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 respons
17、ible for this document is ISO/TC 164, Mechanical testing of metals, Subcommittee SC 1, Uniaxial testing.This first edition of ISO 6892-4 cancels and replaces ISO 19819:2004, which has been technical revised.ISO 6892 consists of the following parts, under the general title Metallic materials Tensile
18、testing: Part 1: Method of test at room temperature Part 2: Method of test at elevated temperature Part 3: Method of test at low temperature Part 4: Method of test in liquid heliumiv ISO 2015 All rights reservedBS ISO 6892-4:2015ISO 6892-4:2015(E)IntroductionThe force-time and force-extension record
19、s for alloys tested in liquid helium using displacement control are serrated. Serrations are formed by repeated bursts of unstable plastic flow and arrests. The unstable plastic flow (discontinuous yielding) is a free-running process occurring in localized regions of the parallel length at higher ra
20、tes than nominal strain rates with internal test piece heating. Examples of serrated stress-strain curves for a typical austenitic stainless steel with discontinuous yielding are shown in Figure 1.Key1 stress, N/mm22 strain3 temperature, KFigure 1 Example of typical stress-strain curves and test pie
21、ce temperature histories at four different nominal strain rates, for AISI 304L stainless steel tested in liquid heliumA constant test piece temperature cannot be maintained at all times during testing in liquid helium. Due to adiabatic heating, the test piece temperature at local regions in the para
22、llel length rises temporarily above 4 K during each discontinuous yielding event (see Figure 1). The number of events and the magnitude of the associated force drops are a function of the material composition and other factors such as test piece size and test speed. Typically, altering the mechanica
23、l test variables can change the type of serration but not eliminate the discontinuous yielding. Therefore, tensile property measurements of alloys in liquid helium (especially tensile strength, elongation, and reduction of area) may lack the usual significance of property measurements at room temper
24、ature where deformation is more nearly isothermal and discontinuous yielding typically does not occur.Strain control is the preferred control mode (Method A, 6892-1) and displacement control is the secondary method, according to Method B 6892-1. ISO 2015 All rights reserved vBS ISO 6892-4:2015BS ISO
25、 6892-4:2015Metallic materials Tensile testing Part 4: Method of test in liquid helium1 ScopeThis part of ISO 6892 specifies the method of tensile testing of metallic materials in liquid helium (the boiling point is 269 C or 4,2 K, designated as 4 K) and defines the mechanical properties that can be
26、 determined.This part of ISO 6892 may apply also to tensile testing at cryogenic temperatures (less than 196 C or 77 K), which requires special apparatus, smaller test pieces, and concern for serrated yielding, adiabatic heating, and strain-rate effects.To conduct a tensile test according to this pa
27、rt of ISO 6892 at 4 K, the test piece installed in a cryostat is fully submerged in liquid helium (He) and tested using displacement control at a nominal strain rate of 103s1or less.NOTE The boiling point of the rare 3He isotope is 3,2 K. Usually, the tests are performed in 4He or a mixture of 3He a
28、nd 4He with a high concentration of 4He. Therefore, the temperature is, as designated before, 4 K.2 Normative referencesThe following documents, in whole or in part, are normatively referenced in this document and are indispensable for its application. For dated references, only the edition cited ap
29、plies. For undated references, the latest edition of the referenced document (including any amendments) applies.ISO 6892-1:1), Metallic materials Tensile testing Part 1: Method of test at room temperatureISO 6892-3, Metallic materials Tensile testing Part 3: Method of test at low temperatureISO 7500
30、-11, Metallic materials Calibration and verification of static uniaxial testing machines Part 1: Tension/compression testing machines Calibration and verification of the force-measuring systemISO 9513, Metallic materials Calibration of extensometer systems used in uniaxial testing3 Terms and definit
31、ionsFor the purpose of this document, the terms and definitions given in ISO 6892-1 and in ISO 6892-3 apply.3.1adiabatic heatinginternal heating of a test piece resulting from deformation under conditions such that the heat generated by plastic work cannot be quickly dissipated to the surrounding cr
32、yogen1) To be published.INTERNATIONAL STANDARD ISO 6892-4:2015(E) ISO 2015 All rights reserved 1BS ISO 6892-4:2015ISO 6892-4:2015(E)3.2axial strainlongitudinal strains measured at opposite or equally spaced surface locations on the sides of the longitudinal axis of symmetry of the test pieceNote 1 t
33、o entry: The longitudinal strains are measured using two or more strain-sensing transducers located at the mid-length of the parallel length.3.3bending straindifference between the strain at the surface of the test piece and the axial strainNote 1 to entry: The bending strain varies around the circu
34、mference and along the parallel length of the test piece.3.4dewarvacuum-insulated container for cryogenic fluids3.5discontinuous yielding strengthRipeak stress at the initiation of the first measurable serration on the stress-strain curves3.6tensile cryostattest apparatus for applying tensile forces
35、 to test pieces in cryogenic environmentsNote 1 to entry: See Figure 2.2 ISO 2015 All rights reservedBS ISO 6892-4:2015ISO 6892-4:2015(E)112111098723456Key1 force 7 extensometer2 room temperature load frame 8 vacuum-insulated dewar3 vent 9 dewar seal4 vacuum-insulated transfer tube 10 electrical fee
36、d-through5 cryogenic load frame 11 load cell6 test piece 12 pull rodFigure 2 Schematic illustration of typical cryostat for tensile testing at 4 K ISO 2015 All rights reserved 3BS ISO 6892-4:2015ISO 6892-4:2015(E)4 Symbols and designationsSymbols and corresponding designations are given in Table 1.T
37、able 1 Symbols and designationsSymbol Unit Designationdomm diameter of the parallel length of a cylindrical test piece or diameter of a circular wireLomm original gauge lengthLumm final gauge length after fractureLcmm parallel lengthLemm extensometer gauge lengthSomm2original cross-sectional area of
38、 the parallel lengthSumm2minimum cross-sectional area after fracture (final cross-sectional area)Z % percentage reduction of area:ZSSS=ouo100A % percentage elongation after fracture:ALLL=uoo100FmN maximum forceRmN/mm2tensile strengthRp0,2N/mm20,2 % proof strength, plastic extensionRiN/mm2discontinuo
39、us yielding strength5 PrincipleThe test consists of straining a test piece in liquid helium by a tensile force, generally to fracture, for the purpose of determining one or more of the mechanical properties defined in Clause 4.6 Apparatus6.1 Testing machineThe testing machine shall be verified and c
40、alibrated in accordance with ISO 7500-1 and shall be of at least class 1, unless otherwise specified in the product standard.6.1.1 Testing machine complianceCompliance (displacement per unit of applied force of the apparatus itself) of the test facility (tensile machine and the cryogenic load frame)
41、 should be known. Measure the compliance by coupling the load train with a rigid test piece or by using a special calibration test piece. Then, measure the compliance at a low force and at the highest force used to qualify the machine, as indicated in 6.1.4. A practical procedure for the determinati
42、on of the compliance respective of the stiffness is described in ISO 6892-1:, Annex F.NOTE Different system compliances may result in different stress-extension curves and material properties (e.g. elongation after fracture, tensile strength) of the material because a larger discontinuous deformatio
43、n occurs in a lower compliance test facility.4 ISO 2015 All rights reservedBS ISO 6892-4:2015ISO 6892-4:2015(E)6.1.2 System designTypically, alloys in liquid helium exhibit double or triple their ambient strengths at ambient temperature. For the same test piece geometry, higher forces shall be appli
44、ed to the cryostat, test piece, load train members, and grips at cryogenic temperatures. Since many conventional test machines have a maximum force of 100 kN or less, it is recommended that the apparatus be designed to accommodate one of the small test pieces cited in 7.2.6.1.3 Construction material
45、sMany construction materials, including the vast majority of ferritic steels, are brittle at 4 K. To prevent service failures, fabricate the grips and other load train members using strong, tough, cryogenic alloys. Materials that have low thermal conductivity are desirable to reduce heat flow. Auste
46、nitic stainless steels (AISI 304LN), maraging steels (200, 250, or 300 grades, with nickel plating to prevent rust), wrought nickel-base superalloys, and titanium alloys (Ti-6Al-4V and Ti-5Al-2,5Sn) have been used with proper design, for grips, pull rods, and cryostat frames. Non-metallic materials
47、(for example, glass-epoxy composites) are excellent insulators and are sometimes used for compression members.6.1.4 AlignmentProper system alignment is essential to minimize bending strains in the tensile tests. The machine and grips should be capable of applying force to a precisely machined calibr
48、ation test piece so that the maximum bending strain should be according to ISO 23788 class 10. Reduce bending strain to an acceptable level by making proportional adjustments to a cryostat with alignment capability, or by using spacing shims to compensate an unadjustable fixture. Calculate the strai
49、n based on readings taken while the calibration test piece is subjected to a low force, as well as at the highest force for which the machine and load train are being qualified.Qualify the apparatus by making axiality measurements at room temperature and at 4 K. To perform axiality tests of the apparatus, the test piece form and cryostat should be the same as that used during cryogenic tests, and the test piece concentricity should be as nearly perfect as possible. No plastic strain should occur in the
