BS ISO 28079-2009 Hardmetals - Palmqvist toughness test《硬质合金 巴氏韧性试验》.pdf
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1、BS ISO28079:2009ICS 77.040.10; 77.160NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWBRITISH STANDARDHardmetals Palmqvist toughnesstestThis British Standardwas published under theauthority of the StandardsPolicy and StrategyCommittee on 31 August2009 BSI 2009ISBN 978 0 580 6175
2、5 3Amendments/corrigenda issued since publicationDate CommentsBS ISO 28079:2009National forewordThis British Standard is the UK implementation of ISO 28079:2009.The UK participation in its preparation was entrusted to TechnicalCommittee ISE/65, Sintered metal components.A list of organizations repre
3、sented on this committee can be obtained onrequest to its secretary.This publication does not purport to include all the necessary provisionsof a contract. Users are responsible for its correct application.Compliance with a British Standard cannot confer immunityfrom legal obligations.BS ISO 28079:2
4、009Reference numberISO 28079:2009(E)ISO 2009INTERNATIONAL STANDARD ISO28079First edition2009-07-15Hardmetals Palmqvist toughness test Mtaux durs Mthode dessai de duret de Palmqvist BS ISO 28079:2009ISO 28079:2009(E) PDF disclaimer This PDF file may contain embedded typefaces. In accordance with Adob
5、es 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 Adobes licensing policy.
6、 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
7、 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 2009 All rights reserved. Unless otherwise specified, no
8、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 ISOs member body in the country of the requester. ISO copyright office Case postal
9、e 56 CH-1211 Geneva 20 Tel. + 41 22 749 01 11 Fax + 41 22 749 09 47 E-mail copyrightiso.org Web www.iso.org Published in Switzerland ii ISO 2009 All rights reservedBS ISO 28079:2009ISO 28079:2009(E) ISO 2009 All rights reserved iiiContents Page Foreword iv Introduction v 1 Scope . 1 2 Normative refe
10、rences . 1 3 Symbols and units 1 4 Test pieces and sample preparation. 2 4.1 Test piece size and sampling 2 4.2 Surface preparation 2 4.3 Surface condition 2 5 Apparatus 3 5.1 General. 3 5.2 Indentation. 3 5.3 Indentation and crack measurement 3 6 Procedure and conditions of testing 3 6.1 Indentatio
11、ns. 3 6.2 Indentation and crack length measurement 3 6.3 Test validity . 5 7 Analysis . 6 7.1 Vickers hardness 6 7.2 Toughness. 6 8 Measurement uncertainty 6 9 Test report . 7 Annex A (informative) Report pro forma Palmqvist toughness measurements on hardmetals . 8 Bibliography . 10 BS ISO 28079:200
12、9ISO 28079:2009(E) iv ISO 2009 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
13、 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 Internationa
14、l 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
15、 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
16、 patent rights. ISO shall not be held responsible for identifying any or all such patent rights. ISO 28079 was prepared by Technical Committee ISO/TC 119, Powder metallurgy, Subcommittee SC 4, Sampling and testing methods for hardmetals. BS ISO 28079:2009ISO 28079:2009(E) ISO 2009 All rights reserve
17、d vIntroduction Good test methods are those which enable a user or manufacturer to clearly discriminate between different materials. Fracture toughness values are required for three reasons: a) for product design and performance assessment; b) for selection of materials; c) for quality control. A sp
18、ecific International Standard for the toughness of hardmetals 1)has not been developed to date, primarily because of the difficulty of introducing stable precracks into these tough but hard materials. However, Palmqvist tests for toughness are widely used because of their perceived apparent simplici
19、ty. Cracks are formed at the corners of Vickers hardness indentations and these can be used to calculate a nominal surface toughness value. This value is sensitive to the method of measurement and to the method of surface preparation of the sample. This International Standard outlines good practice
20、to minimize uncertainties due to these issues. There are several possible methods for the measurement of the fracture toughness of hardmetals. The results can be expressed either as a stress intensity factor, in MNm3/2, or as a fracture surface energy, in Jm2. The range of values for typical WC/Co h
21、ardmetals is from 7 MNm3/2to 25 MNm3/2. There is a general inverse trend of hardness against fracture toughness (see 1 and 2 in the Bibliography). When applied unqualified to hardmetals, “toughness” can have several meanings. a) Plane-strain fracture toughness, KIc, in MNm3/2, is a value obtained fr
22、om tests on specimens with appropriate geometries for plane-strain conditions and containing a well-defined geometry of crack. There is no standard method for hardmetals and different organizations use different test methods for introducing the precrack. b) Strain-energy release rate (or work of fra
23、cture), G, is an alternative expression for toughness, often obtained by converting plane-strain toughness, K, to G i.e. G = K2/E(1 2), where E is Youngs modulus and is Poissons ratio. G has units of Jm2. Again, there is no standard method. c) Palmqvist toughness, W, is a value obtained by measuring
24、 the total length of cracks emanating from the four corners of a Vickers hardness indentation. For a given indentation load, the shorter the crack, the tougher the hardmetal. d) Finally, toughness is also widely used, in a loose sense, to describe the empirical relation between perceived resistance
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