ISO-4545-2-2005.pdf

Reference number ISO 4545-2:2005(E) © ISO 2005 INTERNATIONAL STANDARD ISO 4545-2 First edition 2005-11-15 Metallic materials Knoop hardness test Part 2: Verification and calibration of testing machines Matériaux métalliques Essai de dureté Knoop Partie 2: Vérification et étalonnage des machines d'essai ISO 4545-2:2005(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. © ISO 2005 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 copyrightiso.org Web www.iso.org Published in Switzerland ii © ISO 2005 All rights reserved ISO 4545-2:2005(E) © ISO 2005 All rights reserved iii Contents Page Foreword iv 1 Scope . 1 2 Normative references. 1 3 General conditions . 1 4 Direct verification 2 5 Indirect verification. 4 6 Intervals between verifications . 6 7 Verification report/calibration certificate . 6 Annex A (informative) Notes on diamond indenters 7 Annex B (informative) Uncertainty of measurement of the calibration results of the hardness testing machine. 8 Bibliography. 14 ISO 4545-2:2005(E) iv © ISO 2005 All rights reserved Foreword 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 4545-2 was prepared by Technical Committee ISO/TC 164, Mechanical testing of metals, Subcommittee SC 3, Hardness testing. ISO 4545-2 cancels and replaces ISO 4546:1993, which has been technically revised. ISO 4545 consists of the following parts, under the general title Metallic materials Knoop hardness test: Part 1: Test method Part 2: Verification and calibration of testing machines Part 3: Calibration of reference blocks Part 4: Table of hardness values INTERNATIONAL STANDARD ISO 4545-2:2005(E) © ISO 2005 All rights reserved 1 Metallic materials Knoop hardness test Part 2: Verification and calibration of testing machines 1 Scope This part of ISO 4545 specifies the method of verification of testing machines for determining Knoop hardness for metallic materials in accordance with ISO 4545-1-1. It covers test forces from 0,098 07 N to 19,614 N. The method is recommended only for indentations with diagonals W 0,020 mm. It specifies a direct verification method for checking the main functions of the machine, and an indirect verification method suitable for the overall checking of the machine. The indirect verification method may be used on its own for periodic routine checking of the machine in service. If a testing machine is also to be used for other methods of hardness testing, it should be verified independently for each method. 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. ISO 376:2004, Metallic materials Calibration of force-proving instuments used for the verification of uniaxial testing machines ISO 4545-1:2005, Metallic materials Knoop hardness test Part 1: Test method ISO 4545-3, Metallic materials Knoop hardness test Part 3: Calibration of reference blocks 3 General conditions Before a Knoop hardness testing machine is verified, it shall be checked to ensure that it is properly set up in accordance with the manufacturer's instructions. Especially, it should be checked that: a) the mount holding the indenter is capable of moving freely without any friction or excess side play; b) the indenter is firmly mounted in the mount; c) the test force can be applied and removed without shock or vibration and in such a manner that the readings are not influenced; ISO 4545-2:2005(E) 2 © ISO 2005 All rights reserved d) the measuring system is integral with the machine: the change in mode from the application and removal of the test force to the measuring mode does not influence the readings, illumination does not affect the readings, the centre of the indentation is near the centre of the field of view. 4 Direct verification 4.1 General 4.1.1 Direct verification should be carried out at a temperature of (23 ± 5) °C. If the verification is carried out at a temperature outside this range, it shall be noted in the verification report. 4.1.2 The instruments used for verification and calibration shall be traceable to national standards. 4.1.3 Direct verification involves: a) calibration of the test force; b) verification of the indenter; c) calibration of the measuring system; d) verification of the testing cycle. 4.2 Calibration of the test force 4.2.1 Each test force used (see Table 2 in ISO 4545-1:2005), within the working range of the testing machine, shall be measured. 4.2.2 The test force shall be measured by one of the following two methods: by means of an elastic proving device in accordance with ISO 376:2004, class 1, or by balancing against a force, accurate to ± 0,2 %, applied by means of calibrated masses or another method with the same accuracy. 4.2.3 Three readings shall be taken for each test force. Immediately before each reading is taken, the indenter shall be moved in the same direction as during the test. All readings shall be within the tolerances defined in Table 1. Table 1 Test-force tolerances Test force, F N Tolerance % 0,098 07 u F 0,001 mm, the repeatability of the testing machine is satisfactory when rrel is less than or equal to the percentages indicated in Table 2. Table 2 Relative repeatability Hardness range of standardized test blocks Test force N Maximum permissible rrel % 100 u HK u 250 250 650 0,098 07 u F u 4,903 9 5 4 100 u HK u 250 250 650 4,903 0,000 5 mm, the error of the testing machine is satisfactory when Erel u ± 2 %. 5.9 The determination of the uncertainty of measurement of the calibration results of the hardness testing machine is given in Annex B. ISO 4545-2:2005(E) 6 © ISO 2005 All rights reserved 6 Intervals between verifications The specifications for the direct verifications of hardness testing machines are given in Table 3. Indirect verification shall be performed at least once every 12 months and after a direct verification has been performed. Table 3 Direct verifications of hardness testing machines Requirements of verification Force Measuring system Test cycle Indenter a before setting to work first time x x x x after dismantling and reassembling, if force, measuring system or test cycle are affected x x x failure of indirect verificationb x x x indirect verification 14 months ago x x x a In addition, it is recommended that the indenter be directly verified after 2 years of use. b Direct verification of these parameters may be carried out sequentially (until the machine passes indirect verification) and is not required if it can be demonstrated (e.g. by tests with a reference indenter) that the indenter was the cause of the failure. 7 Verification report/calibration certificate The verification report/calibration certificate shall contain the following information: a) a reference to this part of ISO 4545; b) method of verification (direct and/or indirect); c) identification data of the hardness testing machine; d) means of verification (reference blocks, elastic proving devices, etc.); e) test force(s) used; f) hardness values of standardized blocks used; g) verification temperature, if it is outside the range specified in Clause 4; h) the result obtained; i) date of verification and reference to the verification institution; j) uncertainty of the verification result. ISO 4545-2:2005(E) © ISO 2005 All rights reserved 7 Annex A (informative) Notes on diamond indenters Experience has shown that a number of initially satisfactory indenters can become defective after use for a comparatively short time. This is due to small cracks, pits or other flaws in the surface. If such faults are detected in time, regrinding may reclaim many indenters. If not, any small defects on the surface rapidly worsen and make the indenter useless. Therefore, the condition of indenters should be monitored by visually checking the appearance of the indentation on a reference block, each day the testing machine is used; the verification of the indenter is no longer valid when the indenter shows defects; reground or otherwise repaired indenters shall meet all of the requirements of 4.3. ISO 4545-2:2005(E) 8 © ISO 2005 All rights reserved Annex B (informative) Uncertainty of measurement of the calibration results of the hardness testing machine The metrological chain necessary to define and disseminate hardness scales is shown in Figure B.1 in ISO 4545-1:2005. B.1 Direct calibration of the hardness testing machine B.1.1 Calibration of the test force The combined relative standard uncertainty of the test force calibration is calculated according to the following equation: 22 FFRSFHTM uuu=+ (B.1) where uFRS is the relative uncertainty of measurement of the force transducer (from calibration certificate); uFHTM is the relative standard uncertainty of the test force generated by the hardness testing machine. The uncertainty of measurement of the reference instrument, force transducer, is indicated in the corresponding calibration certificate. The influence quantities, like temperature dependence, long-term stability, and interpolation deviation, should be considered for critical applications. Depending on the design of the force transducer, the rotational position of the transducer related to the indenter axis of the hardness testing machine should be considered. EXAMPLE Uncertainty of measurement of the force transducer (from calibration certificate): UFRS = 0,24 % (k = 2) Calibration value of the force transducer FRS = 9,806 7 N Table B.1 Results of the test force calibration Number of height position for test force calibration Series 1, F1 N Series 2, F2 N Series 3, F3 N Mean value ,F N Relative deviation Frel, % Relative standard measurement uncertainty uFHTM, % 1 9,809 9,815 9,822 9,815 0,08 0,04 ISO 4545-2:2005(E) © ISO 2005 All rights reserved 9 where RS rel FF F F = (B.2) F FHTM 1 ,(3) n i s un F = (B.3) sFi is the standard deviation of the test-force indication values in the i-th height position Table B.2 Calculation of the uncertainty of measurement of the test force Quantity Xi Estimated value xi Relative limit values ai Distribution type Relative standard measurement uncertainty u(xi) Sensitivity coefficient ci Relative uncertainty contribution ui(H) uFRS 294,2 N Normal 1,2 × 103 1 1,2 × 103 uFHTM Normal 4,0 × 104 1 4,0 × 104 Relative combined standard uncertainty u(F) 1,26 × 103 Relative expanded uncertainty of measurement U(F) (k = 2) 2,5 × 103 Table B.3 Calculation of the maximum relative deviation of the test force including the uncertainty of measurement of the reference instrument Relative deviation of test force Frel, % Expanded relative measurement uncertainty of test force UF, % Max. relative deviation of test force including measurement uncertainty of reference instrument Fmax, % 0,08 0,25 0,33 where maxrelF FFU= + (B.4) The result of the example means that the deviation of the test forces including the uncertainty of measurement of the reference instrument specified in 4.2.3, amounting to ± 1,0 % is complied with. B.1.2 Calibration of the optical measuring system The combined relative standard uncertainty of the reference instrument for the measuring system is calculated as follows: 222 LLRSmsLHTM uuuu=+ (B.5) where uLRS is the relative uncertainty of measurement of the object micrometer (reference standard) from the calibration certificate for k = 1; ums is the uncertainty of measurement due to the resolution of the measuring system; uLHTM is the relative standard uncertainty of measurement of the hardness testing machine. ISO 4545-2:2005(E) 10 © ISO 2005 All rights reserved The uncertainty of measurement of the reference instrument for the optical measuring system, the object micrometer, is indicated in the corresponding calibration certificate. The influence quantities, for example, temperature dependence, longterm stability, and interpolation deviation, do not exert an essential influence on the uncertainty of measurement of the object micrometer. EXAMPLE Uncertainty of measurement of the object micrometer: ULRS = 0,000 5 mm (k = 2) Resolution of the measuring system ms = 0,1 µm Table B.4 Results of the calibration of the measuring system Indication value of the object micrometer LRS, Series 1, L Series 2, L2 Series 3, L3, Mean value, L Relative deviation Relative standard measurement uncertainty mm mm mm mm mm Lrel, % uLHTM, % 0,05 0,050 1 0,050 0 0,050 1 0,050 1 0,13 0,07 0,10 0,100