ISO-7800-2003.pdf

Reference number ISO 7800:2003(E) © ISO 2003 INTERNATIONAL STANDARD ISO 7800 Second edition 2003-09-01 Metallic materials Wire Simple torsion test Matériaux métalliques Fils Essai de torsion simple ISO 7800:2003(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 2003 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 2003 All rights reserved ISO 7800:2003(E) © ISO 2003 All rights reserved iii Contents Page Forewordiv 1 Scope1 2 Symbols and designations.1 3 Principle.1 4 Testing equipment2 5 Test piece.2 6 Testing conditions2 7 Procedure.3 8 Test report3 Annex A (informative) Recommended types of grip depending on the diameter, d, or characteristic dimension, D, of the wire.5 Annex B (informative) Recommended method of straightening curved wires sufficiently to place them in test grips 6 Annex C (informative) Evaluation of fractures occurring during simple torsion test.7 ISO 7800:2003(E) iv © ISO 2003 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 7800 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 7800:1984), which has been technically revised. INTERNATIONAL STANDARD ISO 7800:2003(E) © ISO 2003 All rights reserved 1 Metallic materials Wire Simple torsion test 1 Scope This International Standard specifies a method for determining the ability of metallic wire of diameter or characteristic dimension 0,1 mm to 10 mm inclusive to undergo plastic deformation during simple torsion in one direction. 2 Symbols and designations The symbols and designations used in the simple torsion test of wires are shown in Figure 1 and listed in Table 1. 3 Principle The test consists of twisting a test piece of wire around its own axis in one direction. Key 1 grip Figure 1 Table 1 Symbols and designations Symbol Designation Unit d Diameter of a round wire mm D Characteristic dimension for non-circular wires a mm L Free length between grips mm Nt Number of turns a The characteristic dimension for non-circular wires is the maximum dimension of the cross section and is usually specified in the relevant standard. ISO 7800:2003(E) 2 © ISO 2003 All rights reserved 4 Testing equipment 4.1 Grips, having a minimum hardness of 55 HRC, and parallel faces. The recommended types of grips are given in Annex A. 4.2 Testing machine, constructed so that a change of length between the grips, caused by contraction of the test piece during testing, is not prevented and that an appropriate tensile stress (see 7.1) may be applied to the test piece. The grips shall be placed in the testing machine in such a way that during testing they remain on the same axis and do not apply any bending force to the test piece. One of the grips shall be capable of being rotated around the axis of the test piece while the other shall not be subject to any angular deflection, except for such deflection as may be necessary to measure the torque. The distance between the grips shall be capable of adjustment for different test piece lengths. 5 Test piece 5.1 The length of wire to be used as the test piece shall be as straight as possible. 5.2 If straightening is necessary, it shall be done by a suitable method. A recommended method is given in Annex B. During straightening, the surface of the wire shall not be damaged and the test piece shall not be subjected to any twisting. Wire with localized sharp curvature shall not be tested. Unless otherwise specified, the nominal free length between the grips shall be as given in Table 2. Table 2 Dependence of free length between the grips on nominal diameter or characteristic dimension of the wire Nominal diameter, d, or characteristic dimension, D mm Free length between grips (nominal) a 0,3 u d (D) 3 V-grooved ISO 7800:2003(E) 6 © ISO 2003 All rights reserved Annex B (informative) Recommended method of straightening curved wires sufficiently to place them in test grips The following is a method of straightening wires sufficiently to be able to place them in test grips of a torsion wire tester. This procedure is suggested for thick, high strength wire, which may present a safety hazard to the test operator if an attempt is made to place the wire in the test grips without first securing the wire. Equipment includes: a bench mounted vice, two adjustable vice grips and a piece of wood approximately 45 mm wide by 20 mm thick by a length slightly less than the free length between the grips given in Table 2, column 2 of this International Standard. The 20 mm dimension may be tapered from the centre to each end so that the ends of the wood are approximately 15 mm thick. Place the wood (45 mm dimension) securely between the jaws of the vice and clamp. Wrap a cushioning agent (such as masking tape) around the jaw of each vice grip that will be in contact with the wire when it is clamped to the board. The masking tape will protect the wire from being damaged (nicked). Place the wire (curvature down) on top of the board so that an equal length of the wire will extend beyond each end of the board. Adjust the vice grip and place the cushioned jaw on top of the wire near one end of the board. Grasp the other end of the wire and bend it down on the board. Clamp the wire in place with the other adjusted vice grip ensuring that the cushioned jaw is in contact with the wire. Insert the ends of the wire in the grips, apply a tensile stress not exceeding 2 % of the nominal tensile strength of the wire, release the vice grips and remove the board. Duplicate set-ups may be made so that the next wire to be tested will be available when needed. -,-,- ISO 7800:2003(E) © ISO 2003 All rights reserved 7 Annex C (informative) Evaluation of fractures occurring during simple torsion test Type No. Aspect Description and characteristics Fracture plane Type of fracture Product Normal torsion fracture 1 a b Smooth: fracture plane perpendicular to wire axis (or slightly oblique). No cracks in fracture plane. Brittle: fracture plane at an angle of 45° to wire axis. No cracks in fracture plane. Fracture with local cracks Regular fracture (material defects) 2 a b c Smooth: fracture plane perpendicular to wire axis and partially cracked. Stepped: a part of the fracture plane is still smooth: partially cracked. Irregular fracture plane: no cracks in fracture plane. Fracture with spiral cracks over the whole length (or large part of it) Crack formation already occurs after a low number (3 to 5) of torsions and is best visible at that moment 3 a b c Smooth: fracture plane perpendicular to wire axis and partially or entirely cracked. Stepped: a part of the fracture plane is still smooth and partially or entirely cracked. Brittle: fracture plane at an angle of 45° and partially or entirely cracked or irregular fracture plane and partially or entirely cracked ISO 7800:2003(E) ICS 77.040.10 Price based on 7 pages © ISO 2003 All rights reserved