1、October 2008DEUTSCHE NORM English price group 6No part of this standard may be reproduced without prior permission ofDIN Deutsches Institut fr Normung e. V., Berlin. Beuth Verlag GmbH, 10772 Berlin, Germany,has the exclusive right of sale for German Standards (DIN-Normen).ICS 77.040.10!$R24“1471517w
2、ww.din.deDDIN ISO 7801Metallic Materials Wire Reverse bend test (ISO 7801:1984)English version of DIN ISO 7801:2008-10Metallische Werkstoffe Draht Hin- und Herbiegeversuch (ISO 7801:1984)Englische Fassung DIN ISO 7801:2008-10SupersedesDIN 51211:1978-09www.beuth.deDocument comprises 6 pagesDIN ISO 78
3、01:2008-10 2 National foreword This standard has been prepared by Technical Committee ISO/TC 164 “Mechanical testing of metals” (Secretariat: CNI, Czech Republic). The responsible German body involved in its preparation was the Normenausschuss Stahldraht und Stahldraht-erzeugnisse (Steel Wire and Wi
4、re Products Standards Committee), Technical Committee NA 099-00-01 AA Stahldraht. International Standard ISO 7801:1984 has been adopted without any changes to its content. This document contains phrasings and formats that are appropriate to the structure and character of an International Standard bu
5、t which, in terms of detail, do not necessarily meet the current rules of presentation for German Standards. Wherever possible, German technical terms were used in the German translation. The national standard DIN 51211 will be withdrawn upon the publication of DIN ISO 7801. Attention is drawn to th
6、e possibility that some of the elements of this document may be the subject of patent rights. DIN shall not be held responsible for identifying any or all such patent rights. Amendments This standard differs from DIN 51211:1978-09 as follows: a) The range of application for wires of non-ferrous meta
7、ls is no longer restricted to 1,5 mm minimum. b) Other distances h between the top tangential plane of cylindrical supports and the bottom face of the guide than specified in Table 2 are no longer permitted. c) Minimum material hardness values for cylindrical supports and gripping faces of supports
8、are no longer specified. d) During the test, the maximum tensile stress between test piece and cylindrical support shall be not greater than 2 % of the value of the nominal tensile strength for all wire materials. e) The standard has been brought up-to-date with the current rules of presentation. Pr
9、evious editions DIN DMV 1211: 1931-09 DIN 51211: 1934-11, 1961-09, 1978-09 1 Scope and field of application 2 Principle This International Standard specifies the method for determin- ing the ability of metallic wire of diameter or thickness 0,3 to 10 mm inclusive to undergo plastic deformation durin
10、g reverse bending. The range of diameters or thicknesses for which this International Standard is applicable may be more exactly specified in the relevant product standard. The reverse bend test consists of repeated bending, through 90 in opposite directions, of a test piece held at one end, each be
11、nd being over a cylindrical support of a specified radius. 3 Symbols and designations Symbols and designations used in reverse bend testing of wires are specified in table 1 and shown in figure 1. 3DIN ISO 7801:2008-10 Metallic Materials Wire Reverse bend test d 9 Nearest point of - contact with tes
12、t piece Bending arm ,-Guide Pivoting axis of the bending arm Figure 1 Cylindrical supports A and B Gripping faces of supports supports Table 1 Symbol Designation Unit d Diameter of round wire mm a Minimum thickness of wire of non-circular mm section capable of being held between parallel grips (see
13、figure 2) r I I Radius of cylindrical supports mm h Distance from the top tangential plane of mm cylindrical supports to the bottom face of guide Diameter of guide hole I I mm ds Y Distance from a plane, defined by the axes of mm the cylindrical supports, to the nearest point of contact with the tes
14、t piece I Nb ( Number of reverse bends - 4DIN ISO 7801:2008-10 4 Testing equipment 4.1 General The testing machine shall be constructed so as to conform with the principles indicated in figure 1 and the essential dimensions given in table 2. 4.2 Cylindrical supports and gripping faces 4.2.1 The cyli
15、ndrical supports and the gripping faces shall be of sufficient hardness (to provide rigidity and/or resistance to abrasion 1. 4.2.2 The radius of cylindrical support r shall not differ from its nominal dimension by more than the tolerance given in table 2. 4.2.3 The axes of the cylindrical supports
16、shall be perpen- dicular to the plane of bend and shall be parallel and in the same plane to within 0,l mm. 4.2.4 The gripping faces shall project slightly beyond the face of the cylindrical supports to a distance which does not exceed 0,l mm, as measured by the clearance between the test piece and
17、each cylindrical support on a line joining the centres of cur- vature. 4.2.5 The top edge of the gripping faces shall be below the centres of curvature of the cylindrical supports by a distance y of 1,5 mm for supports of radius equal to or less than 2,5 mm and by 3 mm for supports of larger radius.
18、 (If r 2,5mm,y = 3mm.) 4.3 Bending arm and guide 4.3.1 The distance of the pivoting axis of the bending arm from the top of the cylindrical supports shall be 1,0 mm for all sizes of supports. Nominal diameter or thickness of wire d (a) 0,3 d (a) 0,5 0,5 d (a) 0,7 0,7 d (a) I,0 l,Od(a) I,5 1,5 d (a)
19、2,0 2,0 d (a) 3,0 3,0 d (a) 4,0 4,0 d (a) 6,0 6,0 d (a) G 8,0 8,0 d (a) 10,O 4.3.2 The holes in the guide shall widen out at each end and have a diameter in accordance with table 2. 5 Test piece 5.1 The length of wire to be used as the test piece is to be as straight as possible, but it may exhibit
20、slight curvature in the plane in which it will be bent during the test. 5.2 If straightening is necessary, it shall be done by hand or, if this is not possible, by hammering on a level surface of wood, plastic material or copper using a hammer of a similar material. 5.3 During straightening, the sur
21、face of the wire must not be damaged and the test piece must not be subjected to any twisting. 5.4 Wire with a localized sharp curvature shall not be straightened. 6 Procedure 6.1 In general, the test is carried out at ambient temperature between 10 and 35 OC. Tests carried out under controlled con-
22、 ditions shall be made at a temperature of 23 + 5 OC. 6.2 The radius of the support r, the distance h, and the diameter of the hole dg shall be selected according to the wire diameter as given in table 2. 6.3 Insert the test piece, with the bending arm vertical, through one of the holes in the guide
23、 as indicated in figure 1. Hold the lower end of the test piece between the grips so that Table 2 Dimensions and tolerances in millimetres Radius of cylindrical support r I,25 k 0,05 15 1,75 IfI 0,05 15 2,5 f 0,l 15 3,75 + 0,l 20 5 III 0,l 20 7,5 I!z 0,l 25 10 + 0,l 35 15 * 0,l 50 20 I!I 0,l 75 25 I
24、!I 0,l 100 Distance Diameter of h guide hole) 28 TO TO 28 2,0 and 2,5 2,5 and 3,5 3,5 and 4,5 4,5 and 7,0 7,0 and 9,0 9,0 and 11,0 I) Where appropriate, the smaller diameter of hole is to be used for the smaller nominal diameter of wire (see column l) and the larger diameter of hole for the larger n
25、ominal diameter of wire (also see column 1). For diameters within ranges given in column 1, the appropriate size of hole is to be chosen to ensure free movement of the wire. 5DIN ISO 7801:2008-10 the test ports. piece is perpendicular to the axes of the cylindrical sup- NOTE - Non-circular test piec
26、es are to be placed so that the greater dimension is parallel, or approximately parallel, to the gripping faces as shown in figure 2. Figure 2 6.4 Bend the test piece through 90 alternately in opposite directions. One bend consists of bending the free end of the test piece through 90 and returning i
27、t to its original position. Make the following bend in the opposite direction as shown in figure 3. Do not interrupt the testing between successive bends. Second bend Figure 3 6.5 Bend at a uniform rate without shock, not exceeding one bend per second. If necessary, reduce the rate of bending to ens
28、ure that the heat generated does not affect the result of the test. 6.6 To ensure continuous contact between the test piece and the cylindrical supports during the test, some form of con- straint may be applied. This may be in the form of a tensile stress not greater than 2 % of the value of the nom
29、inal tensile strength, unless otherwise specified in the relevant standard. 6.7 Continue the test until the number of bends specified in the relevant standard is completed, or cracking visible without the use of magnifying aids is seen to occur. Alternatively, if specified in the relevant standard,
30、con test until complete fracture of the test piece occurs. tinue the 6.8 The bend during which the failure of test piece occurs shall not be counted into the number of bends b) identification of the test piece (e.g. type of the material, cast number, etc.) ; c) nominal diameter d or minimum thickness a of the test piece ; d) details rega straightening) ; rding the preparation of the test piece (e.g. e) test conditions (e .g . radius application of tensile stress) ; f) 9) r of the cylindrical supports, criterion for ending the test; test result. 6DIN ISO 7801:2008-10
