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1、 Reference number ISO 24213:2008(E) ISO 2008 INTERNATIONAL STANDARD ISO 24213 First edition 2008-03-01 Metallic materials Sheet and strip Method for springback evaluation in stretch bending Matriaux mtalliques Tles et bandes Mthodes dvaluation du retour lastique lors dun cintrage sous traction Copyr
2、ight International Organization for Standardization Provided by IHS under license with ISO Licensee=Boeing Co/5910770001 Not for Resale, 07/25/2008 02:47:53 MDTNo reproduction or networking permitted without license from IHS -,-,- ISO 24213:2008(E) PDF disclaimer This PDF file may contain embedded t
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5、ptimized 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. COPYRIGHT PROTECTED DOCUMENT ISO 2008 All rights reserved
6、. 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 ISOs member body in the country of the requester.
7、 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 2008 All rights reserved Copyright International Organization for Standardization Provided by IHS under license with ISO Licens
8、ee=Boeing Co/5910770001 Not for Resale, 07/25/2008 02:47:53 MDTNo reproduction or networking permitted without license from IHS -,-,- ISO 24213:2008(E) ISO 2008 All rights reserved iii Contents Page Foreword iv Introduction v 1 Scope . 1 2 Normative references. 1 3 Terms and definitions. 1 4 Symbols
9、 and designations 3 5 Principle. 3 6 Test apparatus 3 7 Test piece 5 8 Procedure 5 9 Test report . 6 Annex A (normative) Method for calculating blank holding pressure 7 Annex B (normative) Method for calculating nominal tensile stress . 9 Annex C (normative) Device for determining radius of curvatur
10、e using a dial gauge 10 Bibliography. 11 Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=Boeing Co/5910770001 Not for Resale, 07/25/2008 02:47:53 MDTNo reproduction or networking permitted without license from IHS -,-,- ISO 24213:2008(E) iv IS
11、O 2008 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
12、 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 Comm
13、ission (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 technic
14、al 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 sha
15、ll not be held responsible for identifying any or all such patent rights. ISO 24213 was prepared by Technical Committee ISO/TC 164, Mechanical testing of metals, Subcommittee SC 2, Ductility testing. Copyright International Organization for Standardization Provided by IHS under license with ISO Lice
16、nsee=Boeing Co/5910770001 Not for Resale, 07/25/2008 02:47:53 MDTNo reproduction or networking permitted without license from IHS -,-,- ISO 24213:2008(E) ISO 2008 All rights reserved v Introduction This International Standard has been established to evaluate the amount of springback occurring in met
17、allic sheets deformed by stretch-bending. It may be used for specifying a material, directly controlling a forming operation, designing dies, or calibrating finite element programs. In metallic sheet forming processes, the geometry of the formed parts may deviate from the design geometry after the p
18、arts are removed from the dies due to elastic recovery. This phenomenon is referred to as springback. Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=Boeing Co/5910770001 Not for Resale, 07/25/2008 02:47:53 MDTNo reproduction or networking per
19、mitted without license from IHS -,-,- Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=Boeing Co/5910770001 Not for Resale, 07/25/2008 02:47:53 MDTNo reproduction or networking permitted without license from IHS -,-,- INTERNATIONAL STANDARD ISO
20、 24213:2008(E) ISO 2008 All rights reserved 1 Metallic materials Sheet and strip Method for springback evaluation in stretch bending 1 Scope This International Standard specifies a method for evaluating the amount of springback of sheets of metallic materials known to exhibit large amounts of spring
21、back subjected to plane-strain stretch bending, which is a typical deformation mode generated in press-formed panels. By using this method, the amount of springback under stretch bending is evaluated accurately and quantitatively. 2 Normative references The following referenced documents relate to t
22、he 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 31-0, Quantities and units Part 0: General principles 3 Terms and definitions For the purposes of this
23、document, the following terms and definitions apply. 3.1 curvature reciprocal of the radius of curvature r determined at the centre of a stretch-bent specimen on the inner surface in the longitudinal direction 1 r = (1) 3.2 amount of springback relative change in curvature of a test piece under forc
24、e and after removal of the force shown in Figure 1 rr r = (2) Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=Boeing Co/5910770001 Not for Resale, 07/25/2008 02:47:53 MDTNo reproduction or networking permitted without license from IHS -,-,- IS
25、O 24213:2008(E) 2 ISO 2008 All rights reserved a) Under force b) After removal of the force Figure 1 Radius of curvature of test piece under force and after removal of the force 3.3 stretch bending method of bending a test piece under tension 3.4 blank holding pressure force applied on the test piec
26、e in the direction of its thickness, divided by the surface area of the test piece contacting the die NOTE The method for calculating the blank holding pressure is shown in Annex A. 3.5 nominal tensile stress tensile force per unit cross-sectional area of the test piece NOTE The method for calculati
27、ng the nominal tensile stress is shown in Annex B. Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=Boeing Co/5910770001 Not for Resale, 07/25/2008 02:47:53 MDTNo reproduction or networking permitted without license from IHS -,-,- ISO 24213:200
28、8(E) ISO 2008 All rights reserved 3 4 Symbols and designations The symbols used in this International Standard and the corresponding designations are given in Table 1. Table 1 Symbols and corresponding designations Symbol Designation Unit a Thickness of test piece mm b Width of test piece mm Fh Blan
29、k holding force N h Amount of punch penetration mm Fp Punch force N p Blank holding pressure MPa Rp Punch radius mm r Radius of curvature of the inner surface of the test piece under force mm r Radius of curvature of the inner surface of the test piece after removal of the force mm rd Die profile ra
30、dius mm S Total surface area of test piece in contact with dies mm2 T Nominal tensile stress applied to test piece MPa W Distance between dies mm w Width of the base of a dial gauge for measuring the curvature of the test piece after removal of the force, see Annex C mm x Measured value by a dial ga
31、uge for measuring the curvature of the test piece after removal of the force (length of AD in Figure C.1) mm Curvature of the inner surface of the test piece under force (= r 1) mm1 Curvature of the inner surface of the test piece after removal of the force = (r) 1 mm1 Amount of springback 2 Spread
32、angle of test piece around punch rad 5 Principle This test is a method for evaluating the springback of a metal sheet using a stretch-bending method. The amount of springback is determined as the change in curvatures of a test piece under force and after removal of the force (see Equations in 3.1 an
33、d 3.2). The nominal tensile stress applied to the test piece is determined using the measured value of punch penetration and punch force (see Annex B). 6 Test apparatus The test apparatus is described below. 6.1 Stretch-bending testing device for springback evaluation. An example of the stretch-bend
34、ing device used in the test is shown in Figure 2. The radius of the semi- cylindrical punch shall be (100 1) mm. However, the radius of the punch tip and its tolerance may be determined by agreement between the parties involved. Copyright International Organization for Standardization Provided by IH
35、S under license with ISO Licensee=Boeing Co/5910770001 Not for Resale, 07/25/2008 02:47:53 MDTNo reproduction or networking permitted without license from IHS -,-,- ISO 24213:2008(E) 4 ISO 2008 All rights reserved 6.2 Device for determining the radius of curvature of a test piece. The principle for
36、determining the radius of curvature with a dial gauge is shown in Annex C, in which a dial gauge with an accuracy of 0,001 mm shall be employed. The use of optical micrometers or other non-contacting length probes is also recommended. Dimensions in millimetres a) Test apparatus b) Tool setup Key 1 l
37、oad cell 2 blank holding force 3 die top plate 4 die 5 blank holder 6 punch (R100) 7 die bottom plate 8 draw beads Figure 2 Example of stretch-bending test apparatus for springback evaluation Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=Boe
38、ing Co/5910770001 Not for Resale, 07/25/2008 02:47:53 MDTNo reproduction or networking permitted without license from IHS -,-,- ISO 24213:2008(E) ISO 2008 All rights reserved 5 7 Test piece The test piece used for the test shall be as follows. a) The test piece shall be rectangular in shape, (500 10
39、) mm in length and (50 1) mm in width. b) Its thickness shall be the original thickness of the sheet. c) The test piece shall be cut parallel and perpendicular to the rolling direction. d) The edges of the test piece shall be as cut. Unnecessary alteration or heating of the test piece shall be avoid
40、ed, unless otherwise specified or caused by cutting. e) The surface of the test piece shall be free from harmful defects, such as scratches, that may affect the test results. 8 Procedure Testing shall be conducted as follows. a) Testing temperature. The ambient temperature shall be within the range
41、of 10 C to 35 C, and the temperature shall be recorded, if necessary. When the temperature control is especially necessary, it shall be kept in the range of (23 5) C. b) Stretch bending. A test piece shall be fixed in position on the blank holder (see Figure 2); the blank holding pressure shall then
42、 be applied. The maximum blank holding pressure should be 2 % to 3 % of the tensile strength of the test material. The punch is pushed up until the amount of punch penetration h reaches a predetermined value. The amount of punch penetration, which should be determined so that the spread angle 2 of t
43、he test piece around the punch tip becomes greater than 120 (see Figure B.1), and lubricant shall be agreed between the parties involved. The amount of friction between the test piece and the punch surface should be as small as possible; preferably the coefficient of friction should be less than 0,0
44、5, so that the nominal tensile stress applied to the test piece should be distributed uniformly over the punch head. A thin sheet of polymer film and machine oil is recommended for the lubricant on the punch surface. The polymer film shall be replaced with a new one before each test. The amount of p
45、unch penetration shall be measured with a displacement gauge, and the punch force Fp with a load cell. The minimum levels of resolution on the displacement gauge for punch penetration and on the load cell for the punch force should be less than 0,5 mm and 100 N, respectively. c) Calculation of tensi
46、on. The calculation shall be as shown in Annex B. d) Determination of radius of curvature and calculation of springback. The radius of curvature r of the inner surface of the test piece, after removal of the force, shall be determined at the centre of the stretch- bent specimen in its longitudinal d
47、irection, using a dial gauge as described in Annex C. The radius of curvature r of the inner surface of the test piece under force shall be the radius of the punch tip. The amount of springback is calculated using the equation in 3.2. The width of the base of a dial gauge w, for determining the curv
48、ature of the test piece, after removal of the force, is recommended to be 20 mm, see Annex C. This is based on the observation, in preliminary experiments, that the curvature of the specimen after springback was almost uniform in the central 20 mm section of the specimen. e) Rounding. Measured data shall be rounded