ISO 24213:2017

INTERNATIONAL ISO
STANDARD 24213
Second edition
2017-07
Metallic materials — Sheet and strip
— Method for springback evaluation
in stretch bending
Matériaux métalliques — Tôles et bandes — Méthode d’évaluation du
retour élastique lors d’un cintrage sous traction
Reference number
ISO 24213:2017(E)
©
ISO 2017

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ISO 24213:2017(E)

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ISO 24213:2017(E)

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols 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 curvature using a dial gauge .10
Bibliography .11
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ISO 24213:2017(E)

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
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electrotechnical standardization.
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described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/ directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
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on the ISO list of patent declarations received (see www .iso .org/ patents).
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URL: w w w . i s o .org/ iso/ foreword .html.
This document 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 24213:2008), which has been technically
revised.
The main changes compared to the previous edition are:
— the Normative references has been updated;
— Clause 7 c) and Clause 9 a) have been revised to specify the test piece more clearly;
— In Figure 2 b), a label to the test piece has been added;
— Clause 8 d) has been revised because the use of dial gauge is one of the methods for determining the
radius of curvature;
— the Bibliography has been updated.
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ISO 24213:2017(E)

Introduction
This document has been established to evaluate the amount of springback occurring in metallic 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 parts are removed from the dies due to elastic recovery. This phenomenon is
referred to as springback.
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INTERNATIONAL STANDARD ISO 24213:2017(E)
Metallic materials — Sheet and strip — Method for
springback evaluation in stretch bending
1 Scope
This document specifies a method for evaluating the amount of springback of sheets of metallic
materials known to exhibit large amounts of springback subjected to plane-strain stretch bending,
which is a typical deformation mode generated in press-formed panels. By using this method, the
[1][2]
amount of springback under stretch bending is evaluated accurately and quantitatively .
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements 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 80000-1, Quantities and units — Part 1: General
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— IEC Electropedia: available at http:// www .electropedia .org/
— ISO Online browsing platform: available at http:// www .iso .org/ obp
3.1
curvature
κ
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
κ =
r
3.2
amount of springback
η
relative change in curvature of a test piece under force and after removal of the force shown in Figure 1
′
κκ−
′
rr−
η = =
κ r′
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ISO 24213:2017(E)

a)  Under force b)  After removal of the force
Figure 1 — Radius of curvature of a 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 piece in the direction of its thickness, divided by the surface area of the test
piece contacting the die
3.5
nominal tensile stress
tensile force per unit cross-sectional area of the test piece
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ISO 24213:2017(E)

4 Symbols and designations
The symbols used in this document and the corresponding designations are given
...