ISO 24213:2017

Metallic materials - Sheet and strip - Method for springback evaluation in stretch bending

ISO 24213:2017 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 amount of springback under stretch bending is evaluated accurately and quantitatively.

Matériaux métalliques — Tôles et bandes — Méthode d'évaluation du retour élastique lors d'un cintrage sous traction

General Information

• Status: Published
• Publication Date: 06-Jun-2017
• ICS: 77.040.10 - Mechanical testing of metals
• Technical Committee: ISO/TC 164/SC 2 - Ductility testing
• Drafting Committee: ISO/TC 164/SC 2 - Ductility testing
• Current Stage: 9093 - International Standard confirmed
• Start Date: 05-Sep-2022
• Completion Date: 13-Dec-2025

Relations

• Consolidated By: ISO/FDIS 14982-2 - Agricultural and forestry machinery - Electromagnetic compatibility - Part 2: Additional EMC requirements for functional safety
• Effective Date: 06-Jun-2022
• Revises: ISO 24213:2008 - Metallic materials - Sheet and strip - Method for springback evaluation in stretch bending
• Effective Date: 10-Dec-2016

Overview

ISO 24213:2017 - "Metallic materials - Sheet and strip - Method for springback evaluation in stretch bending" defines a standardized laboratory method to quantitatively evaluate springback of metallic sheet and strip produced by plane‑strain stretch bending, a deformation mode typical in press‑formed panels. The standard enables consistent measurement of elastic recovery (springback) by comparing curvature under load and after removal of load, supporting material specification, die design, process control and finite‑element model calibration.

Key topics and requirements

• Test principle: Measure curvature of a stretch‑bent specimen under load (punch contact) and after release; compute the amount of springback as the relative change in curvature.
• Test specimen: Rectangular specimen (500 ± 10 mm long × 50 ± 1 mm wide); thickness equals original sheet thickness; cut orientation (parallel or perpendicular to rolling direction) agreed by parties.
• Test apparatus: Stretch‑bending device with a semi‑cylindrical punch (radius (100 ± 1) mm typical). Figure and tool setup defined in the standard.
• Loading and measurement:
  • Apply calculated blank holding pressure (Annex A); maximum recommended blank holding pressure ≈ 2–3 % of material tensile strength.
  • Control nominal tensile stress from measured punch penetration and force (Annex B).
  • Measure radius of curvature after unloading using a dial gauge or optical probes; dial gauge accuracy 0.001 mm recommended and base width typically 20 mm (Annex C).
  • Environmental/control conditions: ambient 10 °C to 35 °C (preferably 23 ± 5 °C).
• Friction and lubrication: Minimize friction (recommended μ < 0.05); polymer film + machine oil suggested; replace film before each test.
• Reporting: Test conditions (punch radius, penetration, lubricant, blank holding pressure, orientation), results (nominal tensile stress, springback η), material details and measurement uncertainty.

Applications and who uses it

• Materials engineers specifying sheet alloys with known springback behavior.
• Stamping and forming engineers for process control and troubleshooting of press‑formed panels.
• Tool and die designers to design compensation for expected elastic recovery.
• CAE/FEM analysts to calibrate and validate springback predictions in numerical models.
• Quality laboratories performing repeatable, comparative springback tests for supplier control and material acceptance.

Related standards

• ISO 80000‑1 (quantities and units) is normatively referenced for measurement rounding and units.
• Published by ISO/TC 164 (Mechanical testing of metals), second edition replaces ISO 24213:2008.

Keywords: ISO 24213:2017, springback evaluation, stretch bending, metallic sheet, plane‑strain, punch radius, blank holding pressure, nominal tensile stress, radius of curvature, press‑formed panels.

Standards Content (Sample)

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 2017
© ISO 2017, Published in Switzerland
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form
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the requester.
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ii © ISO 2017 – All rights reserved

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
Foreword
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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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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.
iv © ISO 2017 – All rights reserved

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.
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
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′
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
2 © ISO 2017 – All rights reserved

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