SIST EN ISO 7438:2021

SLOVENSKI STANDARD
01-marec-2021
Nadomešča:
SIST EN ISO 7438:2016
Kovinski materiali - Upogibni preskus (ISO 7438:2020)
Metallic materials - Bend test (ISO 7438:2020)
Metallische Werkstoffe - Biegeversuch (ISO 7438:2020)
Matériaux métalliques - Essai de pliage (ISO 7438:2020)
Ta slovenski standard je istoveten z: EN ISO 7438:2020
ICS:
77.040.10 Mehansko preskušanje kovin Mechanical testing of metals
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EN ISO 7438
EUROPEAN STANDARD
NORME EUROPÉENNE
October 2020
EUROPÄISCHE NORM
ICS 77.040.10 Supersedes EN ISO 7438:2016
English Version
Metallic materials - Bend test (ISO 7438:2020)
Matériaux métalliques - Essai de pliage (ISO Metallische Werkstoffe - Biegeversuch (ISO
7438:2020) 7438:2020)
This European Standard was approved by CEN on 8 August 2020.

CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this
European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references
concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN
member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by
translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management
Centre has the same status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and
United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2020 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 7438:2020 E
worldwide for CEN national Members.

Contents Page
European foreword . 3

European foreword
This document (EN ISO 7438:2020) has been prepared by Technical Committee ISO/TC 164
"Mechanical testing of metals" in collaboration with Technical Committee CEN/TC 459/SC 1 “Test
methods for steel (other than chemical analysis)” the secretariat of which is held by AFNOR.
This European Standard shall be given the status of a national standard, either by publication of an
identical text or by endorsement, at the latest by April 2021, and conflicting national standards shall be
withdrawn at the latest by April 2021.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN shall not be held responsible for identifying any or all such patent rights.
This document supersedes EN ISO 7438:2016.
According to the CEN-CENELEC Internal Regulations, the national standards organizations of the
following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria,
Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland,
Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Republic of
North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the
United Kingdom.
Endorsement notice
The text of ISO 7438:2020 has been approved by CEN as EN ISO 7438:2020 without any modification.

INTERNATIONAL ISO
STANDARD 7438
Fourth edition
2020-10
Metallic materials — Bend test
Matériaux métalliques — Essai de pliage
Reference number
ISO 7438:2020(E)
©
ISO 2020
ISO 7438:2020(E)
© ISO 2020
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting
on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address
below or ISO’s member body in the country of the requester.
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Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii © ISO 2020 – All rights reserved

ISO 7438:2020(E)
Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols, designations and units . 1
5 Principle . 2
6 Test equipment. 2
6.1 General . 2
6.2 Bending device with supports and a former . 4
6.3 Bending device with a V-block. 4
6.4 Bending device with a clamp . 4
7 Test piece . 4
7.1 General . 4
7.2 Edges of rectangular test pieces. 4
7.3 Width of the test piece . 5
7.4 Thickness of the test piece . 5
7.5 Test pieces from forgings, castings and semi-finished products . 5
7.6 Agreement for test pieces of greater thickness and width . 5
7.7 Length of the test piece . 5
8 Procedure. 6
9 Interpretation of results . 7
10 Test report . 7
Annex A (informative) Determination of the bend angle from the measurement of the
displacement of the former . 8
Annex B (normative) Bend test at plane strain conditions . 9
Bibliography .13
ISO 7438:2020(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
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.
The procedures used to develop this document and those intended for its further maintenance are
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
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www .iso .org/ patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to the
World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www .iso .org/
iso/ foreword .html.
This document was prepared by Technical Committee ISO/TC 164, Mechanical testing of metals,
Subcommittee SC 2, Ductility testing, in collaboration with the European Committee for Standardization
(CEN) Technical Committee CEN/TC 459, ECISS – European Committee for Iron and Steel Standardization,
in accordance with the Agreement on technical cooperation between ISO and CEN (Vienna Agreement).
This fourth edition cancels and replaces the third edition (ISO 7438:2016), which has been technically
revised.
The main change compared to the previous edition is the addition of new Annex B, describing bending
test at plane strain condition.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www .iso .org/ members .html.
iv © ISO 2020 – All rights reserved

INTERNATIONAL STANDARD ISO 7438:2020(E)
Metallic materials — Bend test
1 Scope
This document specifies a method for determining the ability of metallic materials to undergo plastic
deformation in bending.
This document applies to test pieces taken from metallic products, as specified in the relevant product
standard. It is not applicable to certain materials or products, for example tubes in full section or
welded joints, for which other standards exist.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
No terms and definitions are listed in this document.
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 https:// www .iso .org/ obp
4 Symbols, designations and units
Symbols and designations used in the bend test are shown in Figures 1 and 2 and specified in Table 1.
Table 1 — Symbols, designations and units
Symbol Designation Unit
a Thickness or diameter of test piece (or diameter of the inscribed circle mm
for pieces of polygonal cross-section)
b Width of the test piece mm
c Distance between the plane including the horizontal axis of supports mm
and the central axis of the rounded portion of the former before test
D Diameter of the former mm
f Displacement of the former mm
Lode angle parameter, i.e. strain path direction —
θ
L Length of the test piece mm
l Distance between supports mm
η Triaxiality factor —
p Distance between the vertical planes including the central axis of each mm
support and the vertical plane including the central axis of the former
R Radius of the supports mm
r Internal radius of bend portion of test piece after bending mm
α Angle of bend degrees
ISO 7438:2020(E)
5 Principle
The bend test consists of submitting a test piece of round, square, rectangular or polygonal cross-
section to plastic deformation by bending, without changing the direction of loading, until a specified
angle of bend is reached.
The axes of two legs of the test piece remain in a plane perpendicular to the axis of bending. In the case
of a 180° bend, the two lateral surfaces may, depending on the requirements of the product standard,
lie flat against each other or can be parallel at a specified distance, an insert being used to control this
distance.
6 Test equipment
6.1 General
The bend test shall be carried out in testing machines or presses equipped with the following devices:
a) bending device with two supports and a former as shown in Figure 1;
b) bending device with a V-block and a former as shown in Figure 2;
c) bending device with a clamp as shown in Figure 3.
Figure 1 — Bending device with two supports and a former
2 © ISO 2020 – All rights reserved

ISO 7438:2020(E)
Figure 2 — Bending device with a V-block and a former
Key
1 clamp
2 former
Figure 3 — Bending device wi
...