ISO 8491:1998

Metallic materials - Tube (in full section) - Bend test

Matériaux métalliques — Tubes — Essai de cintrage sur tronçon

General Information

• Status: Published
• Publication Date: 21-Oct-1998
• 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: 9020 - International Standard under periodical review
• Start Date: 15-Oct-2025
• Completion Date: 15-Oct-2025

Relations

• Consolidated By: ISO 10352:2010 - Fibre-reinforced plastics - Moulding compounds and prepregs - Determination of mass per unit area
• Effective Date: 06-Jun-2022
• Revises: ISO 8491:1986 - Metallic materials - Tube (in full section) - Bend test
• Effective Date: 15-Apr-2008

Overview

ISO 8491:1998 is an international standard published by the International Organization for Standardization (ISO) that specifies a bend test method for metallic tubes in full section. Specifically aimed at metallic tubes with circular cross-sections and outside diameters up to 65 mm, this standard provides a clear procedure to assess the ductility and plastic deformation capacity of tubes when subjected to bending forces. The bend test is critical for verifying tube quality and structural integrity in manufacturing and industrial applications.

This second edition of ISO 8491 replaces the first edition published in 1986 and includes updated technical provisions. It is applicable primarily to testing tubes under defined bending conditions using a groove former, ensuring the tube section does not become oval during testing.

Key Topics

• Scope: Applies to full-section bend testing of metallic tubes, typically with outside diameters up to 65 mm.
• Test Principle: The tube is bent around a grooved former with a defined inside radius until a specific bend angle is achieved.
• Testing Equipment: Requires a tube-bending machine designed with a groove matching the tube’s outside diameter; prevents cross-sectional deformation.
• Test Piece Requirements: Straight tube segments of sufficient length to accommodate the bending process.
• Testing Conditions: Performed at ambient temperature (10°C to 35°C), with preferred control at around 23 ± 5°C.
• Weld Positioning: For welded tubes, the weld must be positioned at a 90° angle to the bending plane unless otherwise specified.
• Result Interpretation: No visible cracks under normal inspection signifies passing the test unless additional criteria are defined in relevant product standards.
• Test Reporting: Mandatory information includes reference to ISO 8491, test piece identification, dimensions, bend angle, radius, weld location, and test results.

Applications

ISO 8491:1998 bend test standard is widely utilized in industries where metallic tubes are critical structural or functional components. Key applications include:

• Manufacturing Quality Control: Ensures that tubes conform to mechanical performance requirements before shipment or assembly.
• Metallurgical Testing: Assesses ductility and toughness of various metal tubes used in construction, automotive, aerospace, and pipelines.
• Product Certification: Supports compliance with international quality standards by providing a recognized test methodology.
• Weld Integrity Assessment: Verifies the mechanical performance of welded tubes, inspecting the influence of weld positioning on bend resistance.
• Research and Development: Used in material science laboratories for testing new metallic tube alloys under deformation stress.

Related Standards

For comprehensive bend testing and metallic materials assessment, ISO 8491:1998 is often used alongside other relevant standards:

• ISO 7438: Metallic materials - Bend test of strips and other shapes - complementing tube bend testing by covering transverse strip bend tests.
• ISO/TC 164: Technical Committee on Mechanical Testing of Metals, responsible for standards related to metallic material testing.
• Other product-specific ISO standards specifying detailed tube dimensions, bending radii, and test parameters.

By adhering to ISO 8491:1998, manufacturers and quality control engineers can reliably evaluate the bending performance of metallic tubes, ensuring safety, durability, and compliance across a diverse range of industrial applications. This standard plays a vital role in industrial quality assurance and product lifecycle management for metallic tube products.

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 8491
Second edition
1998-11-01
Metallic materials — Tube (in full section) —
Bend test
Matériaux métalliques — Tubes — Essai de cintrage sur tronçon
A
Reference number
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.
Draft International Standards adopted by the technical 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.
International Standard ISO 8491 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 8491:1986), of which it constitutes a technical
revision.
Annex A of this International Standard is for information only.
©  ISO 1998
All rights reserved. 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 the publisher.
International Organization for Standardization
Case postale 56 • CH-1211 Genève 20 • Switzerland
Internet [e-mail]
Printed in Switzerland
ii
INTERNATIONAL STANDARD  © ISO ISO 8491:1998(E)
Metallic materials — Tube (in full section) — Bend test
1 Scope
This International Standard specifies a method for determining the ability of full-section metallic tubes of circular
cross-section to undergo plastic deformation in bending. It is intended for tubes with an outside diameter no greater
than 65 mm, although the range of the outside diameter for which this International Standard is applicable may be
more exactly specified in the relevant product standard.
NOTE — Bend tests of the test pieces taken from tubes in the form of transverse strips should be made in accordance with
ISO 7438 so as to increase the original curvature of the test piece.
2 Symbols, designations and units
Symbols, designations and units for the bend test of tubes in full section are given in table 1 and are shown in
figure 1.
Table 1
Symbol Designation Unit
a
Wall thickness of the tub
...

NORME ISO
INTERNATIONALE 8491
Deuxième édition
1998-11-01
Matériaux métalliques — Tubes — Essai
de cintrage sur tronçon
Metallic materials — Tube (in full section) — Bend test
A
Numéro de référence
Avant-propos
L'ISO (Organisation internationale de normalisation) est une fédération mondiale d'organismes nationaux de
normalisation (comités membres de l'ISO). L'élaboration des Normes internationales est en général confiée aux
comités techniques de l'ISO. Chaque comité membre intéressé par une étude a le droit de faire partie du comité
technique créé à cet effet. Les organisations internationales, gouvernementales et non gouvernementales, en
liaison avec l'ISO, participent également aux travaux. L'ISO collabore étroitement avec la Commission
électrotechnique internationale (CEI) en ce qui concerne la normalisation électrotechnique.
Les projets de Normes internationales adoptés par les comités techniques sont soumis aux comités membres pour
vote. Leur publication comme Normes internationales requiert l'approbation de 75 % au moins des comités
membres votants.
La Norme internationale ISO 8491 a été élaborée par le comité technique ISO/TC 164, Essais mécaniques des
métaux, sous-comité SC 2, Essais de ductilité.
Cette deuxième édition annule et remplace la première édition (ISO 8491:1986), dont elle constitue une révision
technique.
L’annexe A de la présente Norme internationale est donnée uniquement à titre d’information.
©  ISO 1998
Droits de reproduction réservés. Sauf prescription différente, aucune partie de cette publication ne peut être reproduite ni utilisée sous quelque
forme que ce soit et par aucun procédé, électronique ou mécanique, y compris la photocopie et les microfilms, sans l'accord écrit de l'éditeur.
Organisation internationale de normalisation
Case postale 56 • CH-1211 Genève 20 • Suisse
Internet [e-mail]
Imprimé en Suisse
ii
NORME INTERNATIONALE  © ISO ISO 8491:1998(F)
Matériaux métalliques — Tubes — Essai de cintrage
sur tronçon
1 Domaine d’application
La présente Norme internationale spécifie une méthode de détermination de l'aptitude à la déformation plastique
par cintrage sur tronçon de tubes métalliques, de section circulaire. Elle est applicable aux tubes de diamètre
extérieur au plus égal à 65 mm, bien que la gamme de diamètres extérieurs à laquelle s'applique la présente Norme
internationale puisse être définie de façon plus explicite dans la norme de produit concernée.
NOTE — Il convient que les essais de pliage d’éprouvettes prélevées sur des tubes sous forme de bandes transversales
soient réalisés conformément aux prescriptions de l’ISO 7438 par augmentation de la courbure initiale de la bande.
2 Symboles
Les symboles à utiliser pour l’essai de cintrage sont donnés dans le tableau 1 et représentés à la figure 1.
Tableau 1
Symbole Significati
...