National foreword

This British Standard is the UK implementation of ISO 23296:2025. It supersedes BS ISO 23296:2022, which is withdrawn.

The UK participation in its preparation was entrusted to Technical Committee ISE/101/6, Fatigue testing of metals and metal matrix composites.

A list of organizations represented on this committee can be obtained on request to its committee manager.

Contractual and legal considerations

This publication has been prepared in good faith, however no representation, warranty, assurance or undertaking (express or implied) is or will be made, and no responsibility or liability is or will be accepted by BSI in relation to the adequacy, accuracy, completeness or reasonableness of this publication. All and any such responsibility and liability is expressly disclaimed to the full extent permitted by the law.

This publication is provided as is, and is to be used at the recipient’s own risk.

The recipient is advised to consider seeking professional guidance with respect to its use of this publication.

This publication is not intended to constitute a contract. Users are responsible for its correct application.

Compliance with a British Standard cannot confer immunity from legal obligations.

This British Standard was published under the authority of the Standards Policy and Strategy Committee on 30 November 2025.

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 document 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).

ISO draws attention to the possibility that the implementation of this document may involve the use of (a) patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a) patent(s) which may be required to implement this document. However, implementers are cautioned that this may not represent the latest information, which may be obtained from the patent database available at www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.

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 4, Fatigue, fracture and toughness testing.

This second edition cancels and replaces the first edition (ISO 23296:2022), which has been technically revised.

The main changes are as follows:

terms and definitions expanded;
keys to drawings and text clarification improved.

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.

Introduction

Thermo-mechanical fatigue (TMF) test method was developed in the early 1970’s to simulate, in the laboratory, loading behaviour of materials under conditions experienced in their service environment, such as turbine blades and vanes. The TMF test belongs to one of the most complex mechanical testing methods that can be performed in the laboratory. TMF is cyclic damage induced under varying thermal and mechanical loadings. When a specimen is subjected to temperature and mechanical strain phasing it is called strain controlled TMF. ASTM E2368 and ISO 12111 concern strain controlled TMF. However, these do not allow for specimens where no compensation for free thermal expansion and contraction is required. Therefore, this document addresses the need for a separate procedure for force controlled TMF testing.

This document covers the determination of TMF properties of materials under uniaxial loaded force-controlled conditions. A thermo-mechanical fatigue cycle is defined as specimen tests where both temperature and force amplitude waveform are simultaneously varied and independently controlled over the specimen gauge or test section. A series of such tests allows the relationship between the applied force and the number of cycles to failure to be established.

The specific aim of this document is to provide recommendations and guidance for harmonized procedures for preparing and performing force controlled TMF tests using various specimen geometries. The purpose of this document is to ensure the compatibility and reproducibility of test results. It does not cover the evaluation or interpretation of results. Health safety issues, associated with the use of this document, are solely the responsibility of the user.

The following clauses of this document are intended to provide the steps to be implemented in sequence, during the process of carrying out force controlled TMF tests.

1 Scope

This document applies to force-controlled thermo-mechanical fatigue (TMF) testing. Both forms of control, force or stress, can be applied according to this document. This document describes the equipment, specimen preparation, and presentation of the test results to determine TMF properties.

2 Normative references

3 Terms and definitions

4 Test methods

4.1 Apparatus

4.2 Specimens

5 Test preparatory issues

5.1 Temperature measurement

5.2 Verification of temperature uniformity - Thermal profiling

5.3 Force waveform optimisation

5.4 Temperature force optimisation

5.5 The application of an extensometer to measure maximum and minimum mechanical strain to observe the effects of ratcheting

6 Test execution

6.1 Test start

6.2 Test termination

7 Analysis and reporting

7.1 Validation of analysis software

7.2 Test report

Bibliography

BS ISO 23296:2025

Metallic materials — Fatigue testing — Force controlled thermo-mechanical fatigue testing method

Current

Published:

30 Nov 2025