ISO 23296:2025

International
Standard
ISO 23296
Second edition
Metallic materials — Fatigue
2025-11
testing — Force controlled thermo-
mechanical fatigue testing method
Matériaux métalliques — Essai de fatigue — Méthode d'essai de
fatigue thermomécanique à force contrôlée
Reference number
© ISO 2025
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ii
Contents Page
Foreword .v
Introduction .vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Test methods . 4
4.1 Apparatus .4
4.1.1 Testing machine .4
4.1.2 Testing machine calibration .4
4.1.3 Cycle counting .4
4.1.4 Waveform generation and control .4
4.1.5 Force measuring system .6
4.1.6 Test fixtures .6
4.1.7 Alignment verification .7
4.1.8 Heating device .7
4.1.9 Cooling device .7
4.2 Specimens .7
4.2.1 Geometry .7
4.2.2 Specimen preparation .9
4.2.3 Specimen measurement .9
4.2.4 Circular or rectangular sections .9
4.2.5 Sampling, storage and handling .10
4.2.6 Specimen insertion .10
4.2.7 Thermocouple attachment .10
4.2.8 Spot welding of thermocouples .10
4.2.9 Heating the specimen . .11
4.2.10 Cooling the specimen .11
5 Test preparatory issues .11
5.1 Temperature measurement .11
5.1.1 General .11
5.1.2 Temperature control .11
5.2 Verification of temperature uniformity - Thermal profiling. 12
5.2.1 General . 12
5.2.2 Maximum permissible temperature variation along the specimen . 12
5.2.3 Data recorders . 13
5.2.4 Furnace positioning . 13
5.3 Force waveform optimisation . 13
5.4 Temperature force optimisation.14
5.5 The application of an extensometer to measure maximum and minimum mechanical
strain to observe the effects of ratcheting .14
6 Test execution .15
6.1 Test start . 15
6.1.1 General . 15
6.1.2 Data recording . 15
6.1.3 During the test. 15
6.1.4 Test monitoring . 15
6.2 Test termination .16
6.2.1 Accuracy of control parameters .16
6.2.2 Test validity .16
7 Analysis and reporting . 17
7.1 Validation of analysis software .17
7.2 Test report .17

iii
7.2.1 General .17
7.2.2 Essential information .17
7.2.3 Additional information .17
7.2.4 Examination of fracture surface .18
Annex A (informative) Guidelines on specimen handling and degreasing . 19
Annex B (informative) Thermocouple arrangement for a specimen containing a notch feature .20
Annex C (informative) Thermal imaging for thermal profiling .25
Annex D (informative) Measurement of strain during force controlled TMF testing .26
Annex E (informative) Measurement uncertainty.27
Bibliography .29

iv
Foreword
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