Fatigue crack initiation detection by an infrared thermography method
Article first published online: 25 NOV 2009
© 2009 Blackwell Publishing Ltd.
Fatigue & Fracture of Engineering Materials & Structures
Volume 33, Issue 1, pages 12–21, January 2010
How to Cite
WAGNER, D., RANC, N., BATHIAS, C. and PARIS, P.C. (2010), Fatigue crack initiation detection by an infrared thermography method. Fatigue & Fracture of Engineering Materials & Structures, 33: 12–21. doi: 10.1111/j.1460-2695.2009.01410.x
- Issue published online: 9 DEC 2009
- Article first published online: 25 NOV 2009
- Received in final form 22 October 2009
- infrared pyrometry;
- number of cycles at crack initiation;
- temperature recording;
- very high cycle fatigue
In this paper, the study of the temperature variation during fatigue tests was carried out on different materials (steels and aluminium alloys). Tests were performed at ambient temperature using a piezoelectric fatigue system (20 kHz). The temperature field was measured on the surface of the specimen, by means of an infrared camera.
Just at the beginning of the test, it was observed that the temperature increased, followed by a stabilization which corresponds to the balance between dissipated energy associated with microplasticity and the energy lost by convection and radiation at the specimen surface and by conduction inside the specimen. At the crack initiation, the surface temperature suddenly increases (whatever the localization of the initiation), which allows the determination of the number of cycles at the crack initiation and the number of cycles devoted to the fatigue crack propagation. In the gigacycle fatigue domain, more than 92% of the total life is devoted to the initiation of the crack.
So, the study of the thermal dissipation during the test appears a promising method to improve the understanding of the damage and failure mechanism in fatigue and to determine the number of cycles at initiation.