INFRARED TEMPERATURE MEASUREMENT AND X-RAY TOMOGRAPHY FOR INTERNAL FATIGUE CRACK MONITORING DURING ULTRASONIC FATIGUE TESTS [Keynote]

The observation of fatigue cracks in the gigacycle fatigue regime is very difficult because they are very often initiating and propagating in the core of the specimens. This paper presents a methodology for detecting and monitoring internal fatigue cracks during ultrasonic fatigue tests. Using both the heat source located in the reverse cyclic plastic zone at the crack tip and the 3D geometry of the crack (from X-Ray tomography), finite element analysis is done to solve the heat transfert problem. This allow us to related the internal crack growth rate and the temperature field evolution versus time at the surface of the specimen. This proposed method has been successfully applied on specimens in cast aluminum alloy.
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