Evaluation of vibration induced local fatigue in aluminum alloy structure by using laser ultrasonic technique

Vibration induced fatigue is one of the main forms of structural failure. Especially, the failure mode of aircraft and mechanical structures, which are in complex vibration environment for a long time, usually belongs to vibration fatigue. However, due to the limitations of existing measurement technology, the generation and development process of vibration fatigue damage is still uncertain. A guided wave based method is proposed that a laser ultrasonic system is set up to scan the 2024-O aluminum alloy intermittently in the vibration fatigue process. The propagation characteristics of wave in the specimen are collected, so that the fatigue degree of local area can be characterized based on the change of wave velocity. This experimental method can track the development of fatigue damage, record the process of fatigue accumulation, and further realize the stiffness calculation of the most serious fatigue area.