Saw NDE Techniques for Monitoring the Growth Behavior of Small Surface Fatigue Cracks

Recent experiments have demonstrated that surface acoustic waves (SAW), or Rayleigh waves, can be used to predict the size and normalized stress intensity factor of small surface fatigue cracks. In particular, SAW methods have been able to monitor the growth of small surface fatigue cracks during the early stages of crack propagation in 7075-T651 aluminum, quenched and tempered martensitic 4340 steel, and to predict the fracture stress of Pyrex glass containing small surface cracks. The SAW technique has considerable promise as a new research tool for the study of the early stages of fatigue, and it has important implications for the practical non-destructive evaluation of components made of ceramics and metals.