Fatigue damage monitoring of round shape specimen by acoustic microscopy

Acoustic microscope can detect microstructural features with high resolving power compared to other lower frequency acoustic techniques. Many non-destructive evaluations using acoustic microscope, several of them used in industrial fields, were investigated. However, acoustic measurement of curved surface structure was restricted to basic studies as conventional acoustic microscope system was designed for flat specimen. We have developed a modified acoustic microscope for curved surface specimen testing and have measured acoustic image of round bar specimen. In this study, using this system, velocities of round bar specimen during fatigue test are monitored using the V(z) curve method. Measurement errors depending on curved surface measurement were investigated and it was found that the acoustic velocity tends to increase as fatigue damage increases.