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-dest ructive evaluations using acoustic microscope, several of them used in indu strial fields, were investigated. However, acoustic measurement of curved s urface structure was restricted to basic studies as conventional acoustic m icroscope system was designed for flat specimen. We have developed a modifi ed acoustic microscope for curved surface specimen testing and have measure d acoustic image of round bar specimen. In this study, using this system, v elocities of round bar specimen during fatigue test are monitored using the V(z) curve method. Measurement errors depending on curved surface measurem ent were investigated and it was found that the acoustic velocity tends to increase as fatigue damage increases. (C) 1999 Elsevier Science Ltd. All ri ghts reserved.