Acoustic Emission (AE) is a non-destructive testing (NDT) with potential applications for locating and monitoring fatigue cracks during structural health management. In this paper, the AE signal properties for identifying the presence of a small initial crack is assessed to provide the presence of the onset of a potential growing crack. The approach is based on establishing any association between particular features of AE and fatigue crack initiation. Experimental investigation from uniform cyclic loading tests performed on compact tension samples of 7075 aluminium alloys indicated that onset of crack can be identified through a multivariate statistical analysis of AE data. Optical microscopy is used as a measurement tool to size the actual small crack. Result from this testing showed that certain properties of the AE events noticeably change after crack initiation. It was concluded that AE technology can successfully detects crack initiation. The proposed method has significant potential to be used for in-situ monitoring and evaluation of health of structures.
