Development and Future Aspects in AE Source Characterization

The acoustic emission (AE) source characterization has been developed to understand the dynamic process of microfracture in metals, ceramics and composites. The development of AE source characterization can be summarized firstly. This paper is concerned with the theoretical background of AE source characterization. An infinitesimal deformation in a material can be represented as a moment tensor by the ‘eigenstrain method’ of micromechanics. In this treatment a microcracking can be modeled as a dislocation source with moment tensor components. AE signals can be represented as the convolution integral of the source function due to microcracking, the dynamic Green's function of the media and the transfer function of the measuring system. Secondly, our method of AE source characterization is described. We developed the advanced analysis system to evaluate AE signals quantitatively. Source location of each AE is determined from the signals recorded using six transducers. Each dynamic Green's function of the compact tension specimen concerning each source location is calculated by a finite difference method. The transfer function of the measuring system is calibrated by the breaking pencil lead method. Moment tensor components are determined by the developed deconvolution algorithm. Then the size, fracture mode, orientation and nucleation time of microcracks are obtained from the moment tensor. This analysis system was applied to the fracture toughness tests in various materials. Finally, the future aspects in AE source characterization will be discussed.