An experimental evaluation of Helmholtz potentials as a source of acoustic emission due to fatigue crack

Abstract

A novel method is proposed in this paper to extract acoustic emission (AE) source using Helmholtz potentials approach. In order to characterize the source in terms of potentials the underlying physics is to detect the AE signals and then develop an inverse algorithm to characterize the source. According to the new concept, the source can be characterized it provides the excitation potential information from the crack and that can be used to diagnose the crack (crack type and crack growth etc.). An AE experiment was designed to measure the acoustic emissions from the fatigue crack growth. A test specimen was made of 1 mm thick 304-steel material. A small hole (1 mm diameter) was drilled at the center of the specimen to initiate the fatigue crack. The specimen was subjected to the cyclic loadings by using the hydraulic MTS machine. AE waveforms are generated by convolutions of AE source functions, plate transfer functions. An inverse algorithm was developed to characterize the source of AE signal. AE signal analysis are done to determine AE source function using deconvolution process.