New acoustic parameter characterizing loading history effects

A new parameter of acoustic emission (T-AE) is proposed, which determines the period of acoustic gap before the final fracture under tension of specimens of low- and medium-carbon steels after preliminary cyclic loading. The beginning of the acoustic gap period T-AE corresponds to the achievement of the maximum load. T(AE )increases with the number of cycles of pre-cycling loading, the fracture magnitude and material strength; as the amplitude of the preliminary cyclic loading increases, it decreases. Values of the b(AE) and the total number of acoustic signals Sigma N-AE are estimated and the changes of these characteristics at various tension stages are considered. It is shown that the beginning of the plateau in the time dependence of the total number of acoustic signals is accompanied by a sharp decrease in the b(AE)-value.