(The) influence of environments on acoustic emission during plastic deformation of zinc crystals

Abstract

Acoustic emission (AE) release in zinc polycrystals has been studied in air, glycerin, and silicon oil environments on the same testing condition with large(L) and small(S) specimens. Total AE energy release increased rapidly up to the critical strain (0.16 and 0.15 for L and S specimens respectively), then further increase was minimal. Generally this variation shows the same behavior as yielding and work-hardening curve. However, the behavior of total AE energy with strain showed quite irrelevant to the stress-strain curve. The analysis of the accumulated peak amplitude distribution and the accumulated event energy spectra showed that the rapid increase up to the critical strain was caused by release of high amplitude AE signals, whereas the low amplitude emissions was dominant beyond this critical strain. The influence of environments on the AE energy release, firstly studied in the present work, showed that the magnitude of energy release was observed in the sequence of air, glycerin, and silicon oil environments. The greater emission energy observed during plastic deformation of zinc polycrystals in glycerin environment than in silicon oil environment, in spite of its greater density and viscosity in glycerin environment, is explained in terms of the ratio of the density to the coefficient of viscosity and the rate of diffusing.