Thermally Induced Acoustic Emission in Homogeneous Metals and Composites

摘要

Both nonuniform heating in a homogeneous material and uniform heating in an inhomogeneous material produce local stresses. Inhomogeneous materials include polycrystals with anisotropic grains, two or more phase materials and composites. The thermally generated stresses can potentially induce acoustic emission via microscopic deformation and dynamic stress relieving mechanisms. It is anticipated that the ability to follow the history and characteristics of acoustic emission would be useful as a research tool for the study of microscopic deformation mechanisms, and could serve as a basis for establishing accept/reject criteria during thermal proof-testing of these inhomogeneous materials and composites. The current work reports some results on acoustic emission detected by a simple system equipped with energy processing capabilities, during thermal cycling in anisotropic, polycrystalline alumina, silicon carbide whisker reinforced aluminum, and a continuous graphite fiber reinforced epoxy.