Acoustic emission for polycrystalline graphite under compressive loading

Abstract

The continuous-type acoustic emission (AE) from nuclear-grade isotropic graphite under compressive loading was examined to make clear the deformation behavior of the graphite. The type of AE for the graphite increased gradually with increasing strain in the initial stage of loading followed by the decreasing behavior for further loading to the failure point. A model was proposed to explain qualitatively the phenomenon, which was based on dislocation piled up at grain boundaries. To clarify the back stress effect at grain boundaries oxidized specimens were prepared. The type of AE for oxidized specimens increased monotonically up to the failure point. The model proposed was supported by the experimental results. Moreover, the qualitative relationships of total plastic strain rate and plastic strain rates by slip deformation and by microcracking as a function of total strain were given from the AE behavior.