Cyclic Deformation Response of Polycrystalline OFHC Copper under Pure Compression Fatigue

Abstract

Systematic experimental investigation was carried out to examine the cyclic deformation response and study the crack nucleation mechanisms under pure compression fatigue condition using OFHC Cu. Results show that the cyclic stress strain response and micro-structural evolution of copper under pure compression fatigue exhibits rather dissimilar responses compared to those under general push-pull fatigue conditions. Both rapid hardening and the compressive cyclic creep were observed in all tested conditions. Like under all fatigue conditions, surface micro-structural changes were detected by optical, SEM, and specifically AFM. It was revealed that cyclic plastic strain accommodated by the sample was not in any major way through dislocation activities, as there was only moderate slip activities observed on the surface and no PSB features were detected from TEM observations. Instead, cyclic creep was observed to be the major form of plastic strain accommodation. In addition, the observed surface phenomenon was found to have led to the eventual crack nucleation when the applied stress amplitude was high.