Tensile ductility of AA5182: Effect of impact loading

Abstract

The tensile ductility of an AA5182-O rolled sheet under impact loading (strain rate of ∼ 170 s⁻¹) was found to be larger than under quasi-static loading (strain rate of 0·001 s⁻¹). In particular, the local equivalent plastic strain at fracture was 0·862 in the first case and 0·811 in the second case, and the plastic elongation at fracture was 0·338 and 0·244 respectively. This result was attributed to the local strain triaxiality at the fracture region. In fact, the high strain rate during impact loading alleviates the local strain triaxiality, reducing the void growth rate and, in turn, the critical equivalent strain for ductile fracture. However, void nucleation rate was found to be higher in the case of impact loading, since the increased local strain hardening favours the attainment of the critical stress necessary to void nucleation, that occurs by particle decohesion and by particle brittle fracture.