Ductile Materials Stress Upturn at High Strain Rates

Abstract

Ductile materials (mainly metals) exhibit a sharp stress upturn, which is not specific to a certain type of material, at strain rates around 10³ to 10⁴/s. It is important to consider such stress high-rate upturn when dealing with shock loading and unloading. Using classical strength models, usually calibrated at not so high rates, may lead to errors when considering high-rate loading under not so high pressures. Here we model high-rate upturn on the macroscale. We assume that the upturn mechanism is also the mechanism responsible for the 4^th power law mechanism, put forward by Swegle and Grady. In the past we calibrated our overstress dynamic viscoplasticity model for aluminium from 4^th power law data. Here we use this calibration to predict the high-rate stress upturn response.