Recent findings about combined size and rate effects on material properties

Abstract

The need for modeling and simulating multiscale structural responses to extreme loading conditions has brought about the challenging tasks of bridging different spatial and temporal scales within a unified framework. Based on the available experimental and computational capabilities, a simple approach has been proposed to formulate a hyper-surface in both spatial and temporal domains to predict combined specimen size and loading rate effects on the material properties. A systematic investigation has been performed over the last several years to understand the combined size, rate and thermal effects on the properties and deformation patterns of representative materials with different nanostructures and under various types of loading conditions. In this presentation, recent findings are presented about combined size and rate effects on the material properties of single crystal copper nanobeams under impact loading, with a focus on the link between the inverse Hall-Petch phenomenon and classical Hall-Petch phenomenon. It appears from the preliminary results that the inverse Hall-Petch behavior in single crystal materials is mainly due to the formation and evolution of disordered atoms as compared with the physics behind the inverse Hall-Petch behavior in nanocrystalline materials.