Dynamic Fracture of Ductile Metals at High Strain Rate

Abstract

Dynamic fracture of ductile metals at different strain rates and temperatures is studied via molecular dynamic simulations. The results show that both increase of temperature and decrease of strain rate reduce the yield strength, but the stress-strain curves separate prior to yield point at different temperatures. Both increase of temperature and strain rate shorten the duration of the stage of dislocation nucleation and slip. The stress-strain curves for various materials indicate that void nucleation needs not only lower yield strength but also lower fault energy. After the yield point, initially some defect clusters form along the loading direction. With the increasing of strain, small dislocation loops nucleate from some larger defect clusters, then quickly multiply and move on slip plane. When the stress exceeds a critical value, some voids nucleate in dislocation aggregation regions. The incipient void shapes are clavate and void distributions predominantly are along the perpendicular directions of tensile loading. Nucleated voids gradually grow into spherical-like shapes via emitting dislocations.