High strain rate tensile testing.

摘要

Ductile fracture is a dominant tensile failure mechanism for ductile metals. This failure mechanism occurs through the nucleation, growth and coalescence of voids to form a crack whose propagation across the material leads to complete failure. The ductile fracture mechanism is strongly influenced by loading rate, triaxiality, strain hardening rate and particle population.; The research for this graduate program comprised the design and commissioning of a Tensile Split Hopkinson Bar facility. The facility was used to investigate high strain rate ductile fracture of brass, which was selected as a model material for the study. Scanning electron and optical microscopy and numerical modelling were incorporated as part of the research.; Two effects of the elevated loading rate on the ductile fracture behaviour of brass were found. At high strain rates, inertial stabilization of void growth occurs which delays the onset of failure by coalescence and increases the ductility. The triaxiality is increased at high strain rates and accelerates the accumulation of damage in the material which decreases ductility. These two effects are competitive; however, inertial stabilization of void growth dominates and therefore the ductility of brass is increased at elevated loading rates.