Investigation of dynamic fractures under varying stress states

Abstract

The dynamic fracture behaviours of metallic materials vary significantly under different stress states, and the study on them is of great significance in guiding the design of engineering structures and improving their fracture resistance. To investigate the effect of the stress state on dynamic fractures, five newly designed specimens were proposed to produce different loading states, and the investigation was conducted using the traditional Split Hopkinson Pressure Bar (SHPB) device. In this study, the macroscopic fracture behaviour and microscopic void morphology were analysed under different loading rates and stress states. Subsequently, dynamic fractures under different stress states were investigated via numerical simulations using different damage models. Finally, the effects of specimen factors on the reliability of studying dynamic fractures using the newly proposed method were analysed using both experimental and numerical methods. All the results confirmed that the proposed experimental method is effective and simple for studying dynamic fractures under shear-to tensile-dominated states. The stress states are stable and controllable by changing the specimen shape. Moreover, both the microscopic void coalescence orientation and macroscopic fracture features are determined by the competition between the tensile and shear stresses. The proposed experimental method provides a new and reliable method for testing dynamic fracture behaviour of typical metallic materials under shear- to tensile-dominated states using the traditional SHPB device.