Controlled normal/shear loading and shear fracture in bulk metallic glasses

Limited plasticity inhibits the engineering applications of bulk metallic glasses (BMGs), which often deform by the formation of localized shear bands. Overcoming the brittleness of BMGs necessitates advances in our understanding of the mechanisms of shear band initiation and propagation. Up to now, a major hurdle has been the ability to control the generation of shear bands and the associated fracture (e.g., by conventional uniaxial loading). Here we demonstrate a unique loading fixture that allows one not only to control the locations of shear band formation and shear fracture but also to alter the ratio of the normal to shear stress on the fracture plane. The capability of altering the stress ratio allows one to systematically examine how the normal stress affects shear fracture of BMGs. While some preliminary results with limited data have been presented in a prior publication, a comprehensive description of the unique test fixture is described here.