Development of a biaxial tensile machine for characterization of sheet metals

A new stand-alone biaxial testing machine with out-of-plane loading system has been developed to study the anisotropic plastic behavior of metal sheets on cruciform specimens. In this apparatus a single screw driven actuator is used and the variation of the load ratio along the two main directions is achieved by adjusting the geometry of a link mechanism. This design firstly combines the advantages of biaxial displacement devices, typically mounted in a universal tensile tester, with stand-alone machines and by at the same time providing a solution to the limitations associated with each of these types. The used specimen is discussed and compared through numerical simulations to a prominent geometry proposed in the literature. Experiments are presented and the results are implemented in identifying classical and advanced yield criteria and though represented as yield surfaces.