Failure analysis in superplastic materials

Superplastic alloys and metals possess the ability to undergo large uniform strains prior to failure. Isothermal superplasticity of sheet metal is a phenomenon due to both peculiar process condition and material intrinsic characteristics. The material must have a grain size of less than 10 μm, the forming temperature of around half the absolute melting point and a very low strain rate (in the order of 10−5–10−3 s−1).The instability of superplastic flow under uniaxial stress state has been the subject of different studies. In this paper, under biaxial stress conditions, instability analysis of superplastic PbSn60 alloy using the finite element method is investigated. An original model has been implemented successfully in commercial finite element code in order to predict the imminent failure of material during superplastic forming processes.