VBO: A state variable constitutive equation for a solder alloy

Data showing the influence of strain rate at five different high homologous temperatures for a 60Sn-40Pb solder alloy are used to determine the material constants in a minimal version of the viscoplasticity theory based on overstress (VBO) accounting for static recovery effects. VBO is a unified state variable theory that does not use a yield surface and has three state variables with appropriate growth laws. It is shown that the effects of strain rate can be modeled well by this theory which has fewer material constants than comparable theories. Tensile behavior at strain rates not used in the identification of material constants is predicted. This VBO for a solder alloy will be used for inelastic analyses of solder joints.