Constitutive modeling of viscoplastic damage in solder material

This paper presents a constitutive modeling of viscoplastic damage in 63Sn-37Pb solder material taking into account the effects of microstructural change in grain coarsening. Based on the theory of damage mechanics, a two-scalar damage model is developed by introducing the damage variables and the free energy equivalence principle. An inelastic potential function based on the concept of inelastic damage energy release rate is proposed and used to derive an inelastic damage evolution equation. The validation of the model is carried out for the viscoplastic material by predicting monotonic tensile behavior and tensile creep curves at different temperatures. The softening behavior of the material under monotonic tension loading can be characterized with the model. The results demonstrate adequately the validity of the proposed viscoplastic constitutive modeling for the solder material