A Damage Coupling Framework of Unified Viscoplasticity for the Fatigue of Solder Alloys

A damage coupling framework is proposed with a unified viscoplastic constitutive model for the fatigue life prediction of solder alloys, including a consistent and systematic procedure for the determination of material parameters. The model also incorporates the effects of grain size and cyclic hardening/softening. The phenomenological framework of continuum damage mechanics (CDM) is modified to embed intensive researches on the ductile damage fracture by void nucleation, growth, and coalescence, based on a lower bound for the viscoplastic potential of voided materials. The damage coupling with elasticity and viscoplasticity is formulated by irreversible thermodynamic approach. The constitutive model is also extended to large deformation kinematics. The preliminary application of the model to creep damage is presented.