A damage coupling framework of unified viscoplasticity for the fatigue of solder alloys

A damage coupling framework is proposed with a rmified viscoplastic constit utive model for the fatigue life prediction of solder alloys including a co nsistent and systematic procedure for the determination of material paramet ers. The model also incorporates the effects of grain size and cyclic harde ning/softening. The phenomenological framework of continuum damage mechanic s (CDM) is modified to embed intensive researches on the ductile damage fra cture by void nucleation, growth, and coalescence, based on a lower bound f or 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 kin ematics. The preliminary application of the model to creep damage is presen ted.