Time-independent formulation for creep damage modeling in metals based on void and crack evolution

An advanced creep modeling, based on dislocation mechanics and incorporating damage effects, is developed at continuum scale. In the proposed formulation, creep damage does not depend on time (time-independent damage formulation) but on the accumulated creep strain. Thus, the tertiary creep stage can be predicted as the evolution of the secondary stage in which the current stress is increased by damage effects, and possible other microstructural instability processes, in addition to geometry modifications. The proposed formulation extends the initial continuum damage mechanics approach proposed by Kachanov in order to have a more explicit correlation between material creep response, damage mechanics and material microstructure. The possibility to account for possible microstructure modifications that may occur as a result of solid-solution kinetics, by means of the identification of the evolution law of damage parameters is discussed. An example of the applicability of the proposed model to IMI834 titanium alloy is given.