Modelling ductile damage of a Ni-base alloy considering the microstructure evolution during hot working By Guntram Rüf, Christof Sommitsch and Bruno Buchmayr
Macro- and microscopically based continuum damage failure criteria as well as the model of effective stresses (MES) are vali-dated for a nickel-base alloy by means of an experimental database from hot compression tests. Most models show maximum damage for cylindrical specimens at the experimentally determined fracture site but do not predict the correct fracture site for collar test specimens with adequate precision. For all models excepting the MES, a lack of transferability of critical values to different testing conditions can be determined.
Additionally, a semi-empirical grain structure model is coupled to the damage evolution in order to describe the influence of materials’ softening by dynamic recrystallization on lifetime consumption. With the onset of recrystallization the accumulated deformation, i. e. the effective plastic strain is reduced by recrystallization and hence the damage evolution rate is decreased. EBSD analyses of hot deformed samples are performed to validate the model and to investigate the interaction of crack initia-tion as well as of crack progress with dynamic recrystallization.
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