The influence of cavitation damage upon high temperature creep under stationary and non-stationary loading conditions. Pt. 2

The object of this investigation is to examine the influence of different tensile loading procedures and that of high temperature cavitation upon plastic flow. In the preceding Part I the phenomenological damage model (A-model) was introduced. In the present paper the creep behaviour of materials (in the absence of work hardening) is examined for specimens which are subjected to tensile loading at constant load F and constant true stress s respectively. It is shown that, independent of the material, in accordance with experiments, the lifetimes tsub(f,F) and tsub(f,s) (in creep at dF/dt=0 and ds/dt=0 respectively) obey the relationship tsub(f,F)=0.63 tsub(f,s). For comparable conditions in the same time t the material is more damaged in creep at constant load than in creep at constant true stress. The volume change ΔV/V0 calculated for creep at dF/dt=0 is in good agreement with experiments. The A-model is compared to Kachanov's damage model (ω-model) and it is shown that although from both the models the same life fraction rule can be deduced, the HTC behaviour described by the ω-model is in disagreement with experiments. (orig.)