Abstract: The relationship and the conversion model between creep and stress relaxation for age forming process are studied. Through analyzing the mechanism of creep and stress relaxation behaviors of metal materials and the relationship between them, two types of conversion models from creep data to stress relaxation behavior based on work hardening hypothesis and aging hypothesis are established respectively. Then according to the feature that creep and aging coexist synchronously in the process of creep/stress-relaxation age forming, a set of prediction model for aging stress-relaxation behavior is established based on aging creep equations. In order to verify the theoretical model, creep and stress-relaxation experiments at the aging temperature of 120 ℃ and different stress levels on aluminum alloy 7055T6 are carried out separately. Using the software of Origin and SPSS, material constants in the creep constitutive equations are achieved by regressive analysis. Then the established aging stress-relaxation prediction model based on creep equations is introduced to predict stress-relaxation behaviors. Comparisons between experiment results and prediction ones at different initial stress levels show that the established model can be used to predict stress-relaxation behaviors in the process of creep age forming.

Key words: Aging hypothesis, Prediction model, Stress-relaxation, Work hardening hypothesis