Engineering Analysis of the Inelastic Stress Response of a Structural Metal Under Variable Cyclic Strains

Inelastic stress response under strain cycling conditions is analyzed in terms of the three important governing phenomena, namely, memory of prior history, cyclic hardening or softening, and cyclic mean stress relaxation.Independent formulations to describe these respective features consist of a set of hysteresis rules, a set of transient stress-strain relations, and an empirical exponential model. A new approach to accurately describe the hysteresis loop shape characteristics is also presented. While strain amplitude and number of cycles are used as the primary variables influencing cyclic hardening, softening, and relaxation, the effect of other variables on these features and hence their mutual interactions are observed to be small. Therefore, as a first approximation it is postulated that independent formulations based on constant amplitude test data are applicable to spectrum loading situations. Computer based models resulting from this analysis are suitable for predicting the cyclic stress-strain and fatigue response of ductile structural metals and also provide a basis for developing general flexural response models.