Computer based simulation of cyclic stress strain behavior

To extend the present methods for predicting cyclic stress strain behavior, a mathematical model is developed. This model uses the expression for the stable cyclic stress strain curve to describe hysteresis loop shape and employs a familiar rheological model to achieve the memory necessary to account for load history dependence. However, the model is altered so as to relax mean stress and to simulate the effect of cyclic hardening and softening. This method of analysis is used to predict the behavior of 2024-T4 aluminum. Comparisons are made between the simulation results and material test data. These comparisons are designed to show the accuracy with which the model can reproduce loop shape and follow complicated as well as simple load spectra. The model lends itself to fatigue problems such as prediction of failure by cumulative damage. To demonstrate its applicability to fatigue, a recently developed failure theory is utilized and its predictions compared to actual test results. Comparisons are made for both smooth specimens and notched plates.Aeronautical Structures Laboratory, Naval Air Engineering Center, Contract No. NOO-156-67-C-1875; Defense Research Board of Canada, Grant No. 9536-4