STUDY ON THE EFFECT OF COMPRESSION LOADING ON FATIGUE CRACK GROWTH OF ALUMINIUM UNDER TENSION-COMPRESSION CYCLE

The effect of compressive loading on fatigue crack growth was studied using an elastic-plastic finite element analysis and incremental plastic damage theory. The results show that the effect of compressive loading on fatigue crack growth results from the plastic damage of a crack tip. A double parameter model of predicting fatigue crack propagation rate under tension-compressive loading is established. The fatigue crack growth test of the high-strength aluminum alloy LY12-M at the stress ratio R=0, -0.5, -1 and -2 is performed. The results show that the fatigue crack growth rate at R<0 (R=-0.5, -1 and -2) is significantly higher than the one at R=0 for the same K_max. The compressive loading in the load cycle promotes the fatigue crack propagation of LY12-M aluminum alloy. The model has been proved to be in agreement with the experimental data.