In order to ascertain the effects of the combined cycle situation on the fatigue life

the high and low combined cycle fatigue tests

high cycle fatigue tests and low cycle fatigue tests on titanium alloy TC11 were performed.The results indicate that the combined cycle loading degrades the fatigue resistance of TC11 related to low cycle or high cycle fatigue loading.The CCF life is highly effected by the mean stress σ major and stress ratio R minor of the minor stress cycles.Fractograph and macrograph of fracture aspects under different kinds of loadings were investigated using scanning electron microscope(SEM).The fractograph of CCF fracture surfaces obviously differs from that of high cycle fatigue fracture surfaces.The slippage due to low cycle is the main reason of reducing the CCF life.