Effect of Shot-peening Residual Stress on Fatigue Life and Relaxation of TC4
TC4 titanium alloy is an important material used in the aerospace industry for the development of engine blades,turbine disks,and other aerospace components.However,under actual operating conditions,blades are subjected to high centrifugal,aerodynamic,and other vibratory loads during operation and are highly susceptible to fatigue failure or even fracture.Shot peening(SP)can introduce a residual compressive-stress field on the surface of the workpiece to counteract external loads,thereby significantly improving the fatigue resistance of the component.To date,the effects of SP residual stresses on the fatigue life of TC4 titanium alloys and the relaxation behavior of residual stresses have been sparsely investigated.In this study,the effect of residual stress on the fatigue life of TC4 titanium alloy and the relaxation change in shot-peening residual stress were studied.To study the effect of SP residual stress on fatigue life and the relaxation law of residual stress change,a finite-element model of a TC4 titanium alloy specimen was established using ABAQUS,and a fatigue life simulation was performed.The results of the static analysis were imported into FE-SAFE for fatigue life prediction.The fatigue life change rule and its influence under different shot-peening residual stress fields were studied.Shot-peening experiments were conducted at different shot-peening intensities.The residual stresses of the specimens were determined using an X-ray residual stress diffractometer.In addition,the number of cycles of the fatigue specimens under different surface residual compressive stresses was obtained,and the results of the simulation model were verified.On this basis,the influence law of the residual stress relaxation was experimentally investigated with the load level and number of cycles as factors.The residual stresses of the specimens after cyclic loading with a stress ratio of 0.1 and a frequency of 10 Hz were measured.The changes in the effects of different cycles and load intensities on the relaxation of residual stresses in SP were compared.The results showed that the fatigue life of TC4 specimens with load intensities between 600 and 700 MPa was close to the critical value.The magnitude of the residual compressive stress at different shot-peening intensities had a large influence on the fatigue life of the TC4 titanium alloy within a certain range.Moreover,the fatigue life of the specimen with a surface residual compressive stress of-750 MPa at a load intensity of 600 MPa was substantially better than that of the specimen at other stress levels.Under the experimental conditions used in this study,the amount of residual stress relaxation of SP showed an increasing trend and then gradually stabilized with an increase in the number of cycles.When the number of cycles was increased to 104,the residual stress relaxation was particularly evident,and the average stress relaxation was approximately 23.64％.In the range of 105-107 cycles,the residual stress relaxation tended to stabilize,and the average stress relaxation was approximately 19.68％.With an increase in the load intensity,the residual stress relaxation was evident,and with an increase in the cycle time,the effect of the load intensity gradually decreased.However,the surface residual compressive stress remained high.This provides a reference for improving the performance of TC4 titanium alloy in production and predicting the fatigue life in a reasonable and efficient manner.
万方数据
维普
