Investigation Of Fatigue Reliability Factor And P-S-N Curve Of Part With Hole By Laser Shock Processing

Due to the stress concentration characteristics in the structure,the fatigue under cyclic loading is the main reason for the failure of the small hole components.The fatigue reliability of the small hole components can be improved by Laser shock processing(LSP).LSP mainly through the change of residual stress field to improve life.Residual stress field has many influencing factors.It is very important to study the influence factors of the laser peeningt factors of the hole parts,and the establish of the P-S-N curve can be used to control the influencing factors.In this paper,through the combination of simulation and experiment to study the residual stress on the basis of the influence of various laser peening impact factors on the fatigue life,establish P-S-N curve which can describe the relationship between stress and life under different reliability.The main research contents and achievements are as follows.(1)Based on the elasto-plastic mechanics analysis of the mechanism of residual stress after laser shock,the mechanism of fatigue crack growth rate and fatigue life is studied on the basis of stress intensity factor theory and residual stress field.The results show that LSP can produce residual stress field which can reduce the crack stress intensity factor and crack propagation rate,and the residual compressive stress can decrease the cyclic stress amplitude to improve the crack propagation life.(2)The influence factors of the fatigue life and the influence regular pattern of LSP hole components are studied from the view of the residual stress field.The results show that the influence factors are mainly material,thickness and LSP.The material and thickness will affect fatigue life by t the effect of residual stress field formation.(3)The distribution of residual stress field under different thickness,material,peak pressure and three factors was analyzed by ABAQUS.The results show that the increase of thickness will increase the residual tensile stress and interval.The residual compressive stress of the hole corner of titanium alloy is larger than that of aluminum alloy.The maximum pressure stress on the hole wall is the most important material.The material affects the maximum wall stress.The influence of power density on the surface residual compressivestress is large.(4)The orthogonal test was carried out,and the P-S-N curve was established.The P-S-N curve was fitted by the life data,and the mathematical model of stress intensity and fatigue life was obtained.The life of the 4mm titanium alloy high power density hole was the highest,and the multi-point laser impact Spot size,lap rate,impact layer number,impact range,power density,energy and other parameters to determine the method.The results show that treated hole component fatigue reliability is high,when the use of thinner plate thick titanium alloy and treated by high laser power density.The P-S-N curve of the relationship between life and fatigue strength under different reliability was established by statistical analysis of fatigue life data.It is very important to improve the fatigue reliability of components and choose the optimal process plan.