Study On High Temperature Fretting Fatigue Life Of TC11 Alloy Under Laser Shock Peening

Fretting fatigue damage is very common in the joint structure,which greatly accelerates the fatigue failure and greatly reduces the safety of the entire system.Therefore,people try to use surface protection technology to enhance the ability to resist fretting damage.Laser shock peening,as a new type of surface strengthening technology,has developed rapidly in recent decades and has shown great potential in improving the fatigue life.However,at present,there are few studies on high-temperature fretting fatigue under the laser shock peening process.The ability of the laser shock peening process to resist fretting fatigue in high-temperature environment is still unclear.Therefore,the high-temperature fretting fatigue test of the structure before and after laser shock peening is carried out.The influence mechanism of laser shock strengthening on fretting fatigue is analyzed,and the high temperature fretting fatigue life is predicted.The above work can provide reference for laser shock strengthening in the field of high temperature fretting fatigue.It has certain theoretical significance and engineering reference.value.The main research contents of this paper are as follows:Selection of laser shock peening technological parameters and study on surface characteristics of TC11 material after laser shock peening.Based on the laser shock peening experimental principle and the fretting fatigue test results of the laser-shock-peening piece at normal temperature,the power density 4.8GW/cm~2 is selected to carry out the laser shock peening process on the titanium alloy piece.The effects of high temperature and fretting fatigue load on the hardness and residual stress of the surface layer of the material were analyzed.The experimental results show that the hardness of the material changes little at different temperatures after laser shock peening,but the stress relaxation phenomenon occurs at high temperature.The higher the temperature,the greater the relaxation rate,the relaxation rate will be further increased after the fatigue load is applied to the test piece.High temperature fretting fatigue test of TC11 titanium alloy specimens strengthened by laser shock peening.Based on high-temperature fretting fatigue device,the high-temperature fretting fatigue test was carried out before and after laser shock peening,and the fretting wear zone and fretting fatigue fracture were analyzed.The test results show that at room temperature,300�C and 500�C,the fretting fatigue life of the specimen after laser shock strengthening is increased by 5.5 times,3.5 times and 1.7 times,respectively,And as the temperature increases,the degree of wear in the fretting contact area becomes more serious..Observing the fatigue fracture,it is found that only at normal temperature,the crack source is located in the laser shock-strengthening strengthening layer.At 300�C and 500�C,cracks are initiated on the surface of the test piece.High temperature fretting fatigue life prediction.High temperature fretting fatigue life prediction.In the modeling process,the variation of the clamping stiffness of the device at different temperatures is considered,and the residual compressive stress is taken as the main characterization of the laser shock strengthening effect.It is applied to the finite element model by pre-adding the initial stress.The stress and strain analysis of the TC11 test piece after laser shock strengthening is carried out,and the fretting fatigue life of the test piece under different temperature environments is predicted based on the fretting fatigue life prediction model considering the temperature influence.The results show that the predicted life expectancy results of the prediction model are all within the double error dispersion band,which is in good agreement with the experimental values.