The Finite Element Simulation Study Of Laser Shock Peening And Fretting Fatigue Resistance Of Titanium Alloy Connection Holes

A large number of components in the helicopter rotor system are connected and assembled with hole structures,and the position of fatigue failure often occurs at the hole connection parts.During the service of the helicopter,the structural parts not only bear the alternating loads,but also occur fretting wear on the contact surface of the holes,which is a typical fretting fatigue,which causes the fatigue strength to deteriorate dramatically.With the fast growth of the civilian helicopter industry,the fatigue life requirements for this type of hole structures are gradually increasing.In recent years,the laser shock peening(LSP)technology has gradually become one of the important and effective means to improve the performance of the resistance to fretting fatigue of components.The deep residual compressive stress field caused by the shock wave on the surface of the target material to suppress crack initiation and propagation has been successfully applied to the resistance of fretting fatigue of the turbine blade tenon structure.In this paper,the laser shock peening technology was used to modify the fretting contact surface of the TB6 titanium alloy hole structure,and the effect of the laser shock peening technology and process parameters on the surface residual stress field and fretting fatigue performance was studied.The finite element software was used to establish the laser shock peening model of the hole structure and the fretting fatigue model of the hole structure.The experimental data and numerical simulation were combined to provide guidance for the design of the laser shock peeing process of the hole structure and the prediction of peeing effect against fretting fatigue.Firstly,The distribution characteristics of the residual stress field caused by laser shock peening were studied in TB6 hole structure.The finite element model of LSP was established by ABAQUS.The dynamic relaxation(DR)method was used to analyze the influence of process parameters such as the laser shock peening angle,overlapping rate and shock number on the residual stress field of the hole structure,and compared with the experimental test results.Then,with the help of ABAQUS finite element software,a two-dimensional finite element model of hole / bolt fretting contact was established to study the effect of the fretting on the fatigue life of the hole structure and the effect of the fretting on stress and strain of hole structure after LSP.The SWT parameter model was used to predict the failure position and fatigue life of the hole structure during the fretting process.The results show that:The angle of LSP has an important influence on the residual stress value at the hole Inner wall.The residual stress value increases with the increase of the laser shock peening angle.The overlapping rate has no obvious effect on the stress state of the hole angle.As the number of shock increases,the residual stress also increases,but it will gradually become saturated.Finite element results including the residual stress value and evolution trend caused by the laser shock peening have a good agreement with the experimental test results.Further research show that the presence of fretting significantly change the distribution of stress and strain in the pore structure,and greatly reduce the fatigue life of the pore structure.The crack initiation position of the pole structure predicted by the SWT model is in good agreement with the experimental results,and the failure positions all occur at the position of 90 °.After benchmarking the finite element data with the experimental data,the finite element prediction results are consistent with the experimental test results.