Researches On The Blades Strengthening And Plastic Forming Of Wing Panels Based On Laser Shock Peening Technology

During the aircraft takeoff and landing,the coupling loads of high frequency vibration and centrifugal force on the engine blade cause the high-cycle vibration fatigue crack in the 1st-order bending vibration nodal line of the blade,which rapidly reduces the fatigue life of the blade.At the same time,the foreign object inhaled by strong airflow impinges on the leading edge of the blade,which causes the stress concentration or failure source at the leading edge of the blade,and leads to the rapid fracture of the blade.In addition,the stiffened wing panel has the characteristics of large local bending forming and difficult plastic forming,which makes it difficult to reach the target surface of the wall panel by traditional shot peen forming.However,Laser Shock Peening(LSP)has the advantages of high pressure,superposition property,easy accurate positioning and control,etc,which is widely used to the applications of fatigue life extension of the blade and the plastic forming of wing panel.In this paper,based on the mechanical effect of LSP,blade notched simulators are designed to study the core process parameters of anti-Foreign Object Damage(FOD)fatigue life extension and fatigue life extension mechanism at the leading edge of the blade with LSP.Optimized strengthening technology: LSP of the blade material is used to study the anti-high cycle vibration fatigue life extension mechanism in the 1st-order bending vibration nodal line of the blade.The saturated value of shot peening and plastic strain are used to study the upper limit values of laser energy and impact times of the mid-thick wall panels with Laser Peen Forming(LPF).Orthogonal experimental design is used to study the bending deformation rule in the span-wise direction of the mid-thick wall panels with LPF.Different prestress forces are used to study the bending deformation capacity,bending deformation mechanism and surface modification in the span-wise direction of the mid-thick wall panels with LPF.The following conclusions and innovative results are obtained:(1)Evaluation of the strengthening effect of the blade material: The modification rules in the surface layer of β forging TC17 alloy are compared with three different strengthening technologies.It is obtained that small surface roughness value Ra 0.124 μm of TC17 alloy is induced by LSP.No new phase in the surface layer of TC17 alloy is generated by three different strengthening technologies.Deep micro-hardness affected layer 1.1 mm of TC17 alloy is induced by LSP.The saturated surface residual compressive stress values of TC17 alloy are induced by LSP and LSP process parameters are 4 impact times and laser energy of 30 J.Surface residual compressive stress value-523.25 MPa of TC17 alloy is induced by one LSP impact.It is revealed that the microstructure strengthening mechanism of TC17 alloy with LSP.The results provide the theoretical basis for the fatigue life extension of the blades with LSP.(2)Evaluation of the fatigue strengthening effect of the compressor blade: Blade notched simulators are designed with the section shape similar to the blade leading edge and the U-shaped notch similar to FOD.It is obtained that the core process parameters of fatigue life extension of TC17 alloy blade notched simulators with LSP.It makes the fatigue strength of the blade notched simulators from 180 MPa of as-received material to 280 MPa.It is obtained that two-way bending at the edge of the blade with LSP.It is revealed that the bending deformation mechanism at the edge of the blade with LSP.The high cycle vibration fatigue life of the blade is extended by an order of magnitude by optimized strengthening technology: LSP.It is revealed that anti-high cycle vibration fatigue life extension mechanism of the blade is residual compressive stress and nano-grains.(3)Plastic forming of the wall panel with LPF: It is obtained that the bending deformation rule,bending deformation types and their transition values of process parameters of Al2024-T351 thin wall panels treated by LPF with different process parameters.The surface morphologies and bending deformations in the span-wise direction of the mid-thick wall panels with LPF are analyzed to obtain the upper limit value of laser energy: 25 J.The nonlinear relation curves between the impact times and the arc height values,the forming curvature radii and the plastic strain in the span-wise and chord-wise directions of the mid-thick wall panels are established to obtain the upper limit value of the impact times: 4 impact times.Orthogonal experimental design is used to study the bending deformation rule in the span-wise direction of the mid-thick wall panels treated by LPF with different process parameters.It is obtained that the impact area is proportional to the forming curvature radii,the laser energy is inversely proportional to the forming curvature radii,and the plate thickness is proportional to the forming curvature radii.It is obtained that the main and secondary factors affecting the forming curvature radii in the span-wise direction of the mid-thick wall panels,which in order are impact area,laser energy and plate thickness.It is revealed that the bending deformation mechanism of the mid-thick wall panels treated by LPF with different prestress forces.The refined grains layers are induced by convex bending deformation in the topmost and bottom surface layers of the mid-thick wall panels.The above results provide the theoretical basis for achieving the high quality and high efficiency industrial applications of the fatigue life extension of the blade with LSP,and provide the possibility for achieving the mass plastic forming of the wall panels with LPF.It has high value in the application of engineering.