Optimization And Experimental Study On The Stretching-straightening Clamping Jaw Of Hard Aluminum Alloy Heavy Plate

The super-large pre-stretching heavy plate of aluminum alloy(referred to as the hard aluminum alloy heavy plate)is an indispensable material for modern large aircraft manufacturing.After being rolled and quenched,there will be a lot of residual stress in the hard aluminum alloy heavy plate.If this residual stress is not removed in time,it will lead to increased stress corrosion and fatigue fracture sensitivity of hard aluminum alloy heavy plate,thus reducing the service life of components and affecting the flight safety performance of ai rcraft.Therefore,effectively eliminating the residual stress inside the hard aluminum alloy heavy plate is an indispensable link to realize the production process of hard aluminum alloy heavy plate for aviation.At present,the most effective way to eliminate the residual stress in the hard aluminum alloy heavy plate is to conduct pre-stretching straightening after hardening.The early stage of plastic deformation is used to release the stress so that the interior residual stress in along the thickness direction is redistributed and tends to be uniform.In order to eliminate the residual stress inside the hard aluminum alloy heavy plate,Northeast Light Alloy Co.,Ltd.(hereinafter referred to as: 101 plant)has introduced the pre-stretching straightening equipment "8500T aluminum plate stretcher(hereinafter referred to as: stretcher)" from Italy.However,in the stretching process of the 180-200 mm thick hard aluminum alloy heavy plate,local fracture often occurs to the plate in the stretcher jaws.It no t only affects the quality,yield and economic benefits of the hard aluminum alloy heavy plate,but also easily causes damage to the stretcher itself,causing equipment failure and safety accidents.According to the a.m.situation,this paper starts with c ause analysis of local fracture on the plate in the jaws,sets the object as eliminating local fracture on the 180-200 mm thick hard aluminum alloy heavy plate,optimizes the stretcher jaws and carries out experimental study,to solve the technical problem that local fracture frequently occurs at the jaws during the prestretching and straightening process of hard aluminum alloy heavy plate.Firstly,the mechanical properties of the interaction between the stretcher jaws and the hard aluminum alloy heavy plate are analyzed,the composition and function parameters of the stretcher system are introduced,the reason of uneven stress distribution at the jaws is analyzed according to the structure and working principle of the stretcher jaws.In view of the interaction form between the jaw component of the stretcher and the hard aluminum alloy heavy plate,the mechanical characteristics analysis of the hard aluminum alloy heavy plate,the mechanical characteristics analysis of the end actuator and the mechanical characteristics analysis of the supporting structure are carried out respectively.The stress size and distribution of hard aluminum alloy heavy plate are obtained by means of analysis of mechanical properties of materials.Secondly,the numerical simulation of the tensile fracture mode of hard aluminum alloy heavy plate is carried out according to the mechanical interaction between the jaw component of the stretcher and the hard aluminum alloy heavy plate.Based on the finite element analysis theory,the finite element simulation software ANSYS is used to establish the simulation model of the tensile component,and the finite element method is used to conduct numerical simulation analysis of the tensile characteristics of the jaws and the clamping end of hard aluminum alloy heavy plate.According to the analysis results,the clamping jaws are modeled again and the corresponding clamping stiffness and stress distribution simulation analysis are carried out,to optimize the design parameters of the jaws.Finally,in order to verify with the results of mechanical analysis and numerical simulation,the tensile test of hard aluminum alloy heavy plate based on improved clamping jaws is carried out.According to the optimized structure parameters of the jaws in the the oretical force analysis and simulation,the design of jaws is improved,and several groups of tensile tests of hard aluminum alloy heavy plates are carried out,and the tensile effects are compared with those before the improvement of jaws.The technical feasibility of the optimization of the stretcher jaws is verified after the tensile properties measurement,the tensile test verification and the tensile quality analysis are carried out on the hard aluminum alloy heavy plate after the optimization of the stretcher jaws.In the end,with the minimum capital investment,the shortest time effect and the minimum equipment modification,the technical problem of local fracture of the 180-200 mm thick hard aluminum alloy heavy plate at the stretcher jaws in the pre-stretching process is solved,and the smooth production of the super-large hard aluminum alloy heavy plate for domestic large aircraft is realized.