Study On Numerical Simulation Of Extrusion Process,Die Optimization And Heat Treatment Of Large Complex Aluminum Alloy Profile

In the field of aerospace,in order to pursue higher flight speed and increase flight distance,it is necessary to reduce the weight of aircraft structure.The mass of the spacecraft can be reduced effectively by changing the important structural parts of the space cabin from circular structure to various special-shaped structures.The special-shaped structure has the characteristics of large wall thickness variation and high geometric accuracy,so it is necessary to accurately control its forming accuracyIn view of the application of large section hollow aluminum profile in aerospace field,6005A aluminum alloy extrusion profile is required to have high strength,plasticity and excellent corrosion resistance.Therefore,studying the material deformation law and die optimization method of extrusion process of 6005A large section hollow aluminum profile,clarifying the influence law of heat treatment process on the mechanical properties and corrosion resistance of aluminum alloy,and obtaining the optimal die structure and the optimal solution and aging parameters can not only provide technical guidance for the actual production,It can provide theoretical guidance for the accurate control of extrusion forming of large section hollow profile and the improvement of its performance.Aiming at the extrusion forming and heat treatment of a 6005A large section hollow aluminum alloy profile,the influence of die structure parameters on metal flow uniformity in extrusion process was studied by numerical simulation.The multi-objective optimization model was established,and the design method of extrusion die for large section and large wall thickness difference profile was discussed;The effects of solution and aging heat treatment on the mechanical properties and corrosion resistance of 6005A aluminum alloy profile were studied by experiments.The results can provide theoretical guidance for die optimization and heat treatment process formulation of 6005 A aluminum alloy profile.The main research work is as follows:(1)Taking the large section thin-walled hollow aluminum profile as an example,the split extrusion die was designed.Taking the maximum transverse deformation of the profile as the optimization objective,the influence of the length of drainage groove,choke block and working belt on the material deformation,temperature distribution,extrusion load and die stress was studied by using the finite element numerical simulation software.Based on this theory,the optimization design of die structure was carried out,the distribution law of material physical field in the optimization die was analyzed systematically,and the metal flow law in the extrusion process of large section thin-walled hollow aluminum profile was clarified.(2)The welding chamber shape of large section thin-walled hollow aluminum profile was further optimized by response surface method.Taking the key parameters of welding chamber shape(height of choke,height of welding chamber and inclination angle)as design variables,combined with BBD experimental design and response surface method,the models of SD V,Fand Tmax were established.Based on the response surface model with Max as the optimization objective,the structure size of the primary welding chamber is obtained,which makes the maximum extrusion force F and the velocity mean square deviation SD V smaller.The strength of the die was checked,and it was found that the deformation and stress of the final die met the actual production requirements.(3)Taking a hollow profile with large wall thickness difference as an example,the split extrusion die was designed.Taking the mean square error of profile section velocity as the optimization objective,the influence of the size and shape of the shunt hole on the metal flow was further studied,The results show that the velocity distribution at the exit of hollow profile with large cross-section and large wall thickness difference is extremely uneven,and it is easy to produce defects such as deformation,bending and twisting.However,adjusting the length of working belt and setting flow blocking block have no obvious effect on improving the metal flow uniformity.In view of this phenomenon,this paper puts forward a variety of diversion hole design schemes,and ultimately ensures the forming accuracy of hollow aluminum profile with large wall thickness difference.(4)In order to study the effect of heat treatment process on the microstructure and mechanical properties of 6005A aluminum alloy,the effects of solution temperature and holding time on the hardness and mechanical properties of 6005A aluminum alloy were studied.It was found that the mechanical properties of 6005A aluminum alloy could be improved by increasing solution temperature(470 ??510 ?)and holding time(0?1h)within a certain range;The effects of single-stage aging and multi-stage aging on mechanical properties and corrosion resistance of 6005A aluminum alloy were studied.Combined with the change of elongation,the fracture mechanism of tensile fracture morphology of aluminum alloy is clarified,which provides theoretical guidance for determining the heat treatment process of 6005A aluminum alloy large profile.