Numerical Calculation Of Extrusion Process Of Special-Shaped Aluminum Alloy Profile And Design Of Shunt Bridge

Aluminum alloy profiles have the characteristics of low density,high strength and easy recycling.It is widely used in transportation,aerospace,construction,electrical appliances and other fields.For the extrusion forming process of special-shaped aluminum alloy profiles with high precision,large wall thickness and complex cross-section,there were problems such as easy fatigue failure of die and high product scrapping rate.This dissertation take the special-shaped aluminum alloy profile as the study object,and take the life of the die and the forming quality of the profile as the goal.The key issues such as the high temperature flow behavior and hot processing map of 6082 aluminum alloy material,the optimal design of the shunt bridge and die structure,and the optimization of key extrusion process parameters were deeply investigated.The specific study results were as follows:（1）The high temperature flow behavior of 6082 aluminum alloy was studied,and the constitutive equation and hot processing map were also established.The high temperature stress-strain curve of 6082 aluminum alloy was obtained by one-way hot compression experiment.The results showed that the flow stress of 6082 aluminum alloy was positively correlated with the strain rate and negatively correlated with the deformation temperature.The correlation coefficients and mean absolute errors of the established Modified Johnson-Cook,strain-compensated Arrhenius,improved strain-compensated Arrhenius and Hensel-Spittel constitutive equations were 0.967,0.981,0.995,0.987 and 12.64%,4.759%,3.222%,4.57%,respectively.The optimal process parameters for the alloy is the deformation temperature of 450～475℃,the strain rate of 0.01～0.1 s^-1and deformation temperature of 500～550℃,the strain rate of 0.1～0.3 s^-1.（2）The principal stress method was used to study the force of the rectangular split bridge,the conical split bridge and the curved split bridge in the process of separating metal materials.The force was analyzed and verified by numerical simulation.The results showed that compared with the rectangular shunt bridge,the extrusion force required by the extrusion die with the curved shunt bridge was reduced by 5.39%.The results also declared that the mean square deviation of the exit velocity of the profile was reduced to 0.308 mm/s,and the welding pressure was increased to 182.13～221.78 MPa,improved welding quality.（3）Taking the special-shaped aluminum alloy profile as the research object,the extrusion die was designed and optimized.Taking the mean square deviation of the exit velocity of the profile as the optimization objective,the influence of the optimization of the die structure such as the welding chamber,baffle block and working belt on the flow rate of the metal material was studied.The results showed that after the die structure was optimized,the mean square deviation of the exit velocity of the profile was reduced to 1.71 mm/s.The results also revealed that the maximum stress of the die was 676.14 MPa.The maximum deformation of the die appeared in the Z-axis direction,and the value was 0.39 mm.（4）Taking the mean square deviation of the profile exit velocity and extrusion force as the optimization objectives,a multi-objective optimization die was established to optimize the key process parameters of the extrusion forming process of special-shaped aluminum alloy profiles.The results showed that the optimal combination of extrusion process parameters were as follwing:the blank temperature was 500℃,the die temperature was 480℃,the extrusion barrel temperature was430℃and the extrusion speed was 1 mm/s.Under optimal process parameters,the mean square deviation of the exit velocity of the profile was 0.446 mm/s,and the maximum stress on the die was 603.94 MPa,which was lower than the yield strength of the die material by 1020 MPa,which ensured the service life of the die.