Study On Pre Expanding And Hydroforming Temperature Forming Of Aluminum Alloy Parts With Irregular Bottom

In recent years,aluminum alloy sheet is more and more widely used in the field of automobile,but in general drawing,aluminum alloy has poor formability and is prone to wrinkle,crack and other defects.In this paper,the formability and forming accuracy of aluminum alloy in the environment of liquid filled drawing are studied.Taking 6061 series of aluminum alloy slab as the research object,the finite element software is used to simulate the liquid filled drawing of the cylinder,and the forming performance is further analyzed.In view of the particularity of special-shaped bottom forming,this paper proposes to adopt the reverse expansion forming process,that is,to apply liquid chamber pressure in the early stage of drawing,to make the sheet close to the punch,reduce the hanging area,increase the contact area between the sheet and the punch,and effectively avoid the occurrence of fracture defects;another function of the reverse expansion forming process is to enable the special-shaped bottom to be formed in advance,so as to solve the problem that the special-shaped bottom will not be formed in the late stage of drawing Enough.It is found that the reverse expansion height has an important influence on the forming of the tube.The appropriate reverse expansion height can reduce the flow resistance of the sheet metal,and the appropriate reverse expansion pressure can improve the formability and die sticking accuracy of the irregular bottom.The influence of the pressure loading curve of the liquid chamber on the wall thickness of the cylinder is studied.When the liquid chamber pressure is small,the sheet metal is easy to crack because of the large hanging area of the sheet metal.The appropriate liquid chamber pressure has an important influence on the forming of the cylinder.In order to further improve the formability of aluminum alloy high cylinder parts,the formability of aluminum alloy with different drawing speed at 25 ?,50 ?,100 ?,150 ?,200 ? and 250 ? was studied by warm forming process.It is found that the maximum strain range of the sheet metal is changed by increasing the forming temperature within a certain range,which improves the forming accuracy of the special-shaped bottom compared with that of the cold forming,and the wall thickness of the straight wall part of the tubular part is more uniform than that of the cold forming.When the temperature rises to100 ?-150 ?,the wall thickness value is large and evenly distributed.When the drawing temperature is high,the cylinder is easy to crack.The effect of drawing speed on the formability of cylindrical parts is studied.The results show that different drawing speed has a certain effect on the wall thickness of cylindrical parts,but the effect is not significant.Warm forming not only improves the uniformity of the wall thickness of the cylinder,but also improves the forming accuracy of the irregular bottom.Under the condition that the wall thickness is uniform and within the safe range,a high forming accuracy can be obtained at the irregular bottom fillet.