Investigation Into Hydromechanical Deep Drawing Of 5A06 Aluminum Alloy Conical Cup

With the development of China's automobile and aerospace industry ,complicated-shaped sheet metal parts made of aluminum alloy has found increasing application in this field. However, due to poor plasticity and appearance of a large non-supporting area, it is easy to rupture and wrinkle, and it is very difficult to be formed with conventional deep drawing.Hydro-mechanical deep drawing, with its unique advantages, can significantly improve the forming limit, and especially be suitable for forming complicated-shaped sheet metal parts. 5A06 aluminum alloy conical part was studied in this paper, the forming mechanism of conical parts and the effects of the forming parameters on formability were analyzed numerically and experimentally. Punches with stem diameter 94mm and cone angle 5°, 10°, 15°and 20°have been designed and constructed. The effect of cone angle on the sheet deformation was studied in detail.Through the radial stress distribution analysis, the critical radial stress expressions in a conventional deep drawing and in a hydro-mechanical deep drawing were given. It is known that the bigger the cone angle is, the higher the critical radial stress is, so it is very difficult to achieve high drawing ratios for the influence of cone angle. By comparison, it is found that the fracture factor in hydro-mechanical deep drawing is much higher than one in conventional deep drawing because of chamber pressure, thus can significantly improve the material's forming limit.The reasonable chamber pressure curve in hydro-mechanical deep drawing of conical parts was selected by using FEM simulation, and an important characteristic of chamber pressure turning point was proposed according to its characteristics. The chamber pressure forming areas in different cone angles were obtained after several FEM simulations, and the optimal hydraulic loading curves for each cone angle were given by index of minimal thinning ratio. The failure types including fracture and wrinkling were investigated in detail, and control measures were proposed. The influences of cone angle on thickness distribution, strain distribution, the maximum chamber pressure range and forming limit were analyzed respectively, and it was founded that the effect on the formability is more and more obvious as cone angle increases. When cone angle reached 20°, a sharp deterioration had been observed in all formability. Moreover, the effect of maximum chamber pressure on thickness distribution was discussed. The research results showed that thinning ratio can be lessened remarkably by increasing maximum chamber pressure when it is low, but not obviously when it reaches a certain value.Hydro-mechanical deep drawing of conical parts was investigated in experiment finally. It was shown that the results from the simulation were in reasonable agreement with those from the experiment. Extended limiting drawing ratio of 3.38 for 20°conical cup has been achieved successfully.