| In recent years, there are great efforts of our country to develop high-speed railway,and there is increasing demand for the high speed train made by aluminum alloy. At present, as in most cases it needs mold to process the skin of the driver's cab which is part of the aluminum body,so that design, manufacturing, commissioning, maintenance of the mold is a time consuming task. Thus to develop a fast, low-cost, advanced technology and new equipment to manufacture the skin of the driver's cab which is part of the aluminum body will become a trend.Multi-point forming (MPF) is a novel manufacturing technology for sheet metal parts. In MPF, the conventional solid die is replaced with a matrix of discrete punch. Each punch's height can be controlled by computer. The flexible forming of sheet metal is implemented by the contour surface of elements group. MPF can achieve low-cost production of more variety, small batch of parts. Recently, MPF technology has been applied to aircraft skin , pressure vessels, urban sculpture medical engineering (titanium sheet forming),and other fields.Relative to the traditional stamping technique, the MPF has more advantages, such as forming instead of solid dies, optimum deformed path and using the MPF press to form large parts. However, because the load condition is complex, in the process of multi-point forming, dimple and wrinkle are the main defects which influence the forming ability and quality of the parts and limit the development of the multi-point forming technology. Currently by constructing FEA mold CAE numerical simulation can well forecast all kinds of defects in the course of forming. So CAE is powerful tool and instrument to avoid and decrease bugs in sheet forming. Finite element method has been applied to this paper to simulate the process of Multi-point forming for aluminum skin panels. According to the simulations, those main defects can be predicted and eliminated. And the reference to numerical simulation results using the optimized process parameters was experimentally verified. Main works and results are as following:1) Numerical simulation on the process of MPF for skin panelsThrough the simulation of MPF process for skin panels, production and distribution of dimples were analyzed. Through the simulation of elastic cushion with different thickness, the effect of elastic cushion with different thickness controlling dimples is studied. The results show that, when the thickness of Elastic cushion reaches 10mm, the dimples disappeared. For the consideration of the lightweight body, the driver's cab often use High-strength aluminum alloy. Based on explicit-implicit algorithm, unloading process was analyzed. The effect of different thickness on springback was studied.2) Numerical simulation on the process of sectional multi-point forming for s skin panelsFor skin panels of the larger size, sectional multi-point forming has great advantage in manufacturing large-scale sheet metal. Through the simulation of sectional MPF process for skin panels, the forming rule was investigated. Forming quality of skin panels was compared with two different forming methods. Strain of sectional forming skin panels was smaller than one-step forming parts. So the quality of sectional forming parts was better than one-step forming parts.3) Experimental study on sectional multi-point forming of aluminum skin panelsBased on numerical simulation technology, through the test of sectional MPF process for different skin panels using SM25-1200 MPF machine, the dimples and springback problem were analyzed. And qualified skin panels were obtained. Under appropriate design of transition area, sectional multi-point forming technology can be applied to the forming of aluminum skin panels. |
PDF Full Text Request