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3.4 Punch Corner and Die Corner Radii for the First Stage：
After the determination of optimum punch diameter, it is necessary to determine the punch corner and die corner radii. Table 2 shows the simulation matrix used for this purpose. Initial values of punch corner and die corner radii were taken from the design handbook (8). Also, the ratio of punch corner radius to die corner radius was kept to less than 1 based on the guidelines obtained from the investigation of the die design of the example part, A. The last column in Table 2 shows the wall thinning values for different sets of punch corner and die corner radii at the first stage. Punch and die corner radii of 19.5 and 21.5 mm, respectively, were selected to meet the thinning criterion (i.e., to keep wall thinning below 4%) and reduce the number of forming stages. A similar approach was adopted to determine the optimum set of punch and die corner radii for the subsequent stages.
3.5 Final Progressive Die Sequence：
The progressive sequence design using FEM simulation consisted of ten forming stages and a final piercing/wall ironing stage. Figure 7 shows the progressive die sequence and the corresponding maximum thinning in percentage for each stage.
4 Progressive Die Design - Comparison Between FEM and
Experience Based Methods：
Figure 8 shows the comparison of punch diameters obtained from FE assisted and experience based approaches. FEM predicted ten forming stages while experience based approach predicted nine forming stages. As observed from the slope of two curves, punch diameter change in FEM assisted approach is gradual. However, larger draw ratios were used for the first five stages in the experience based approach. Figure 9 shows the comparison of thickness distributions obtained from FEM assisted approach and experience based approach. Thickness distributions obtained from these two designs show that gradual change in punch diameter would result in a more uniform wall thickness distribution in the final part. Figure 1 shows the comparison of punch corner for FEM assisted and experience based approaches. Similar trends were observed for corner radii as well.
5 Conclusions：
In this study, FEM has been used to design progressive die sequence for a deep drawn round cup. The die design obtained from FEM simulations was compared with that obtained from experience based approach. The study has demonstrated that integration of computer aided engineering (CAE) capability and the experience of process from tool designers can reduce the progressive die development time. Furthermore, CAE can also help in designing geometrically more complex parts that would require increased manual design effort as well as more trial and error. With process simulation via FEM, field variables such as strain distribution, stress distribution, material flow, and forming defects can also be estimated. This information will enhance the design capability and know-how of an experienced process designer. The major conclusions drawn from this study are:
•Integration of FEM and past experience can reduce the number of die-tryout tests and associated time and cost.
•The use of FEM can allow further refinement and optimization of the die design so that product properties, i.e., wall thickness tolerances, can be improved.
•To make FEM a practical tool for designing progressive and transfer dies in the stamping industry, close cooperation between the experienced die designers and the FEM engineers is necessary. Alternatively, the experienced designer can be trained in the use of FEM codes.
运用有限元法设计圆杯拉深级进模
1 摘要：
近日就基于使用有限元法的模拟设计圆杯拉深级进模的设计方法进行了探讨。与以往设计经验相比，用于汽车开发的流程顺序设计有了一定的提高。本文提出的方法表明，一体化的设计经验和有限元法模拟能够提高模具设计的稳健性，并且能够大大降低模具的开发成本。论文网