In order to see the effect of die deformation on the forming of sheet metals, the draw-ins, strains, and springbacks of an automotive fender panels are numerically simulated considering the die deformation, which is found by the simultaneous structural analysis of press and dies. By coupling the forming analysis and the structural analysis, the die deformation is simultaneously taken into account in the forming process. Furthermore, for the consideration of load difference transferred among the upper die, punch, and blank holder due to the changes in sheet thickness, the gap elements are employed instead of the blank sheet in the structural analysis. The numerical simulation results of an automotive fender draw panel are compared with the measurements. The comparison of the forming and spring-back analysis results between the rigid die and the deformed die shows that the deformed tool provides more accurate forming and spring-back prediction.

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To support the latest automobile technology, the next generation of diesel engines is expected to require higher injection pressures than the third generation which can operate at high injection pressures up to 1,800bar. A component in the common rail system, the common rail pipe must have higher strength because it is directly influenced by the high-pressure fuel. Preform design is very important for preventing the head of the common rail pipe from folding in the heading process. In this study, the angle, curvature and outer diameter of the die and the length of the trapped part are selected as main parameters in the design of the optimal preform shape that minimizes the radius of folding. The optimal design is carried out by finite element analysis and the Taguchi method using the main parameters and then fatigue-life analysis is preformed for predicting fatigue life according to the amount of folding. Also, a closed form equation to predict fatigue life was suggested by Goodman theory and life-prediction method for pressure vessels pursuant to ASME Code. In order to verify the reliability of common rail pipe, fatigue-structural coupled field analysis is performed. The results of the finite element analysis were in good agreement with those of the experiments at the actual site and theoretical analysis.

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