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정동원(D. W. Jung),김봉천(B. C. Kim),김동홍(D. H. Kim) 한국소성가공학회 2012 한국소성가공학회 학술대회 논문집 Vol.2012 No.5
The purpose of this study is to evaluate the influence of the scatter in mechanical properties and stamping process parameters on an industrial sheet metal forming process. Based on a previously optimized forming process, a robustness analysis has been performed. The robustness analysis clearly showed production problems for the part not initially revealed by the analysis of the process that was trimmed for “optimality”. The sensitivity of the results on the variation of the parameters was evaluated. It was shown that all parts of the sheet do not react equally sensitively to the variation of the input. Zones of critical response could be identified in accordance with the zones on the actual part that showed failure in mass production. The results reveal that the common practice of performing evaluations with fixed safety margins is non-effective and hence very dangerous, or is extremely conservative and thus costly. The application of stochastic simulation methods reduces the need for wide safety margins while simultaneously increasing the reliability of the process by incorporating uncertainty into the simulation.
정동원(D. W. Jung),김봉천(B. C. Kim),김동홍(D. H. Kim) 한국소성가공학회 2012 한국소성가공학회 학술대회 논문집 Vol.2012 No.5
In this study, roll-bending process was proposed to manufacture the door panel produce using pre-coated material. In order to obtain desired curvature radius and wall angle of final product, finite element method (FEM) was adopted to predict die radiuses and bending angles. First, combined kinematic/isotropic hardening law with new way to determine material parameters in tension/compression tests was applied to predict stress strain curves at various pre-strain. This hardening model was then investigated for roll-bending spring-back prediction. To verify the effects of die radius and bending angle on the curvature radius and wall angle, several values of them were changed to simulate and predict roll products after spring-back.