에너지법에 의한 축대칭 디프드로잉의 해석

An Analysis of Axisymmetric Deep Drawing by the Energy Method

본 연구에서는 에너지법으로 축대칭 박판성형 공정을 해석할 때, Lee와 Yang 이 제안한 방법을 적용함에 있어 굽힘효과를 효과적으로 고려할 수 있는 방법을 제안 하고 축대칭 컵드로잉 공정을 해석하여 본 이론의 타당성을 입증하고자 한다. 굽힘 효과는 박판소재를 몇개의 층(layer)으로 나눈 뒤, 각 층에서 소비되는 변형에너지를 합하여 전체 에너지를 최소화시킴으로써 고려하였다. 해석시 펀치 목부분과 다이목 부분에서의 접촉압력은 각각 균일한 분포를 갖는 것으로 가정하였다. 본 이론의 타 당성을 입증하기 위하여 계산결과를 실험치 및 탄소성 유한요소해석 결과와 비교하였 다.

A systematic approach of the energy method is proposed for analysis of axisymmetric deep drawing in which the total deforming region is divided into five sections by the geometric characteristic. The corresponding solution is found through optimization of the total energy dissipation with respect to some parameters assumed in the kinematically admissible velocity field defined over each region. The sheet blank is divided into three-or five-layers to consider the bending effect. For the evaluation of frictional energy, it is assumed that the blank holding force acts on the outer rim of the flange and that the contact pressure acting on punch shoulder or die shoulder has uniform distributions, respectively. The computed results by the present method are compared with the experiment and the computed results by the elastic-plastic finite element method for the distribution of thickness strain and the relation between the punch stroke and punch load. The results for the case of multi-layers show better agreements than for the case of a single layer in load vs. stroke relation and strain distribution. It is thus shown that the multi-layer technique can be effectively employed in analyzing axisymmetric deep drawing in connection with the energy method.