국소 가열 방법을 이용한 2단계 축대칭 디프 드로잉 공정의 해석 및 설계

Abstract

The study is concerned with finite element analysis and design of axisymmetric deep drawing by local heating. When the bottom shape of a cup is not flat but in complex-shaped, i. e. hemispherical, the cup cannot be drawn in one or two processes in the conventional deep drawing process and the limit drawing ratio is limited as well. By introducing local heating selectively with regards to the heating position, the formability of the sheet metal can be greatly increased with the reduced number of processes. In the Process analysis the rigid-viscoplastic finite element method is employed and the temperature effect is incorporated. Bishop`s step-wise decoupled method is employed to analyze the thermomechanical interaction between deformation and heat transfer. Axisymmetric deep drawing of a hemisphere-bottomed cup has been analysed for various combinations of heat application in the punch and the die. At the first stage of deep drawing stretch forming is practically carried out by firmly pressing the blankholder with the punch and the die heated at various levels of temperature. Then at the second stage the same cup is drawn for the same or different combination of temperature. From the computation, it has thus been shown that the formability of a cup is greatly increased in two-stage deep drawing with increased limit drawing ratio.