• Transactions of the Korean Society of Automotive Engineers
• /
• v.1 no.1
• /
• pp.140-148
• /
• 1993

When a large automobile sheet metal part is formed in a draw die, the binder wrap is first calculated to predict the initial punch contact location for avoiding wrinkles and severe stretching of its thin blank sheet. Since the boundary of a pseudo blank in calculating a binder wrap by means of a geometrically nonlinear finite element method is unknown in advance, an iteration method is generally used. This paper presents an effective iteration method for correction of the pseudo blank in a binder wrap calculation. For the performance test, two examples are adopted. The calculated results for both examples show the good convergence which wasted solutions are obtained in the second iteration step.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 1996.06a
• /
• pp.87-95
• /
• 1996

The stamping process consists of two stages : First, the blank is held by the blank holder and then it is further formed into the die cavity by punch stroke. In actual stamping process, the accurate prediction of binder wrap is an indispensable step in sheet metal forming analysis because the initial plastic buckling induced by improper die design is directly related with fatal defect at the final stage. In the present work, an approach including the gravity effect of blank material and proper consideration of contact and friction is proposed. Computations are carried out for some actual auto-body parts using 3D FEM code to investigate the validity of the proposed methodology. Comparisons with experimental results show that the suggested scheme can be effectively applied to the precise prediction of binder wrap for arbitrarily curved die faces in which gravity and contact effect must be taken into account.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 1995.03a
• /
• pp.196-202
• /
• 1995

Drawbead formulation is the first process together with a binder wrap process in a sheet metal forming process. The purpose of a drawbead is to control the flow of the metal into the die in panel press forming. To simulate the drawbead formation process, an elasto-plastic finite element formulation is derived from the equilibrium equation an drelated boundary conditions considering the proper contact conditons. The developed finite element program is applied to drawbead formation in the plane strain condition. The simulation of drawbead formation produces the distribution fo stress and strain along the bead and the resultant elongation of the sheet in the cavity region with respect to various cavity dimensions of the sheet as well as the punch force of a drawbead and the amount of draw-in with respect to the stroke fo a drawbead. The numerical resutls provides the fundamental information as a boundary condition to analyze the complex binder wrap phenomena and panel press forming in simple way.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 1996.06a
• /
• pp.75-86
• /
• 1996

Three-Dimensional finite element analysis is performed using PAM-STAMP for design evaluation of automotive back door inner panel die. Gravity process by blanks own weight, binder-wrap process, and drawing process in the forming operations are sequentially simulated with Virtual Manufacturing Method. The most valuable result in this research is that 3-D FEM analysis can be applied to the design evaluation of draw die in the die try-out, though effects of mesh size and drawbead resistance force on the numerical accuracy are much sensitive. For the intensive application to draw-die design and try-out, the experimental know-hows about the forming variables such as friction coefficient, punch velocity, drawbead force, etc are necessary.

• Transactions of Materials Processing
• /
• v.9 no.6
• /
• pp.567-573
• /
• 2000

An analysis system for evaluating the design of dieface of stamping press dies is developed. The die design analysis system interfaced with CATIA via universal or NASTRAN data format provides the design information such as binder-wrap, punch contact status, section length change ratio, wrinkle symptom etc., which are crucial in predicting the defects of initial shape of the sheet in the dieface design stage. The graphic post-processor of developed system which displays 3-dimensional shapes of tool and die and analysis results, helps the interpretation of design evaluation. The dieface design analysis system was tested in draw dies of front floor panel and quarter panel of auto-body in order to verify the usefulness and validity of the system The examples show that the developed system would be a good tool in evaluating dieface designs.

• Transactions of Materials Processing
• /
• v.11 no.6
• /
• pp.503-512
• /
• 2002

The drawbead is used to control material flow into the die during the binder wrap process and the stamping process in the sheet metal forming process. Since the dimension of drawbead is relatively small in comparison with the typical dimensions, it is difficult to include drawbeads in finite element analysis of the sheet metal forming process. It is because the mesh system has to be fine enough to describe the drawbead and the computation time is drastically increased. In this paper, simulation of drawbead forming has been carried out to obtain the equivalent boundary conditions in the binder wrap process and the stamping process. In order to investigate the effect of various die geometries, parameter studies are performed with the variation of parameters such as the blank length, the drawbead depth, the drawbead radius, the inclination of die and the friction coefficient.

• Transactions of Materials Processing
• /
• v.6 no.2
• /
• pp.152-160
• /
• 1997

Three-Dimensional finite element analysis is performed using PAM-STAMP for design evaluation of automotive back door inner panel die. Gravity process by blank own weigth, binder-wrap process, and drawing process in the forming operations are sequentially simulated with Virtual Manufacturing Method. The most valuable result in this research is that 3-D FEM analysis can be applied to the design evaluation of draw dies in the die try-out, though effects of mesh size and drawbead resistance force on the try-out, the experimental knowhows about the forming variables such as friction coefficient punch velocity, drawbead force, etc are necessary.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.17 no.6
• /
• pp.1389-1403
• /
• 1993

A procedure has be developed to optimize the product's tipping position in designing a die face for manufacturing automobile outer panels. Two design requirements are considered in optimizing the tipping position. One is to satisfy that all the points on the product should have a uniform distribution of drawing depths. The other is to guarantee that the user-specified area on the product should first contact with the binder wrap. The problem to satisfy the design requirements described above is analogous to the flatness calculation problem in the area of metrology if some constraints can be imposed. Thus the problem can be solved by the simulated annealing method, which is one of the optimization methods. The developed procedure was tested with the real die face design problem and the usefulness was verified by the diagram of the drawing depth.

• Journal of the KSME
• /
• v.29 no.3
• /
• pp.294-305
• /
• 1989

소성가공 공정설계의 컴퓨터를 이용한 최적설계를 위하여 선결되어야 기술적 과제를 (i) 구성방 정식, (ii) 윤활 및 마찰조건, 그리고 (iii) 적응적 유한요소망 재구성법 등 3가지 분야로 대별하여 논의하였다. 적절히 선택된 마찰/구속조건 등 경계조건 (boundary condition) 과 적절한 유한 요소망의 구성을 통하여 최종제품의 형상을 만들어내기 위한 금형의 형상 등을 유한요소법으로 해석하여 공정설계상의 시행착오의 범위와 횟수를 줄일 수 있다(7,8). 또 하나의 예로서 자동 차의 자체 등 비교적 대형의 판재가공에서 펀치에 의한 본격적인 가공행정이 이루어지기 전에 판재 자체가 중력에 의하여 처지게 되는데 이러한 중력에 의한 피가공재의 초기 처짐은 최종제 품의 형상에 직접적인 영향을 주게 된다. 이 경우 기존의 유한요소 해석 기법을 사용하여 초 기처짐을 제어하기 위한 판재의 가공전 고정용 금형(binder wrap)의 최적설계를 훌륭히 수행할 수 있다. 이같이 현재의 유한요소 해석법은 많은 기술적 과제를 지니고 있으나 동시에 소성가 공의 컴퓨터 응용설계를 실현하기 위한 궁극적 도구로서 매우 큰 활용 잠재력을 지니고 있다.

• Transactions of Materials Processing
• /
• v.7 no.4
• /
• pp.382-392
• /
• 1998

Computer simulations and test trials were carried out to obtain the optimal stamping conditions of the die design of the laser welded automotive body. The stamping process including gravity deflection bead calibration binder wrap, forming and spring back was simulated and compared with the results obtained from test trials. The production variables were determined from a preliminary operation and they were investigated in the simulation and the test trials. The formability was tested under the various conditions, such as the initial position of blank, blank holding force, corner radius and the shape of drawbead. Sound products without fracture, wrinkling and excessive weldline movement were produced by applying results obtained this investigation.