Papers by Author: Tsung Chia Chen

Abstract: The squaring process to shape a circular tube into a symmetric square clad tube is examined by a three-dimensional incremental elastic-plastic finite-element method based on an updated Lagrangian formulation. The effects of various parameters, such as geometric ratio R/t, strain hardening exponent n, friction coefficient μ, and the length of tube L, on the occurrence of collapse in the squaring process are discussed and interpreted in a theoretical manner. The findings show that geometric ratio is the major factor in the process of squaring circular tubes. When R/t=25, serious collapse is likely to appear. Aiming at circular tubes with geometric ratio R/t=25, this study proposes six analysis configurations for clad tubes to discuss the possibility of clad tubes avoiding collapse. The findings showed that clad tubes could effectively reduce the collapse ratio.

Abstract: This study aims to analyze the effects of angular U-bending process on the springback of metal sheets. Based on Updated Lagrangian Formulation (ULF), the 3D incremental elastic-plastic Finite Element Method was inferred to simulate the U-bending process of metal sheets. The die/blank holder profile with angles of α=-4°, α=-2°, α=0°, α=2°, α=4° and die/punch profile with radiuses of Rp=Rd=6.0mm were analyzed to determine the influence of tool angles on the springback. With different tool angles to proceed the U-bending process of metal sheets, it is found that the larger or smaller die angles, the more springback magnitude. When perpendicular U-sheets are required, θ₁ of the U-sheet presents 90 degree on the tool angle α=-1.2° and θ₂ shows 90 degrees on the tool angle α=-0.4°. The aim of this study is to investigate the effects of angle variables on the springback in the U-bending process and to obtain useful data from the industrial field.

Abstract: This study aims to clarify the process conditions of the radial compression of aluminum tube. It provides a model that predicts not only the correct punch load for compression, but also the precise final shape of products after unloading, based on the compression properties of the material and the geometry of the tools used. An elasto-plastic incremental finite-element computer code, based on an updated Lagrangian formulation, was developed to simulate the radial compression of aluminum tube. In particular, selective reduced integration was adopted to formulate the stiffness matrix. The extended r-minimum technique was used to deal with the elasto-plastic state and contact problems at the tool-metal interface. A series of simulations were performed to validate the formulation in the theory, leading to the development of the computer codes. The whole deformation history and the distribution of stress and strain during the forming process were obtained by carefully considering the moving boundary condition in the finite-element method. Results in this study clearly demonstrated that the computer code for simulating the radial compression of aluminum tube was efficient.

Abstract: This study aims to clarify the process conditions of the UO-tube of a sheet metal of steel. It provides a model that predicts not only the correct punch load for drawing, but also the precise final shape of products after unloading, based on the tensile properties of the material and the geometry of the tools used. An elasto-plastic incremental finite-element computer code, based on an updated Lagrangian formulation, was developed to simulate the UO-tube process of sheet metal; the results are compared with corresponding experimental results. Special care was taken to formulate accurate boundary conditions of penetration, separation and alternation of the sliding-sticking state of friction, as the contact conditions between the tools and the sheet varied throughout the entire processes of U-bending and successive O-bending. Calculated sheet geometries and forming force agree well with experimental data. In particular, selective reduced integration was adopted to formulate the stiffness matrix. The extended r-minimum technique was used to deal with the elasto-plastic state and contact problems at the tool-metal interface. A series of simulations were performed to validate the formulation in the theory, leading to the development of the computer codes. The whole deformation history, the distribution of stress and the distribution of strain during the forming process were obtained by carefully considering the moving boundary condition in the finite-element method. The simulation demonstrates clearly the efficiency of the code to simulate various bending processes that proceed under complicated deformation- and contact-history.

Abstract: This study aims to clarify the process conditions of the hat-type drawing of a sheet metal of steel. It provides a model that predicts not only the correct punch load for drawing, but also the precise final shape of products after unloading, based on the tensile properties of the material and the geometry of the tools used. An elasto-plastic incremental finite-element computer code, based on an updated Lagrangian formulation, was developed to simulate the hat-type drawing of sheet metal. In particular, selective reduced integration was adopted to formulate the stiffness matrix. The extended r-minimum technique was used to deal with the elasto-plastic state and contact problems at the tool-metal interface. A series of simulations were performed to validate the formulation in the theory, leading to the development of the computer codes. The whole deformation history and the distribution of stress and strain during the forming process were obtained by carefully considering the moving boundary condition in the finite-element method. Results in this study clearly demonstrated that the computer code for simulating the hat-type drawing process was efficient.