Tomiso Ohata

Development of optimum process design system by numerical simulation

Abstract Now, the development of optimum forming process design system based on computer simulation to reduce the time consumption is strongly required in the industries. In this study, the optimum process design system is newly developed in conjunction with the nonlinear FEA code and the nonlinear optimization code. In the latter code, “Sweeping Simplex Method” is newly proposed, which can find the global minimum. The accuracy and quickness of this method to find the global minimum of objective function, which have several local minimum points, is confirmed by comparison with the grid method. This numerical system is applied to the process design of complicate shaped cup deep drawing. In order to form the sheet metal with uniform thickness, “Deviation of thickness from uniform average thickness” is employed as the objective function, and the global minimum point in the design variable space is searched by “Sweeping Simplex Method”. For the design variables, the heights of two punches in first stage forming are employed. The optimum process condition was determined by using this numerical code and also the validity of this code was confirmed by the comparison with the experimental observation results.

Development of optimum process design system for sheet fabrication using response surface method

Abstract The aim of this optimum process design system is to assist the decision of material process condition for making a sheet metal which has better formability for stamping. This system is realized by combining finite element analysis and discretized optimization algorithms. In this system, optimization algorithm is required to search the optimum condition quickly. Therefore, the response surface method was newly suggested to improve the efficiency of the retrieval. This system is applied to find the annealing conditions suitable for a sheet forming condition. Annealing temperature and time are chosen for the process parameters. Formability is evaluated by thickness uniformity of stamped part. As the result, this system could search optimum condition quickly. The effectiveness of this system was confirmed through experimental verification. It is demonstrated that this optimum process design system is a useful tool for deciding a material process and sheet metal fabrication design.

Improvement of optimum process design system by numerical simulation

Abstract Recently, the optimum forming process design systems based on computer simulation have been actively developed. Until now, the optimum process design system was developed in conjunction with the nonlinear FEA code and nonlinear optimization code. In the latter code, the ‘sweeping simplex (S.S.) method’ which could find the global minimum was recently proposed. This numerical system was applied to the process design with two design variables of complicated shape cup deep drawing. This system could search optimum condition efficiently. In the present paper, we applied the system to a working process design with three design variables. To consider three design variables, we make the searched region a 3-D region and improve this system to increase its efficiency to search. The improved system is applied to the optimum process design of the complex cup deep drawing. Further, the validity of this system is verified by comparison to experimental results.

Development of Dynamic Explicit Crystallographic Homogenization Finite Element Analysis Code to Assess Sheet Metal Formability

The crystallographic texture evolution induced by plastic deformation in the sheet metal forming process has a great influence on its formability. In the present study, a dynamic explicit finite element (FE) analysis code is newly developed by introducing a crystallographic homogenization method to estimate the polycrystalline sheet metal formability, such as the extreme thinning and “earing.” This code can predict the plastic deformation induced texture evolution at the micro scale and the plastic anisotropy at the macro scale, simultaneously. This multi‐scale analysis can couple the microscopic crystal plasticity inhomogeneous deformation with the macroscopic continuum deformation. In this homogenization process, the stress at the macro scale is defined by the volume average of those of the corresponding microscopic crystal aggregations in satisfying the equation of motion and compatibility condition in the micro scale “unit cell,” where the periodicity of deformation is satisfied. This homogenization a...

Research on Strength Design of Channel Clips for Suspended Ceilings

Suspended ceilings consist of ceiling boards, furring channels, channel clips, furring brackets, hangers and ceiling bolts. The ceilings are easy to drop down when the large earthquake occurred. The channel clips deform and disengage from the ceilings or break at that time. Design engineers calculate and evaluate the stress in the clips by using method with mechanics of materials. The evaluation depends on the experiences of the engineers. Mechanics of materials is considered in elastic region, but the channel clips are in plastic deformation. Therefore, after the design, the clips are manufactured and are subjected to verification tests as the design evaluation. Sometimes the prototype tests become multiple times. The purpose of this research is to build a simple method of an efficient design for the channel clips. It is ordinary to use elastic-plastic analysis at strength design in the case of plastic deformation. But software for elastic-plastic analysis is expensive, so the design method of the channel clips depends on the elastic stress analysis function of 3D CAD in this research. Instead, we designed and evaluated the equivalent stress corresponding the tensile strength in plastic deformation as the evaluation criterion. As a result, it was possible to evaluate the design that the channel clips are not broken when assuming earthquake occurrence with a seismic intensity of 7. This evaluation is reliable compared to the verification test conducted in the past.