In this thesis, an integrated optimal design software system for structural components has been developed which interfaces existing commercial codes for CAD, CAE and Optimization. Various previously developed software systems for optimal design have been analyzed in terms of modularity and independence of analysis activities, flexibility of optimal design formulation, user convenience and so on. They include specialized optimal design software codes such as iSIGHT and VisualDOC, optimization module imbedded in CAD software developed by CAD developers, and optimal design software systems based on API of commercial CAD software. The advantages of the CAD imbedded optimal design approach and those of specialized optimal design software are taken to develop the system called DS/I-DEAS. The user defines optimal design formulation in the user interface for problem definition in the CAD control stage, where design variables are directly selectable from the CAD model and various properties and performance functions defined. The commercial CAD codes, I-DEAS and Open I-DEAS(API) are used for the development. The interface program also connects external libraries and codes such as DOT for optimization, Grid Control for spreadsheet and PGL for graphing. Windows 2000 and Visual C++ have been utilized. The resulting software is minimally connected to CAD and CAE systems while keeping maximum independence from each other. This assures flexibility and freedom for problem definition.
Fatigue life optimization is taken as a nontrivial application area. For stress history and life calculation, ABAQUS and Fe-Safe are used and interfaced. As a specific example, the shape design of a knuckle part of an automobile is performed, where the minimum fatigue life over the material domain in terms of the number of cycles of a curb strike are maximized under the constraint of not exceeding the current mass. The fatigue life has been improved by four times of the initial life. The developed software is illustrated to maintain the advantages of existing optimal design software systems while improving independency and flexibility.
