Yasuaki Tsurumi

Concurrent Design and Evaluation Based on Structural Optimization using Structural and Function-oriented Elements at the Conceptual Design Phase

Computer-aided engineering (CAE) has been successfully used in mechanical industries such as automotive industries. CAE enables us to quantitatively evaluate the mechanical performances of products and to propose an effective way to improve their performances using optimization techniques without building physical prototypes. However, CAE tools are usually utilized not at the conceptual design phase, but at the evaluation phase following the detailed design phase. This is because current CAE tools require detailed design data that does not yet exist at the conceptual design phase, and such tools also inhibit the provision of useful design suggestions that, ideally, match the way of thinking and insight of design engineers. Thus, at present, no CAE tools exist that can assist the conceptual design decision making process of design engineers. On the other hand, conceptual design processes are of great significance when seeking to create innovative and high-performance products and to shorten their development time. In order to fulfill the designer’s needs during the conceptual design phase, a new type of CAE method must be constructed, one that enables concurrent design support and evaluation, and fits the way design engineers think and explore design insights. This article presents a new structural optimization method that supports concurrent decision making so that design engineers can work to obtain innovative designs and evaluate the mechanical design details of mechanical structures at the conceptual design phase. This method is developed based on the concept of product-oriented analysis and discrete, function-oriented elements, such as beam and panel elements, since these can provide design suggestions concerning the structural evaluation of reasons as to why certain design ideas obtained are reasonable or optimal in the design sense. The basic ideas and specifications needed to construct the method are explained and the construction of the structural optimization design method is discussed. The optimization algorithm is developed using the ground structure approach and CONLIN sequential convex programming. The examples provided demonstrate the utility of the proposed methodology for supporting design engineers’ concurrent decision making, so that innovative mechanical designs can be evaluated at the conceptual design phase.

First Order Analysis for Automotive Body Structure Design-Part 2: Joint Analysis Considering Nonlinear Behavior

We have developed new CAE tools in the concept design process based on First Order Analysis (FOA). Joints are often modeled by rotational spring elements. However, it is very difficult to obtain good accuracy. We think that one of the reasons is the influence of the nonlinear behavior due to local elastic buckling. Automotive body structures have the possibility of causing local buckling since they are constructed by thin walled cross sections. In this paper we focus on this behavior. First of all, we present the concept of joint analysis in FOA, using global-local analysis. After that, we research nonlinear behavior in order to construct an accurate joint reduced model. (1) The influence of local buckling is shown using uniform beams. (2) Stiffness decrease of joints due to a local buckling is shown. (3) The way of treating joint modeling considering nonlinear behavior is proposed.