Hidekazu Nishigaki

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.

First order analysis for automotive body structure design - : Part 1 : Overview and applications

Computer Aided Engineering (CAE) has been successfully utilized in automotive industries. CAE numerically estimates the performance of automobiles and proposes alternative ideas that lead to the higher performance without building prototypes. Most automotive designers, however, cannot directly use CAE due to the sophisticated operations. In order to overcome this problem, we proposed a new concept of CAE, First Order Analysis (FOA). The basic ideas include (1) graphic interfaces using Microsoft/Excel to achieve a product oriented analysis (2) use the knowledge of the mechanics of materials to provide the useful information for designers, and (3) the topology optimization method using beam and panel elements. In this paper, outline of FOA and application are introduced.

Development of an Abdominal Deformation Measuring System for Hybrid III Dummy

In order to evaluate the abdominal injury by using the dummy, a new abdominal deformation measuring system for Hybrid III dummy has been developed. The abdominal compression velocity V, the compression ratio C, and the maximum value of the product VC, can be calculated from the dynamic abdominal deformation of the dummy. This abdominal deformation measuring system consists of an abdominal insert having the same compression characteristics as those of the human body, a dynamic deformation sensor, and an analysis program. This system makes it possible to obtain the abdominal deformation in the impact tests using a cylindrical bar or a lap belt within an error of 10%. SAE Tech Paper 942223 Language: en

Fundamental Study of Dynamic Analysis of Lumbar Vertebrae

This paper describes the results of fundamental study of dynamic analysis of the lumbar vertebrae for the accidental injury. A finite element model with linear brick elements and nonlinear truss elements is constructed for the study of dynamic responses of the fifth and fourth lumbar vertebrae. The results of the analyses show the folio wings: In case of the estimation of the global behavior of vertebrae, it is efficient method to treat the stiff parts of the bone as rigid elements and apply the 8-points integration to the other soft brick elements. To determine the stiffness of ligament for various modeling cases, response surface methodology using design of experiment is applied and the usefulness is verified. And this design of experiment is also applied to examine the influence of the disk properties on the lumbar vertebral stiffness. This bending stiffness of the lumbar vertebrae is rapidly increasing when Poisson’s ratio of nucleus pulposus is very close to 0.5. If Poisson’s ratio is close to 0.5, nucleus pulposus changes its characteristic from compressible to incompressible. In this case, the disk is expected to function as rotator in the extension or flexion of the lumbar vertebrae. To verify this function of rotator, the impact response analyses that dropped block comes into contact with the upper side of the lumbar vertebrae is performed and this function is verified quantitatively.

Synthesis Method of Lightweight Framed Structures with Consideration of Impact Load Using Fuzzy Set Theory.

We present a numerical synthesis of topological and size optimization of lightweight framed structures with consideration of impact load using fuzzy set theory and FEM. The dynamic response of a mechanical system composed of joints, springs, masses and framed structure is analyzed to obtain the loading conditions used for the static finite-element analyses. In the sensitivity analyses of the framed structure, minimum weight, strength and displacements at certain boundaries are considered simultaneously using fuzzy set theory. During optimization, insignificant elements are neglected. This method is applied to a beam structure composed of thin-walled members. The results demonstrate the reliability and efficiency of the proposed method.