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Low noise and vibrations are requirements for engineering structures to realize comfort and ensure systems are environmental friendly. Periodic structures such as phononic crystals have been investigated to suppress noise and vibrations because they inhibit elastic wave propagation in the frequency ranges referred to as the band gap. This study led to the proposal of a metaplate (MP) with periodic hollow structures to form band gaps by changing the surface shapes of the thin plates. MPs such as this can be beneficial from the viewpoints of manufacturing cost and structural reliability when applied to engineering structures. To evaluate the potential ability of the proposed MP to suppress vibrations, we obtained the band gap frequency of out-of-plane deformation waves using the wave finite element method. To efficiently evaluate the band gaps, the internal degrees of freedom in a unit cell are reduced based on the modal analysis technique. Furthermore, the out-of-plane and in-plane deformation waves are separated using kinematic energy to extract the band gap related to the out-of-plane deformation waves. Based on this numerical framework, we demonstrate that periodic hollow shapes can form a band gap in the frequency range of interest in engineering problems. Moreover, the potential of the MP was investigated using hollow shape design and material selection, and the results indicate that the proposed MP is beneficial for tuning the band gap frequency in a unit cell of which the size is acceptable for engineering structures. Finally, vibration suppression caused by band gap is experimentally demonstrated via impact testing of an MP fabricated using additive manufacturing.

A CAE-based process design method was developed to improve formability in hot stamping by controlling the temperature distribution during the forming step. Specifically, areas where deformation is not desired should be cooled to make them harder, and areas where deformation is desired should be kept at higher temperature. In this study, a tailored initial temperature distribution was calculated through three-step analysis of the deformation behavior by a thermo-mechanical forming simulation. First, the deformation severity was evaluated from the damage value for each finite element by using a forming limit diagram (FLD) at elevated temperature. The cautionary damage value was then defined to determine whether the element should be cooled. Finally, the tailored initial temperature was calculated based on the temperature-dependent flow stress. This procedure was applied to a high-rigidity pillar model that could not be formed by the conventional hot stamping process without cracking. The improved formability was confirmed experimentally. Thus, controlling the temperature distribution increases the diversity of shapes achievable by hot stamping.

By creating a frame structure of a new layout and dividing it into modules with little coupling with each other using topology optimization and clustering, we have found out the assembly units of the product and the assembly process with less rework. Replacing with a lightweight material is an effective method for reducing the weight of the structure, but in order to minimize the influence such as adhesiveness and difference in coefficient of thermal expansion due to the use of different materials, it seems reasonable to replace by module as a functional unit. Therefore, we constructed a system for structural evaluation by material replacement and the cross section that maintains equivalent stiffness for each module. We present the method of constructing the system and the effectiveness using machine learning confirmed by applying it to the box structure.

Vehicle horns must satisfy sound pressure level regulations in each country. Therefore, it is essential to optimize the horn location inside the front grille of the vehicle to maximize sound transmission through the grille opening and adhere to sound pressure level regulations. This study developed a computational method to determine optimal horn locations during early stages of vehicle development to reduce the number of trials during later stages. Therefore, an analytical model based on a one-dimensional standing-wave model was established using parameters obtained in the early stages. Subsequently, spectral changes were predicted for the transfer characteristics based on the horn location (i.e., from the horn to the exterior of the front grille). The analytical model was validated by comparing computed spectral images with those obtained experimentally from sample commercial vehicles. Image correlations between the analytical model and experimental results were greater than 80%. The high correlation suggests that the analytical model sufficiently represented the sound propagation phenomena, including transmission from the front grille. Finally, the model results established the optimal horn placement, which was validated using a commercial vehicle as a case study. The placement obtained by the proposed analytical model was in good agreement with that of the commercial vehicle.

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.

Computer Aided Engineering (CAE) has been successfully utilized in mechanical industries, but few CAE tools that include structural optimization can be utilized at the conceptual design phase, since the development of such tools has been based on continuum mechanics that limit the provision of useful design suggestions at this phase. In order to mitigate this problem, a new type of CAE based on classical structural mechanics, First Order Analysis (FOA), is proposed. In this paper, we present a topology optimization method that corresponds to FOA concepts. This optimization method is constructed, based on discrete and function-oriented elements such as frame, panel and spring elements, and sequential convex programming. In addition, examples are provided to show the utility of the methodology presented here for mechanical design engineers.

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.

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.

This paper discusses an automated method for designing modular components that can be shared within multiple structural products, such as automotive bodies for sibling vehicles. The method is an extension of the concept of decomposition-based assembly synthesis. A beam-based topology optimization method, originally developed for First Order Analysis (FOA) of the automotive body structures, is utilized in order to obtain the “base” structures subject to decomposition. It is expected that the method will facilitate the early decisions on module geometry in automotive body structures, by enhancing the capability of the FOA system. Several case studies with two-dimensional structures are reported to demonstrate the effectiveness of the proposed method. The results indicate that two structures optimized for a similar, but slightly different boundary loading conditions are successfully decomposed to contain a component that can be shared by the structures. Several Pareto optimal decompositions are presented to illustrate the trade-offs among multiple decomposition criteria, with different weights for each objective function.

In current automotive development, innovations to reduce development time and to use a virtual prototype have been numerous and progressive. Computer Aided Engineering (CAE) has played an important role in these innovations. CAE numerically estimates the performance of automobiles and proposes alternative ideas that lead to higher performance without building physical prototypes. However, current CAE can not usually be used at the initial design phase due to their difficult, and complex functions and characteristics. In this paper, we propose a new type of CAE, First Order Analysis (FOA). The basic ideas include: (1) graphic interfaces using Microsoft /Excel to achieve a product-oriented analysis, (2) use of mechanics of materials to provide useful information regarding structural mechanisms, and (3) a topology optimization method using function oriented elements. Also, some prototype software is presented to confirm the applicability of method presented here to the automotive designs.