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In the primary design step, a well established design guide would be useful for vehicle body design engineers, to avoid trial and error for the desired design. In this paper, an integrated design program B-SOPT is presented. The B-SOPT is composed of vibration analysis, section property analysis, and section optimization. Vibration analysis procedure is necessary to evaluate the target frequency constraints for optimization. B.I.W. vibration analysis model can be generated and joint stiffness can also be generated automatically by explicit formula derived from using RSM (Response surface method) in the B-SOPT. The presented design program provides a systematic design guide for the vehicle side body structure. For design engineers, graphic user interface environment is developed with the visual C++ program. A B.I.W design example is given to demonstrate the design procedure using the B-SOPT program.

This paper presents a new method for the 5mph vehicle's bumper section shape optimization. The Intermediate Response Surface Modeling (IRSM) technique is newly introduced to approximate the nonlinear force-deflection curves. This can avoid the excessive 3D nonlinear FEM analysis during the optimization process. Then, the accuracy of the IRSM models is examined by comparing their results with those of the 3D nonlinear FEM. Finally it is shown that the proposed approach is effective to design the 5mph vehicle bumper section.

In this paper, resonance durability analysis is performed for the fatigue life assessment of suspension component considering the dynamic effect of vehicle system. In the resonance durability analysis, the frequency response data and the dynamic load data of frequency domain are used. The multi-body dynamic analysis, finite element analysis and fatigue life prediction method are applied for the resonance durability analysis. To obtain the dynamic load history, the computer simulations running over typical pothole and Belgian road are carried out respectively by utilizing multi-body dynamic vehicle model. The durability estimation for the rear suspension system of the small-sized passenger car is performed by using the resonance durability analysis technique, and the estimation result is compared with the quasi-static durability analysis result. The study shows that the fatigue life considering the resonance frequency of vehicle system can be effectively estimated in early design stage.

Design for six sigma (DFSS) with sigma based robust design will have a major influence on the future design, if it is applied during the conceptual design phase or design change phase. DFSS will result in more improved but less expensive quality products. This paper presents the implementation of DFSS for robust design of a brake judder of heavy-duty trucks. The problem of brake judder is typically caused by quality defects in manufacturing. However this quality problem can't be controlled deterministically and requires a design considering the uncertainty. In this paper sigma based robust design methodology is applied to improve the brake judder quality problem at the last step of DFSS. Results between conventional deterministic optimization and the proposed sigma based robust design are compared. The robust design by DFSS shows that the manufacturing cost may increase as the quality level increase.

In this paper, an optimization technique for thin walled beams of vehicle body structure is proposed. Stiffness of thin walled beam structure is characterized by the thickness and typical section shape of the beam structure. Approximate functions for the section properties such as area, area moment of inertia, and torsional constant are derived by using the response surface method. The approximate functions can be used for the optimal design of the vehicle body that consists of complicated thin walled beams. A passenger car body structure is optimized to demonstrate the proposed technique.

Low frequency vibration characteristics of a vehicle are mainly influenced by the stiffnesses of the beam type structures such as pillars and rockers, and by the stiffnesses of the joint structures, at which several beam structures are jointed together. In the early design stage of the car body structure a simple FE model has been used, in which joints are modeled as linear springs to represent the stiffnesses of the joint structures. In this paper a new modeling technique for the joint structure is presented using an equivalent beam, instead of using a spring. The modeling technique proposed is utilized to design optimal joint structures that meet the required vibration performance of the total vehicle structure.

This paper discusses the flexible foundation effects on dynamic responses of engine-mount systems using computer simulation techniques. Equations of motion for the engine-mount systems including flexible foundations are derived. The dynamic flexibility of the foundation is represented by modal information from finite element analysis or experimental modal analysis. Solving the derived equations, natural frequencies and forced vibration responses of an engine-mount system can be simulated accurately. It is shown that the flexibility of the supporting structure may have a significant effect on the idle shake vibration and mounting forces transmitted from the engine to the structure. The computational method developed is applied to an example engine-mount system and the results are compared to those of an associated experiment.

In this paper, joint modelling techniques are investigated in a box beam T-joint, which may be viewed as a simplified model of typical vehicle body joints. For low-frequency vibration analysis, joints are typically modelled by torsional spring elements and the importance of reasonable spring rates has been noted in many investigations. The effects of the joint branch lengths on the spring rates are investigated and it is shown that converging results are obtained only with proper branch lengths. We also discuss some facts to consider for estimating consistently the spring rates when the branches of T-joints meet at oblique angles. Finally, a possibility of using short beam elements instead of conventional spring elements to account for the joint flexibility is examined. The consequence of short beam modelling is that the sensitivity analysis on the natural frequencies with respect to the joint flexibility can be easily performed.

This paper discusses the flexible chassis effects on dynamic response of engine-mount systems using computer simulation techniques. Equations of motion for the engine-mount systems including flexible foundations are derived. The dynamic flexibility of the chassis is represented by modal information from finite element analysis or experimental modal tests. Solving the derived equations, natural frequencies and forced vibration response of an engine-mount system can be simulated accurately. It is shown that the flexibility of the engine-mount frame structure may have a significant impact on the idle shake vibration and mounting forces transmitted from the engine to the structure. The computational method developed is applied to an example engine-mount system and the results are compared to those of an associated experiment.