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The understeer of vehicle is desired for the vehicle's handling performance, and the roll rate of rear suspension is one of the key characteristics to achieve the understeer performance. A proper roll rate of the rear suspension is required to assure a certain level of understeer. Generally, in the vehicle dynamic tuning process, several methods are available for improving understeer performance, e.g., changing the hard-points of suspensions, adjusting stiffness of bushings, etc. On the other hand, structure optimization of components can be used in some case to improve the performance. In this paper, the optimization method is applied to the twist beam of rear suspension. The change in local geometry by optimized design leads to appropriate adjustment of the roll rate. Finally the vehicle understeer performance reaches design target.

Stiffness is one of the key points for research and development of vehicle body in white (BIW). Fast and effective evaluation of stiffness is very important for reducing the time and cost of research and development. How to realize weight reduction with proper stiffness is also a focus point of automobile design. In general, commercial software is used to optimize the BIW design. But the optimization process is time consuming. Therefore a simple but effective tool for fast evaluation is desired. A method to evaluate stiffness with sensitivity coefficients of sheet metal thickness of body structure is proposed in this paper. The simple mathematical relation of the sensitivity coefficients, the thickness variation of sheet metals, and the stiffness of body structure is established. The stiffness can be evaluated quickly for various combination of sheet metal thickness without running large-scale simulation using commercial software.

Rubber bushing is an important connection component in vehicle suspensions. It plays an important role in vehicle performance. In the past years, the theories of rubber have been studied, and several forms of the strain energy potential, incompressible or almost incompressible, have been developed. But not all of these models are suitable for all kinds of applications. Therefore, when investigating the rubber bushing, it is necessary to find the effective constitutive equations. Two bushings with different shapes are studied. One is an ax-symmetric uniform bushing. The other one has additional two longitudinal holes. A process of parameter identification is conducted. The axial stiffness and radial stiffness of the bushing are tested and used as objectives. The parameters of constitutive equations are defined as design variables. The nonlinear analysis software ABAQUS and a multi-disciplinary optimization software OPTIMUS are used.

The minimum door closing speed is an important target in vehicle door design. Engineers need a proper method to evaluate the door closing speed during the design phase. Analytical approaches are presented to solve the difficult issues in analyzing the minimum door closing speed. First, the weather strip is simplified into a discrete model with several spring elements. This method does not need to use 3-D contact analysis for the weather strip and can save computing time with acceptable accuracy. Second, the minimum closing speed is solved by using the energy equation which needs one iteration only. The method has high efficiency and can be used to evaluate the door closing speed effectively during the design phase.

Rubber bushing is used in vehicle suspension systems and plays important roles as connection, mounting, or vibration isolation. To study rubber bushings, one method is to acquire parameters of the constitutive models of rubber from tests of material sample, and to obtain stiffness curves by simulation. Generally, the low-cost uni-axial tension or compression test is used for this method. But parameters from these uni-axial tests are not accurate enough and only part of the properties is represented. To get more accurate parameters, other costly tests and special equipments will be needed. Another method is to directly test stiffness of rubber bushing parts in six loading directions. The stiffness can also be approximated by using empirical formulas with dimensions of bushings. This method simplifies the bushing model and is limited. A new approach is proposed in this paper. First, radial and axial stiffness tests of rubber bushing are conducted and stiffness curves are acquired.

Anti-roll bar is a suspension component used at the front, rear, or at both ends of a car that reduces body roll by resisting any uneven vertical motion between the pair of wheels, to which it is connected. Modeling accuracy for anti-roll bar is very important for vehicle dynamics analysis because of large deformation induced by suspension motion. There are two modeling methods commonly used in multi-body dynamics software (ADAMS). One is a standard modeling method provided by Adams software, named nonlinear beam method. The other one is a three dimensional flexible modeling method through the interface provided by ADAMS and finite element software such as NASTRAN etc. In order to satisfy the requirements of vehicle dynamics performance, a lot of similar and repetitive modeling work must be done in automobile suspension development stage due to design changes, such as diameter of anti-roll bar, etc.

To assess the fatigue life of a knuckle more accurately by FEM approach, several types of modeling methodologies, including the component level method, the sub-system level method, and the system level method, used to simulate the knuckle stress/strain distribution are investigated. The simulation results of several load cases by these methods are analyzed. A practical approach for evaluating suspension knuckle at different design phases is proposed, which could be used to guide design and durability evaluation for knuckle.

A design procedure is developed to simulate the durability behavior of an electric wiper linkage mechanism subjected to operation cycles. The first stage determines the stress and strain levels that the linkage components are subjected to during the operation cycles. This requires the reaction loads at the joints of the wiper linkage. It is achieved by performing the mechanism dynamic analysis using multi-body dynamics software (MSC.ADMAS) together with a three dimensional transient finite element analysis (MSC.NASTRAN). Once the stress and strain of the wiper linkages are obtained during the operation cycle, the low cycle fatigue analysis is applied in the time domain. This analysis is based on strain-life curve, the Palmgreen-Miner’s rule, to compute the cumulative damage, the rain flow method for cycles counting, and the mean stress effect. Using the methodology presented in this paper, good correlation with laboratory test can be achieved.

Ten sets of mesh parameters are considered in building the model for aerodynamic numerical simulation of a CHERY sedan. It is found that, in comparison with the wind tunnel test data, the error in drag coefficient computed by using these meshes is less than 4%. Especially, in one case, the error is found within 1%. The CAE method discussed in this paper can be used to assist the design of vehicle aerodynamics.