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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.

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.

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.

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.