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Technical Paper

A Hybrid Road Loads Prediction Method with Full Vehicle Dynamic Simulation

A hybrid approach to predict road-induced loads in vehicle structures is presented. The technique involves full vehicle dynamic simulation using measured wheel forces, absolute wheel vertical displacements, and steering angle as input. The wheel vertical displacement is derived from the measured wheel acceleration. This approach avoids the use of tire-road interface modeling. It also improves the conventional loads measuring process with minimum instrumentation and data acquisition. Existing load data from a test vehicle is used to validate this approach. Computed component loads show good agreement with measurements.
Technical Paper

A New Tire Model for Vehicle NVH Analysis

Since road roughness is an important source of vehicle vibration, a system model for NVH analysis requires a tire model which accurately predicts spindle response to road input. Most tire models currently used in the auto industry do not meet this requirement, because they are based on static stiffness of the tire and do not produce realistic response to input at the patch. This paper investigates a new modal tire model with patch input capability as a component within a vehicle system model. Comparisons are also presented between the behavior of the new tire model and a conventional spring model. To validate the performance of the tire model for NVH analysis, simulated vehicle responses to bump input are compared to chassis roll test results. Good correlation between the model prediction and the chassis roll measurements is observed.
Technical Paper

On the Determination of Strain Energy Functions of Rubbers

Methodology of determining coefficients of material strain energy functions of rubbers from experimental measurements of homogeneous deformations is examined within the scope of the 3rd order deformation theory [3]. Closed-form solutions of most frequently employed material testing deformations - simple tensile, pure shear and equal bi-axial deformations - are examined to reveal the shortcomings of using any one deformation in characterizing the strain energy function, In order to obtain a more representative material strain energy function, employment of more than one homogenous deformation is recommended along with improved material sampling. In situations, however, where data from simple-tensile deformation alone are available a set of constraints on the coefficients have been derived that improves the extrapolation characteristics of the fitted function.
Technical Paper

Finite Element Analysis of Viscoelastic Elastomeric Structures Vibrating about Non-Linear Statically Stressed Configurations

This paper concerns the finite element method as applied to the analysis of small oscillations about the non-linear equilibrium position in elastomeric components. The capability, which was developed at Ford, has been implemented in the general-purpose finite element program, MARC. The material behavior is treated by use of a modified form of the constitutive equations derived by Lianis [Proc. Fourth International Congress on Rheology, Pt. 2, 109 (1965)] using the finite linear viscoelasticity theory of Coleman and Noll [Rev. Mod. Phys., 33 239 (1961)]. In order to establish numerical accuracy, program predictions are compared with a closed form solution for the torsional and axial vibrations in a cylinder under axial and twisting pre-loads: differences between the finite element solutions and exact results are less than two (2) percent.