Optimum Damping in a Randomly Excited Non-Linear Suspension

Analogue computer studies of an automobile suspension on a simulated random road show that optimum ride and road holding can be achieved with linear damping for all magnitudes of road roughness. Unsymmetrical damping, however, provides better isolation from large bumps and obstacles at the expense of only very moderate increases in the mean-squared values for random inputs. Optimum values for the ratio of bump to rebound damping rates are obtained by use of an integral-square criterion. For a linear system the effects of the seat dynamics and road power spectrum characteristics are illustrated using the results of a digital computer program. The influence of the non-linearities on mean-square values is analysed theoretically and the statistical describing function method applied.

Computer-Aided Design Applied to a Model of a Chassis Type Structure Using Finite Element Techniques

The finite element technique has been used for the examination of a chassis-type structure. A computer program was developed to predict the static and dynamic behaviour of frames. The program is quite general but its use has been restricted to structures consisting of beam elements only. A scale model of a production car chassis was made in perspex. Nodal displacements of the model, in bending and torsion, natural frequencies and corresponding mode shapes were predicted by the computer program and confirmed experimentally in the laboratory. Several coarser idealizations of the model were examined to study the effect on the accuracy of predictions and the computation time.