ABSTRACT
This chapter presents effective engineering formula for torsion stiffness of a long rubber bush in the frequency domain including amplitude dependence. The rubber is assumed to be homogeneous, iso-tropic and incompressible. In order to obtain the complex value of the equivalent shear modulus to be inserted into the dynamic stiffness equation, a rubber model is applied to the average strain. The effect of inhomogeneous amplitude dependence due to the variation of the strain value along the rubber configuration inside the bushing is avoided using an average strain. The frequency domain analysis and the average strain approximation make possible to apply the linear theory of elasticity in order to find the relation between displacement components and strain state. It's important to highlight the fact that working with this average strain, non-linearities due to amplitude dependence are avoided, which always simplify the resolution of the problem and save time in calculations.
