The shape factor must be taken into account when designing rubber mountings for compression loads. The shape factor is understood to be the ratio of the loaded area to the force free area. This is due to the restricted transverse expansion and thus the variable modulus of elasticity, E, of the incompressible rubber material.
The shearing modulus G represents the only material constant of rubber and is specified for each compound in relation to Shore hardness. Therefore, the spring characteristic is linear with parallel shearing stresses. This effect must be accounted for specifically if there are shearing deformations at higher precompression.
|Anti-vibration mountings are often mounted at angles. A bridging connection between them adds stability together with a corresponding increase in the vertical deflection.
Where the rubber-to-metal elements are subjected to tension, peak stresses occur at the edges of the bond. If parts are oxidised, their serviceability may be destroyed due to the notch sensitivity of rubber. Therefore, tensile stresses should be avoided.