ABSTRACT
The fatigue life of rubber components is believed to be determined by the development and growth of cracks from small pre-existing flaws, either at the rubber surface, at the bond line in the case of rubber-metal bonded components, or within the bulk material. According to fracture mechanics, the rate at which the flaws grow is governed by the energy release rate. This chapter presents Finite Element (FE) calculations of energy release rates for small "flaws" in a variety of representative situations, including surface and interior cracks, and finite strains. The results are discussed in the context of classical Linear Elastic Fracture Mechanics (LEFM) solutions. It is concluded that the energy release rate can be calculated with reasonable accuracy from the stress state at the point of interest. An attempt is made to empirically modify Sack's equation for finite strain effects, but difficulties remain when there is a significant hydrostatic pressure.
