THE FATIGUE PROPERTIES OF ELASTOMERS

Fatigue resistance in filled rubbers is largely dependent on the energy available to propagate a crack, but the influence of the stress concentration is undetermined in elastomeric fatigue. In metals fatigue,a stress concentration is virtually unaltered by cyclic loading. Rubber undergoes large reversible strains and it is argued that rubber components have less severe surface flaws when preloaded than in a stress free state. In fatigue, higher stress levels in the pre-stressed (pre-strained) material are thought to be partially compensated for by improvements in surface finish. It is expected that the size of flaws introduced during the manufacturing process, irrespective of whether the part is made by compression, injection or transfer moulding, can induce early failure of the specimen when it is under load. The fundamental question posed is ¿can surface treatments influence fatigue resistance?'' Reducing the size of a flaw has the potential to reduce concentration under load and thereby improve resistance. This book describes an investigation of the influence of surface treatments and surface finish on the fatigue properties of EPDM and Natural Rubbers.