ABSTRACT
ABSTRACT: Elastomeric parts used in the automotive industry can experience irreversible changes of the materials’ properties when exposed to elevated temperatures. This phenomenon is known as thermo-oxidative ageing and has a large influence on the fatigue behavior of natural rubber. To determine the change in the fatigue life due to pre-ageing, an ageing campaign in which the samples are aged with a constant temperature over a certain time, is usually performed. However, in practice, the ageing process must be considered as a discontinuous process as, for instance, pauses may occur that interrupt or decelerate the ageing process. To date, only a few studies are available that investigate the influence of discontinuous ageing on the mechanical fatigue behavior, e.g. (Charrier et al. 2012). For a reliable lifetime prediction of rubber parts, it is however crucial to estimate the error that occurs when continuous pre-ageing is used during the ageing campaign. The goal of this experimental study is to examine the differences between continuous and discontinuous thermo-oxidative ageing with regard to the fatigue life of natural rubber. Three types of discontinuous pre-ageing are performed, i.e. intermittent ageing, multiple succeeding ageing-temperatures and -resting periods after continuous ageing. In comparison with conventionally pre-aged samples, considerable differences regarding the fatigue life become apparent.
