ABSTRACT
The aim of this study is to base the analysis on the dissipated energy, which seems a very promising fatigue criterion (Mars and Fatemi 2004, Le Saux et al. 2010, Ayoub et al. 2012). In a former paper (Le Saux et al. 2011) a so called heat build-up protocol has been developed in which the temperature fields are converted into fields of dissipated energy (Marco et al. 2014, Masquelier et al. 2015). The deterministic Wöhler curve can then predicted throughout an energy based criterion using only one sample, within less than one day (Le Saux et al. 2011). This study presents two sections. In the first one, the method is challenged on many industrial compounds based on filled Natural Rubber (NR), varying the amount and types of Carbon Blacks (CB). In the second part an energetic criterion, using a single parameter is suggested, that couples the evolution of the defects population along the
1 INTRODUCTION
The industrial development of elastomeric compounds optimized for fatigue applications remains a very challenging task. This is induced by the combination of a very wide panel of variable parameters (ingredients, processing parameters during mixing, injection and curing) to heavy test campaigns, requiring numerous samples and long durations because low frequency is required to avoid any coupling to heat build up. Speeding up the fatigue characterization is therefore a crucial industrial need to assess quickly newly developed compounds. This is also a precious tool to enlarge the scope of the parameters tested (environment, mechanical loading, process parameters) in order to improve the understanding of the behaviour of these materials under fatigue solicitations. The understanding and prediction of the fatigue behaviour involve both the description of the thermomechanical response and of the microstructure (Marco et al. 2013). These aspects are usually considered separately macroscopic thermo-mechanic criteria (Mars and Fatemi, 2004), and microscopic observations of the defects population (LegorjuJago 2012, Huneau et al. 2013, Le Saux et al. 2011)
fatigue cycles, obtained from a wide campaign of interrupted fatigue tests, to the dissipation curves. This last case is not focusing anymore on speeding the characterization but on understanding the energetic contribution of fatigue defects and illustrating the strong physical meaning of an approach based on dissipated energy.
