A comparison of rubber stress relaxation models for conveyor belt indentation rolling resistance calculations

Rubber stress relaxation models are the main material input data for numerical and analytical conveyor belt indentation rolling resistance calculations. Stress relaxation data for rubbers, such as those used in the construction of conveyor belts, are difficult to measure directly due to their fast relaxation times and, as such, they are usually derived via a dynamic mechanical analysis; unfortunately, relaxation data for the strain levels reached in conveyor belting cannot be produced with typical dynamic mechanical analysis machines. This paper utilizes high strain level data produced on a high capacity dynamic mechanical analysis machine and compares the indentation rolling resistance predictions derived from the measured high strain relaxation moduli with other high strain relaxation moduli extrapolated from low strain level measurements that can be measured on dynamic mechanical analysers with smaller capacities. Jonker's equation and a two dimensional finite element analysis model are used to compare the different sets of relaxation moduli and these are compared with results from large scale indentation rolling resistance experiments.