Dynamic Torsional Stiffness of Natural Rubber in Shear Couplings

Flexible couplings are used to reduce torsional vibration and noise in drivelines, effectively isolating the prime mover from the driven equipment. The critical dynamic behavior is characterized by the first torsional mode of the system and the dynamic stiffness of the coupling is the primary control for adjusting this natural frequency. The work presented here was undertaken to capture the dynamic torsional stiffness of natural rubber in shear couplings as a function of amplitude, preload, frequency, and rotational speed. This work included physical testing and the development of an analytical model. The analytical model was used to predict the hysteresis response, since the slope along the long axis of a hysteresis loop provides the dynamic torsional stiffness of a coupling. There was a close match between the simulation and measured results. The amplitude has a remarkable influence of the dynamic stiffness of natural rubber in shear couplings. In particular, it was found that stiffness decreases with increasing amplitude. In addition, the influence of varying dynamic stiffness of a flexible coupling on the torsional response of a system under variable loading conditions was investigated. The results of a torsional vibration simulation were compared to measured data, and reasonably good agreement was obtained.