Dynamic Analysis of Sliding Friction in Rotorcraft Geared Systems

Abstract

Abstract : This comprehensive study has examined the key effects of sliding friction in spur and helical gear dynamic models, vibro-acoustic sources and geared system responses. First, many dynamic phenomena that emerge due to the interactions between time-varying mesh stiffness, sliding friction and/or surface finish are successfully formulated. Second, new multi-degree-of-freedom models considering both torsional and translational dynamics of spur and helical gear pairs have been developed. These include time-varying mesh stiffness, sliding friction excitation and shaft/bearing compliances. Line-of-action and off-line-of-action motion predictions, based on the lumped gear dynamic models, match well with a benchmark finite element/contact mechanics code. Third, new mathematical models have been proposed to examine structure-borne and air-borne noise that should arise due to surface asperities as a function of operating speed and surface finish. Fourth, mobility type frequency response studies of the system vibro-acoustic characteristics provide new insights into dynamic forces at the bearings and sound radiation. Fifth, two sets of experimental studies at ARL/NASA Glenn were conducted. Gear noise source and lumped system models match well with experiments on ARL/NASA spur gears. Finally, a set of helical gears has been designed that clearly isolate the effects of sliding friction. Suggestions for future research are included.