Sensitivity of Spline Self-excited Vibration to Structure Parameters

Many aviation splines have to work in grease-lubricated or non-lubricated environments because of structural, weight and space restrictions. When a spline rotor system works at speeds above the critical speed, a poor lubrication or a specific misalignment will lead the spline in such a rotor experiencing self-excited vibration. In this paper, a constant stiffness and time-varying damping model is established for the spline coupling used in helicopter tail transmission shaft system. A multi-degree-of-freedom model for helicopter tail transmission shaft system is developed according to Timoshenko beam theory and lumped-mass method. The coupled differential equations are solved using Newmark-β method. According to the magnitude of low-frequency component, the self-excited vibration sensitivities to critical system parameters (i.e., spline tooth number, modulus, pressure angle and tooth width) are investigated for splines used in helicopter tail transmission shaft system. This study provides a reference for the mechanism research and suppression of the self-excited vibration of splines encountered in helicopter tail transmission shaft system.