Study on the stiffness loss and its affecting factors of the spline joint used in rotor systems

The spline joint is a kind of widely used joint structures in the rotor system. Its discontinuous mechanical characteristics results from the contact surface. The surface will slide and deform when the spool deforms. As a consequence, the joint stiffness is always smaller than that of the integral configuration. This affects the rotor stiffness distribution and the rotor dynamics further. The objective of this study is to investigate the stiffness mechanical characteristics of the spline joint and their affecting factors. Based on the characteristics of structure and mechanical state, a spline joint stiffness mechanical model is built to explain the stiffness loss and its affecting factors. The cylindrical coordinate contact model is used to describe the contact of the cylindrical centering surface. And then a spline joint simulation model, taking the characteristics of the contact into account, is built by the nonlinear finite element method. At last, in the static stiffness experiment, the displacement of the spline joints is measured in different assembling and loading conditions. The results show that, the linear and angular stiffness loss of spline joint is significant and has a close relationship with the load and assembling condition. The study shows the effectiveness in controlling the mechanical properties of the rotor with spline joints by carefully adjusting structural design, load and assembling parameters.