Stability of a multi-body driveshaft system excited through U-joints

The disk-shaft system is a power transmission system with several industrial applications. The shafts, depending on the mechanism application, can be connected by U-joints through different rotating axes. In spite of the many advantages, these joints transform a constant rotating speed into a variable output one. Therefore, the multi-body system is self-excited that lead to dynamic instability. Here, a driveline system including three elastic shafts, which carry three disks, is considered. The oscillating behavior and resonance phenomenon of this fluctuating mechanism are investigated qualitatively and quantitatively. The angle of joints, damping and stiffness effects are the major topics of the present contribution. Eventually, dynamic stability diagrams are obtained by using a reliable and exact method based on the Floquet theory. It can be found that variations of the first U-joint angle and the intermediate shaft characteristics have greater impact on the machine instability. It is revealed how the stability of the system can be achieved by changing the geometry, shaft damping and stiffness, which should be considered in design and practical applications.