Quenching of Self-Excited Vibrations by Impact Damper

This study deals with the quenching problem of self-excited vibrations by using an impact damper composed of a ball and impact walls. First, the quenching problem of a single-degree-of-freedom self-excited system was treated. The Runge-Kutta-Gill method with variable time division is applied to the numerical analysis of a Rayleigh's type self-excited system. The solutions obtained from this method are divided into two main categories; periodic solutions and chaos. Further, two types of chaos are found, namely, chaos after period doubling bifurcation and that of the intermittent type. An optimum approach for quenching the self-excited vibration was discussed. As a result, it was clarified that for the optimum design of the impact damper there existed a certain relation between the coefficient of restitution and clearance. It was found that the condition for vibration quenching was located at the edge of chaos. This quenching of self-excited vibration was a unique example of chaos utilization in the problem of vibration quenching. Experiments were performed to quench vortex-induced vibration by using the impact damper. The experimental results agreed well, qualitatively, with those from the numerical analysis. Secondly, since a wide quenching range of the impact damper was confirmed in the above-mentioned system, the problem of quenching vortex-induced vibration of a two-degree-of-freedom system using this range was treated. From the experiment and numerical analysis, it turns out that the vortex-induced vibrations of the first and the second modes are quenched by a single impact damper. It was confirmed that there existed optimum parameters for the quenching vibration, and this quenching of vortex-induced vibration employed chaos utilization.