Friction-Induced Limit Cycling in Flexible Rotor Systems: An Experimental Drill-String System

Friction-induced limit cycling deteriorates system performance in a wide variety of mechanical systems. In this paper, we study the way in which essential friction characteristics affect the occurrence and nature of friction-induced limit cycling in flexible rotor systems. This study is performed on the level of both numerical and experimental bifurcation analyses. Hereto, an experimental drill-string set-up is used. The synthesis of these numerical and experimental results confirms that friction-induced limit cycling is due to a subtle balance between a velocity weakening characteristic of the friction (Stribeck effect) at lower velocities and viscous friction at higher velocities. Moreover, it is shown how these essential friction characteristics depend on physical conditions such as temperature and normal forces in the frictional contact in the experimental set-up.