Analysis of Friction-Induced Limit Cycling in an Experimental Drill-String System

In this paper, we aim for an improved understanding of the causes for torsional vibrations that appear in rotary drilling systems used for the exploration of oil and gas. For this purpose, an experimental drill-string setup is considered. In that system, torsional vibrations with and without stick-slip are observed in steady state. In order to obtain a predictive model, a discontinuous static friction model is proposed. The steady-state behavior of the drill-string system is analyzed both numerically and experimentally. A comparison of numerical and experimental bifurcation diagrams indicates the predictive quality of the model. Moreover, specific friction model characteristics can be linked to the existence of torsional vibrations with and without stick-slip.