The dynamics of drill strings, which are long structures used in drilling operations, are explored numerically and experimentally within this article. A reduced-order distributed parameter model that allows for coupled bending and torsional motions is presented along with forces that take into account interactions between the drill string and the wellbore. Further, a scaled experimental apparatus is presented along with results. Both experimental results and model predictions show backward whirling. Stick-slip interactions are investigated numerically, and the simulation results are seen to be in good agreement with experimental observations. These results could prove useful when designing control schemes for mitigating undesirable torsional and bending motions.

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