INVESTIGATION ON TORSIONAL VIBRATION OF DRILL STRING IN CYLINDRICAL CAVITIES OF VERTICAL BORE-HOLE WITH LIQUID MEDIUM

The research work deals with the torsional vibration of a drill string in a vertical cylindrical cavity of a borehole with liquid medium. The mechanical interaction models of the drill string with viscous liquid are investigated, Also this paper describes the vibrations of the drill string bit with allowance made for viscous friction, the nonlinear deferential equation with partial derivatives is used. The oscillation scheme of torsional auto-vibration of homogeneous drill string in the form of oscillation pendulum is stated. It was found that the properties of the liquid medium in which the rotating column, lead to a small range of angular velocity value, which are generated during the self-oscillation