Stability Analysis of Drill Rods as Shells in the Gas Stream

In the paper steadiness of the compressed and twisted drill rod is examined. The rod is presented in the form of a circular cylindrical shell, which is circulated from the outer side by a supersonic stream of gas. The rod is affected by the uniformly distributed on its length axial force and the torque. The problem of stability is solved by means of reviewing of a small deviation from the periodic solution of the problem. Boundaries of instability zones of the mechanical system are defined with application of the method of harmonic balance.