Research Article

Nonlinear Model and Qualitative Analysis for Coupled Axial/Torsional Vibrations of Drill String

Figure 9

Period responses of the system ().
(a) Phase diagram of the axial modal
(b) Oscillogram of the axial modal
(c) Phase diagram of the torsional modal
(d) Oscillogram of the torsional modal
(e) Three-dimensional phase diagram
(f) Poincare section