Research Article

Chaotic Vibration Analysis of the Bottom Rotating Drill String

Figure 7

Calculation of the largest Lyapunov exponent of the lateral vibration and longitudinal vibration and the effective expansion rate , of which the linear slope in dependence on is a robust estimate for the Largest Lyapunov exponent (using Tisean package [1], version 3.01).
429164.fig.007a
(a) Lateral vibration
429164.fig.007b
(b) Longitudinal vibration