Seminar Details
2005-11-22 (14.00 pm) : Self-Excited Vibrations of Drilling Systems with Drag Bits, a consequence of a regenerative effect
At Auditoire Euler
Organized by Mathematical Engineering
Speaker :
Christophe Germay (ULg)
Abstract :
Self-excited stick-slip oscillations of a rotary drilling system with a
drag bit are commonly modeled by reducing the bit-rock interface to an equivalent
velocity weakening law. A novel attempt in the comprehension of the self-excited
nature of the vibrations was formulated recently. It relies on a detailed
description of both the cutting processes and frictional contact mobilized at
bit-rock interface. The nature of this boundary condition complicates greatly
the model and its analysis as the axial and torsional modes of vibrations are
coupled through the boundary conditions via a state-dependent delay (regenerative
effect) and a rate-independent discontinuous friction. Nevertheless, this new
approach offers new perspectives in the comprehension of the mechanisms responsible
for the self-excitation undergone by the drilling system.