Reducing critical effects of torsional vibrations induced by PDC bits during rock destruction

Torsional Vibrations of Nonhomogeneous

ABSTRACT. This paper is concerned with the torsional vibrations of a nonhomogeneous magnetostrictive elastic cylinder. The cylinder is subjected to the action of a circumferential magnetic field produced by an axial current of constant density and the deformation of a magnetostrictive cylinder is produced by a constant longitudinal magnetic field. The frequency equation is determined, and the d...

Development of Pdc Bits for Downhole Motors

Axial and Torsional Free Vibrations of Elastic Nano-Beams by Stress-Driven Two-Phase Elasticity

Size-dependent longitudinal and torsional vibrations of nano-beams are examined by two-phase mixture integral elasticity. A new and efficient elastodynamic model is conceived by convexly combining the local phase with strain- and stress-driven purely nonlocal phases. The proposed stress-driven nonlocal integral mixture leads to well-posed structural problems for any value of the scale parameter...

Power Electronic Devices for Damping Torsional Vibrations

Torsional vibrations and resonance problems with synchronous machines are most frequently encountered in rotor systems with long shafts and large inertias constituting a weakly damped mechanical resonator which exhibits a low resonance frequency. It is impossible to obtain a effective mechanical damping for these torsional vibrations, but by using a power electronics device and an inductive or ...

Vibrations induced by trains

This work describes a set of research studies that were made with the intent of studying vibrations created by the circulation of trains. In the last decades, the development of high-speed trains emphasized the need to closely monitor this phenomenon. The purpose of this study is to provide a state-of-the-art about data acquisition process. It also presents a new experience, including important...