Self-excited oscillations in drilling systems

In this work, we explored the interaction of multi-mode deformation and stick-slip vibrations in drilling systems. Stick-slip vibrations are self-excited oscillations that are associated with regenerative instability in the system, and need to be mitigated in order to ensure efficient drilling. However, the analysis of stick-slip vibrations in drilling are typically limited to lumped spring-mass models, and there is still a need to understand how multi-mode deformations of the drill string affect stick-slip dynamics, and their consequent effect on mitigation mechanisms.

Nonlinear waves in periodic structures

In this work, we studied the dynamic response of nonlinear mechanical metamaterials subjected to harmonic excitations (wave propagation), using a combination of semi-analytical perturbation analysis, finite element numerical simulations, and experimental verification using 3-D Scanning Laser Doppler Vibrometry. Specifically, we investigated the manifestation of higher-harmonic generation in these structures, which results in the activation of deformation modes corresponding to high-frequency excitation even for low-frequency harmonic forcing. This ability to access higher-order deformation mechanisms provides the ability to augment the response with complementary functionalities inaccessible in linear systems, and endows the structure with the capability to adaptively respond to external excitations.

Finite element modeling of microsystems

To be updated

Free vibrations of rotating beams

To be updated