# Research topics: Coupled systems, uncertainty quantification and propagation and stick-slip oscillators

**At LMSSC, Paris, July 17th 2018, 4.30 p.m.**

Roberta de Queiroz Lima

Assistant professor, Department of Mechanical Engineering, Pontifícia Universidade Católica (PUC), Rio de Janeiro, Brazil

In the talk, three research topics were discussed.

- Dynamics of coupled electromechanical systems and, a hypothesis that is usually found in the literature that deals with the subject. Apparently, the hypothesis seems nice since it simplifies the dynamics greatly. However, it leads to wrong results. The hypothesis decouples the system.
- Definition of what is and what is not uncertainty quantification and propagation. The objective was to clarify the concepts and to show, with simple examples, that several strategies found in literature called strategies to compute uncertainty quantification and propagation are not. They can lead to errors and misleadingness. The examples were chosen to be as simple as possible in order to highlight different problems that can arise when one uses these strategies.
- Stochastic dynamics of a stick-slip oscillator. The aim was to understand how is the dynamics of a dry friction oscillator from a stochastic point of view. Some of the questions are:

- when the sticks appear, and how long they last?
- fixed an observation period, how is the average process?
- how to characterize the uncertainty of the process?