In this letter, non-linearity and energy localization are experimentally tuned in an electromagnetic vibration energy harvester in order to enhance its output performances. The non-linear device consists of two moving magnets guided by elastic beams and coupled by a repulsive magnetic force. The mechanical non-linearity is introduced by considering large displacements of the beams and the energy localization is achieved by mistuning the mass of one of the moving magnets. The critical load resistance is determined experimentally in order to tune the non-linearity level and to drive the harvester beyond its critical amplitude. Consequently, the performances of the device, in terms of harvested power only from the perturbed dof oscillator and frequency bandwidth, are enhanced respectively up to 19.4% and 116% compared to the performances of the non-linear periodic system.

In this work a reliability based optimization (RBO) strategy of Tuned Mass Damper (TMD) parameters is presented. The strategy is based on an energetic approach. The strategy consists to optimize the TMD parameters so that we minimize the failure probability (objective function) characterized by the exceedence of the power dissipated in the primary structure of a certain threshold value during some interval time. The evaluation of the objective function is carried out using the classical Rice’s formula. The strategy is, firstly, applied to linear single-degree of freedom (SDOF) system, subjected to seismic motion, and then extended to linear multi-degree of freedom (MDOF) system. The use of the Rice’s formula requires the knowledge of the joint probability density function (PDF) of the considered processes; to this end, exact expression of the joint PDF is presented for the SDOF system and an approximation is presented for the evaluation of the failure probabilities for the MDOF system. By making use of the obtained joint PDF, for the SDOF system, as the a priori joint PDF, the approximation of the joint PDF, for the MDOF system, has been performed using the Minimum cross-entropy method (MinxEnt). To highlight the good effectiveness of the proposed strategy, a ten-story shear building, subjected to different earthquakes, is considered. The obtained results are compared with other from literature, and it has been shown the superiority of the proposed strategy.

The modal parameters of a structure that is estimated from ambient vibration measurements are always subject to bias and variance errors. Accordingly the concept of the stabilization diagram is introduced to help users identify the correct model. One of the most important problems using this diagram is the appearance of spurious modes that should be discriminated to simplify modes selections. This study presents a new stabilization criterion obtained through a novel numerical implementation of the stabilization diagram and the discussion of model validation employing the power spectral density. As an application, an aircraft skeleton is used.