http://popups.lib.uliege.be/2684-6500/index.php?id=55 Issues fr Thu, 01 Jul 2021 15:04:27 +0200 Wed, 06 May 2026 14:25:09 +0200 http://popups.lib.uliege.be/2684-6500/index.php?id=55 0 http://popups.lib.uliege.be/2684-6500/index.php?id=56 Coupled bending-torsion vibrations of a beam with a single cross-section axis of symmetry are mitigated by a two-degree-of-freedom (dof) tuned mass damper with a coupling analogous to that of the beam. By modal truncation a four-degree-of-freedom model is derived for tmd tuning. Because of the analogous tmd properties, a stiffness tuning formula identical to that for the classic tuned mass damper secures inverse relations between all four undamped natural frequencies. Expressions for the tmd damping are subsequently found by a numerical search, which maximizes the smallest of the four damping ratios, resulting in equal damping in three of the four modes. The two-dof coupled tmd is finally assessed by numerical root locus and frequency response analysis for a full flexible beam. Thu, 01 Jul 2021 15:06:54 +0200 http://popups.lib.uliege.be/2684-6500/index.php?id=56 http://popups.lib.uliege.be/2684-6500/index.php?id=63 This work aims at comparing the damping performances of two passive damping treatments based on piezoelectric or viscoelastic patches. The motivation for such a comparison stems from the fact that the two damping techniques have been developed fairly independently, and are rarely compared. First, the dynamic response of a simply-supported metallic plate is measured experimentally after being equipped with constrained viscoelastic patches or piezoelectric patches connected to an electrical network. In order to extend the comparison, a numerical model of the structure is set up and validated to evaluate the damping performances of both passive treatments under different configurations (for instance equal-mass and equal-thickness configurations). Finally, with regard to these experimental and numerical results, the advantages and the limitations in using viscoelastic or piezoelectric treatments are discussed. Tue, 14 Sep 2021 13:14:00 +0200 http://popups.lib.uliege.be/2684-6500/index.php?id=63 http://popups.lib.uliege.be/2684-6500/index.php?id=72 The study of contact is an engineering pursuit that spans multiple disciplines and scales. Structural dynamics, as well as aspects of nonlinear dynamics and vibrations, is concerned with contact in systems at the macroscale. At the microscale, tribology is concerned with the evolution of two surfaces in contact in terms of frictional and wear behavior. Between these two scales, solid mechanics investigates the development of stresses within two bodies due to contact through elasticity and plasticity solutions (amongst other methods). Lastly, contact research within material science investigates the interaction of grains and the evolution of a material's structure due to impact and other damaging events. These four fields, structural dynamics, solid mechanics, tribology, and material science, are traditionally separate even though they are each concerned with interfaces and the contact of two bodies. By integrating all four fields, new opportunities for advancing the understanding of contact emerge. In this paper, open challenges and potential paths forward for future directions in contact-based research is discussed. Mon, 13 Dec 2021 17:27:15 +0100 http://popups.lib.uliege.be/2684-6500/index.php?id=72 http://popups.lib.uliege.be/2684-6500/index.php?id=84 The aim of this paper is to provide an introduction to using normal form transformations for linear and nonlinear structural dynamics examples. Starting with linear single-degree-of-freedom systems, a series of examples are presented that eventually lead to the analysis of a system of two coupled nonlinear oscillators. A key part of normal form transformations are the associated coordinate transformations.This review includes topics such as Jordan normal form and modal transformations for linear systems, while for nonlinear systems, near-identity transformations are discussed in detail. For nonlinear oscillators, the classical methods of Poincaré and Birkhoff are covered, alongside more recent approaches to normal form transformations. Other important topics such as nonlinear resonance, bifurcations, frequency detuning and the inclusion of damping are demonstrated using examples. Furthermore, the connection between normal form transformations and Lie series is described for both first and second-order differential equations. The use of normal form transformations to compute backbone curves is described along with an explanation of the relationship to nonlinear normal modes. Lastly, conclusions and possible future directions for research are given. Mon, 17 Jan 2022 13:50:12 +0100 http://popups.lib.uliege.be/2684-6500/index.php?id=84 http://popups.lib.uliege.be/2684-6500/index.php?id=96 This paper describes a hybrid approach for modeling nonlinear vibrations and determining essential (normal form) coefficients that govern a reduced-order model of a structure. Incorporating both computational and analytical tools, this blended method is demonstrated by considering a micro-electro-mechanical vibrating gyroscopic rate sensor that is actuated by segmented DC electrodes. Two characterization methods are expatiated, where one is more favorable in computational tools and the other can be used in experiments. Using the reduced model, it is shown that tuning the nonuniform DC bias results in favorable changes in Duffing and mode-coupling nonlinearities which can improve the gyroscope angular rate sensitivity by two orders of magnitude. Wed, 02 Mar 2022 13:01:33 +0100 http://popups.lib.uliege.be/2684-6500/index.php?id=96 http://popups.lib.uliege.be/2684-6500/index.php?id=107 In this article, an overview of Bayesian methods for sequential simulation from posterior distributions of nonlinear and non-Gaussian dynamic systems is presented. The focus is mainly laid on sequential Monte Carlo methods, which are based on particle representations of probability densities and can be seamlessly generalized to any state-space representation. Within this context, a unified framework of the various Particle Filter (PF) alternatives is presented for the solution of state, state-parameter and input-state-parameter estimation problems on the basis of sparse measurements. The algorithmic steps of each filter are thoroughly presented and a simple illustrative example is utilized for the inference of i) unobserved states, ii) unknown system parameters and iii) unmeasured driving inputs. Mon, 21 Mar 2022 13:22:10 +0100 http://popups.lib.uliege.be/2684-6500/index.php?id=107