ORBi Open Repository and Bibliography
In may 2007, the ULg's Administrative Board (joined in June 2007 by the FUSAGx) decided to create an institutional repository and defined a strong institutional self-archiving policy to increase the visibility, accessibility and impact of the University's publications (Board's decision).
This decision led to the official launch, in November 2008, of the ORBi platform including both the Academic Bibliography and the Institutional Repository of the Wallonia-Europe University Academy.
Testing of a Spacecraft Structure with Non-Smooth Nonlinearities - Renson, Ludovic; Noël, Jean-Philippe; Kerschen, Gaëtan
The dynamics of the SmallSat, a real-life spacecraft possessing a complex isolation device with multiple nonsmooth nonlinearities is investigated. Experiments show that nonlinearities induce modal interactions between modes with non-commensurate linear frequencies. A model of the structure with a simplified description of the nonlinear connections is first built using techniques available in industry. Numerical continuation is then exploited to compute nonlinear normal modes and uncover interaction phenomena that can jeopardize the structural integrity.
Rapport Final, Projet BLISK, Convention RW 6247 : BLaded dISK - Lecomte-Beckers, Jacqueline; Paydas, Hakan
L’unité MMS de l’ULg s’est concentrée dans le cadre de ce projet sur les aspects
métallurgiques des composants produits de manière à garantir dès le départ leur qualité et
ainsi adapter les paramètres de fabrication. D’autre part, elle a également étudié les
relations microstructures – propriétés mécaniques et s’est occupée de la caractérisation
mécanique et thermophysique des composants soudés par friction et claddés dont la structure a été
Bridging the gap between Nonlinear Normal Modes and Modal Derivatives - Sombroek, Cees; Renson, Ludovic; Tiso, Paolo; Kerschen, Gaëtan
Nonlinear Normal Modes (NNMs) have a clear conceptual relation to the classical linear normal modes (LNMs), yet they offer a solid theoretical framework for interpreting a wide class of non-linear dynamical phenomena with no linear counterpart. The main difficulty associated with NNMs is that their calculation for large-scale models is expensive, particularly for distributed nonlinearities. Repeated direct time integrations need to be carried out together with extensive sensitivity analysis to reproduce the frequency-energy dependence of the modes of interest.
In the present paper, NNMs are computed from a reduced model obtained using a quadratic transformation comprising LNMs and Modal Derivatives (MDs)....
On the Use of Principal Component Analysis for Parameter Identification and Damage Detection in Structures - Golinval, Jean-Claude
Modal analysis is used extensively for understanding the dynamic behaviour of structures as well as for structural health monitoring or damage detection based on output-only measurements. In this presentation, a different approach based on principal component analysis is considered.
Principal component analysis (PCA), also called proper orthogonal decomposition (POD), is a multi-variate statistical method that aims at obtaining a compact representation of the data. In the present paper, PCA (POD) is used for three purposes, namely damage detection, structural health monitoring and identification of nonlinear parameters.
The key idea of PCA is to reduce a large number of measured data to a...
Experimental demonstration of a 3D-printed nonlinear tuned vibration absorber - Grappasonni, Chiara; Habib, Giuseppe; Detroux, Thibaut; Kerschen, Gaëtan
Engineering structures are designed to be lighter and more flexible, hence reducing the extent of application of linear dynamic models. Concurrently, vibration mitigation is required for enhancing the performance, comfort or safety in real-life applications. Passive linear vibration absorbers are purpose-built, often designed using Den Hartog's equal-peak strategy. However, nonlinear systems are known to exhibit frequency-energy-dependent oscillations which linear absorbers cannot effectively damp out. In this context, the paper introduces a new nonlinear tuned vibration absorber (NLTVA) whose nonlinear functional form is tailored according to the frequency-energy dependence of the nonlinear primary structure. The NLTVA design aims at ensuring equal...
Experimental nonlinear identification of an aircraft with bolted connections - De Filippis, Giovanni; Noël, Jean-Philippe; Kerschen, Gaëtan; Soria, Leonardo; Stephan, Cyrille
Aircraft structures are known to be prone to nonlinear phenomena, especially as they constantly become lighter and hence more flexible. One specific challenge that is regularly encountered is the modeling of the mounting interfaces between aircraft subcomponents. Indeed, for large amplitudes of vibration, such interfaces may loosen and, in turn, trigger complex mechanisms such as friction and clearances. In this context, the present work intends to investigate the nonlinear dynamics of the Morane–Saulnier Paris aircraft, accessible at ONERA. This aircraft possesses multiple bolted connections between two external fuel tanks and wing tips. The objective of the paper is specifically to...
Experimental modal analysis of nonlinear structures using broadband data - Noël, Jean-Philippe; Renson, Ludovic; Grappasonni, Chiara; Kerschen, Gaëtan
The objective of the present paper is to develop a rigorous identification methodology of nonlinear normal modes (NNMs) of engineering structures. This is achieved by processing experimental measurements collected under broadband forcing. The use of such a type of forcing signal allows to excite multiple NNMs simultaneously and, in turn, to save testing time. A two-step methodology integrating nonlinear system identification and numerical continuation of periodic solutions is proposed for the extraction of the individual NNMs from broadband input and output data. It is demonstrated using a numerical cantilever beam possessing a cubic nonlinearity at its free end. The proposed...
The Harmonic Balance Method for Bifurcation Analysis of Nonlinear Mechanical Systems - Detroux, Thibaut; Renson, Ludovic; Masset, Luc; Kerschen, Gaëtan
Because nowadays structural engineers are willing to use or at least understand nonlinearities instead of simply avoiding them, there is a need for numerical tools performing analysis of nonlinear large-scale structures. Among these techniques, the harmonic balance (HB) method is certainly one of the most commonly used to study finite element models with reasonably complex nonlinearities. However, in its classical formulation the HB method is limited to the approximation of periodic solutions. For this reason, the present paper proposes to extend the method to the detection and tracking of codimension-1 bifurcations in the system parameters space. As an application, the...