Damping material characterization and modeling: an industrial case-study

in International Design Engineering Technical Conferences & Computers and Information in Engineering Conference (IDETC/CIE 2009), San Diego, 2009 (2009, August)

Turbojet engines contain potential nonlinearity sources such as geometric nonlinearities due to the slenderness and the length of modern blades, contacts between the blades and the shrouds, friction in ... [more ▼]

Turbojet engines contain potential nonlinearity sources such as geometric nonlinearities due to the slenderness and the length of modern blades, contacts between the blades and the shrouds, friction in the connections, and material nonlinearities. This paper focuses on the damping material which can be found in some stator stages of low-pressure compression parts. This material makes the shroud and all the blades of the stage interdependent, providing damping and fluid vein airtightness. The objective is to propose a characterization and a numerical modeling methodology that could easily be integrated within an industrial process. Nonlinearity characterization tests, based on the Restoring Force Surface method, are presented as well as viscoelastic characterization. Finally the proposed viscoelastic modeling, based on the Modal Strain Energy method, is validated against experimental data. [less ▲]

In-orbit vibration testing of spacecraft structures

in International Conference on Noise and Vibration Engineering, Leuven, 2008 (2008)

In-orbit modal testing can be an interesting tool for the monitoring of spacecraft structures. In these applications, it is impossible to measure or to control the excitation resulting, for instance, from ... [more ▼]

In-orbit modal testing can be an interesting tool for the monitoring of spacecraft structures. In these applications, it is impossible to measure or to control the excitation resulting, for instance, from an impact with a small asteroid or from the working engines. Consequently the only realistic methodology must be an outputonly modal analysis, also called Operational Modal Analysis (OMA). This paper proposes another way of doing OMA where the post-processing (i.e. the physical modal parameter extraction) is simplified and automated. The methodology uses the Blind Source Separation (BSS) techniques which attempt to recover the source signals only from their observed mixtures. In case of structural dynamic responses, the source signals and the mixing matrix are equivalent to the modal coordinates and the mode matrix, respectively. The paper describes the complete methodology including the post-processing, and its feasibility is demonstrated using a numerical application modeling a truss satellite with the FE method. [less ▲]

Physical interpretation of independent component analysis in structural dynamics

in Mechanical Systems & Signal Processing (2007), 21

This paper focuses on the relation between the vibration modes of mechanical systems and the modes computed through a blind source separation technique called independent component analysis (ICA). For ... [more ▼]

This paper focuses on the relation between the vibration modes of mechanical systems and the modes computed through a blind source separation technique called independent component analysis (ICA). For free and random vibrations of weakly damped systems, a one-to-one relationship between the vibration modes and the ICA modes is demonstrated using the concept of virtual source. Based on this theoretical link, a time-domain structural system identification technique is proposed and is illustrated using numerical examples. [less ▲]

BLIND SOURCE SEPARATION TECHNIQUES FOR MODAL ANALYSIS: EXPERIMENTAL DEMONSTRATION

in International Conference on Engineering Dynamics, Carvoeiro, 2007 (2007)

The present study carries out output-only modal analysis using two blind source separation (BSS) techniques, namely independent component analysis and second-order based identification. It is shown under ... [more ▼]

The present study carries out output-only modal analysis using two blind source separation (BSS) techniques, namely independent component analysis and second-order based identification. It is shown under which circumstances the normal coordinates of the vibration modes may be interpreted as virtual sources, which renders the application of these BSS techniques possible. To support the theoretical findings, numerical experiments are first carried out using a discrete system of three masses. Secondly the method is applied to a real-life structure which is a blade extracted from a turbojet engine stator. The results are compared with the stochastic subspace identification method. [less ▲]

System Identification in Structural Dynamics Using Blind Source Separation Techniques

in 7th International Conference on ICA and Signal, Londres, 2007 (2007)

This paper proposes to explore the potential of Blind Source Separation (BSS) techniques for the estimation of modal parameters, namely the resonant frequencies, vibration modes and damping ratios. The ... [more ▼]

This paper proposes to explore the potential of Blind Source Separation (BSS) techniques for the estimation of modal parameters, namely the resonant frequencies, vibration modes and damping ratios. The concept of virtual sources, which was introduced in recent publications, allows to consider BSS as a simple way of doing output-only modal analysis. This work illustrates the proposed methodology using free and random responses of an experimental truss structure. [less ▲]

Second-order blind identification for operational modal analysis

Conference given outside the academic context (2005)

For modal analysis of large structures, it is unpractical and expensive to use artificial excitation (e.g., shakers). However, engineering structures are most often subject to ambient loads(e.g., traffic ... [more ▼]

For modal analysis of large structures, it is unpractical and expensive to use artificial excitation (e.g., shakers). However, engineering structures are most often subject to ambient loads(e.g., traffic and wind) that can be exploited for modal parameter estimation. One difficulty is that the actual loading conditions cannot generally be measured, and output-only measurements are available. This paper proposes to explore the utility of blind source separation (BSS) techniques for operational modal analysis. The basic idea of BSS is to recover unobserved source signals from their observed mixtures. The feasibility and practicality of the proposed method are demonstrated using an experimental application. [less ▲]

A Topological optimisation tool for industrial design

Conference (2005)