Performance, robustness and sensitivity analysis of the nonlinear tuned vibration absorber

The nonlinear tuned vibration absorber (NLTVA) is a recently-developed nonlinear absorber which generalizes Den Hartog's equal peak method to nonlinear systems. If the purposeful introduction of nonlinearity can enhance system performance, it can also give rise to adverse dynamical phenomena, including detached resonance curves and quasiperiodic regimes of motion. Through the combination of numerical continuation of periodic solutions, bifurcation detection and tracking, and global analysis, the present study identifies boundaries in the NLTVA parameter space delimiting safe, unsafe and unacceptable operations. The sensitivity of these boundaries to uncertainty in the NLTVA parameters is also investigated.Comment: Journal pape

Fonctionnement et performances des couloirs oscillants à glissement

This paper is devoted to the study of the efficiency of an oscillating trough for any value of the frequency. It is found that pure slipping or mixed cycles may occur, the latter comprising sticking periods. The results of the present analysis concern the cyclic displacement, the mean velocity and the dissipated power.Cet article traite du fonctionnement et des performances des couloirs oscillants, pour une pulsation quelconque. Le régime de fonctionnement peut être purement glissant ou mixte, avec des temps d'adhérence. Sont calculés, le déplacement par cycle, la vitesse moyenne et la puissance dissipée.Peer reviewe

Form error assessment from 3-D measures

peer reviewedOwing to the fact that a correct evaluation of form errors is particularly difficult by the classical ways, it seems more efficient to develop numerical algorithms from 3D measures. Several methods are described, including direct and iterative ones. A new method is proposed, which is based on Lp-norms and a specialized algorithm. It proved to be the most effective and robust one in every studied application. Another problem which is seldom studied, concerns the sensibility of form errors to measure errors. A theory is presented which leads to a very simple result.Partant de la considération du fait qu'il est très malaisé de déterminer les erreurs de forme par les procédures métrologiques classiques, on s'attache à décrire diverses méthodes de calcul de ces erreurs à partir de mesures tridimensionnelles. Diverses méthodes sont proposées, dont des méthodes directes et des méthodes itératives. On présente en particulier une méthode nouvelle, fondée sur les normes d'ordre p, qui, dans toutes les applications étudiées, s'est révélée très rapide et très stable. On aborde ensuite le problème raremenmt étudié de la sensibilité des erreurs de forme aux imprécisions de mesure, pour lequel un résultat particulièrement simple est obtenu

Концепция личности и истории в эпопее В. Гроссмана «Жизнь и судьба»

Статья в сборнике материало

The harmonic balance method for bifurcation analysis of large-scale nonlinear mechanical systems

The harmonic balance (HB) method is widely used in the literature for analyzing the periodic solutions of nonlinear mechanical systems. The objective of this paper is to extend the method for bifurcation analysis, i.e., for the detection and tracking of bifurcations of nonlinear systems. To this end, an algorithm that combines the computation of the Floquet exponents with bordering techniques is developed. A new procedure for the tracking of Neimark-Sacker bifurcations that exploits the properties of eigenvalue derivatives is also proposed. As an application, the frequency response of a structure spacecraft is studied, together with two nonlinear phenomena, namely quasiperiodic oscillations and detached resonance curves. This example illustrates how bifurcation tracking using the HB method can be employed as a promising design tool for detecting and eliminating such undesired behaviors

Partition of the circle in cells of equal area and shape

In the present paper, a new method for partitioning a circle in cells is presented. Cells have equal areas and shapes, so the method is termed the Isocell method. Its most interesting property is that cell centres are uniformly distributed inside the circle. Among possible applications of the Isocell method, the calculation of view factors by ray-tracing (image rendering, radiative heat transfer modelling) is presented

Prédiction numérique des défauts de forme engendrés par l'usinage

peer reviewedPresentation of a prediction method of form errors arising during machining which has been developed in the manufacturing laboratory of the University of Liège. It combines empirical force models and a finite element model of the machined part. A particularly efficient solution scheme has been developed, leading to a valuable tool for the industry

Chatter maps for process design of powertrain components

peer reviewedDuring rough machining operations of powertrain components, chatter vibrations may occur on the edges of flexible structures. This paper presents a numerical method, based on the finite element method and Tlusty's theory, which gives a chatter map of the machined surface. Each map point represents the greatest depth of cut leading to unconditionally stable cut. Each value depends on the structural damping, the cutting stiffness and the local static stiffness, which is computed using conventional linear elastic FEA. Chatter maps offer a convenient and effective decision support system for robust process design. As a case study, the rough milling operation of a crankcase deck face with a two-stage cutter is presented