Practical application of active noise control in a duct using predictive control

This paper presents a practical application of Active Noise Control (ANC) using the Generalised Predictive Control (GPC) algorithm. The main objective of this application was to reduce significantly the noise level in a duct using this technique. It is shown that the experimental results obtained using GPC are very close from those obtained with the classical LMS algorithm on the same experimental set-up. On the other side, no adaptation time is needed and a single controller is used over a broad band. The predictive controller is synthetized using a realistic simulation of the process based upon some rough assumptions on the transfer functions

Numerical implementation of the eXtended Finite Element Method for dynamic crack analysis

A numerical implementation of the eXtended Finite Element Method (X-FEM) to analyze crack propagation in a structure under dynamic loading is presented in this paper. The arbitrary crack is treated by the X-FEM method without re-meshing but using an enrichment of the classical displacement-based finite element approximation in the framework of the partition of unity method. Several algorithms have been implemented, within an Oriented Object framework in C++, in the home made explicit FEM code. The new module, called DynaCrack, included in the dynamic FEM code DynELA, evaluates the crack geometry, the propagation of the crack and allow the post-processing of the numerical results. The module solves the system of discrete equations using an explicit integration scheme. Some numerical examples illustrating the main features and the computational efficiency of the DynaCrack module for dynamic crack propagation are presented in the last section of the paper

Identification expérimentale et simulation numérique de l'endommagement en dynamique rapide : application aux structures aéronautiques

Ce travail concerne le développement de nouveaux outils numériques et expérimentaux afin de compléter et améliorer une plate-forme d'identification paramétrique pour les matériaux soumis à de grandes transformations thermomécaniques rapides. Sur le plan numérique un nouveau logiciel pour l'analyse numérique de la fissuration dynamique a été développé en C++ Orienté-Objet après l'implémentation de la méthode des éléments finis étendue (XFEM). La partie experimentale du travail est relative à la conception et la mise en oeuvre d'un nouvel essai d'impact, capable de caractériser le comportement des matériaux en endommagement et rupture dynamique. Afin de déterminer les valeurs des paramètres des lois et critères constitutifs en dynamique rapide, une nouvelle procedure d'identification paramétrique à été développée, basée sur une combinaison d'algorithmes de Monte-Carlo et de Levenberg-Marquardt. Le comportement d'un alliage d'aluminium a été caractérisé en déterminant les paramètres de la loi de visco-plasticité de Johnson-Cook et ceux du critère d'endommagement cohésif. ABSTRACT : This works concerns the development of new numerical and experimental tools in order to complete and improve a parametric identification procedure intended for materials under fast dynamic loads. On the numerical aspect, a new code for dynamic crack analysis was developed in C++ Object-Oriented language, implementing Extended Finite Element Method. The experimental part of this work relates to the design and experimentation of a new impact test able to characterize the dynamic fracture and damage behaviour of materials. In order to find the parameters values for constitutive laws and criteria, a new identification procedure was developed based on a combination of both Monte-Carlo and Levenberg-Marquardt algorithms. The behavior of an aluminium alloy was described determining numerical values for Johnson-Cook model and cohesive-damage criteria

A new dynamic test for the identification of high speed friction law using a gas-gun device

In the framework of metal forming, which involves high speed loads, the determination of the friction law is one of the most essential topics. Especially for Finite-element simulation the development of innovative local friction laws improves the quality of the numerical results. One of the most critical point reside in the accuracy of the identification of the governing friction law parameters. A new experimental test is based on conical extrusion. The idea is to launch a cylindrical projectile into a target provided with a conical bore prolonged with a cylindrical one. The projectile is stopped by friction forces occurring at the interface between those materials. After impact the length of extrusion is taken into account for friction law identification. The experimental set-up used is a ballistic gas-gun device capable to launch the projectile, in vacuum conditions, up to 300 m/s. The experiment is simulated by a numerical model using ABAQUS Explicit finite-element code. This code allows the implementation of various user friction laws through a FORTRAN subroutine. In order to obtain accurate results, the viscoplastic constitutive law used for both materials (projectile and target) was previously experimentally identified. The friction law identification uses a combined Monte-Carlo and Levenberg-Marquardt algorithm which provides a very precisely set of parameters law. The test presented in this paper involves two metallic materials: steel 42CrMo4 for the target and aluminum 2017 for the projectile. The friction law for the pair of materials used was validated using experimental test at different speeds of impact (149 up to 235 m/s) and the results are quite good proving a good identification of the friction law parameters

Modes non-linéaires de structures élastiques dotées de non-linéarités de contact

National audienceCet article propose une méthode de calcul des modes non-linéaires de structures élastiques dotées de non-linéaritées de contact localisées. Les lois de contact sont régularisées au moyen de relations polynomiales comportant un paramètre de régularisation. La procédure de calcul est basée sur le couplage de la méthode de balance harmonique et de la méthode asymptotique numérique

Calcul des modes non-linéaires de modèles réduits de structures avec conditions aux limites à jeu

On analyse, à l'aide des modes non-linéaires, le comportement vibratoire des structures soumises à des conditions aux limites à jeu. Les applications concernent les composantes des installations de centrale nucléaire. Dans cette perspective, on considère un système à 1 ddl avec impact unilatéral, et un système à 2 ddl doté d'un contact bilatéral. Pour ces deux problèmes, l'influence de la régularisation de l'impact sur les modes non-linéaires sera analysée à partir des solutions analytiques et numériques obtenues avec MANLAB

A spatially explicit database of wind disturbances in European forests over the period 2000-2018

Strong winds may uproot and break trees and represent a major natural disturbance for European forests. Wind disturbances have intensified over the last decades globally and are expected to further rise in view of the effects of climate change. Despite the importance of such natural disturbances, there are currently no spatially explicit databases of wind-related impact at a pan-European scale. Here, we present a new database of wind disturbances in European forests (FORWIND). FORWIND is comprised of more than 80 000 spatially delineated areas in Europe that were disturbed by wind in the period 2000-2018 and describes them in a harmonized and consistent geographical vector format. The database includes all major windstorms that occurred over the observational period (e.g. Gudrun, Kyrill, Klaus, Xynthia and Vaia) and represents approximately 30% of the reported damaging wind events in Europe. Correlation analyses between the areas in FORWIND and land cover changes retrieved from the Landsat-based Global Forest Change dataset and the MODIS Global Disturbance Index corroborate the robustness of FORWIND. Spearman rank coefficients range between 0.27 and 0.48 (p value < 0.05). When recorded forest areas are rescaled based on their damage degree, correlation increases to 0.54. Wind-damaged growing stock volumes reported in national inventories (FORESTORM dataset) are generally higher than analogous metrics provided by FORWIND in combination with satellite-based biomass and country-scale statistics of growing stock volume. The potential of FORWIND is explored for a range of challenging topics and scientific fields, including scaling relations of wind damage, forest vulnerability modelling, remote sensing monitoring of forest disturbance, representation of uprooting and breakage of trees in large-scale land surface models, and hydrogeological risks following wind damage. Overall, FORWIND represents an essential and open-access spatial source that can be used to improve the understanding, detection and prediction of wind disturbances and the consequent impacts on forest ecosystems and the land-atmosphere system. Data sharing is encouraged in order to continuously update and improve FORWIND

Identification expérimentale et simulation numérique de l'endommagement en dynamique rapide (application aux structures aéronautiques)

Ce travail concerne le développement de nouveaux outils numériques et expérimentaux afin de compléter et améliorer une plateforme d'identification paramétrique pour les matériaux soumis à de grandes transformations thermomécaniques rapides. Sur le plan numérique, un nouveau loiciel pour l'analyse numérique de la fissuration dynamique a été développé en C++ Orienté-Objet après l'implémentation de la méthode des éléments finis étendue (XFEM). La partie expérimentale du travail est relative à la conception et la mise en oeuvre d'un nouvel essai d'impact, capable de caractériser le comportement des matériaux en endommagement et rupture dynamique. Afin de déterminer les valeurs des paramètres des lois et critères constitutifs en dynamique rapide, une nouvelle procédure d'identification paramétrique a été développée, basée sur une combinaison d'algorithmes de Monte-Carlo et de Levenberg-Marquardt.This works concerns the development of new numerical and experimental tools in order to complete and improve a parametric identification procedure intended for materials under fast dynamic loads. On the numerical aspect, a new code for dynamic crack analysis was developed in C++ Object-Oriented language, implementing Extended Finite Element Method. The experimental part of this work relates to the design and experimentation of a new impact test able to characterize the dynamic fracture and damage behaviour of materials. In order to find the parameters values for constitutive laws and criteria, a new identifiation procedure was developed based on a combination of both Monte-Carlo and Levenberg-Marquardt algorithms.TOULOUSE-ENSEEIHT (315552331) / SudocTARBES-ENIT (654402301) / SudocSudocFranceF

Numerical Analysis Concerning the Harmfulness of Crack Turbine Rotors Using a Multi-Scale Approach Based on a Dynamic Finite Element Method

International audienceThis work is placed in the context of the simulation of the behavior and the harmfulness of cracked rotors by Electricité de France (EDF) in order to evaluate its impact on the industrial system. Several numerical tools have been developed by the Research and Development Division of EDF and a feasibility study was conducted to prove its capacities to simulate the behavior of a rotor subject to a crack. Since the industrial context request fast response to such situation, the numerical simulation must be performed as quickly as possible. For this reason a multi-scale 1D-3D modeling has been proposed: the healthy part of the rotor is modeled by reduced Timoshenko beam finite elements since the part including the crack is modeled by 3D finite elements. The aim of the work is to prove the accuracy of this multi-scale approach, its feasibility and its CPU performance

Computation of nonlinear normal modes of structures with elastic stops

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