CNRS Brest Laboratory of Mechanics and Systems Laboratory

Bretagne, France

CNRS Brest Laboratory of Mechanics and Systems Laboratory

Bretagne, France
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Jacques N.,CNRS Brest Laboratory of Mechanics and Systems Laboratory | Mercier S.,CNRS Study of Microstructures, Mechanics and Material Sciences lab | Molinari A.,CNRS Study of Microstructures, Mechanics and Material Sciences lab
Journal of the Mechanics and Physics of Solids | Year: 2012

The aim of this paper is to investigate the role of microscale inertia in dynamic ductile crack growth. A constitutive model for porous solids that accounts for dynamic effects due to void growth is proposed. The model has been implemented in a finite element code and simulations of crack growth in a notched bar and in an edge cracked specimen have been performed. Results are compared to predictions obtained via the GursonTvergaardNeedleman (GTN) model where micro-inertia effects are not accounted for. It is found that microscale inertia has a significant influence on the crack growth. In particular, it is shown that micro-inertia plays an important role during the strain localisation process by impeding void growth. Therefore, the resulting damage accumulation occurs in a more progressive manner. For this reason, simulations based on the proposed modelling exhibit much less mesh sensitivity than those based on the viscoplastic GTN model. Microscale inertia is also found to lead to lower crack speeds. Effects of micro-inertia on fracture toughness are evaluated. © 2012 Elsevier Ltd. All rights reserved.


Cognard J.Y.,ENSTA Bretagne | Sohier L.,CNRS Brest Laboratory of Mechanics and Systems Laboratory | Davies P.,French Research Institute for Exploitation of the Sea
Composites Part A: Applied Science and Manufacturing | Year: 2011

Composite materials are a key element in weight reduction strategies, so the analysis of the mechanical behavior of assemblies of composite modules is of great importance. Failure initiation in bonded assemblies involving composites is often associated with crack initiation in the adhesive or delamination of the composite plies close to the adhesive joint, caused by interlaminar or through-thickness stresses. Thus, the analysis of the behavior of composites and their assemblies under out-of-plane loadings is necessary in order to optimize such structures. However, few experimental devices are proposed in the literature and they often require thick composite specimens which are not representative of most industrial applications. This paper describes the use of a modified Arcan test to determine the behavior of composites and hybrid bonded assemblies over a wide range of tensile-shear out-of-plane loadings. The key advantages of this fixture are the testing of thin composite plates and the use of an adhesive to fix samples. Moreover, an optimization of the design of the proposed device, based on finite element simulations, significantly limits the influence of edge effects in order to obtain accurate experimental results. Some test results are presented which underline the potential of the proposed approach. © 2010 Elsevier Ltd. All rights reserved.


Bouchikhi E.H.E.,CNRS Brest Laboratory of Mechanics and Systems Laboratory | Choqueuse V.,CNRS Brest Laboratory of Mechanics and Systems Laboratory | Benbouzid M.E.H.,CNRS Brest Laboratory of Mechanics and Systems Laboratory
IEEE Transactions on Energy Conversion | Year: 2013

Induction machines are widely used in industrial applications. Safety, reliability, efficiency, and performance are major concerns that direct the research activities in the field of electrical machines. Even though the induction machine is very reliable, many failures can occur such as bearing faults, air-gap eccentricity, and broken rotor bars. The challenge is, therefore, to detect them at an early stage in order to prevent breakdowns. In particular, stator current-based condition monitoring is an extensively investigated field for cost and maintenance savings. In this context, this paper deals with the assessment of a new stator current-based fault detection approach. Indeed, it is proposed to monitor induction machine bearings by means of stator current spectral subtraction, which is performed using short-time Fourier transform or discrete wavelet transform. In addition, diagnosis index based on the subtraction residue energy is proposed. The proposed bearing faults condition monitoring approach is assessed using simulations, issued from a coupled electromagnetic circuits approach-based simulation tool, and experiments on a 0.75-kW induction machine test bed. © 1986-2012 IEEE.


Mekri F.,Saida University | Elghali S.B.,Aix - Marseille University | Benbouzid M.E.H.,CNRS Brest Laboratory of Mechanics and Systems Laboratory
IEEE Transactions on Sustainable Energy | Year: 2013

This paper deals with the use of permanent magnet multiphase generators in marine current turbines with the aim to highlight their fault-tolerance. In this context, the performances and the fault-tolerant capabilities of a five-phase permanent magnet synchronous generator are evaluated within a marine current turbine and compared to a classical three-phase generator. For both topologies, a robust nonlinear control strategy is adopted. The adopted control consists of an adaptive control approach that combines three strategies: a maximum power point tracking (MPPT), an optimal fault-adaptive reference current generation, and high-order sliding modes. Simulations are carried-out using a Matlab/Simulink-based marine current turbine simulator to analyze the generator performances during open-circuit faults. Conclusions are then derived regarding multiphase generators' key features for marine applications. © 2010-2012 IEEE.


Ben Elghali S.E.,CNRS Brest Laboratory of Mechanics and Systems Laboratory | Benbouzid M.E.H.,CNRS Brest Laboratory of Mechanics and Systems Laboratory | Charpentier J.-F.,French Naval Academy Research Institute
IET Renewable Power Generation | Year: 2010

This paper deals with the modelling and control of a variable speed doubly fed induction generator-based marine current turbine with and without tidal current speed sensor. The proposed maximum power point tracking control strategy relies on the resource and the marine turbine models that were validated by experimental data. The sensitivity of the proposed control strategy is analysed regarding the swell effect because it is considered as the most disturbing one for the resource model. Tidal current data from the Raz de Sein (Brittany, France) are used to run simulations of a 7.5-kW prototype over various flow regimes. Simulation results are presented and fully analysed. © 2009 The Institution of Engineering and Technology.


Choqueuse V.,CNRS Brest Laboratory of Mechanics and Systems Laboratory | Benbouzid M.E.H.,CNRS Brest Laboratory of Mechanics and Systems Laboratory | Amirat Y.,CNRS Brest Laboratory of Mechanics and Systems Laboratory | Amirat Y.,Institute Superieur Of Lelectronique Et Du Numerique | Turri S.,CNRS Brest Laboratory of Mechanics and Systems Laboratory
IEEE Transactions on Industrial Electronics | Year: 2012

This paper deals with the diagnosis of three-phase electrical machines and focuses on failures that lead to stator-current modulation. To detect a failure, we propose a new method based on stator-current demodulation. By exploiting the configuration of three-phase machines, we demonstrate that the demodulation can be efficiently performed with low-complexity multidimensional transforms such as the Concordia transform (CT) or the principal component analysis (PCA). From a practical point of view, we also prove that PCA-based demodulation is more attractive than CT. After demodulation, we propose two statistical criteria aiming at measuring the failure severity from the demodulated signals. Simulations and experimental results highlight the good performance of the proposed approach for condition monitoring. © 2011 IEEE.


Scolan Y.-M.,CNRS Brest Laboratory of Mechanics and Systems Laboratory
Journal of Fluids and Structures | Year: 2014

The linearized Wagner theory is used to describe the initial stage of the penetration of an elliptic paraboloid on the crest of a regular wave. It is shown that the asymptotic solution for small wave steepness and large enough radii of curvature of the body is obtained from a slight modification of the standard impact problem without a wave. In practice the boundary value problem is formulated for a fictitious elliptic paraboloid: its radii of curvature are modified compared to the actual ones and its kinematics of penetration makes mainly a horizontal velocity appear due to the velocity of the propagating crest.To validate the present approach, an experimental campaign is carried out. The combined choice of the wave parameters and the geometric characteristics of the body leads to a circular expanding wetted surface. The experimental data confirm the theoretical results. Comparisons made for the pressure and the force show a satisfactory agreement. © 2014 Elsevier Ltd.


Vandellos T.,ONERA | Huchette C.,ONERA | Carrere N.,CNRS Brest Laboratory of Mechanics and Systems Laboratory
Composite Structures | Year: 2013

A new framework is proposed for the development, in an implicit finite element code, of cohesive zone models adapted to the description of the mixed-mode delamination in Carbon-Fiber Reinforced Plastic (CFRP) laminated composites. The main advantage of this new framework is to take into account both the interlaminar strength and the fracture toughness of the interface which are experimentally identified. Moreover, this model also takes into consideration the influence on the interfacial properties of the possible out-of-plane compression at the crack tip and of the damage in the plies adjacent to the interface. Using this new framework, a tri-linear cohesive zone model is proposed. The advantages of the tri-linear model compared to the bilinear one are emphasized by comparing the results obtained from the numerical simulations of some fracture tests, using these two models. © 2013 Elsevier Ltd.


Beltran B.,CNRS Brest Laboratory of Mechanics and Systems Laboratory | Benbouzid M.E.H.,CNRS Brest Laboratory of Mechanics and Systems Laboratory | Ahmed-Ali T.,University of Caen Lower Normandy
IEEE Transactions on Energy Conversion | Year: 2012

This paper deals with power extraction maximization of a doubly fed induction generator (DFIG)-based wind turbine. These variable speed systems have several advantages over the traditional wind turbine operating methods, such as the reduction of the mechanical stress and an increase in the energy capture. To fully exploit this latest advantage, many control schemes have been developed for maximum power point tracking (MPPT) control schemes. In this context, this paper proposes a second-order sliding mode to control the wind turbine DFIG according to references given by an MPPT. Traditionally, the desired DFIG torque is tracked using control currents. However, the estimations used to define current references drive some inaccuracies mainly leading to nonoptimal power extraction. Therefore, using robust control, such as the second-order sliding mode, will allow one to directly track the DFIG torque leading to maximum power extraction. Moreover, the proposed control strategy presents attractive features such as chattering-free behavior (no extra mechanical stress), finite reaching time, and robustness with respect to external disturbances (grid) and unmodeled dynamics (generator and turbine). Simulations using the wind turbine simulator FAST and experiments on a 7.5-kW real-time simulator are carried out for the validation of the proposed high-order sliding mode control approach. © 2012 IEEE.


Amirat Y.,CNRS Brest Laboratory of Mechanics and Systems Laboratory | Choqueuse V.,CNRS Brest Laboratory of Mechanics and Systems Laboratory | Benbouzid M.,CNRS Brest Laboratory of Mechanics and Systems Laboratory
Mechanical Systems and Signal Processing | Year: 2013

Failure detection has always been a demanding task in the electrical machines community; it has become more challenging in wind energy conversion systems because sustainability and viability of wind farms are highly dependent on the reduction of the operational and maintenance costs. Indeed the most efficient way of reducing these costs would be to continuously monitor the condition of these systems. This allows for early detection of the generator health degeneration, facilitating a proactive response, minimizing downtime, and maximizing productivity. This paper provides then an assessment of a failure detection techniques based on the homopolar component of the generator stator current and attempts to highlight the use of the ensemble empirical mode decomposition as a tool for failure detection in wind turbine generators for stationary and non-stationary cases. © 2013 Elsevier Ltd.

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