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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.

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.

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.

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.

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