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Keryvin V.,University of Southern Brittany | Keryvin V.,French National Center for Scientific Research | Meng J.-X.,University of Southern Brittany | Meng J.-X.,French National Center for Scientific Research | And 10 more authors.
Acta Materialia | Year: 2014

The mechanical response of amorphous silica (or silica glass) under hydrostatic compression for very high pressures up to 25 GPa is modelled via an elastic-plastic constitutive equation (continuum mechanics framework). The material parameters appearing in the theory have been estimated from the ex situ experimental data of Rouxel et al. [Rouxel T, Ji H, Guin JP, Augereau F, Rufflé B. J Appl Phys 2010;107(9):094903]. The model is shown to capture the major features of the pressure-volume response changes from the in situ experimental work of Sato and Funamori [Sato T, Funamori N. Phys Rev Lett 2008;101:255502] and Wakabayashi et al. [Wakabayashi D, Funamori N, Sato T, Taniguchi T. Phys Rev B 2011;84(14):144103]. In particular, the saturation of densification, the increase in elasticity parameters (bulk, shear and Young's moduli) and Poisson's ratio are found to be key parameters of the model. © 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Duhamel D.,University Paris Est Creteil | Mencik J.-M.,CNRS Mechanics and Rheology Laboratory
COMPDYN 2015 - 5th ECCOMAS Thematic Conference on Computational Methods in Structural Dynamics and Earthquake Engineering | Year: 2015

The wave finite element (WFE) method is investigated to describe the dynamic behavior of periodic structures like those composed of arbitrary-shaped substructures along a certain straight direction. A generalized eigenproblem based on the so-called S + S-1 transformation is proposed for accurately computing the wave modes which travel in right and left directions along those periodic structures. Besides, a model reduction technique is proposed which involves partitioning a whole periodic structure into one central structure surrounded by two extra substructures. In doing so, a few wave modes are only required for modeling the central periodic structure. A comprehensive validation of the technique is performed on a 2D periodic structure. Also, its efficiency in terms of CPU time savings is highlighted regarding a 3D periodic structure that exhibits substructures with large-sized FE models.

Suresh K.S.,Indian Institute of Science | Geetha M.,Vellore Institute of Technology | Richard C.,CNRS Mechanics and Rheology Laboratory | Landoulsi J.,University Pierre and Marie Curie | And 3 more authors.
Materials Science and Engineering C | Year: 2012

We report investigations on the texture, corrosion and wear behavior of ultra-fine grained (UFG) Ti-13Nb-Zr alloy, processed by equal channel angular extrusion (ECAE) technique, for biomedical applications. The microstructure obtained was characterized by X-ray line profile analysis, scanning electron microscope (SEM) and electron back scattered diffraction (EBSD). We focus on the corrosion resistance and the fretting behavior, the main considerations for such biomaterials, in simulated body fluid. To this end, potentiodynamic polarization tests were carried out to evaluate the corrosion behavior of the UFG alloy in Hanks solution at 37°C. The fretting wear behavior was carried out against bearing steel in the same conditions. The roughness of the samples was also measured to examine the effect of topography on the wear behavior of the samples. Our results showed that the ECAE process increases noticeably the performance of the alloy as orthopedic implant. Although no significant difference was observed in the fretting wear behavior, the corrosion resistance of the UFG alloy was found to be higher than the non-treated material. © 2012 Elsevier B.V. All rights reserved.

Nait-Abdelaziz M.,University of Lille Nord de France | Nait-Abdelaziz M.,Lille Laboratory of Mechanics | Zairi F.,University of Lille Nord de France | Zairi F.,Lille Laboratory of Mechanics | And 4 more authors.
Mechanics of Materials | Year: 2012

Using the fracture mechanics framework, a fracture criterion based upon the intrinsic defect concept was developed to predict the failure of rubber parts under biaxial monotonic loading. This fracture criterion requires as input data the fracture toughness of the material in terms of critical value of the J integral, the constitutive law of the material and the breaking stretch of a smooth specimen under uniaxial tension. To develop this criterion a generalized expression of the J integral under biaxial loading is proposed on the basis of finite element calculations on a RVE containing a small circular defect. The estimated failure elongations were found in very nice agreement with experimental data on two kinds of rubber materials. Moreover, we have also shown that this criterion could be extended to the failure analysis of thermoplastic polymers. © 2012 Elsevier Ltd. All rights reserved.

Mencik J.-M.,CNRS Mechanics and Rheology Laboratory
Computational Mechanics | Year: 2014

The wave finite element (WFE) method is investigated to describe the harmonic forced response of one-dimensional periodic structures like those composed of complex substructures and encountered in engineering applications. The dynamic behavior of these periodic structures is analyzed over wide frequency bands where complex spatial dynamics, inside the substructures, are likely to occur. Within the WFE framework, the dynamic behavior of periodic structures is described in terms of numerical wave modes. Their computation follows from the consideration of the finite element model of a substructure that involves a large number of internal degrees of freedom. Some rules of thumb of the WFE method are highlighted and discussed to circumvent numerical issues like ill-conditioning and instabilities. It is shown for instance that an exact analytic relation needs to be considered to enforce the coherence between positive-going and negative-going wave modes. Besides, a strategy is proposed to interpolate the frequency response functions of periodic structures at a reduced number of discrete frequencies. This strategy is proposed to tackle the problem of large CPU times involved when the wave modes are to be computed many times. An error indicator is formulated which provides a good estimation of the level of accuracy of the interpolated solutions at intermediate points. Adaptive refinement is carried out to ensure that this error indicator remains below a certain tolerance threshold. Numerical experiments highlight the relevance of the proposed approaches. © 2014 Springer-Verlag Berlin Heidelberg.

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