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El-Qoubaa Z.,CNRS Research Institute in Civil Engineering and Mechanics | Othman R.,King Abdulaziz University
Materials and Design | Year: 2015

Semi-crystalline polymers are increasingly used in structural applications where they can withstand dynamic loads. It is then, of highly importance, to measure and model their mechanical behavior over a wide range of strain rates. In this paper, the polyetheretherketone's yield stress is investigated under quasi-static (0.0001-0.1/s), intermediate (5-500/s) and high (500-10,000/s) strain rates. Four experimental set-ups were used to achieve this task. It was shown that the mechanical behavior is highly sensitive to strain rate. The yield stress at 10,000/s is 115% higher than at 0.0001/s. Moreover, the strain rate sensitivity increases with increasing strain rate. A new three-material-constant constitutive equation is proposed to take into account the increase of strain rate sensitivity at very high strain rates. An identification approach is also developed to consider the influence of the strain rate range. The material constants, of the new constitutive equation and of three constitutive equations available in the literature, are identified. For each equation, we have reported the strain rate range where each model best fits the experimental data. The new model gives the best trade-off of fitting the experimental data with a good accuracy while minimizing the number of material constants. © 2014 Elsevier Ltd. Source

Bastidas-Arteaga E.,CNRS Research Institute in Civil Engineering and Mechanics | Stewart M.G.,University of New South Wales
Structural Safety | Year: 2015

Reinforced concrete (RC) structures are subject to environmental actions affecting their performance, serviceability and safety. Among these actions, chloride ingress leads to corrosion initiation and its interaction with service loading could reduce its operational life. Experimental evidence indicates that chloride ingress is highly influenced by weather conditions in the surrounding environment and therefore by climate change. Consequently, both structural design and maintenance should be adapted to these new environmental conditions. This work focuses on the assessment of the costs and benefits of two climate adaptation strategies for new RC structures placed in chloride-contaminated environments under various climate change scenarios. Their cost-effectiveness is measured in terms of the benefit-to-cost ratio (BCR) and the probability that BCR exceeds unity - i.e., Pr(BCR. > 1). It was found that increasing concrete strength grade is more cost-effective than increasing design cover. The results also indicate that the cost-effectiveness of a given adaptation strategy depends mainly on the type of structural component, exposure conditions and climate change scenarios. © 2014 Elsevier Ltd. Source

Verron E.,CNRS Research Institute in Civil Engineering and Mechanics
Rubber Chemistry and Technology | Year: 2010

Our objective is twofold: (1) to offer a short state of the art on the framework of configurational mechanics to rubber researchers and engineers, and (2) to show that it is well adapted to rubber mechanics. The state of the art presents the general theory but also highlights the physical meaning of the Eshelby stress tensor and of its path integrals; then, we propose a list of recent applications involving configurational mechanics. Attention is then focused on rubber applications: recent work on the simulation of fracture in inelastic materials and on the development of predictors for fatigue crack initiation is presented. Source

Nouy A.,CNRS Research Institute in Civil Engineering and Mechanics
Archives of Computational Methods in Engineering | Year: 2010

Uncertainty quantification and propagation in physical systems appear as a critical path for the improvement of the prediction of their response. Galerkin-type spectral stochastic methods provide a general framework for the numerical simulation of physical models driven by stochastic partial differential equations. The response is searched in a tensor product space, which is the product of deterministic and stochastic approximation spaces. The computation of the approximate solution requires the solution of a very high dimensional problem, whose calculation costs are generally prohibitive. Recently, a model reduction technique, named Generalized Spectral Decomposition method, has been proposed in order to reduce these costs. This method belongs to the family of Proper Generalized Decomposition methods. It takes part of the tensor product structure of the solution function space and allows the a priori construction of a quasi optimal separated representation of the solution, which has quite the same convergence properties as a posteriori Hilbert Karhunen-Loève decompositions. The associated algorithms only require the solution of a few deterministic problems and a few stochastic problems on deterministic reduced basis (algebraic stochastic equations), these problems being uncoupled. However, this method does not circumvent the "curse of dimensionality" which is associated with the dramatic increase in the dimension of stochastic approximation spaces, when dealing with high stochastic dimension. In this paper, we propose a marriage between the Generalized Spectral Decomposition algorithms and a separated representation methodology, which exploits the tensor product structure of stochastic functions spaces. An efficient algorithm is proposed for the a priori construction of separated representations of square integrable vector-valued functions defined on a high-dimensional probability space, which are the solutions of systems of stochastic algebraic equations. © CIMNE, Barcelona, Spain 2010. Source

Stainier L.,CNRS Research Institute in Civil Engineering and Mechanics
Mechanics Research Communications | Year: 2011

In this paper, we detail a consistent approximate expression for incremental dissipation pseudo-potentials which appear in the variational formulation of coupled thermo-mechanical boundary-value problems. We explain why the most intuitive expression does not work in the case of an explicit temperature dependence in the dissipation, and propose an alternative expression ensuring consistent results when reducing the time increment towards zero. © 2011 Elsevier Ltd. Source

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