Mechanical behavior of recrystallized Zircaloy-4 under monotonic loading at room temperature: Tests and simplified anisotropic modeling

Mechanical behavior of recrystallized Zircaloy-4 was studied at room temperature in the rolling-transverse plane of a thin sheet. Uniaxial constant elongation rate tests (CERTs) were performed along with creep tests, over a wide range of strain rates. Based on a simplified formulation, different sets of parameters for an anisotropic viscoplastic model were found to fit the stress–strain curves. Notched specimen tensile tests were carried out with a digital image correlation (DIC) technique in order to determine the strain field evolution. From these measurements and the determination of Lankford coefficients, the most consistent model was selected and simulated data were successfully compared with the experimental observations

A new isotropic cell for studying the thermo-mechanical behavior of unsaturated expansive clays

This paper presents a new suction-temperature controlled isotropic cell that can be used to study the thermo-mechanical behavior of unsaturated expansive clays. The vapor equilibrium technique is used to control the soil suction; the temperature of the cell is controlled using a thermostat bath. The isotropic pressure is applied using a volume/pressure controller that is also used to monitor the volume change of soil specimen. Preliminary experimental results showed good performance of the cell

Comportement en température des argiles de barrières ouvragées (réexamen de la phénoménologie et amélioration des modèles existants)

Certains concepts de stockage envisagent d'intercaler une barrière ouvragée argileuse entre la roche et le colis de déchets radioactifs. Les niveaux de température, que pourrait subir l'argile, mettent en péril son aptitude à remplir les fonctions assignées à la barrière ouvragée. Afin d'apprécier les enjeux de conception, on simule le comportement thermo-hydro-mécanique d'une barrière ouvragée pour différentes sollicitations thermiques. L'étude est menée en partie sous forme de benchmark (codes ASTER et CAST3M). Elle révèle qu'une amélioration du modèle thermo-mécanique est nécessaire. Pour ce faire, on retient le formalisme énergétique et on propose un réexamen des phénomènes affectant les argiles en température. La contraction thermique de la double couche, propre aux argiles gonflantes, se révèle une interprétation intéressante des expériences. Aussi, on propose d'intégrer les phénomènes électrochimiques dans une formulation énergétique pour milieux poreux partiellement saturés.In some common concepts of a radioactive waste repository, waste is surrounded by an engineered barrier consisting of a swelling clay. Performance of this engineered barrier may be affected by temperature distribution in the clay. To discuss this issue, thermo-hydro-mechanical simulations of the argillaceous barrier submitted to different heating sources are performed. Part of this study is a comparison between the codes ASTER and CAST3M. According to our results, it is necessary to improve the mechanical model. We choose the thermodynamic approach and we propose to re-examine thermal clay behaviour from a phenomenological point of view. Thermal contraction of the double layer in swelling clays is a possible interpretation of the experimental results. Thus we decide to introduce electrochemical phenomena in a thermodynamic formulation dedicated to partially saturated porous media.EVRY-BU (912282101) / SudocSudocFranceF

Combining a Fatigue Model and an Incremental Capacity Analysis on a Commercial NMC/Graphite Cell under Constant Current Cycling with and without Calendar Aging

Reliable development of LIBs requires that they be correlated with accurate aging studies. The present project focuses on the implementation of a weighted ampere-hour throughput model, taking into account the operating parameters, and modulating the impact of an exchanged ampere-hour by the well-established three major stress factors: temperature, current intensity (rated), and state of charge (SoC). This model can drift with time due to repeated solicitation, so its parameters need to be updated by on-field measurements, in order to remain accurate. These on-field measurements are submitted to the so-called Incremental Capacity Analysis method (ICA), consisting in the analysis of dQ/dV as a function of V. It is a direct indicator of the state of health of the cell, as the experimental peaks are related to the active material chemical/structural evolution, such as phase transitions and recorded potential plateaus during charging/discharging. It is here applied to NMC/graphite based commercial cells. These peaks’ evolution can be correlated with the here-defined Ah-kinetic and t -kinetic aging, which are chemistry-dependent, and therefore, has to be adjusted to the different types of cells

Modèle d'arc en courant continu des fusibles gG et aR pour le dimensionnement des convertisseurs

The sizing of AC/DC converter in the context of LVDC distribution grid represents a new challenge. This paper suggests a DC arcing model based on measurements to determine gG and aR fuses behavior, and it is applied to the sizing of a twolevel voltage source converter (2L-VSC).Le dimensionnement d'un convertisseur AC/DC dans le contexte d'un réseau de distribution LVDC représente un nouveau défi. Cet article propose un modèle d'arc CC basé sur des mesures pour déterminer le comportement des fusibles gG et aR, et il est appliqué au dimensionnement d'un convertisseur de source de tension à deux niveaux (2L-VSC)