Application of the proper generalized decomposition method to a viscoelastic mechanical problem with a large number of internal variables and a large spectrum of relaxation times

We here extend the use of the PGD to the case of a viscoelastic mechanical problem with a large number of internal variables and with a large spectrum of relaxation times. Such a number of internal variables leads to solving a system of non linear differential equations which correspond to the return to the equilibrium state. The feasibility and the robustness of the method are discussed in a simple case; a future application is the simulation of a polymer reaction under cyclic loading

Mechanical Effects in PEM Fuel Cell: Application to Modeling of Assembly Procedure

Mechanical effects can influence significantly electrical performance and life time of PEM fuel cells. A linear elasticplastic 2D model of fuel cell with hardening is used for modeling of assembly procedure of fuel cells. The model simulates mechanical behavior of the main components of real fuel cell (the membrane, the gas diffusion layers, the graphite plates, and the seal joints) and clamping elements (the steel plates, the bolts, the nuts). The stress and plastic deformation in MEA have been calculated using ABAQUS code. The results are presented on the local and the global scales with respect to the realistic clamping conditions. The first one corresponds to the single tooth/channel structure. The global scale deals with features of the entire cell and takes into account the border effects, in particular the influence of seal joints

Antiretroviral-naive and -treated HIV-1 patients can harbour more resistant viruses in CSF than in plasma

Objectives The neurological disorders in HIV-1-infected patients remain prevalent. The HIV-1 resistance in plasma and CSF was compared in patients with neurological disorders in a multicentre study. Methods Blood and CSF samples were collected at time of neurological disorders for 244 patients. The viral loads were >50 copies/mL in both compartments and bulk genotypic tests were realized. Results On 244 patients, 89 and 155 were antiretroviral (ARV) naive and ARV treated, respectively. In ARV-naive patients, detection of mutations in CSF and not in plasma were reported for the reverse transcriptase (RT) gene in 2/89 patients (2.2%) and for the protease gene in 1/89 patients (1.1%). In ARV-treated patients, 19/152 (12.5%) patients had HIV-1 mutations only in the CSF for the RT gene and 30/151 (19.8%) for the protease gene. Two mutations appeared statistically more prevalent in the CSF than in plasma: M41L (P = 0.0455) and T215Y (P = 0.0455). Conclusions In most cases, resistance mutations were present and similar in both studied compartments. However, in 3.4% of ARV-naive and 8.8% of ARV-treated patients, the virus was more resistant in CSF than in plasma. These results support the need for genotypic resistance testing when lumbar puncture is performe

Experimental characterization of thermo-oxidation induced shrinkage and damage onset in polymer matrix composites at high temperature

This paper focuses on the experimental characterization of thermo-oxidation in carbon fibre reinforced polymers (CFRP) exposed to “high” temperatures (up to 150°C) and “high” oxygen pressures (up to 5 bars). Thermo-oxidation induces matrix shrinkage and damage in CFRP. In this study these are both investigated at room temperature by means of confocal interferometric microscopy (CIM) and scanning electron microscopy (SEM)

Effects of sorption and desorption of CO2 on the thermomechanical experimental behavior of HNBR and FKM O-rings - Influence of nanofiller-reinforced rubber

International audienceDespite its importance in sealing, a fundamental understanding of the behavior of elastomeric O-rings in a gas environment is still incomplete. Further experimental research is needed to obtain a precise predictive model which can describe the combined effects of gases and mechanical loading. The effect of CO2 pressure (2, 4 and 6 MPa) on the mechanical compression behavior of HNBR and FKM seals at two temperatures (60 and 130 °C) is described in the paper. To evaluate the contribution of nanofiller reinforcement, experimental tests were carried out on two kinds of rubber which are reinforced or not with nanofiller (10 phr of expanded graphite). A ranking of materials was performed thanks to experimental database. HNBR seems to be the better candidate in the service conditions applied. Furthermore, the nanofillers which are introduced in the rubber can lead some damages in Rapid Gas Decompression conditions, notably when the zero pressure was applied (desorption)

Non-contact method used to determine the swelling/shrinking coefficients under CO2 sorption/desorption on an HNBR O-ring - Study of coupling with temperature and pressure

International audienceTo make use of an O-ring under different pressures and temperatures and to procedure predictive numerical simulations of its use, it becomes important to identify the O-ring behavior under coupled CO 2 sorption (i.e. swelling) and desorption (i.e. shrinking) together with the effect of temperature. Therefore, the presented study deals with an experimental non-contact measurement technique to identify the swelling and shrinking coefficients during pressurization and depressurization under carbone dioxide (CO 2) of an HNBR O-ring. In order to ensure the feasibility of CO 2 sorption (or desorption) measurement from the non-contact method, a purely thermal expansion test permits to identify the thermal expansion coefficient of HNBR, which is well known by other methods including a standard. Numerical simulations complete this section. The simulations ensure that the chosen analysis methodology allows direct identification of swelling and shrinking coefficients and thus determine the seal volume change. CO 2 pressurization and CO 2 depressurization tests at pressures (2, 4 and 6 MPa) under isothermal conditions (60 and 130°C) and a coupled temperature-pressure CO 2 tests are conducted. The measurements made during these tests show that the CO 2 swelling and shrinking coefficients are independent of pressure but temperature dependent. Besides, a good measurements reproducibility was observed and the order of magnitude of these coefficients leads to a strain in the same order as the thermal strain

Essais instrumentés sur réservoir composite (type IV) sous pression soumis à une pression interne d’eau, JNC 21 – Bordeaux INP – 1-3 juillet 2019

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