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Effects of nano-voids and nano-cracks on the elastic properties of a host medium: xfem modeling with level-set function and free surface energy

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Acta Mechanica sinica 2019年第4期35卷 799-811页

作者： B.E. Hachi d. Hachi M. Haboussi laboratoire de développement en Mécanique et Matériaux (LdMM) Université de Djelfa PB 3117 Djelfa Algérie laboratoire d’Automatique Appliquée et diagnostics industriels (LAAdI) Université de Djelfa PB 3117 Djelfa Algérie laboratoire des sciences des procédés et des Matériaux (LsPM) Université Paris 13 UPR 3407 CNRS Paris France

This work deals with the influences of nano-heterogeneities in the form of voids/cavities or cracks on the elastic (please confirm which word is correct. effective or elastic? According to the title of paper, I choose elastic.) properties of a host medium. With a relatively large ratio of apparent-surface to volume and particularly strong physical interactions with the surrounding medium at nano-scale, nano-heterogeneities can potentially affect the elastic(effective or elastic?) properties of the parent medium (matrix) containing them in a significant manner. This has been reported by various theoretical and experimental studies, some of them are discussed in the present paper. To describe the positive (reinforcement) or negative (degradation) effect of the nano-heterogeneities from the modeling perspective, it is necessary to take into account the energy of interfaces/surfaces between nano-heterogeneities and the matrix which, by the fact of the relatively large extent of their apparent surface and their strong physical interaction with their neighborhood, can no longer be neglected compared to those of the volume energy. Thus, to account for the effects of interfaces/surfaces in a nanostructured heterogeneous medium, the coherent interface model is considered in the present investigation within a periodic homogenization procedure. In this interface/surface model, the displacement vector is assumed to be continuous across the interface while the stress vector is considered to be discontinuous and satisfying the Laplace-Young equations. To solve these equations coupled to the classical mechanical equilibrium problem, a numerical simulation tool is developed in a two-dimensional (2d) context using the eXtended Finite Element Method (XFEM) and the Level-set functions. The developed numerical tool is then used to carry out a detailed analysis about the effect of nano-heterogeneities on the overall mechanical properties of a medium. The nano-heterogeneities are present

关键词： Interface/surface energy XFEM Level-set function Periodic homogenization Nano-voids/Nano-cavities Nano-cracks Nano-inclusions/Nano-heterogeneities

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Physico-chemical and mechanical properties of Ti_3siC_2-based materials elaborated from siC/Ti by reactive spark plasma sintering

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Journal of Advanced Ceramics 2019年第1期8卷 47-61页

作者： Faten TURKI Houyem ABdeRRAZAK Frédéric sCHOENsTEIN Florent TêTARd Mohieddine ABdeLLAOUI Noureddine JOUINI laboratoire des Matériaux Utiles Institut National de Recherche et d’Analyse Physico-chimique laboratoire de sciences des procédés et Matériaux Université Paris 13 Sorbonne Paris Cité CNRS

In this paper, the synthesis of Ti_3 siC_2 from siC/Ti powder using reactive spark plasma sintering(R-sPs) in the temperature range of 1300-1400 ℃ is reported. The results show that the purity of Ti_3 siC_2 is improved up to 75 wt% when the holding time is increased from 10 to 20 min at1400 ℃. The thermodynamic and experimental results indicate that Ti_3 siC_2 formation takes place via the reaction of a pre-formed TiC phase with the silicides, formed from the eutectic *** analysis of mechanical behaviour indicates that samples with higher percentage of secondary phases exhibit higher microhardness and better resistance compared to the near single phase Ti_3 siC_2.

关键词： Ti3siC2 reactive spark plasma sintering(R-sPs) density mechanical properties

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degradation of direct azo dye by Cucurbita pepo free and immobilized peroxidase

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Journal of Environmental sciences 2013年第6期25卷 1235-1244页

作者： Nabila Boucherit Mahmoud Abouseoud Lydia Adour Université Mouloud Mammeri laboratoire de Biomatériaux et de Phénomènes deTransports Université Dr.Yahia Fares laboratoire de Biomatériaux et de Phénomènes de Transports Université Dr.Yahia Fares laboratoire de Génie de la Réaction Faculté de Génie Mécanique et Génie des ProcédésUniversité Houari Boumediene laboratoire des Biotechnologies Environnementales et Génie des procédés

Enzymatic decolourization of the azo dye, direct Yellow （dY 106） by Cucurbita pepo （courgette） peroxidase （CP） is a complex process, which is greatly affected by pH, temperature, enzyme activity and the concentrations of H202 and dye. Courgette peroxidase was extracted and its performance was evaluated by using the free-CP （FCP） and immobilized-CP （ICP） forms in the decolourization of dY106. Immobilization of peroxidase in calcium alginate beads was performed according to a strategy aiming to minimize enzyme leakage and keep its activity at a maximum value by optimizing sodium alginate content, enzyme loading and calcium chloride concentration. The initial conditions ~it which the highest dY106 decolourization yield was obtained were found at pH 2, temperature 20~C, H202 dose 1 mmol/L （FCP） and 100 mmol/L （ICP）. The highest decolourization rates were obtained for dye concentrations 50 mg/L （FCP） and 80 mg/L （ICP）. Under optimal conditions, the FCP was able to decolorize more than 87% of the dye within 2 min. While with ICP, the decolourization yield was 75% within 15 rain. The decolourization and removal of dY106 was proved by UV-Vis analysis. Fourier transform infrared （FF-IR） spectroscopy analysis was also performed on dY106 and enzymatic treatment precipitated byproduct.

关键词： Cucurbita pepo peroxidase immobilization decolourization azo dye

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Evaluation of stress intensity factors for bi-material interface cracks using displacement jump methods

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Acta Mechanica sinica 2017年第6期33卷 1051-1064页

作者： K. C. Nehar B. E. Hachi F. Cazes M. Haboussi laboratoire de développement en mécanique et matériaux (LdMM) Université de Djelfa PB 3117 Djelfa Algeria laboratoire des sciences des procédés et des Matériaux (LsPM) UPR 3407 CNRS Université Paris 13 Paris France

The aim of the present work is to investigate the numerical modeling of interfacial cracks that may appear at the interface between two isotropic elastic materials. The extended finite element method is employed to analyze brittle and bi-material interfacial fatigue crack growth by computing the mixed mode stress intensity factors(sIF). Three different approaches are introduced to compute the sIFs. In the first one, mixed mode sIF is deduced from the computation of the contour integral as per the classical J-integral method,whereas a displacement method is used to evaluate the sIF by using either one or two displacement jumps located along the crack path in the second and third approaches. The displacement jump method is rather classical for mono-materials,but has to our knowledge not been used up to now for a bimaterial. Hence, use of displacement jump for characterizing bi-material cracks constitutes the main contribution of the present study. several benchmark tests including parametric studies are performed to show the effectiveness of these computational methodologies for sIF considering static and fatigue problems of bi-material structures. It is found that results based on the displacement jump methods are in a very good agreement with those of exact solutions, such as for the J-integral method, but with a larger domain of applicability and a better numerical efficiency(less time consuming and less spurious boundary effect).

关键词： Bi-material interface crack Mixed mode stress intensity factor displacement jump X-FEM Fatigue crack growth

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Theoretical prediction of structural,electronic and optical properties of quaternary alloy Zn_(1-x)Be_xs_yse_(1-y)

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Chinese Physics B 2012年第3期21卷 321-327页

作者： Hacini K Meradji H Ghemid s El Haj Hassan F laboratoire LPR D'epartement de PhysiqueFaculté des SciencesUniversité de Annaba laboratoire de physique des Matériaux Faculté des SciencesUniversité Libanaise

Within density functional theory based on the full potentiM-linearized augmented plane wave method, we carry out the first-principles calculation of the structural, electronic, and optical properties of the zinc blende quaternary alloy Zn1-xBexsyse1-y. The Perdew-Burke-Ernzerhof generaized gradient approximation based on the optimization of total energy and the Engel-Vosko generalized gradient approximation based on the optimization of the corresponding potential are used. Our investigation on the effect of the composition on lattice constants, bulk modulus, band gap, optical dielectric constant, and refractive index shows a non-linear dependence. The energy gap Eg（x, y） has been determined over the entire compositions x and y. In addition, the energy band gap of the technologically important quaternary alloy Znl-xBexsyse1-y in conditions of being lattice matched to Zns substrate has been investigated. It is noteworthy that the present work is the first theoretical study of the quaternary alloy of interest.

关键词： density functional theory full potential-linearized augmented plane wave method qua-ternary alloy lattice-matched substrate

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Numerical study of Greenhouse Nocturnal Heat Losses

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Journal of Thermal science 2011年第4期20卷 377-384页

作者： F.Berroug E.K.Lakhal M.El Omari M.Faraji H.El Qarnia laboratoire d'Automatique de l'Environnement et procédés de Transfert UniversitéCadi AyyadFacultédes Sciences Semlalia-Département de PhysiqueMarrakech-MarocAffiliéau CNRSTURAC 28 laboratoire de Physique des Materiaux MicroelectroniqueAutomatique et TechniqueDepartement de PhysiquesFaculte des Sciences Ain ChockUniversite Hassan IICasablanca-Maroc

In this study we quantify and analyze different components of nocturnal losses from a heated greenhouse with the presence of vegetation for typical winter weather conditions in Marrakesh-Morocco,using a non linear model,based on the greenhouse heat and mass *** was found that 12% of the total input heat was dissipate as a sensible and latent leakage losses,66% was lost by convective exchange through air-inner *** gain of energy at the inner-cover is dissipated at the outer-cover by radiation(66%)and convection(34%).This results point toward some practical measures to reduce heat losses:increasing air tightness,using covering materials with low-emissivity in the long wave band or putting up an external thermal curtain should provide significant energy savings.

关键词： Greenhouse energy balance heat losses numerical analysis.

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doppler Global Velocimeter-development and Validation with Measurements in a Round Free Jet

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Journal of Thermal science 2009年第1期18卷 74-84页

作者： X.Ottavy s.Goguey J.Berthiau I.Trébinjac laboratoire de Mécanique des Fluides et d’Acoustique(LMFA)

doppler global velocimetry （dGV） has already been shown to be an interesting technique capable of measuring the three components of velocity in a plane. A 1-component dGV system is currently under development at the LMFA, using a stabilized continuous wave （CW） argon ion laser for ermssion, lne receiver Ieatures only one camera for both signal and reference images and incorporates a deF1 system to adjust the incident laser light frequency and its transmission coefficient on the iodine cell absorption line. A description of the whole system is presented and a validation with measurements of axial velocities at several positions in a round free jet is proposed.

关键词： laser anemometry doppler shift iodine vapor absorption line filter deFI system image processing.

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studying on the increasing temperature in IT-sOFC:Effect of heat sources

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Journal of Zhejiang University-science A(Applied Physics & Engineering) 2007年第9期8卷 1500-1504页

作者： ZITOUNI Bariza BEN MOUssA Hocine OULMI Kafia Laboratore d'étude des systèmes énergétiques industriels (LEseI) Faculty of EngineeringUniversity of BatnaBatnaAlgeria laboratoire de Chimie et de Chimie de L'environnement Faculty of ScienceUniversity of BatnaBatnaAlgeria

The dimensions and the materials type limit the performance of fuel cell. The increase of the temperature in electrodes and electrolyte of the cell,is due to the over potential of activation (transfer of load),the over potential Ohmic (resistance of polarization),the over potential of reaction (heat released by the chemical reaction) and the over potential of diffusion. In this paper,we studied the thermo-electrical performance of an intermediate temperature solid oxide fuel cell (IT-sOFC) with electrode supported. The aim of this work is to study this increasing temperature of a single cell of an IT-sOFC under the influence of the following parameters: heat sources,functioning temperature and voltages of the cell,geometric configuration and materials type. The equation of energy in one dimension is numerically resolved by using the method of finite volumes. A computing program (FORTRAN) is developed locally for this purpose in order to obtain fields of temperature in every element of the cell.

关键词： IT-sOFC Thermo-electrical Joule effect Activation energy Temperature Voltage Geometric configuration

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Topological studies of Three-dimensional Flows in a High Pressure Compressor stator Blade Row without and with Boundary Layer Aspiration

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Chinese Journal of Aeronautics 2011年第5期24卷 541-549页

作者： Ankit sACHdeVA Francis LEBOEUF laboratoire de Mécanique des Fluides et d'Acoustique Ecole Centrale de Lyon

This paper presents a numerical study of the flow topologies of three-dimensional （3d） flows in a high pressure compressor stator blade row without and with boundary layer aspiration on the hub wall. The stator blade is representative of the first stage operating under transonic inlet conditions and the blade design encourages development of highly complex 3d flows. The blade has a small tip clearance. The computational fluid dynamics （CFd） studies show progressive increase of hub corner stall with the increase in incidence. Aspiration is implemented on the hub wall via a slot in the comer between the hub wall and the suction surface. The CFd studies show aspiration to be sensitive to the suction flow rate; lower rate leads to very complex flow struc- tures and increased level of losses whereas higher rate renders aspiration effective for control of hub comer separation. The flow topologies are studied by trace of skin friction lines on the walls. The nature of flow can be explained by the topological rules of closed separation. Furthermore, a deeper analysis is done for a particular case with advanced criterion to test the non-degeneracy of critical points in the flow field.

关键词： high pressure compressor flow topologies three-dimensional flows boundary layer aspiration tip clearance

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Positron Energy Levels in Cd-Based semiconductors

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Communications in Theoretical Physics 2013年第6期59卷 756-762页

作者： B.Abbar s.Mécabih s.Amari N.Benosman B.Bouhafs laboratoire de Modélisation et de simulation en sciences des département de Physique Université djillali Liabès

Using the full potential linearized augmented plane wave FP-LAPW method within local density ap-proximation LdA, we have studied positron diffusion and surface emission in Cd-based semiconductors. This requires the calculation of electron and positron band structures. In the absence of experimental and theoretical data for CdX (X=s,se,Te) we have treated the si, which has been studied by several authors, as a test case. Predictive results on positron effective masses, deformation potentials, positron work functions, diffusion constants and positron mobilities are presented for CdX (X=s, se, Te). Our calculated data for si are compared with experimental and recent theoretical results.

关键词： dFT FP-LAPW semiconductors positron diffusion

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