The concept of equivalent morphology has received much consideration in recent decades. The importance of this concept is reflected in the fact that an inclusion of any morphology can be replaced by a circular one in simulation. If this concept is confirmed, it will facilitate the modeling and simulation of complex configuration microstructures.

To decide on this concept, an in–depth study is carried out in this work, trying to answer it in a clear and definitive way by trying to identify all the possible situations. For this the two types of composites, namely, periodic interpreted by an elementary cell and random interpreted by a Representative Volume Element (RVE) with 200 inclusions are considered. To be sure that the isotropy is provided by the RVE of the periodic microstructure, two types of elementary cells were treated: one circular and the other square. In order to cover all possible situations, the inclusion of the elementary cell is considered with several situations, centered position with different orientations at constant and random steps, random position with orientation at constant steps and random position and orientation at random steps. For each situation, the effective property is determined by the average of 20 cases are processed for elementary cells, while for the large RVE, the properties are obtained by a unit realization. To take into account the effect of contrast, two situations are considered, namely, rigid inclusion case and rigid matrix case. Several results are obtained and given in the conclusion.

It is well argued that stability-initiated failure dominates, especially in older bone, because of the instability of single trabeculae which is prone to inelastic buckling at stresses far less than expected for strength-based failure. It is also well known that when several horizontal struts have disappeared, trabecula fails due to compression-buckling load. In this contribution, our main goal is to improve, from theoretical point of view, the mechanistic understanding of bone buckling failure which is known to be at the core of important clinical problems. For that and with respect to previous works, an attempt is made in order to establish a simplified adaptive-beam buckling model, formulated within the context of the nonlocal adaptive continuum mechanics, from which numerical computations were performed in order to get a better knowledge about bone-column buckling mechanism affected by both bone density and bone density gradient distributions restricted to Euler–Bernoulli beam theory. An attempt is made to compare the experimental data with the response of our simplified model. For that, controlled buckling tests of single trabeculae were carried out from three medial tibia end sections (knee joint).

The objective of this paper is to develop a global modelling approach, that simulates both the resin transfer molding (RTM) manufacturing and the prediction of the effective thermal conductivity (ETC) of a carbon–cpoxy (CE) laminated composite reinforced with particles. This numerical approach is based on two main stages. First, a numerical simulation of the suspension flow and the filtration of the charges during the RTM process. A method, for simulating the flow of a resin, loaded with particles in suspension through a fibrous medium, considering its double porosity scale, has been proposed. It is based on the description of the flow by Stokes–Darcy coupling, filtration phenomenon and particle dynamics. Secondly, the ETC of the composite thus produced is evaluated using a numerical homogenisation technique, considering the spherical particles inserted into the carbon–epoxy laminated composite. These obtained results have shown that, the incorporation of particles in the laminated composite leads to a significant increase in their effective thermal conductivity, which depends on their thermal conductivity. Finally, a simple linear thermal model has been proposed to predict the effective thermal conductivity of the composite carbon–epoxy–particles, as a function of that of the base composite carbon–epoxy and that of the particles.

In this paper, a formula for estimating the effective thermal conductivity of lotus-type porous materials (LTPM) combining an analytical formula with a mean-field homogenisation technique is developed and validated. LTPMs are considered multi-phase materials in which each phase is defined by the pore shape. To estimate the effective thermal conductivities of multi-phase LTPMs, a two-step mean-field homogenisation method is implemented and validated. The validation is applied by comparing the results obtained with those of the representative volume element based finite element homogenisation method, which has been taken as a reference. The proposed formula is applied by replacing the first step of the two-step mean field homogenisation method using a formula for estimating the effective thermal conductivity of two-phase lotus-type materials. The good agreement between the results of the proposed formula and the reference results indicates that the proposed formula ensures an accurate estimation of the effective macroscopic thermal conductivities of multi-phase lotus-type porous materials.

This work consists in a numerically evaluation of elastic fields distribution, caused by intrinsic dislocation networks placed at a nanometric trilayers interfaces, in order to estimate their influence on the surface topology during heterostructure operation. The organization of nanostructures is ensured by the knowledge of different elastic fields caused by buried dislocation networks and calculated in the case of anisotropic elasticity. The influence of elastic fields generated by induced square and parallel dislocation networks at CdTe / GaAs / (001) GaAs trilayer interfaces was investigated. By deposition, the nanostructures organization with respect to the topology was controled.  

In this paper, the study of precipitation reaction in the aluminum alloy known as AGS 6101. For the case of Cold drawn wires process in the open air space and at room temperature for two years, we inspect first the presence of precipitates in the microstructure and study the effect of heat treatment on the activation of this phenomenon [1]. The second objective of this work is to see the effect of natural and thermal aging on the microstructural evolution of cold-drawn aluminum wires (AGS) 6101 [2-5]. The characterization methods used in this work are optical microscopy (OM), scanning electron microscopy (SEM) and X-ray diffraction.

Knowing the stresses and pressures in the contact between two deformable solids is fundamental in order to optimize the strength and the lifetime of mechanical components such as bearings or gears. These constraints can be determined by the calculation (finite element method or Hertz theory) or by experimental methods such as photoelasticity. The objective of this study is to model and compute the stress field and contact pressure using 3D finite element software. The validation of obtained results is done by comparison with the classical results of the non linear Hertz theory between two deformable cylinders. An application to spur gears with a circle involute profile is done and also validate with the same

The objective of the present study is the active flow control of blood in the aorta with atherosclerosis using an External Magnetic Field (EMF) in order to facilitate the blood flow. For that purpose, a numerical investigation has been developed with a Magneto-hydrodynamics flow modelisation. The blood is considered homogeneous, incompressible and Newtonian and the fluid flow is assumed to be unsteady, two-dimensional and laminar. The aorta tissue is electrically conductive. Fluent software has been used to solve the governing equations. The results relating to velocity, pressure and the wall shear stress indicate that the presence of the EMF considerably influences the blood flow. The flow control deals with the effects of the EMF direction of application and its intensity. The results show that by applying an EMF, the blood velocity and pressure in the aorta are entirely affected. The direction and the intensity of the EMF allow minimization of the flow instabilities due to the geometrical singularities. Therefore, applying an EMF can be considered an appropriate method for flow control in order to obtain a uniform blood circulation around the atherosclerosis.

The objective of this work is the development of a Fe-W-Ni sintered steel obtained by the powder metallurgy technique. The latter is widely used today for the design of new alloys based on powders (iron) to meet industrial requirements in strength and wear characteristics. The proposed alloy is based on iron mixed with 5% nickel and various percentages (5, 10, 15 and 20%) of tungsten. The effect of the tungsten W content on mechanical and structural properties is presented.

The energy balance components of a greenhouse as well as the greenhouse design may strongly impact the greenhouse energy. Few studies were devoted to the description of the energy balance components of a greenhouse located in the semi arid region of the southern Mediterranean basin, and no attention was paid to the prediction of the inside air temperature. In this study, experiments were undertaken to investigate the response of a greenhouse to the outside climate conditions considering a naturally ventilated Venlo glasshouse with a tomato crop. The measurements show that the difference between inside and outside air temperature is strongly linked to the incoming solar radiation as well as to the wind speed. From these results a simplified model was established to predict the greenhouse air temperature, knowing the greenhouse characteristics and the outside climate variables. The model is based on the energy balance of the greenhouse. Using a parameter identification technique, the model was calibrated against the experimental results. A sensivity analysis was conducted to assess the impact of several physical parameters such as solar radiation, wind speed and cover transmission on the evolution of the inside air temperature. This model appears to be suitable for predicting the greenhouse air temperature satisfactorily.

The purpose of this study was to establish a method based on an iterative scheme to approximate the numerical solution obtained from finite elements analysis for an RVE in two and three dimensions based on the homogenization concept for the assessment of the effective properties. The bounds of Hashin–Shtrikman and Voigt–Reuss were considered in the iterative process based on an updating of the constitutive relations of these models respectively. In this study, by assumption, we took the particular case of the heterogeneous materials with several elastic isotopic phases. The output variables considered using the iterative process are the bulk, shear modulus and the thermal conductivity. We have found a fast convergence of the iterative solution to the numerical result with a suitable concordance between the two solutions at the final step.

In the present work, (Cu-Sn, Cu-Co) based alloys with different compositions have been obtained by using powder metallurgy (PM). These alloys were created with the purpose of increasing mechanical and structural properties of the industrial parts. The compacts are made according to the sintering manufacturing method, the uniaxial compressed cold samples. Metallographic characterizations, hardness and density measurements were carried out in order to study the influence of the addition of tin and cobalt, the variation of the compaction pressure and the sintering temperature on the finishing product. It has been proved that the addition of tin and cobalt to a copper powder mixture increase the properties of the sintered parts.

In the present work, Fe-Cu based alloys with different compositions have been obtained by using Powder metallurgy (PM). These alloys were created with the purpose of increasing mechanical properties of the parts. Nevertheless, little have been published, once this is a matter of industrial interest. In this work, samples of Fe_100-x Cu_x (x=0.40, 0.55, 0.70, 0.85 and 1) alloys were processed by cold pressing at 10 MPa, followed by sintering at 1250 C°. Structures formed during sintering were studied by EDS. Microstructural aspects were observed by MEB. Densification and microhardness tests were also performed.

The purpose of this study was to establish a method based on an iterative scheme to approximate the numerical solution obtained from finite elements analysis for an RVE in two and three dimensions based on the homogenization concept for the assessment of the effective properties. The bounds of Hashin–Shtrikman and Voigt–Reuss were considered in the iterative process based on an updating of the constitutive relations of these models respectively. In this study, by assumption, we took the particular case of the heterogeneous materials with several elastic isotopic phases. The output variables considered using the iterative process are the bulk, shear modulus and the thermal conductivity. We have found a fast convergence of the iterative solution to the numerical result with a suitable concordance between the two solutions at the final step.

Sun-tracking system is a key factor for solar photovoltaic (PV) future and new answers for the solar market. It will expand large scale PV-projects (PV farms) worldwide, and it is possible to collect more energy from the sun. PV farms consist of thousands of sun-tracking systems (STS) that are subject to dynamic loads (wind, snow, etc.), vibration, and gravitational loads. This paper presents the structural dynamic analysis of a 24 m² bi-axial sun-tracking system (azimuth-elevation) at different elevation angles based on its modal parameters (natural frequencies, modal shapes and modal damping ratios) and dynamic performance indices (Modal participation factors, forcing frequencies and mechanical quality factors) by means of the Finite Element Analysis (FEA). The simulation results show that the structural dynamic design of the STS meets the desired structural requirements and agrees well with structural dynamic standards (EN 1991-1-4 and ASHRAE). These results can be used for further analysis on optimal design and vibration safety verification for the bi-axial sun tracking systems (PV applications).
Structural Dynamics Analysis of Three-Dimensional Bi-Axial Sun-Tracking System Structure Determined by Numerical Modal Analysis | Request PDF. Available from: https://www.researchgate.net/publication/323002148_Structural_Dynamics_Analysis_of_Three-Dimensional_Bi-Axial_Sun-Tracking_System_Structure_Determined_by_Numerical_Modal_Analysis [accessed Oct 31 2018].

In the present work, Fe-Cu based alloys with different compositions have been obtained by using Powder metallurgy (PM). These alloys were created with the purpose of increasing mechanical properties of the parts. Nevertheless, little have been published, once this is a matter of industrial interest. In this work, samples of Fe_100-x Cu_x (x=0.40, 0.55, 0.70, 0.85 and 1) alloys were processed by cold pressing at 10 MPa, followed by sintering at 1250 C°. Structures formed during sintering were studied by EDS. Microstructural aspects were observed by MEB. Densification and microhardness tests were also performed.

A successful osseointegration involves the simultaneous optimization of the primary stability of the implant and the minimization of interfacial stresses bone - implant. In this context, the modeling of these stresses reports a great interest for researchers in last decades.The aim of this work is to study the effects of geometric parameters of a new model of titanium dental implant on the evolution of interfacial stresses bone /implant. For this, a dental implant of the second premolar in the lower jaw was considered, with different diameters, thread pitches and different thread forms. The profile of the interfacial stresses was presented for each case study, the results show a great similarity in the areas concerned, cortical bone, threaded region and cancellous bone, with the results obtained in the literature for other types of geometries.

Modeling and simulation of mechanical structures in development phase are fundamental to optimize and improve the stability and reliability of the final product as well as to reduce the cost of prototyping and testing. Wind turbines are subject to critical loading to the centrifugal force due to wind speed and gravitational force. The present study discusses three-dimensional numerical simulations of combined Darrieus-Savonius wind turbine D-SWT for applications in urban and isolated areas for lighting, pumping water, etc. The Darrieus turbine is used to produce wind power and the Savonius rotor to start the system. Finite Element Analysis (FEA) using SolidWorks 2015 is employed to generate the geometry of the structure and SolidWorks Simulation to investigate the stability and reliability static on the structure of the D-WST built by two types of material of the blade Galvanized Steel (GS) and Aluminum alloys 1060-H18 (ALU). Mechanical parameter of the structure are calculated for critical loading conditions, including the gravity and wind pressure loading due to the wind speed of 23m/s. Simulations results indicate no structural failure is predicted for all components of the D-SWT for both materials used according to Von Mises criterion stresses and the factors of safety of the most fragile material are greater than (the unity) 1. The maximum displacements found (3.84 & 6.81mm), occurred at the tip blades (free ends levels). These displacements are accepted relatively to the structure size.

Silver chloride that is commonly used as a reference electrode in many chemical sensors is stable when its dimensions are relatively large. However, its use in sensors, especially in nanosensors, requires that its size be reduced significantly. In this paper, we report that the stability of very small silver chloride electrodes could be obtained if a specific potential is applied. The AgCl wires produced by electrodeposition are investigated by the chronoamperometry technique. Scanning electron microscopy (SEM) is used to study the properties of the surface of the fabricated wires surface obtained. We found that the stability depends on the silver chloride surface morphology. Indeed, the Ag/AgCl wire provided a more stable potential when its surface morphology is like nanosheets. It seems that this surface morphology obtained for Ag/AgCl wire with a micrometric diameter is a promising element that could be used to measure a variety of biological parameters such as membrane potential, intracellular free ion concentrations and cell-to-cell communication.

Trabecular fatigue fractures are observed as compressive stress fractures in the proximal femur, vertebrae, calcaneus and tibia. These fractures are often preceded by buckling and bending of microstructural elements. But the etiology of these bone fractures is still poorly understood in biomechanical perspective. In the present work, it comes to predicting the buckling mechanism trabeculae in progress remodeling bone and in function of the boundary conditions without experimental data.