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.

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.

Prediction of effective properties for multiphase composite is very important not only to analysis and optimization of material performance, but also to new material designs. In this paper, the effective elastic property of some complex particulate composites is analyzed and compared with numerical results, demonstrating the validity of the proposed approach. We propose the equivalent morphology concept for the numerical homogenization of random composites. In this study, this concept is extended for complex material. A home script based on Python codes is made to automate the generating of Representative volume element with various volume fraction.

A high emergence of wind energy into the electricity market needs a parallel efficient advance of wind power forecasting models. Determining optimal specific speed and drive-train ratio is crucial to describe, comprehend and optimize the coupling design between a wind turbine-rotor and an electric generator (EG) to capture maximum output power from the wind. The selection of the specific design speed to drive a generator is limited. It varies from (1-4) for vertical axis wind turbines and (6-8) for horizontal axis wind turbines. Typically, the solution is an iterative procedure, for selecting the adequate multiplier ratio giving the output power curve. The latter must be relatively appreciated to inlet and nominal rated wind speeds. However, instead of this tedious and costly method, in the present paper we are developing a novel heuristic coupling approach, which is economical, easy to describe and applicable for all types of variable speed wind turbines (VSWTs). The principle method is based on the fact that the mechanical power needed of the wind turbine (WT) to drive the EG must be permanently closer to the maximum mechanical power generated by the (WT).

A numerical homogenization technique and morphological analysis based on the finite element method are used to compute mechanical properties of porous materials. This is achieved by considering two–dimensional matrix containing random distribution of identical non–overlapping circular or elliptical voids. Several microstructure configurations are obtained by varying the voids morphology and the porosity of the matrix. The notion of the representative volume element is used for numerical simulations in order to estimate the morphology effects of the voids on the effective ultimate tensile strength of the called Lotus–Type Porous Metals. A confrontation of the obtained numerical results of the representative microstructures for different morphologies of voids and different porosities to an analytical model and experimental data is performed. Finally, a formula improving the Boccaccini model is proposed to estimate effective tensile strength of porous metals taking into account the voids morphology.

This paper presents an efficient method to automatically generate and mesh random non–periodic three dimensional (3D) microstructures for three classes of complex heterogeneous media having a wide range of important engineering applications, porous media, composites with interfacial debonding and composites with high density particles. The resulting 3D microstructure is intentionally constructed to be easily and efficiently implemented in standard finite element computational codes. Several examples of 3D representative volume elements are shown. The performance of the proposal in finite element analysis is demonstrated in numerical implementation to predict the effective non–linear elastic–plastic response of two–phase particulate composites reinforced with spherical particles. The main result achieved is the estimation of the effective plastic tangent modulus by a simple linear regression equation for different volume fractions.

The greenhouse design as well as the cover material properties in particular may strongly impact the greenhouse energy. To study the effect of these parameters, three typical unheated greenhouses equipped with rows of canopy were considered. Experiments were launched to establish the boundary conditions and validate the model. Two parametric studies were carried out: for the nocturnal period when the energy performance of each type of greenhouse was investigated, and for the diurnal period, when the sun path was simulated taking into account the type of the cover, its spectral optical and thermal properties. Results indicate that for the nocturnal period, the ambient air temperature in the tunnel and vertical wall greenhouse was relatively homogenous and warmer compared with the temperature distribution in the Venlo greenhouse. The plastic greenhouse, especially the tunnel one had better performances concerning the homogenization of the climate and the thermal energy storage. Concerning the diurnal period, and for both plastic greenhouses equipped with fully opened side vents, the air located between the rows of canopy and ground surfaces remained very slow, not exceeding 0.2 ms-1 ; for the Venlo glasshouse, the recirculation loop situated above the crop improved the air mixing and induced a good homogenization. Results indicate that the cover material with highest absorptivity, deteriorated the natural ventilation, increasing the air temperature by convection, and reduced the available Photosynthetically Active Radiation.