This research work focuses on understanding structural morphologies at different scales and studying their mechanical behavior in the context of the development of topology optimization by the concern of creation and valuation of new porous and architectured materials in fields of industrial, aerospace, and even medical applications. We focused on developing a multi-scale modeling approach of porous and architectural structures allowing the production of the structure by Additive Manufacturing for aeronautical and medical applications.
Therefore, we demonstrated an approach based on 3D printing of structure production by displaying the numerical and experimental results in the aerospace and medical field. Firstly, we introduced the design stage of the CAD model equivalent for the designed turbine blade. By applying the method of Topology Optimization for finding the optimal density distribution of lattice structures and selecting the proposed technique for manufacturing the lattice structures. Numerical simulations have been carried out for gas turbine blades and obtaining the deformation and stress values under thermomechanical loads, present some results, and discuss them. On another hand, created a new design based on three lattice structures from triply periodic minimal surfaces (TPMS) with a different volume porosity to replace cancellous bone based on predicting the mechanical stiffness. Finally, present some results and their interpretations and discuss them.

Due to the high degree of randomness in the microstructure of real closed-cell foams, many reported numerical models in the literature are not able to capture precisely the local morphological features found in solid foams geometry. This is still the main impediment that restricts the investigation of this novel material and motivates the development of a sophisticated 3D solid model, which describes properly the complex geometry of real closed-cell foams. In this regard, this paper presents an original approach to generate a realistic and accurate 3D computational model of irregular closed-cell foams with relative density control and detailed finite element analysis of their mechanical performance under quasi-static loading up to densification. The solid model is constructed based on spherical particles inflation simulation. It resembles the real foams in terms of local features such as cell walls irregularities and thickness variation. The modeling approach was successfully
verified by comparing cell-morphological details of the generated models with those produced experimentally available in the literature and by the high-quality of obtained 3D printed models containing complex shapes and irregular cell wall thickness distribution. The evolution of spherical particles during the inflation process is analyzed based on finite element (FE) simulations. It was found that it can produce varying relative densities of foam due to the gradual decrease in the gap between the inflated particles, this makes the geometrical model of the foam suitable for studying the effect of local morphological characteristics on the mechanical performance of closed-cell foam material. To demonstrate that the compressive performance of the proposed closed-cell foam models can be controlled by relative density, 3D foam models were extracted from different inflation times and then subjected to quasi-static compression tests up to densification using the Abaqus software. The results confirm that the plateau stress can be expressed as a function of foam relative density, its accuracy is validated by comparing it to the closed-cell aluminum foam power law equation existing in the literature.
The new design method offers suitable numerical models for AM technology, plenty of experimental works on closed-cell foam can be reduced for engineering applications.

Lotus-type porous materials (LTPMs) are considered as a new category of engineering materials. They are porous materials characterized by long, straight, unidirectional cylindrical pores, and are obtained via unidirectional solidification from a melt under hydrogen and argon atmospheres. The anisotropic pore morphology of lotus-type materials results in the anisotropy of their mechanical and physical properties. This study aims at investigating the effect of cross-sectional pore shapes on the effective Young's modulus (EYM) of LTPMs. The representative volume element-based finite element homogenization method was used to compute the effective bulk and shear moduli. Subsequently, the EYM was deduced from the effective bulk and shear moduli. The numerical results of the circular pores were validated by comparing them with experimental results. Because the results indicated that the EYM is extremely sensitive to the variation in the pore shapes, a formula for estimating the EYM of LTPMs by considering the pore shapes was developed and validated.

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.