Periodic homogenization and damage evolution in RVE composite material with inclusion

This work deals with the coupling between a periodic homogenization procedure and a damage process occurring in a RVE of inclusion composite materials. We mainly seek on the one hand to determine the effective mechanical properties according to the different volume fractions and forms of inclusions for a composite with inclusions at the macroscopic level, and on the other hand to explore the rupture mechanisms that can take place at the microstructure level. To do this; the first step is to propose a periodic homogenization procedure to predict the homogenized mechanical characteristics of an inclusion composite. This homogenization procedure is applied to the theory based on finite element analysis by the Abaqus calculation code. The inclusions are modeled by a random object modeler, and the periodic homogenization method is implemented by python scripts. It is then a matter of introducing the damage into the problem of homogenization, that is to say; once the homogenized characteristics are assessed in the absence of the damage initiated by microcracks and micro cavitations, it is then possible to introduce damage models by a subroutine (Umat) in the Abaqus calculation code. The verifications carried out focused on RVE of composite materials with inclusions.

Three-Dimensional Numerical Simulation of a Flat Plate Solar Collector with Double Paths

Flat air solar collectors are used for heat transfer between the absorber and the heat transfer fluid, to improve this transfer there are several methods. Among these methods, the exchange surface lengthening and the creation of turbulence. In this work is done to give a comparison between two types of solar collectors, so we have made an improvement of Ben Slama Romdhane's solar collector by creating two air flow passages to increase heat transfer. We made a 3D simulation of a flat air solar collector with transverse baffles which causes turbulence and increases the exchange surface; we use the ANSYS calculation code to make the simulation and gives results with a brief time and minimal cost.

Numerical modeling of the contact effect on the parameters of cracking in a 2D Fatigue Fretting Model

The objective of this work is to study the effects of contact parameters on the cracking parameters of a specimen and a pad assembly. These parameters have been studied and evaluated by the finite element method analysis in two dimensions fretting fatigue model through the Abaqus calculation code. Different values ​​of the coefficient of friction of 0.1, 0.3 and 0.6 were applied on the various lengths in contact for a = 0.1, 0.5 and 1mm. Thus, on the various values ​​of angle of orientation of the crack equal to 15 °, 30 ° and 45 °. In addition, elements of the type (CPE4R) and the criterion of maximum tangential stress were applied. The curves of the crack parameters such as the SIF coefficients and the integral J were obtained and discussed.

Major upgrade of the synchrotron radiation calculation code SPECTRA

Since the first release in 2001, the synchrotron radiation calculation code SPECTRA has been used by many users and continuously upgraded to answer the requests and feedbacks from the users. Although such an incremental upgrade made in nearly two decades has significantly enhanced the capability of SPECTRA, the source code has become much more complicated, and thus the maintenance and further improvement are rather troublesome. To solve this issue, and to take advantage of the recent progress in the programming language, a major upgrade has been made as presented in this paper, in which a number of new features and advanced functions are implemented as well.

Spectral modal modeling by FEM of reinforced concrete framed buildings irregular in elevation

The irregular buildings constitute a large part of urban infrastructure and they are currently adopted in many structures for architectural or esthetic reasons. In contrast, the behavior of these buildings during an earthquake generates a detrimental effect on their regularity in elevation which leads to the total collapse of these structures.The objective of this work is essentially to model reinforced concrete framed buildings irregular in elevation subjected to seismic loads by the Finite Element Method (FEM). This modeling aims to evaluate several parameters: displacements, inter-storey drifts and rigidities, using two dynamic calculation methods; one modal and the other spectral modal. The latter is widely used by engineers.For this purpose, a detailed study of the frames which have several setbacks in elevation is carried out to validate the correct functioning of our FEM calculation code in both cases of modal and modal spectral analyses. The performance, accuracy and robustness of the FEM calculation code produced in this study is shown by the good correlation of the obtained results for the treated frames with those obtained using the ETABS software.

A Hashin Criteria Investigation to Predict the Interaction Effect of Defaults on the Damage of Composite Pipe

Composite pipelines carboxyl presence the damage by two defects, under the bending moment M = 1rd ,and various internal pressure (P = 40bar, P = 60bar, P = 80bar) is studied in this work. Using the HASHIN criterion, a numerical prediction through the calculation code ABAQUS took the objective of evaluating the damage by interaction effect between two defects. The results presented by evaluative curves of correlation between the moment to the damage and the parameters of orientation and location of the defects. The interaction effect of defects on damage was conditioned by their locations along the pipeline surface. The results obtained show a strong influence of the defects on the level and the mode of failure as well as their response until the damage.

Theoretical Study of the Input Impedance and Electromagnetic Field Distribution of a Dipole Antenna Printed on an Electrical/Magnetic Uniaxial Anisotropic Substrate

The present work considers the investigation of the effects of both electrical and magnetic uniaxial anisotropies on the input impedance, resonant length, and fields distribution of a dipole printed on an anisotropic grounded substrate. In this study, the associated integral equation, based on the derivation of the Green’s functions in the spectral domain, is numerically solved employing the method of moments. In order to validate the computing method and the evaluated calculation code, numerical results are compared with available data in the literature treating particular cases of electrical uniaxial anisotropy; reasonable agreements are reported. Novel results of the magnetic uniaxial anisotropy effects on the input impedance and the evaluated electromagnetic field are presented and discussed. This work will serve as a stepping stone for further works for a better understanding of the electromagnetic field behavior in complex anisotropic and bi-anisotropic media.

Numerical Study of Heat Transfer in Rectangular Fins for Different Cases of Thermo-Physical Properties

The present work is a contribution to the development of a calculation code that determines the temperature field on fins having rectangular geometry for any bi-dimensional or three-dimensional simulation conditions. Different cases of simulations are presented. An implicit finite volume method, unconditionally stable, is extended in this study for the discretization of the governing equations. The representative results, validated by the Ansys code, show that the fin temperature increases with the increase of the temperature values selected as the boundary conditions, with the addition of a heat flow or any additional heat source. The numerical results are very consistent with the theory and the results obtained from commercialized codes. By increasing the diffusivity one converge more quickly towards the stationary solution. Upon reducing the fin size a very drastic shift occurs from the transient regime to a permanent one. In the case of a refinement of the mesh, the use of a very small epsilon ensures the convergence. Therefore, the results obtained in this study serve as basis of comparison with any other study on heat transfer on rectangular fins.

Numerical Modelling of The Behavior of Tunnel in Soft Surrounding Rock. A Case Study of Djebel El-Ouahch Tunnel, Algeria.

The response of a massif to stresses generated by tunnel excavation depends essentially on the geological conditions, the geometry of the tunnel and its underground position. The major problem related to the construction of these structures is to ensure the stability of the whole tunnel-ground, by controlling the various deformation generated during the constructionIn this context, the present paper examines the effect of these conditions on the behavior of tunnels and the surrounding soil. The study is applied to a real tunnel, in this case the tunnel of Djebel El Ouahch, Algeria was taken as a reference model. The research includes a parametric study to evaluate the effect of several parameters on the behavior of the tunnel and surrounding soil such as the tunnel anchoring depth, the tunnel-soil interface rate, and the shape of the tunnel cross section. The analysis is performed using the PLAXIS 3D TUNNEL calculation code with an elastoplastic Mohr-coulomb model for the soil behavior. The results show that the strongest and most stable position is the mid-deep tunnel with a circular section, with a non-slip interface between the tunnel and the ground. These outcomes can help to understand the effects of various influences parameters which control the stability of the tunnel in a soil with bad characteristics.