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In this paper, the key assumptions in the M-K and effective stress ratio models are investi-gated for Al SI 1018 steel specimens with a thickness of 0.78 mm using experimental and numerical data from Marciniak tests. The experimental procedure included Digital Imag-ing Correlation (DIC) to measure the major and minor in-plane strains. Strain compo-nents were obtained at points inside (i.e., the defect region) and adjacent (i.e., the safe regions) to the high strain concentrations for four different strain paths. In the numerical analysis, FEA simulations with Marc Mentat were performed with shell elements to investigate the four specimen geometries. The key assumptions of interest are the incre-mental major strain ratio from M-K model and the critical stress concentration factor from effective stress ratio model. Thus, the mechanics- and material-based failure phe-nomena in these two analytical models are examined in this paper to provide insight into the material behavior at failure. Also, data are presented that shows clearly the localiza-tion (both size and strain value) for the various strain paths. [ABSTRACT FROM AUTHOR]

Hie doxography for Anaximander's account of the rings of the sky gives proportions for them that are discrepant. So a widely accepted hypothesis proposes that, since the circles of the celestial bodies are compared to wheels, we should add the thickness of their 'rims' to the measurements for the celestial rings. This paper proposes an entirely different hypothesis which avoids this awkward expedient by suggesting that there is a 'geometrical' reading of the numerical data. The discrepancies can then be explained by there being two different methods for calculating the circumference of the circles. [ABSTRACT FROM AUTHOR]

In the deformation analysis of geodetic networks, there are two conventional methods for estimating movement of an area of study: displacement vectors and strain tensors. However, the evaluation and representation of the deformation depend on the priori reference system and the configuration of chosen figures that constitute the entire network. These constraints make difficult the interpretation of the results. Through this present paper, a solution based on the finite element method (FEM) is proposed to refine the estimation and the representation of the deformation of geodetic networks. In this context, a study of the deformation is carried out to analyze the horizontal motion of the geodetic network Cheliff observed by classical triangulation in 1976 (by INCT) and 1981 (by CRAAG), based on a twodimensional elastic finite element model. The different results are illustrated in terms of displacement vectors, strain tensors and stress tensors. Deformation of the area thus determined is interpreted according to previous geophysical studies. In addition, different results revealed the following phenomena: A phenomenon of compressive of Cheliff area, in the NNW-SSE orientation, due to the rapprochement of the African and Eurasian tectonic plates that caused the fault opposite the famous earthquake of 10 October 1980. A phenomenon of block rotation in the SE and NW parts of the fault, in a retrograde direction. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, we prove the following result: let X be a complex manifold, hyperbolic for the Carathéodory distance and let U be an open set relatively compact in X. Then, there exists such that we get, for the Carathéodory infinitesimal metric, . We also get results concerning fixed points of holomorphic mappings from X to U. [Copyright &y& Elsevier]

In this paper, the nonreacting axisymmetric confined turbulent jets are studied by using the second order turbulence model. The aim is to present, in the initial region of the jet, the variable density effects, caused by a difference in temperature between the hot air and the ambient air, on the principal characteristic parameters of such flows. The numerical results obtained are then discussed in comparison with experimental data Djeridane [T. Djeridane, Contribution à l'étude expérimentale de jets turbulents axisymétriques à densité variable, Thèse de doctorat, univ. Aix-Marseille II, 1994] (relating to the air/air and He/air jets) and other found in the literature. Experimental measurements of the axial velocity, the Reynolds stress and the scalar, present qualitatively the same behaviour. The comparison of the numerical simulation to the experiment does not show large difference and the results obtained are in general satisfactory. [ABSTRACT FROM AUTHOR]

The sound quality improvement of a product at stage of its design is a concern of many firms. This design being made starting from tools based on numerical methods such as FEM, BEM or on semi-analytical methods, it is important that their predictions integrate the sound quality expected. The objective of this paper is to show the interest and the benefit of a perceptive step to the vibroacoustic system improvement. Specifically it is more a question of evaluating, through sound perception, the relevance of certain structural parameters and parameters of analysis, in order to refine the sound prediction. The studied system is a vibrating plate coupled to a cavity, in which acoustic pressures are measured, by taking into account variations related to the plate thickness, to the conditions of tightening at the edges of the plate and to the cavity sound absorption. The maximum frequency of analysis is also subjectively studied, by using listening tests of dissimilarity and preference based on the method of pair comparison. [ABSTRACT FROM AUTHOR]

Some forced nonlinear structures present hysteresis leading to jump phenomena and instabilities in the frequency response. in this paper, we investigate these phenomena analytically, numerically and experimentally on a structure whose nonlinear behaviour can be modified. The chosen structure is a free clamped beam; the non linearity is introduced by using electromagnetic actuators. The structure and the actuators are dimensioned in order to highlight this jump phenomenon. The results obtained analytically using a perturbation method on a simplified single mode model have been validated by numerical simulations and through experiments. These results show the possibility of controlling the jump phenomena in frequency forced response by acting on t;he electromagnetic actuators. [ABSTRACT FROM AUTHOR]

Abstract: Highly Active Anti-Retroviral Therapies (HAART) have proven to be extremely effective in improving and prolonging the patient''s life. Though, a concern arises since a long term drug intake induces many strong sides effects and reduces reactivity of the virus to any therapy. The purpose of the paper is to use numerical analysis and optimization tools to suggest improved therapies to handle HIV infection. The evolution of the infection is modelled by an ordinary differential equation system which includes both immune response and multi-drug effects. For a fixed time, one looks for a two drugs control strategy based on Pontryagine''s minimum principle with an objective function which takes into account three contributions: the viral load, the transient evolution of infection and the quantities of drug used. Simulations are carried out using an indirect optimization method along with Runge–Kutta adaptative stepsize algorithm. Numerical solutions to the optimality system are obtained and related histories are shown. The possibility of Scheduled Treatment Interruption is also examined. [Copyright &y& Elsevier]

This paper presents an accelerated test method applicable to complex mechanical devices when no analytical relationship with respect to the stress level can be defined. If a numerical approach remains possible, the numerical model can be fitted to the accelerated test results. Thus, long term failures can be predicted from very short tests. This method is carried out in the case of fatigue, the evolution of the damage leading to the failure having to be modeled by a numerical finite-elements method. [ABSTRACT FROM AUTHOR]

We present in this paper a study on flow evolution during intake stroke in the axial plane of a two valve motored engine cylinder, using a finite-elements numerical method with movable boundary. The movable boundary computation field includes simultaneously the intake port, the inlet valve area and the combustion chamber. An arbitrary Lagrangian-Eulerian kinematics description method (ALE) is adopted to describe the flow and thermal fields, considering the interface movement between the fluid and both inlet valve and piston. The evolution and establishment process of tumbling vortical structures and thermal field in the symmetry axial plane is presented. The modelling adopted in this study leads to a reasonable precision numerical simulation in comparison with experimental results recently published. [ABSTRACT FROM AUTHOR]

This paper presents an enriched bilinear quadrilateral thin shell element for spot welded structures modelling. This element is implemented as an Abaqus user element. The base element is a Simo-Rifaï quadrilateral. The present treatment of spot welds is inspired from the inclusion problem treatment in the extended finite element framework. Each spot weld is considered as a point detail in the steel sheet 2D continuous medium; the enrichment functions to the displacement approximation space are chosen to represent accurately the local deformation modes near the spot weld, and give an acceptable representation of the deformed assembled steel sheets without requiring an explicit meshing of spot welds. Numerical examples demonstrate the method capability to model spot welded structures from independently obtained steel sheets meshes. [ABSTRACT FROM AUTHOR]

This paper presents a numerical analysis of the interaction between shallow tunnelling and structure on surface. The analysis is done using the software Flac3D, based on three-dimensional finite differences. The TBM tunnel excavation is simplified and is taken into account by volume loss. First, a reference calculation without structure on surface is presented. A numerical model coupling ground mass and structure on surface is then used to study the soil-structure interaction. The structure is composed by columns and floors, founded on a raft. The material has elastic properties of a reinforced concrete. Results are analysed in term of ground displacement on surface. The last part presents the influence of the structure stiffness on soil displacements on surface. [ABSTRACT FROM AUTHOR]

Motivated by the superconductivity, we are interested in the fundamental state of the Schoro¨dinger operator with magnetic field. In this paper, we propose a numerical approach based on the finite elements method to determine the bottom of the spectrum of this operator in general domains. We improve the numerical results by using mesh-refinement techniques based on a posteriori error estimators developed elsewhere. We also look at the monotonicity of the bottom of the spectrum in an angular sector according to the angle to complement the theorical study of Bonnaillie (C. R. Acad. Sci. Paris, Ser. I 336 (2) (2003) 135–140). To cite this article: F. Alouges, V. Bonnaillie, C. R. Acad. Sci. Paris, Ser. I 337 (2003). [Copyright &y& Elsevier]

The sequential iterative approach (SIA) scheme is the most efficient method for modelling reactive transport in porous media with the operator-splitting approach. A combination of finite discontinuous and finite mixed-hybrid elements is a powerful method for solving solute transport in porous media, but the use of this method for SIA scheme induces numerical difficulties. In this paper, a new method is developed to solve reactive transport by using both the SIA scheme and a combination of finite discontinuous and finite mixed elements. The proposed method is tested by modelling a column experiment. To cite this article: J. Carrayrou et al., C. R. Mecanique 331 (2003). [Copyright &y& Elsevier]