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991.
992.
Koffi Espoir Koumi Lv Zhao Julien Leroux Thibaut Chaise Daniel Nelias 《International Journal of Solids and Structures》2014
Many materials contain inhomogeneities or inclusions that may greatly affect their mechanical properties. Such inhomogeneities are for example encountered in the case of composite materials or materials containing precipitates. This paper presents an analysis of contact pressure and subsurface stress field for contact problems in the presence of anisotropic elastic inhomogeneities of ellipsoidal shape. Accounting for any orientation and material properties of the inhomogeneities are the major novelties of this work. The semi-analytical method proposed to solve the contact problem is based on Eshelby’s formalism and uses 2D and 3D Fast Fourier Transforms to speed up the computation. The time and memory necessary are greatly reduced in comparison with the classical finite element method. The model can be seen as an enrichment technique where the enrichment fields from the heterogeneous solution are superimposed to the homogeneous problem. The definition of complex geometries made by combination of inclusions can easily be achieved. A parametric analysis on the effect of elastic properties and geometrical features of the inhomogeneity (size, depth and orientation) is proposed. The model allows to obtain the contact pressure distribution – disturbed by the presence of inhomogeneities – as well as subsurface and matrix/inhomogeneity interface stresses. It is shown that the presence of an inclusion below the contact surface affects significantly the contact pressure and subsurfaces stress distributions when located at a depth lower than 0.7 times the contact radius. The anisotropy directions and material data are also key elements that strongly affect the elastic contact solution. In the case of normal contact between a spherical indenter and an elastic half space containing a single inhomogeneity whose center is located straight below the contact center, the normal stress at the inhomogeneity/matrix interface is mostly compressive. Finally when the axes of the ellipsoidal inclusion do not coincide with the contact problem axes, the pressure distribution is not symmetrical. 相似文献
993.
Marius?Mermet-GuyennetEmail author Maureen?Dinkgreve Mehdi?Habibi Nicolas?Martzel Rudolf?Sprik Morton?Denn Daniel?Bonn 《Rheologica Acta》2017,56(6):583-589
Nanosized filler particles enhance the mechanical properties of polymer composites in a size-dependent fashion. This is puzzling, because classical elasticity is inherently scale-free, and models for the elasticity of composite systems never predict a filler-size dependence. Here, we study the industrially important system of silica-filled rubbers, together with a well-characterized model-filled crosslinked gel and show that at high filler content both the linear and nonlinear elastic properties of these systems exhibit a unique scaling proportional to the cube of the volume fraction divided by the particle size. This remarkable behavior makes it possible to predict the full mechanical response of particle-filled rubbers for small but finite deformations based solely on the rheology of the matrix and the size and modulus of the filler particles. 相似文献
994.
The interaction between a viscous fluid and an elastic solid is modeled by a system of parabolic and hyperbolic equations,
coupled to one another along the moving material interface through the continuity of the velocity and traction vectors. We
prove the existence and uniqueness (locally in time) of strong solutions in Sobolev spaces for quasilinear elastodynamics
coupled to the incompressible Navier-Stokes equations. Unlike our approach in [5] for the case of linear elastodynamics, we
cannot employ a fixed-point argument on the nonlinear system itself, and are instead forced to regularize it by a particular parabolic artificial viscosity term. We proceed to show that with this specific regularization, we obtain a time interval
of existence which is independent of the artificial viscosity; together with a priori estimates, we identify the global solution
(in both phases), as well as the interface motion, as a weak limit in strong norms of our sequence of regularized problems. 相似文献
995.
996.
Nonlinear Dynamics - An experimental study of the single-well and twin-well, also referred to as intra-well and inter-well, respectively, nonlinear dynamics of a bistable composite laminate is... 相似文献
997.
Heiner Schwarz Laurent Zimmer Daniel Durox Sébastien Candel 《Experiments in fluids》2010,49(4):809-821
Equivalence ratio non-uniformities may give rise to some of the instabilities observed in modern lean premixed combustion
systems. The present work intends to investigate the influence of equivalence ratio perturbations on the dynamics of premixed
flames. A burner equipped with a secondary injection system is used to generate equivalence ratio perturbations which are
convected by the flow and impinge on a conical flame. Two laser-diagnostics, based on Rayleigh scattering and hydrocarbon
infrared absorption, respectively, are employed to give insight into the spatial and temporal evolution of the mixture composition
field. Rayleigh scattering images also reveal the flame front dynamics providing an indication on the response of a weakly
turbulent flame subject to mixture composition inhomogeneities. Laser light absorption provides a time resolved signal which
is used to estimate the equivalence ratio perturbation level. A theoretical model based on the G-equation is used to interpret
the experimental data and compare the relative effects of velocity and equivalence ratio perturbations. 相似文献
998.
Daniel Michelson 《Journal of Dynamics and Differential Equations》1993,5(3):375-415
Steadily rotating solutions of the Kuramoto-Sivashinsky equationu
t
+
2
u++¦u¦
2
=c
2
are studied. These solutions bifurcate from the steady radial solution of the above equation. For large values ofc and angular velocities such thatN¦¦<2c<(N+1)¦¦, we show that there exists a 2N-1 family of bifurcating solutions. The proof is based on a certain generic transversality assumption. A computer-assisted proof of this assumption is given for 1N10. 相似文献
999.
The interaction of a two-phase flow with a
wedge where a stationary shock wave is initially settled is studied
in a two-dimensional configuration. Before the introduction of
the dispersed phase, the flow around the wedge is a supersonic
one phase flow such as an attached stationary shock wave is
present. Then, the dispersed phase is introduced upstream the
initial position of the stationary shock wave. The purpose of
this study is to point out two-phase and droplets break-up
effects on the oblique shock wave. The two-dimensional
equations are solved by a TVD scheme where fluxes are computed
by using Riemann solver for the gas phase equations and also
for the dispersed phase equations wich is an original approach
due to the authors (Saurel et al. 1994). In addition to drag
forces and heat and mass transfers, the process of droplets
fragmentation based on the particle oscillation is considered.
Accepted April 28, 1995 相似文献
1000.
Isaac M. Daniel 《Experimental Mechanics》1965,5(3):83-89
This paper describes the results of mechanical and optical measurements in plasticized polyvinyl chloride under conditions of creep and relaxation at room temperature. It covers one task of a broader investigation aimed at developing experimental methods for viscoelastic stress analysis. The moiré method of strain analysis was found well suited for continuous recording of axial and transversal deformation in creep tests. The material exhibits linear viscoelastic behavior, both mechanical and optical. Strain, stress and birefringence measured from creep and relaxation tests gave straightline plots on log-log scale and, thus simple empirical formulas were possible to derive. The theoretical prediction that birefringence in a linear viscoelastic material not exhibiting flow can be expressed as a linear relationship of stress and strain was satisfactorily substantiated. 相似文献