Journal of Theoretical and Applied Mechanics
Volume 39, Number 1, 2009
INVESTIGATION OF BORON PRODUCTS USED IN BRAKE PADS
Key word: brake pad, boron products, composite materials, friction coefficient, tribology.
S. G. Hristova
Department of Applied Mathematics and modelling,
Integral stability in terms of two measures for impulsive differential equations
Abstract. This paper investigates integral stability in terms of two measures of systems of nonlinear impulsive differential equations. Piecewise continuous Lyapunov functions have been applied. The obtained sufficient conditions significantly depend on the impulses.
Key words: integral stability, two measures, Lyapunov functions, impulsive differential equations.
P. Kalitzova –Kurteva, S. Slavtchev
Department of Mechanical Engineering,
Technion-Israel Institute of Technology,
LONG-WAVELENGTH MONOTONIC MARANGONI INSTABILITY IN A BINARY MIXTURE LAYER WITH NONLINEAR SORET EFFECT
Abstract. The appearance of mass flux in binary mixtures, due to temperature gradient, is known as thermodiffusion or Soret effect. In addition to the classical diffusive flux, the total mass flux also consists of a thermodiffusive flux initiated by the gradient. The Soret effect is called nonlinear when the thermodiffusive flux is a product of the temperature gradient and a linear function of the solute concentration in the mixture. The nonlinear Soret effect is pronounced mostly in very dilute solutions.
The paper is devoted to the problem of Marangoni instability in a thin horizontal layer of a binary liquid mixture in the presence of the nonlinear Soret effect. The layer is bounded by a rigid plate from below and a gas-liquid non-deformable interface from above. It is subjected to a perpendicular temperature gradient. The case of heating from below is only considered. Based on the linear stability analysis, criteria for the onset of monotonic Marangoni instability with respect to long-wavelength perturbations are obtained in the case of small Biot numbers.
Key words: binary mixture, nonlinear Soret effect, long-wavelenght Marangoni instability.
S. K. Ghosh
Department of Mathematics,
P.O.-Narajole, Dist.- Midnapore
(West), 721 211, West
O. Anwar Bég
Mechanical Engineering Department,
e-mail: O.Beg @shu.ac.uk, email@example.com
Thermal Engineering and Fluids Department,
solutions are presented for the steady magnetohydrodynamic
(MHD) rotating viscous convective flow with thermal radiation and induced pressure
gradient for a fluent regime which is optically-thin i.e. an optically finite
gray gas which does not re-absorb radiation emitted from other
parts of the gas. The conservation equations for momentum and energy are non-dimensionalized
and solved using the Laplace Transform Method, a technique which has been rigorously employed and
validated in numerous previous communications by the authors. The effects of magnetic field
parameter (i.e. Hartmann number squared, M2),
rotational parameter (i.e. the inverse Ekman number, K2), Grashof
number (i.e. free convection parameter, Gr) and radiation-conduction parameter (K1) on the primary (u) and secondary velocity (w) distributions are computed and
described in detail. Both primary and secondary velocities are found to
increase with increasing K1.
reduces considerably both primary velocity (u)
and secondary velocity (w), with flow
reversal present. Increasing
Key words: magnetohydrodynamics, indirect natural convection, thermal radiation, rotating gas,
A. Kouadri-Boudjelthia, M. Elmeguenni, A. Imad
Av. Paul Langevin, 59655 Villeneuve d’Ascq,
Physics, USTHB of Bab Ezzouar
M. Tahar Abbes
Department of Mechanical, University Hassiba Benbouali
EXPERIMENTAL AND MODELING
Abstract. This study shows the temperature effects on the creep parameters of a composite material made out of non saturated polyester and reinforced with randomly oriented glass fibres type C with a density of 450 g/m2. This material works in a medium presenting a large variation in temperature. To better illustrate the complexity of the creep phenomenon and show its dependence on temperature, load, fibre concentration and cristallinity rate, an experimental and numerical simulation behaviour study was carried under several different temperatures and three levels of loading out to determine the evolution of the law in function of the relevant parameters. The creep behaviour was then modelled by using a phenomenological relationship defined as , where are, respectively, creep in tension after time , the instantaneous strain, and the pressure applied on the tube over time . Several samples were tested under varying temperatures and load changes. This paper presents a method to the phenomenological study of primary and secondary creep based on the experimental results and modelling by an empirical approach. Model the tertiary creep behaviour also based on the experimental results by the viscoelastic rheological model of Eyring. The experimental data was then used to determine the phenomenological relationship and its appointed coefficients
Key words: creep, composite material, polymer, viscoelasticity, modelling.