Journal of Theoretical and Applied Mechanics
Volume 39, Number 1, 2009
Contents
ANS Campus,
e-mail: ibrahimmutlu@hotmail.com
INVESTIGATION OF BORON PRODUCTS USED IN BRAKE PADS
Abstract. Recently,
different brake pads have started to be investigated in brake friction industry
by replacing the asbestos with new materials. In this study, boron products were
used as a new material in brake pads. Specifically, refined Boric Acid
(BA) and Borax (Anhydrous) (BX) with raw Ulexite (U) and Colemanite
(C) were used. Different amounts of boron products were
used in the mix of other regular ingredients in brake pad. Newly formulated
brake pad material with eight different ingredients has been tested under
Friction Assessment and Screening Test (FAST). Friction coefficient, wear rate,
and Scanning Electron Microscope (SEM) for friction surfaces were examined to
assess the performance of these samples.
Key word: brake
pad, boron products, composite materials, friction coefficient, tribology.
S. G. Hristova
Department
of Applied Mathematics and modelling,
e-mail: snehri@uni-plovdiv.bg
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
Acad.
e-mail: penka@imbm.bas.bg,
slavcho@imbm.bas.bg
A. Oron
Department of Mechanical Engineering,
Technion-Israel Institute of Technology,
e-mail: meroron@tx.technion.ac.il
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
e-mail:
g_swapan2002@yahoo.com
O. Anwar Bég
Mechanical Engineering Department,
e-mail: O.Beg @shu.ac.uk, docoanwarbeg@hotmail.co.uk
J. Zueco
Thermal Engineering and
Fluids Department,
Campus Muralla
e-mail: joaquin.zueco@upct.es
ROTATING
HYDROMAGNETIC OPTICALLY-
GAS
Abstract. Exact
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.
Increasing Gr
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,
optically-thin approximation,
A.
Kouadri-Boudjelthia, M. Elmeguenni,
A. Imad
Laboratory of
Mechanics of
Ecole Polytech’Lille,
Av. Paul Langevin, 59655 Villeneuve d’Ascq,
e-mail: kouadriba@yahoo.fr
A.
Bouabdallah
Faculty of
Physics, USTHB of Bab Ezzouar
M.
Tahar Abbes
Department of Mechanical, University Hassiba Benbouali
of CHLEF,
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.