IN MEMORIAM - Acad. Georgi Brankov
MECHANICS
L. Le Sceller
C. Letellier
G. Gouesbet
University of Rouen, France
Global vector field reconstruction
for non-autonomous systems
The problem of reconstructing
a model of a non-autonomous system starting from a scalar time series is
addressed. We consider the case when the driving force, also called the
input, is unknown but assumed to be governed by a low-dimensional deterministic
dynamics. It is then shown that an autonomous model whose dimension is
higher than the non-autonomous system may be globally reconstructed.
MECHANICS
M. Sejnoha
J. Sejnoha
P. Procházka
Czech Technical University, Czech
Modelling of Interfacial Separation of MMC Composites
An efficient micromechanics-based
approach is used to evaluate local stress and strain fields in two phase
composite medium with debonded or imperfectly bonded interfaces. An finite
element analysis of the unit cell model of a fibrous ply is used to obtain
changes in local stress and strain fields caused by normal and tangential
separation at the fiber-matrix interfaces. The evolution of decohesion
process confined to a narrow region between the fiber and matrix is analyzed
with the help of a simple cohesive zone model. In the present work, the
onset of interfacial damage is governed by critical normal and shear tractions
that are prescribed as interface fracture criterion. In addition, the constant
shear resistance is assumed to account for presence of asperities at sliding
parts of the interface. An interface element, derived to carry out the
numerical analysis, is incorporated into representative unit cell and the
local fields are found with the ABAQUS finite element code. Examples are
presented for metal matrix SCS6/Timetal-21S system. The effect of time
dependent behaviour of titanium based alloys is also considered.
MECHANICS
C. Rozé
S. Meunier-Guttin-Cluzel
G. Gouesbet
University of Rouen, France
Convective Instabilities Obtained by a Local Heating of a Liquid
Thermal lens oscillations
and hot wire experiments are similar experiments in which a liquid is heated
locally near and below its free surface by a focused laser beam in the
first case or a hot wire in the second case. Last results concerning these
two experiments are presented: Thermal lens oscillations have been conducted
during the 23rd ESA parabolic flight campaign, showing that the instability
stops during microgravity phase proving its convective character. On the
other hand, infra-red imaging of the free surface in the hot wire experiment
allows to visualize the spatio-temporal structure of the travelling waves.
B. Barbet
Joseph Fourier University, Grenoble, France
Electrohydrodynamic and Thermal Stimulation of Capillary Instability of a Conducting Jet
Two different stimulation
techniques are investigated. They consist in imposing an initial perturbation
on a circular jet in order to obtain a very regular production of droplets.
In the first technique, a periodic electrostatic pressure is applied on
the jet surface. Results on multi- electrode EHD stimulation are given
for synchronized and desynchronized regimes. With the two mode EHD stimulation
the deformation shape can be modified and, in particular, a break-up of
the jet without creation of satellite droplets can be obtained. The second
stimulation technique is a thermal one where the light of a laser diode
is focused on the jet surface. Imposing a one mode or two mode periodic
modulation of the light intensity leads to results fully similar to those
obtained with the EHD stimulation. It is shown that Marangoni convection
associated with the gradients of surface tension is the dominant mechanism
for inducing the perturbation.
St. Stefanov
St. Radev
V. Leitsina
A. V. Luikov Heat and Mass
Transfer Institute, N. Ac. Sci. Belarus, Minsk
Institute of Mechanics,
Bulg. Ac. Sci., Sofia
Kinetic Description of the Transfer Processes in Porous Media
Different approaches of kinetic description of the transfer processes in porous media are considered. The Monte Carlo simulation results are presented for one- and two-layer porous medium.
V. Kavardjikov
R. Kotsilkova
D. Pashkouleva
V. Stoyanov
Central Laboratory of Physico-Chemical
Mechanics, Bulg. Ac. Sci., Sofia
Institute of Mechanics,
Bulg. Ac. Sci., Sofia
The Use of Speckle Photography in Composite Material Rheology
The change in particles orientation in different zones of flow is established. An estimation of the wall sleep and the presence of conjugated flow on the behaviour of the anisometric particles in the stream is made. A special attention is paid to the evaluation of the effect of observed phenomena on the chaneges of flow velocity profile.
Some results, obtained by
using speckle photography in hemorheological studies: the solidification
process of the filled liquid polymer composite and the change of its rheological
properties, are demonstrated also.
MECHANICS
A. Baltov
Institute of Mechanics, Bulg. Ac. Sci., Sofia
Theory for Type Deformational Sensitive Material
A new theory for type deformational
sensitive materials is proposed. Many materials possess such properties.
We prefer to describe the mechanical processes with strain type control
which insure in many cases the uniqueness of the stress-strain relation.
The theory is based on: (1) the concept of strain space and strain subspaces
with uniform type; (2) the introduction of the quadratic surfaces with
constant stress level.
S. Shilko
S. Stelmakh
D. Chernous
Yu. Pleskatchevskii
Metal-Polymer Research Institute, N. Ac. Sci., Gomel, Belarus
Structural Simulation of Supercompressible Materials
The work is devoted to study of supercompressibility effect, i.e. anomaly of elasticity, when Poisson's ratio becomes negative.
The numerical results provide
the conclusion that structural modelling of granular media, honeycomb structures
and foams demonstrates the phenomena mentioned above. The new localization
method for structural unity creation and control with predictable elastic
and non-elastic properties has been developed.
EVENTS
Prof. Dr. Dr. h. c. Franz Ziegler - 60 years!