Journal of
Theoretical and Applied Mechanics
Volume
36, Number 4, 2006
D. Maga, J. Halgos, D. Lahucky
Alexander Dubcek
University of Trencin,
1, Studentska, 911
50 Trencin,
Slovakia,
e-mail: maga@tnuni.sk
Finite Element based Analysis of Special Mechatronic Actuator
Abstract. The
presented paper deals with computer based model of mechatronic
actuator – high torque low speed step motor. The paper presents especially the
possible ways of torque computation and their accuracy. This actuator has been
designed and constructed according to the special demands – extremely low speed
and high static torque. Since the speed can be controlled by actuator
construction, the torque depends on a lot of additional parameters and can be
influenced by e.g. current supply size and case, tooth and slot sizes etc. One
of the most important knowledge, suitable for a lot of authors solving similar
problems, is the choice of proper torque computation method with required
accuracy of obtained results.
Penka G. Kalitzova-Kurteva, Slavtcho G. Slavtchev
Institute of Mechanics, Bulgarian Academy of Sciences,
Acad. G. Bonchev
Str., Bl. 4, Sofia 1113,
Bulgaria,
e-mail: penka@imbm.bas.bg, slavcho@imbm.bas.bg
Maria-Alcina Mendes
Department of Chemical
Engineering and Chemical Technology,
Imperial College, London SW7 2AZ, UK,
MARANGONI INSTABILITY OF LIQUID-LIQUID SYSTEMS WITH A SURFACE-TENSION-INCREASING SOLUTE
Abstract. The onset of Marangoni instability in partially miscible liquid-liquid
systems, such as organic-aqueous systems, in the presence of surface-active
solutes that increase the interfacial tension is studied. The organic phase is
initially pre-saturated with water and diffuses in the aqueous phase after both
phases are contacted. The aqueous phase is contaminated with a surface-active
solute, which is also soluble in the organic liquid and is transferred across
the interface between the liquids. Marangoni
instability in such systems may be induced by interfacial tension gradients,
due to the heat of solution released or absorbed on the interface and to the
solute activity. A linear stability analysis is carried out for both cases of
stationary and oscillatory perturbations. The compatible equations derived
previously by the authors for arbitrary solute are analysed numerically in the
case of surface-tension-increasing solutes.
It is shown that the
necessary conditions for marginal instability depend considerably on the solute
diffusivity ratio, the kinematic
viscous ratio and the sign of the product of the heat of solution and the
thermal interfacial tension coefficient.
Key
words:
partially miscible liquid-liquid systems, surface-tension-increasing solutes,
mass and heat transfer, Marangoni instability.
J. Ivanova, V. Valeva
Institute
of Mechanics,
Bulgarian Academy of Sciences,
Akad. G. Bonchev Str., Bl. 4,
1113 Sofia, Bulgaria,
e-mail: ivanova@imbm.bas.bg, valeva@imbm.bas.bg
21, Swietokrzyska Str., 00-49 Warsaw, Poland,
e-mail: zmroz@ippt.gov.pl
MECHANICAL MODELLING OF THE DELAMINATION OF BI-MATERIAL PLATE STRUCTURE
Abstract. A bi-material structure consisting of two
elastic isotropic plates bonded together by an interface under tension loading
is studied. The case for one plate with a crack normal to the interface is
considered. The interface is assumed to exhibit brittle failure at the critical
shear stress value in a cohesive zone preceding debonding.
Using modified Shear Lag model, the analytical solution is provided specifying
the length of debonding and ultimate failure. The
critical length of a partial debonding along the
interface strongly depends on the elastic moduli and the geometry of the bi-material structure. The results are illustrated in
figures and discussed.
Key
words:
elastic plate structure, normal crack, interface, delamination (debonding), constitutive models: elastic-brittle,
elastic-softening (cohesive), elastic-slip, elastic-slip-softening, length of debonding.
Institute of Mechanics, Bulgarian Academy of Sciences,
Acad. G. Bonchev
Str., Bl. 4, 1113 Sofia, Bulgaria,
e-mail: Stoyan@imbm.bas.bg
Viacheslav
I. Egorov,
Volynskaya Hospital,
10, Starovolynskaya Str., 121352
Moscow, Russia
Institute of Chemical
Physics, Russian Academy of Sciences,
4, Kosygin Str., 117977
Moscow, Russia,
e-mail: rob-turusov@yandex.ru
1st Surgical Department, Russian State Medical University,
ZIL Hospital, 26,
Bakinskaya Str., Moscow, Russia
Passive visco-elastic
mechanical properties of small human intestine. Comparative study with other
soft tissues
Abstract. The transport function of the intestinal system is
to a large extent mechanical. The intestinal wall is stretched passively and
this passive deformation predisposes the consequent active contractions,
peristaltic and bolus transport. Thus, the passive constitutive equations of
the intestinal wall are of great importance in understanding the physiological
function of the gastrointestinal tract. We investigated experimentally the visco-elastic properties of the specimens taken from the
jejunum site of the human small intestine. The main hypothesis of the work is
that they obey the quasi-linear visco-elastic theory,
proposed by Fung. The analytical expression for the
elastic response function was sought as an exponential function of the stretch
ratio. The results show that the small intestine tissue manifests orthotropic mechanical behaviour, being much more
deformable in the circumferential direction than in the longitudinal one. The
analysis of the stress relaxation data suggests that the relaxation spectrum
for the small human intestine is broader than for the elements of the cardio-vascular system and for articular
cartilage, but it is shorter compared to papillary muscles and canine ligament.
Therefore, we conclude that the relaxation behaviour of the small human
intestine is similar to other soft biological tissues and can be adequately
described by Fung’s theory. At the same time, the
incorporation of strain rate effects into Fung’s
theory gives unsatisfactory results for strain rates up to 0.3 %/s.
Key words: human intestine,
soft biological tissues, stress-strain relation, stress relaxation,
quasi-linear theory.
Institute of Mechanics, Bulgarian Academy of Sciences,
Acad. G. Bonchev
Str. Bl.4, 1113 Sofia, Bulgaria,
e-mail: gery@mech.bas.bg, ivanova@imbm.bas.bg,
Institute of Fundamental
Technological Research,
21, Swietokrzyska Str., 00-049 Warsaw, Poland,
e-mail: zmroz@ippt.gov.pl
Modelling of thermally induced progressive delamination in a two-plate structure
Key
words: elastic plates,
monotonic thermal loading, delamination (debonding),
transverse crack, constitutive models: elastic-brittle, elastic-softening
(cohesive), elastic-slip and elastic-slip-softening, limit value of
temperature.