Journal of
Theoretical and Applied Mechanics
Volume 37, Number 4,
2007
Contents
F. Chaari, H. Trabelsi, T. Fakhfakh, M. Haddar
Dynamics
of Mechanical Systems Research Unit,
BP
W. 3038-Sfax–Tunisia,
e-mails: fakher.chaari@gmail.com, hassen_4fr@yahoo.ca,
e-mails: tahar.fakhfakh@enis.rnu.tn, mohamed.haddar@enis.rnu.tn
INFLUENCE
OF
Abstract. In this paper
an investigation on the dynamic behaviour of a cam follower system in presence
of cam profile errors is carried out. A lumped parameter dynamic model of a cam
follower transmission including drive system, cam mechanism and load system was
developed. The preloading of the retaining spring, characteristics of the
various motion curves and flexibility of the various components are all taken
into account and an analytical method to calculate the spring constant between
cam and follower considering Hertzian contact is presented.
Key words: cam-follower, dynamic modelling, defects, numerical
simulation.
V. Abadjiev, E. Abadjieva
Acad. G. Bonchev Str., Bl. 4, 1113
e-mail: abadjiev@imbm.bas.bg
VECTOR ANALYSIS OF THE SLIDING VELOCITY
FUNCTION OF RACK DRIVES
Abstract.
The vector analysis of the sliding
velocity function of rack drive conjugate surfaces is investigated in this
work. Algorithms defining the level surfaces of the scalar field and the vector
lines of the vector field of sliding velocity function are developed. A computer program for
synthesis and visualization of the elements of the scalar and the vector field
in mesh region of spatial rack transformer is derived.
Key words: rack
drive, relative velocity vector, vector analysis, mathematical model.
R. Savova
Acad. G. Bontchev Str., Bl.4, 1113
e-mail: radianka@imech.imbm.bas.bg
Ts. P. Ivanov
Faculty of Mathematics
and Informatics,
Sofia University St. Kl.
Ohridski,
5,
e-mail:
tsoloiv@fmi.uni-sofia.bg
ON VISCOUS EFFECTS IN
SURFACE WAVE PROPAGATION
Abstract. In the present paper
we consider the influence of viscous or viscous and thermal properties of the
half-space on the propagation of surface waves of an assigned frequency or of
an assigned wavelength. The relation between the complex Lamé moduli, their constant real parts, connected with the
elastic properties of the material, and the constant relaxation times,
connected with its viscous properties, are discussed.
Key words: complex Lamé moduli, viscoelasticity,
thermoviscoelasticity, surface waves, frequency, wavelength.
A. Nedev, A. Baltov
Acad. G. Bonchev Str., Bl. 4, 1113
e-mail: anedev2005@yahoo.com
J. Genov
8,
e-mail: jgenov@tu-sofia.bg
Numerical ANALYSIS
OF formABILITY
Abstract. A circular cup deep drawing process using magnesium (Mg) alloy material is investigated. It is the lightest practical
material, which during the last decade has been widely used as a basis for production
of constructional components in automotive and electronic industries.
Numerical investigation of Mg alloy (AZ31-O) sheet
formability for Limit Drawing Ratio (
is performed. The material strength constants and
strain hardening exponents, which have been experimentally obtained at elevated
temperatures by S. Yoshihara et al.
[3], are used in calculations. The influence of different friction coefficients
(lubricants) on Drawing Force (DF) is numerically investigated. The effect of
both forming temperatures and lubricants upon LDR is also examined.
The deep drawing process is simulated by
using Finite Element Method (FEM)-ANSYS code. The results are presented by
“Drawing Force-P–Punch Stroke-S” diagrams. A conclusion about the influence of
the friction coefficients and the corresponding to them lubricants upon the DF
based on the obtained “P-S” diagrams is drawn.
Key words: deep drawing, magnesium alloy, friction coefficients.
E. Ergun
Engineering Faculty,
e-mail: eminergun@pau.edu.tr
M. Colakoglu, S. Tasgetiren
Faculty of Technical Education,
Sezer Campus,
e-mail: colakoglu@aku.edu.tr
FINITE ELEMENT BASED PREDICTION OF FATIGUE AND FRACTURE
BEHAVIOR IN A RESISTANCE WELDED STRUCTURE WITH DIFFERENT BOUNDARY CONDITIONS
Abstract. Fatigue and
fracture behaviours of welded straight and L-shaped sheets are investigated
under the tensile and bending loads using a finite element method. The effects
of the boundary conditions are studied for the welded sheet having different
thicknesses and different nugget sizes. The behaviour of the crack propagation
is analyzed under the conditions of the linear elastic fracture mechanics.
Fatigue life of the structure is also estimated. It is observed from the
results that the fatigue life of the welded structure depends on the boundary
conditions, the ratio between the thickness of the sheets and nugget sizes.
Key words: finite element modelling; fracture; fatigue life;
resistance-welding.
L. Parashkevova, N. Bontcheva
Acad. G. Bontchev Str., Bl. 4, BG-1113
e-mails: lusy@imbm.bas.bg; boncheva@imbm.bas.bg
A. Manescu
Universita Politechnica delle Marche,
e-mail: a.manescu@alisf1.univpm.it
PROCESSING OF BULK RAPIDLY SOLIDIFIED Al
Fe-ENRICHED ALLOYS - MODELLING AND MICROSTRUCTURE
Abstract. The
elastic-plastic behaviour of rapidly solidified AlFe9V1Si2 alloy containing
intermetallic compound is considered. The mechanical model for the "in
situ" composite proposed by the authors earlier is specified and developed
for processes of cold and hot extrusion of precompacted material. This model is
developed using information provided by microstructural investigations and EDX
analysis. It is a part of the multistage modelling of the bulk material
manufacturing process from rapid solidified powders or ribbons. The model is
implemented as user defined subroutines into the FE code MARC. Numerical
simulations are provided, corresponding to different values of metal forming
parameters at isothermal and coupled thermomechanical conditions. The influence
of the complience parameter, depending on the properties of the matrix and of
the inclusions is discussed.
Key words: intermetallics, rapidly solidified aluminum alloy, extrusion,
FEM.
N. Petrov
Acad. G. Bontchev Str., Bl. 4, 1113
e-mail: petrov333@gmail.com
GENERAL
THERMODYNAMIC THEORY FOR ACTIVE
BIO-CONTINUUM
Abstract. Molecular motors are nanometric protein-based
devices, essential for the movement in living organisms. The aim of the present
study is to offer a general thermodynamic theory for the active bio-continua
considered as composition including continually distributed assemble of
molecular motors. The restrictions following from Clausius–Duhem inequality
formulation of Second principle of Thermodynamics on the constitutive equations
are under consideration. The capability of the new theory to model active
bio-mechanical processes is demonstrated for muscle mechanics by unifying the
well known classical heuristic models. Also it is shown that the theory is able
to offer an active extension of the classical diffusion model as well.
Key words: active, diffusion, continuum, thermodynamics,
thermomechanics, muscle, mixture.