Journal of
Theoretical and Applied Mechanics
Volume 37, Number
3, 2007
Institute of Mechanics, Bulgarian Academy of Sciences,
Acad. G. Bonchev Str., Bl. 4, 1113 Sofia, Bulgaria,
e-mail: alex_kazakoff@yahoo.co.uk
FORCE RESPONSE TRANSMISSIBILITY PREDICTION
AND FREQUENCY ANALYSIS OF HIGH DEFLECTION DISP
Abstract: An attempt
is performed in this paper to model the dynamic response of vibro isolation mounts utilizing viscoelastic materials using
computer code MATLAB and comparison of the results against the experimental
test results of the same shock input data. This paper describes an
investigation into the use of computer code MATLAB for predicting large (up to
70% strain) dynamic deformations of “benchmark” elements in the form of
viscoelastic solid cylinders. The investigation objective was to establish
guidelines for MATLAB procedures whereby the computationally efficient models
could be used for the early stage of modelling of dynamically scaled models of
geometrically scaled vibro-isolation mounts, but compromising the solution
accuracy. Dynamic transient responses are measured and compared against the
MATLAB predictions.
Key words: computer
modelling, viscoelastic materials, shock-vibration loading, dynamic response.
R. Raghavendra Rao
Department of Mathematics, Eritrea
Institute of Technology,
Mai-Nefhi, Eritrea (North east Africa),
e-mail: rrrsvu@sify.com
Department of Mathematics, RVR & J C
College of Engineering,
Chowdavaram-522019,
EFFECTS OF VELOCITY-SLIP
IN ROLLING AND NORMAL MOTION
Abstract. A
generalized form of Reynolds equation for two symmetrical surfaces is derived
considering velocity-slip at the bearing surfaces. This Reynolds equation is
applied to study the effects of velocity-slip in the lubrication of roller
bearings subjected to combined rolling and normal motion under cavitation
boundary conditions. The load capacity, frictional drag increase as the
squeezing velocity increases when the surfaces are approaching and they
decrease when the surfaces are separating and this decrease is more pronounced
due to slip. The effects of these parameters on cavitation point are also
discussed.
Key words: Reynolds equation,
velocity-slip, viscosity, roller bearings, point of cavitation, load capacity,
coefficient of friction.
Sonia Parvanova
University of Architecture, Civil
Engineering and Geodesy,
1, Christo Smirnenski Blvd,
1046, Sofia, Bulgaria,
e-mail: slp_fce@uacg.bg
Dual Boundary Elements for Cohesive discrete Cracks by Using
“Event-to-Event” Nonlinear Algorithm
Abstract. The
present paper is concerned with the 2D numerical implementation of the fictitious
crack model in the Dual Boundary Element Method (DBEM) context for crack
propagation in plain concrete. The main advantage of the DBEM is that
mixed-mode crack problems can be solved successfully with a single region
formulation, thus avoiding the ineffective sub-region approach. The Fracture
Process Zone (FPZ) is represented in discrete crack manner by Fictitious Crack
Model (FCM). With that end in view an adequate modification of the discretized
system of dual boundary integral equations is presented in order to capture the
behaviour of the points in the undamaged and fracture zones. The nonlinear
solution algorithm adopted in the presented software code is worked out without
iterations by using an “event-to-event” strategy for the multilinear constitutive
law model including the softening branch. The effectiveness of the proposed
approach is demonstrated by two numerical simulations and comparisons with
experimental results are made.
N. Nikolov
Institute of Mechanics, Bulgarian
Academy of Sciences,
e-mail: n.nikolov@imbm.bas.bg
INFLUENCE OF THE ANISOTROPY OF ALUMINUM
BLANK DURING DEEP DRAWING
Abstract. Process
of deep drawing of circular aluminum blank having diameter 105 mm and thickness
1.5 mm is discussed. The influence of transversal anisotropy is investigated by
change of the anisotropy coefficient in the Hill’s quadratic criterion in
limits 0.7-1.3, applied in a numerical simulation. It is established
numerically that lower anisotropy leads to waviness on the blank flange, larger
increase of the blank height and thickness, and causes plastic strain
localization leading to blank failure. Larger anisotropy assures obtaining the
qualitative piece. The distribution of strains in blank elements and changes in
the blank element sizes are given along the blank radius, which affords an
opportunity to predict and investigate the areas of breaking and processes
developed in them.
Key words: deep
drawing, numerical simulation, transversal anisotropy, plastic strain
localization, blank flange waviness.
B. Ould Chikh
Laboratory of LSTE, Department
of Mechanics,
Faculty of Science and
Engineering, University of Mascara,
BP. 763, Route de Mamounia, Mascara, 29000, Algeria,
J. M. Nianga
Hautes Ecoles d’Ingénieur, 13 Rue de Toul, 59046 Lille
cedex, France
A. Imad
Laboratory of Mechanics of
Lille, CNRS UMR 8107,
Ecole Polytech’Lille, University of Lille1,
Cité Scientifique, Av. Paul Langevin, 59655 Villeneuve d’Ascq,
M. Benguediab
Laboratory
of Mechanics, University of Sidi bel Abbes
22000,
CORRELATION
BETWEEN THE PARAMETERS C AND m OF PARIS’ LAW AND THE EFFECT OF THEIR
VARIABILITY ON THE LIFETIME PREDICTION IN THE CASE OF 12NC6 STEEL
Abstract. The general purpose of this work
concerns the effects of the loading parameters on fatigue crack growth in heat
treated 12NC6 steel. Four heat treatments were chosen to get the following
yield stress values, respectively, 270, 480, 830 and 1070 MPa. Fatigue Crack
Propagation (FCP) experiments were performed under room temperature and a
Stress Intensity Factor (SIF) range between 17 and 30 MPaÖm.
Four values of the load ratio were used 0.05, 0.1, 0.3 and 0.5. The correlation
between C and m parameters, obtained in this model, has been examined for this
case of steel with different heat treatments. The variability of C and m parameters has been analysed in order to predict the fatigue life
engineering structures. The influence of some extrinsic and intrinsic factors
on the evolution of these parameters has been also discussed.
Key
words: fatigue, lifetime, Paris’ law.