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Home>Products>Journal and Reviews>I.RE.M.E.>Latest issue International Review of Mechanical Engineering - November 2008 - Papers
International Review of Mechanical Engineering - Papers
Abstract - In this paper, the characteristic equation of the torsional vibration for an AFM cantilever with different contact position is given. By considering the effects of length, mass and contact position of the tip the resonant frequency and amplitude of the torsional vibration of the cantilever were analyzed. Because the tip is not exactly located at one end of the cantilever, the cantilever is modeled as two beams. The results show that the first mode is the most sensitive mode of torsional vibration of an AFM cantilever, while the high-order vibration modes are more sensitive than the first mode with respect to the contact position. The effect of the contact position on the resonant frequency and amplitude are significant and are not negligible especially when the lateral stiffness is greater. Copyright © 2008 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Atomic force microscope; resonant frequency; tip properties; surface properties.
Abstract - In the conception of high voltage isolators the thermo-mechanical and dielectric properties of ceramic materials have a great importance. These materials present the advantage that the raw material is largely available. Electrotechnical porcelain is a clever compromise between electrical, thermal and mechanical resistances. The conceived samples must be tested within conditions that reproduce normal or accidental stresses to which insulators may be subjected while in use. In this paper, the dielectric properties of alumino-silicate was studied in a sandwich structure. This structure was obtained by sputtering deposition of aluminium films in the two sides of ceramic samples. The dielectric constant and the dielectric loss factor were measured with an AC bridge where the frequency was ranging from 20 to 105 Hz. The electrical DC resistivity of the samples was measured and the thermo-mechanical properties of this material were studied. Copyright © 2008 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: High voltage isolators, Ceramic, Dielectric properties, thermo-mechanical properties.
by L. Merad, M. Cochez, F. Jochem, Y. Guedra, M. Ferriol, B. Benyoucef
Abstract -
The thermal stability and kinetic
parameters of epoxy resin RTM6 using non-isothermal thermogravimetry/derivative
thermogravimetry (TG/DTG) analysis a series of different ratios of TiO2-PC500
1%, 2%, 5% and 10% with epoxy resin. The kinetic parameters were
evaluated by integral and approximation methods. Results obtained
indicated that these parameters were dependent on different ration of
TiO2. According to the thermogravimetric curves showed that
the activation energy at high of higher conversion increases with
increasing the percentage of TiO2.
Keywords: Epoxy resin, TiO2, TG/DTG, activation energy, kinetic parameters.
by N. Mezghani, H. Salhi, M. Ayadi, A. Cherouat
Abstract - This study focuses on the determination of optimum sheet metal forming process and parameters effect on deformed sheet. In this paper the elasto plastic constitutive equations taken in account of the non linear anisotropic hardening is adopted. The experimental study allows the identification of material parameters from the measure of the sheet displacement, thickness evolution and internal pressure expansion. In addition to numerical analysis concerning the process, current experimental examination will be presented. The focus is on comparative evaluation of the simulation and production of the conical sheet and the study result of the effect of die shape, anisotropic flow, hardening law and friction coefficient on the hydro-formability of sheet. Copyright © 2008 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Thin sheet, hydro-forming, anisotropy, Experimental tests.
by A. Nasri, M. Ben Said, W. Bouzid, O. Tsoumarev
Abstract -
In this paper a three-dimensional
finite element model is presented to simulate the thermal behaviour of
steady-state ball end milling process. In this model, the appropriate
tool, chip and workpiece geometries are created by using CAD package
techniques. Copyright © 2008 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Ball End Milling, Temperature, Finite Element Method.
Abstract - The determination of heat transfer rate and the characteristics of the flows generated by the forces of Archimedes in cavities is a problem of which the interest so much on the fundamental level than on the one of the practical applications is important. Among these applications one can cite: the storage of the fluids, the flow of air in the rooms and the solar collectors. Very little information are currently available in the literature, on the numerical as well as on experimental levels, about the structure of natural convection flow occurring in a tilted semi-cylindrical cavity, like the natural flow of the air in the agricultural greenhouses, the cylinder-shaped hangars, or the cockpits of the airliners. Copyright © 2008 Praise Worthy Prize S.r.l. - All rights reserved
Keywords:
Thermics, natural convection, laminar mode, pregnant closed,
multi-cellular, Finite volume, CFD2000.
by S. Ben Slima,
J. Briki Abstract
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Elaboration of Continuous Cooling Transformation
(CCT) is tightly connected to the performance of techniques used to find
transformation temperatures, especially dilatometric techniques.
Dilatometry has became more precise during these last years because of
the evolution of electronical components. It is thus possible to detect
minor transformations that induce very low dimensional changes, such as
little carbides precipitation. Copyright © 2008 Praise Worthy Prize S.r.l. -
All rights reserved Keywords:
Heat treating, CCT Diagram, Hot
Work Tool steel, AISI H13, carbides, Splitting phenomena.
by A. Maougal, A.
Chaker, E. Chibat Mohamed Abstract
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This analysis propose a formulation
of the entropy generation in a three-dimensional laminar boundary layer
flow developing around a heated walls of a wedge. We seek for which
value angle parameter β corresponds
to the minimum of entropy generation, and prove that this geometrical
configuration corresponds to the optimal case from dynamic and thermic
point of view. We have proved that the minimum of the entropy generation
corresponds to the best heat transfer, and the weakest friction. The
dynamic and thermal fields obtained are in perfect agreement with the
literature. Copyright © 2008 Praise Worthy Prize S.r.l. -
All rights reserved Keywords:
Boundary Layer, Entropy
Generation, Wedge, Similarity, Shooting.
Abstract
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Numerically and experimentally results
concerning internal convective flows generated in a closed greenhouse by
thermal buoyancy forces were presented, analyzed and discussed.
Experiments were performed in an experimental arc type tunnel greenhouse
with a tomato crop, which was heated by a network of heating pipes or by
an air heater or by its combination according to the outside climate
conditions. A three dimensional (3D) sonic anemometer and fast response
sensors for air temperature and humidity were used in order to map
climate variables in different locations inside the greenhouse. For the
numerical part of the study a commercially available computational fluid
dynamics code was used after its customisation. A 3D model was built and
average values form experimental data was used in order for boundary
conditions. The crop was modelled by means of the concept of porous
medium approach. In general a good quantitative and qualitative
agreement was found between experimental and numerical obtained results.
Afterwards the numerical code was used in order to study the influence
of the heating pipes location on greenhouse microclimate. Copyright © 2008 Praise Worthy Prize S.r.l. -
All rights reserved Keywords:
CFD, convective heat transfer,
climate distribution, greenhouse heating system.
Abstract
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In this work, numerical calculations are performed to
study thermal radiation effects on heat transfer for combustion products
(H2O-CO2-N2) flowing inside circular ducts. Combined heat transfer, by
thermal radiation and forced convection is presented in some cases of
practical situations such as combustion of natural gas, propane and
heavy fuel. Special attention was paid to the treatment of real gaseous
mixture thermal radiation, with its spectral nature, and their effects
on evolution of radiative, convective and conductive fluxes for a steady
laminar flow. The infrared radiative properties of the flowing
H2O-CO2-N2 gas mixtures are taken into account in this analysis by using
the global Absorption Distribution Function model. Some differences
between non gray radiative behaviors of these combustion products, due
to different structures of their spectra, are put in evidence through
the evolution of the volumetric radiative power. The flow and energy
balance equations are solved simultaneously with temperature dependent
fluid properties. The approximations of a boundary layer flow are made,
except for radiative transfer. The results are presented for typical
conditions of combustion products flows. It is shown that radiative
transfer affects significantly the different heat fluxes exchanged, and
thus the Nusselt number and bulk temperatures. Copyright © 2008 Praise Worthy Prize S.r.l. -
All rights reserved Keywords:
Gas
Flow, Thermal radiation, Laminar Convection, Coupled heat transfer,
Circular duct.
Abstract
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In this work, a numerical model has been developed
for the 2D simulation of free surface flows. The front is tracked by the
volume of fluid (VOF) method. This Eulerian approach in which the moving
interface is advected through a fixed mesh eliminates any remeshing
problem and has been developed for the finite volume method. In this
study, two methods are presented: the Navier-Stokes equations are
resolved in the whole domain (double-fluid algorithm: liquid and air),
and in the domain containing liquid only (single-fluid algorithm). A
broken dam problem is used to check on the capability of these numerical
models and to compare with results reported in the literature. In order
to demonstrate the effectiveness of the proposed numerical scheme, mold
filling process was studied. Also, the proposed study exhibits
interesting physical and numerical features in the way it raises a few
questions. Copyright © 2008 Praise Worthy Prize S.r.l. -
All rights reserved Keywords:
Moving free surface, Mold filling, Air entrapment, Volume of fluid (VOF)
method, Finite volume method.
Abstract
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The results presented in this study are related to
the distributions of temperature in the various components of an
internal combustion engine. We are interested in the heat transfer
processes in the various components of the engine (cylinder head, piston,
cylinder liner and valve). In order to appreciate the influence of some
parameters on heat transfer in this engine, a sensitivity study to some
parameters of the problem is done. This sensitivity study approach is
related to the influence of the length of the cylinder liner, the fined
surface and the fined spacing. To solve partial non linear differential
equations given by the mathematical modelling of these phenomena, an
algorithm proposed by PATANKAR is used. Obtained results are compared to
those obtained by others. A good agreement is observed between the
various results. Copyright © 2008 Praise Worthy Prize S.r.l. -
All rights reserved Keywords:
: Heat transfer, Engine, Numerical simulation.
Abstract
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Coil pump is considered one of non-conventional water
pumping devices which use non-conventional energy sources. It is a self
supporting system for pumping water. The performance of coil pump under
different operating parameters is the main objective concerned of the
present study. The parameters considered are submerged ratios,
rotational speed and number of coils of the wrapped hose. The
experimental results showed significant effects on the pump performance
due to the variation in submerged ratio Sr and the pump rotational speed
as well. The presence of air with water for submerged ratios 0 > Sr >
100% gives the coil pump its pumping action. Increasing the submerged
ratio increases the pump flow rate until it reaches its maximum
depending on the pump rotational speed, then decreases to zero when the
pump is fully immersed. Submerged ratio has a minor effect on the pump
maximum static head, it is nearly constant but decreases drastically to
zero when the pump submerged ratio reaches 100%. Increasing the pump
rotational speed increases water flow rate until it reaches its maximum
depending on the working submerged ratio, then the discharge decreases
by increasing the rotational speed. Meanwhile slight changes are
obtained for the pump static head when the pump rotational speed changes.
The number of pump coils is also one of most effective parameters on the
coil pump performance. Increasing number of coils increases the pump
head while pump discharge is nearly constant. Good agreement is obtained
between the present experimental results and theoretical results
developed by other investigators. Copyright © 2008 Praise Worthy Prize S.r.l. -
All rights reserved Keywords:
Pump, Non-conventional, Performance.
Abstract
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The objective of this work is to
present a new simplified formulation of the impulse dynamics. This
formulation will be used to simulate the dynamic behaviour of a system
entering into collision and presenting several unilateral contacts.
These unilateral contacts can be lost during the collision, which
modifies the configuration of the system. The presented formulation has
the advantage of coping with the changes in the configuration of the
system and yielding a linear continuous model, which can be solved
analytically. This formulation will be applied to study the behaviour of
a system, made of a rider and its moped, during a collision. To validate
the application of this simplified formulation, crash tests will be
presented and their results will be discussed. Copyright © 2008 Praise Worthy Prize S.r.l. -
All rights reserved Keywords:
Impulse dynamics, unilateral constraint, reconstruction, crash
test.
Abstract
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This article present a study of the soil pipe
interaction of circular steel buried conduits under an elastic
homogeneous linear or non linear embankment. FEM have been shown to be
more adequate to evaluate the most used theory, namely the empirical
Marston-Spangler theory. A computer program based on the FEM was
developed to highlight the response of such structures. The influence of
the height/diameter ratio (H/D) and the properties of the backfill such
as the linearity and nonlinearity behavior were investigated. The study
was carried out for a single lift elastic method, a linear sequential
method and a nonlinear sequential method. The results of the
investigation highlighted the power of FEM compared to the empirical
Marston-Spangler theory and the importance construction stages of the
solid soil-structure. Copyright © 2008 Praise Worthy Prize S.r.l. -
All rights reserved Keywords:
Behavior, buried, interaction, linear, nonlinear, pipe, soil,
structure.
Abstract
-
The objective of this paper is to
investigate the validity of the mathematical model proposed by Bouabid
et al. [1] to characterize the mechanical behavior of Compressed Earth
Block (CEB). This model addresses the rheology, using the
elasticity-damage coupling, of a CEB to use for masonry construction.
This study investigates the use of the aforementioned model to a subsoil
material taken from the region of Meknes, and known for its use in
ancient earth construction. Static compressive tests were carried out on
cylindrical samples of compressed and stabilized earth. The test results
are obtained by the model, and are the static compressive strength, the
Young modulus and strain-limit of BK material. The difference between
the computational model and the experimental results doesn’t exceed 8%
for the compressive strength, the Young modulus and strain limit
independently of cement adding. This model also allows calculating
damage coefficient for the earth material studied, which serves as a
simple tool to assess the ductility of the material. Copyright © 2008 Praise Worthy Prize S.r.l. -
All rights reserved Keywords:
Compaction, Compressed earth blocks, Compressive strength, Cement
stabilization, Damage, Ductility, Elasticity-damage coupling.
Abstract
-
The aim of this study is to numerically predict the aerodynamic
behaviour of rectangular buildings. Simulations were made for rectangles
of different side coefficients and different angles of attack. The
finite element method is used to simulate fluid flow considered
Newtonian and incompressible. We adopt the LES method acronym Large Eddy
Simulation using the Smagorinsky model. We use the Fast Fourier
Transformation (FFT) method to be able to achieve a frequency analysis
of the calculated wind loads. Regarding the flow around a bluff body of
square section, the Strouhal number and the drag average value are
calculated for different Reynolds numbers. The obtained results show a
good agreement with available experimental and numerical results.
According to the evolution of the RMS of lift and moment coefficients as
well as average values of the drag coefficients depending on various
side factors, it was possible to conclude that the shape of square cross
section is more appropriate. It was also numerically shown the influence
of the change in the angle of attack of air flow on the frequency
evolution of aerodynamic loading. Copyright © 2008 Praise Worthy Prize S.r.l. -
All rights reserved Keywords:
Navier Stokes, Stabilized finite element, Galerkin Least Squares (GLS),
LES (Large Eddy Simulation), Von Karman, Fast Fourier Transformation (FFT),
Vortex. |
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