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Home>Products>Journal and Reviews>I.RE.M.E.>Latest issue International Review of Mechanical Engineering - July 2009 - Papers
International Review of Mechanical Engineering - Papers
Vol. 3. n. 4, pp. 373-381
Abstract - A
numerical analysis was carried out to study the thermal performances of
a solar air collector with rectangular plate fins absorber and baffles
which are arranged on the bottom and top channel walls in a periodically
staggered way. This technique is used to increase the heat transfer
coefficient between the fluid (air) and the absorber in the solar
collector; such as the fixation of baffles and fins to the absorber. To
this end we solved numerically, by the finite volumes method, the
equations of conservation, of the mass, the momentum and energy. The low
Reynolds number k-ε model was adopted for the taking into account of
turbulence. The velocity and pressure terms of momentum equations are
solved by SIMPLE algorithm. Copyright © 2009 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Baffle, Solar collector, Turbulent flow, Fins, Conjugate heat transfer.
Vol. 3. n. 4, pp. 382-395
Abstract - The problem of water distribution system under steady and transient conditions is formulated in this study as an optimization problem under hydraulic reliability. The hydraulic reliability is the probability that a water distribution system can supply consumers’ demands over a specified time interval under specified conditions. The chance constraints formulation is used for the evaluation of the network hydraulic reliability. The approach integrates a genetic algorithm (GA) as an optimization tool, Newton-Raphson as a hydraulic analysis solver, a transient analysis program combined with chance constraint model to evaluate the network reliability. The approach was applied on a network for both steady state and transient conditions. The latter was introduced to the water system by pump power failure and sudden valve closure. The single objective is to minimize the pipe cost for a predefined nodal pressure heads requirements and prescribed level of uncertainty. The application of approach to the case study shows the capability of the chance constraints and the genetic algorithm to find the optimal pipe diameters. This reliability-based optimization technique is an important tool for design and operation of water networks without using hydraulic devices for water hammer control. Copyright © 2009 Praise Worthy Prize S.r.l. - All rights reserved Keywords: Water Distribution Systems, Genetic Algorithms, Optimization, Chance Constraints, Reliability.
Vol. 3. n. 4, pp. 396-409
Abstract - The modeling of heat flux transport past a heated 2-D cylinder flow wake contributes to the design of cross flow heat exchanger. The improvement of the performance characteristics of heat exchanger used for chemical industrial purposes, the nuclear reactors, the re boilers ,and the gas turbines will be burden on the discrete evaluation of the heat flux throughout the cylinder flow wake. The study of the turbulent transport of the passive scalars will be helpful in assessing the distribution of temperature ,humidity, pollutant and other chemical species throughout the flow field. A new turbulence model by T. F. Oda was invoked for the numerical solution of the transport equation of the passive scalars. The model extracts an individual transport equation for the Reynolds stress component from the generation- destruction terms of the momentum equations. The other Reynolds stresses components , will be extracted from handling of the pressure gradient equations. The present work will handle the transport equation of the passive scalars using the gained values of velocity components as well as the Reynolds stresses components from the solution of the momentum equations for flow past a circular cylinder. The numerical solutions based on the SIMPLER algorithm of Patankar and Spalding [2,3,4 ] were used to represent the distribution of the passive scalar quantities through the wake of a heated cylinder. The turbulent energy cascade along the cylinder flow wake will be studied. A new dimensionless number called RTN Number [1 ]will be presented as a parameter of turbulent energy transport will be related to the distribution of the heat flux along the heated cylinder flow wake. Copyright © 2009 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Turbulent flow, Heat Transfer, Cylinder flow wake, Transport of passive scalars.
Vol. 3. n. 4, pp. 410-416
Abstract - This paper is the second part of a thermo-economic analysis of an absorption refrigeration system, ARS. It presents an application of the methodology presented in the first par to three configurations of water bromide ARS. The economic costs of all internal flows and products in each configuration case are calculated, the impact of the heat exchangers efficiency as well as the operating conditions on the thermoeconomic efficiency is analyzed. The results show that the performances obtained when the system operates with only a solution heat exchanger (RHX) is very close to those obtained both the RHX and the solution heat exchanger (SHX) are incorporated in the machine. A similar result is obtained for the costs of all” fuels” and” products” in the system: they are more influenced by the use of the SHX than the RHX. Copyright © 2009 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Absorption, Refrigeration, Exergy, Economic analysis, Water/Lithium Bromide.
Vol. 3. n. 4, pp. 417-426
Abstract -
Generally,
Mechanical systems, such as cars, are comprised of various subsystems.
These subsystems have specific functional purpose and collectively
contribute to the overall performance of the system. The behavior of the
isolated subsystem (substructure) subjected to dynamic loading is
different than the behavior of the same substructure within the system
(structure). This is caused primarily by the boundary conditions imposed
on the substructure from the surrounding subsystem. This work presents
on the development of a technique for performing substructure analysis
on isolated substructures using finite element Analysis (FEA). Here we
propose an approach in substructural testing that produces similar
results between a substructure in isolation and a substructure in situ
using FEA. The developed technique is based on enforcing the mode shapes
around the boundary of the substructure in the full structure (referred
to as sub-full) onto the boundary of isolated substructure. This is
achieved by providing a consistent adjustment to the loading conditions
to account for the loss of restraint at the interface with the full
structure. The advantage of the proposed techniques is that it lends
itself to experimental work.
Keywords: Structural impact, Substructures, Finite element, Crashworthiness.
Vol. 3. n. 4, pp. 427-435
Abstract -
This paper
presents a three-dimensional sequentially coupled thermo-mechanical
analysis of the friction stir welding process suitable for residual
stress prediction. A friction stir butt weld of the aluminium alloy 2024
T3 is simulated using finite element analysis. The thermal model
includes diffusive heat transfer in the work pieces and that backing
plate, convective heat transfer in the work pieces caused by the
material flow, heat generation at the tool, heat loss to the ambient air
and heat transfer between the work pieces and the backing plate. The
mechanical model includes thermal expansion and tool forces acting on
the work pieces. The thermal part of the simulation shows encouraging
results concerning the capability to accurately simulate the temperature
distribution. The simulated temperatures correspond well to
experimentally measured temperatures and the non-symmetric temperature
distribution due to material flow is accurately captured in the
simulation.
Keywords: Friction Stir Welding, Simulation, Finite elements, Mass flow.
Vol. 3. n. 4, pp. 436-441
Abstract -
The mixed
degenerate shell finite element DDSE, incorporating drilling degrees of
freedom, is dedicated to solve some engineering applications directly
and without any numerical tricks. This finite element has shown good
performances in the linear and nonlinear, isotropic and anisotropic,
static problems. Thanks to the application of shear and membrane
substituted strain fields; it is also free from any locking. The very
satisfactory results obtained by its previous application to the
nonlinear dynamic regime have suggested the present work. The
formulation of the problem, the derivation of the time integration
scheme and the mass matrix were conducted in the most appropriate way to
deal with the dynamic buckling load prediction. Both geometrical and
material nonlinearities are considered in this study.
Keywords: Dynamic buckling, Plasticity, Shells, Finite element, Drilling dof.
by Lazarus Teneketzis Tenek Vol. 3. n. 4, pp. 442-450
Abstract - Complementary Work and the Force Method are developed for the analysis of plates and shells. A quadrilateral element is conceived with 4 nodes and nodal unknowns the 3 forces and 3 moments in a global coordinate system. A stress plate and shell theory is developed based on variational arguments which yields in its discrete form the global nodal forces and moments. The Force matrix of the element is established and force equilibrium postulated. The theory accepts applied displacements and rotations but applied loads or moments can be inserted as boundary conditions. The solution of the linear system of equations provide the internal loads. After solution, the displacement/rotation field can be estimated on an element basis. Numerical examples on a membrane specimen and plates and shells are provided. Copyright © 2009 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Complementary Work, Force Method EFM, Quadrilateral element, Force matrix, Plates/shells.
by Mounir Kchaou, Mahmoud Yaakoub, Fakhreddine Dammak Vol. 3. n. 4, pp. 451-455
Abstract -
In inductive
superficial hardening, the heating delimits the hardened zone while the
control of cooling makes it possible to reduce considerably the
distortions. The distortions due to the important gradients and those
due to the change of the phase are studied. The most important
distortions are produced by a nonsimultaneous cooling of different
sections of the quenched layer. This unsynchronism of thermal kinetic
generates a martensitic growth which is responsible of the complementary
deformations. These transformations are sources of residual stress
variations along of the hardened zone. Copyright © 2009 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Distortion, Stress, Superficial quenching, Simulation, Bearing race.
by Paul M. Wambua, Rajesh Anandjiwala Vol. 3. n. 4, pp. 456-460
Abstract - This paper investigates the response of natural fibre and hybrid composites to localised blast loading. Woven glass, carbon, cotton, flax/cotton and flax/cotton/glass hybrid fabric layers were bonded to each other with a polypropylene matrix. Square composite samples were rigidly clamped in a ballistic pendulum and subjected to localised uniform explosive blast using small amounts of PE4 explosives. The test results showed that the dominant failure mode was fibre fracture, delamination and bulging, with several samples exhibiting failure by formation of a complete hole at higher impulses. The glass composites withstood the highest impulses without rupture, followed by the carbon composites. Copyright © 2009 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Blast, Explosives, Biofibres, Hybrid, Composites.
by Aidy Ali, A. B. Sanuddin, C. W. Chieh, Reza Afshar Vol. 3. n. 4, pp. 461-466
Abstract - The paper presents the simulation work on the elastomer subjected to the strain controlled cyclic loads. A three-dimensional finite element model of elastomer specimen which in accordance with ASTM D412 has been developed using CATIA and ANSYS commercial finite element (FEM) packages. The fatigue life predicted from simulation was compared with a well documented published data and show slight disagreement. The simulated strain-life results are slightly lower than the experimental data. Several factors that potentially influenced the variation of the results were noted. Finally, some recommendations have been made at the end of this study to further improve the simulation. Copyright © 2009 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Elastomer, FEM, Strain controlled loading, CATIA, ANSYS.
Vol. 3. n. 4, pp. 467-472
Abstract - The performance of the Chaboche kinematic hardening model has been evaluated in this paper to predict the ratcheting responses for a broad set of uniaxial and biaxial loading histories. The investigations have been performed with reference to both uniaxial and biaxial experimental data, (a) strain and stress controlled uniaxial tests on tensile specimens; (b) biaxial tests. The parameters of the Chaboche model have been calculated from the uniaxial strain controlled test and then optimized using different data bases. Amongst the various parameters in the Chaboche model, it has been found that the optimized parameters play a crucial role in achieving better simulation. The Chaboche model was observed to predict ratchet on uniaxial loading, the model closely simulated the experimental results. The same parameters have been used to analyze the biaxial loading condition; ratchet has been over predicted by the model. In a general way ratcheting simulation studies by the Chaboche model have resulted in reasonably good agreement with experiments. Copyright © 2009 Praise Worthy Prize S.r.l. - All rights reserved
Keywords:
Ratchet,
Kinematics hardening, Uniaxial and biaxial loading, Strain and stress
controlled tests.
by M. R.
Khoshravan, F. Azimpoor Vol.
3. n. 4, pp. 473-780 Abstract -
The aim of this paper is to provide modeling and numerical analysis of
delamination for increasingly complex woven reinforced composite
materials. Modeling of the woven reinforced composite materials due to
the existence of the weft and woof filaments of fibers was a significant
part of this research. The Finite Element (FEM) model of the unit-cell,
which is a small element of the composite which describes all of the
mechanical properties of the material, provided the required results of
the strain energy with a low volume of computation. The computed loads
by FEM were put in derived equations of fracture mechanics. The
criterion of strain energy release rate (Gc) have been used. The
obtained numerical results showed the growth of delamination along the
weft filaments and a sudden change in the point of crossing of the woof
filaments. The curves drawn by finite element method showed that the
best answer would be given by usage of singular elements for modeling of
crack tip comparing by usage brick elements. So results of modeling by
singular elements were developed in this paper. Numerical results were
in good correlation with the experimental results and the difference was
less than 10%. Copyright © 2009 Praise Worthy Prize S.r.l. -
All rights reserved Keywords:
Composite
Material, Woven, Delamination, Modeling, Finite Element, Unit Cell.
Vol.
3. n. 4, pp. 481-488 Abstract -
Disc brake
noise is still considered an elusive problem in the automotive industry.
To date, there are a number of solutions that have been proposed
including modifying the structural and/or attaching the pad insulator
but very few are successful. This paper attempts to describe an active
method to reduce disc brake noise and vibration using an Active Force
Control (AFC) strategy. A two degree-of-freedom (DOF) disc brake model
is considered and adopted in the development of the proposed control
system. First, the disc model is simulated and analysed using a
conventional closed loop proportional-integral-derivative (PID)
controller for vibration and noise control. Later, it is integrated with
the AFC element that is designed to robustly reject the disturbances and
uncertainties based on the given operating environment. It is found that
the integrated PID-AFC scheme is very effective in suppressing the
vibration and hence the noise compared to the pure PID controller. This
paper also looks into the effect of negative damping on the brake
performance. Copyright © 2009 Praise Worthy Prize S.r.l. -
All rights reserved Keywords:
Active force
control, PID controller, Disc brake, Noise and vibration, Negative
damping.
Vol.
3. n. 4, pp. 489-493 Abstract -
Experiment
was conducted to evaluate the performance, emission and combustion
characteristics along with cylinder vibration of direct injection diesel
engine operating in duel fuel mode using Pongamia methyl ester injection
and methanol induction. Preheated methanol is inducted into the engine
at a particular throttle opening along with intake air stream by a
carburetor which is arranged at bifurcated air duct. Pongamia methyl
ester fuel was supplied to the engine by conventional fuel injection.
The present study is to clarify ignition characteristics, combustion
process and knock limit of methanol flow rate in a dual fuel diesel
engine, and also to improve the trade-off between NOx and smoke without
deteriorating the engine performance. Engine vibration is measured on
the cylinder head for different dual fuel combinations to compare the
engine performance. Combustion difference can be identified when the
vibration is recorded and plotted in the wise of FFT spectrums and time
wave forms. The experimental results show that there is minimal change
in exhaust gas temperatures and there is better reduction of NOx, HC, CO
and CO2 at methanol mass flow rate of 16.2mg/sec. Smoke level was
observed to be low and comparable. Improved thermal efficiency of the
engine was observed with methanol induction. Vibration levels are
comparably low with the above mass flow rate of methanol in the dual
fuel operation. Copyright © 2009 Praise Worthy Prize S.r.l. -
All rights reserved Keywords:
PME,
Methanol, Carburetion, Emissions, FFT.
Vol.
3. n. 4, pp. 494-502 Abstract
-
The main
objective of the present paper is to establish a two-dimensional
theoretical and numerical model for the atmospheric pollution by
considering the advection-diffusion-reaction process in a turbulent flow
(k-e
model) of a Newtonian fluid. A finite volume method is used to solve the
equations and to determine the temperature, T, the pollutant
concentration profile, c and the fluid velocities u, w, respectively in
Cartesian coordinates. This study, considered as an important step in
modeling atmospheric pollution, may also be fit to other industrial
applications. Copyright © 2009 Praise Worthy Prize S.r.l. -
All rights reserved Keywords:
Turbulent
flow, Finite volume method, Newtonian fluid, Atmospheric pollution,
Advection-diffusion-reaction process.
Vol.
3. n. 4, pp. 503-509 Abstract
-
This study investigates the resource availability, energetic efficiency,
and economic feasibility of converting jatropha oil into biodiesel, a
substitute diesel fuel. Copyright © 2009 Praise Worthy Prize S.r.l. -
All rights reserved Keywords:
Biodiesel,
Energy ratio, Glycerin, Jatropha, Transesterification.
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