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Home>Products>Journal and Reviews>I.RE.M.E.>Latest issue International Review of Mechanical Engineering - May 2009 - Papers
International Review of Mechanical Engineering - Papers
Vol. 3. n. 3, pp. 265-270
Abstract - The aim of this work is to study the mechanical behavior of the HONEYCOMB sandwich beams. A homogenization method is applied in order to determine the global mechanical characteristics of the core. Three-point bending tests were conducted to determine the mid-span deflection of the beam. Young’s moduli of the skins were determined from tensile tests. The mechanical characteristics obtained were used in a higher order model in order to study the shear and normal stresses according to the geometrical and mechanical properties of sandwich beams. Copyright © 2009 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Sandwich beam, HONEYCOMB, Homogenization, Mechanical test, 3 points bending, Stress.
Vol. 3. n. 3, pp. 271-274
Abstract - In the design projects involving the teeth gears, the designer may find difficulties caused by the fact that the gear's coefficient is not known. This leads to year arbitrary choice of these coefficients which may not respond to all the boundary condition: Interference in generation and gearing, teeth generation, gearing continuity. The investigation presented consists of varying the number of teeth, the angle of inclination and the transmission ratio at the same time. With the optimization of all these parameters, the choice limits of the deport coefficients are materialized by boundary curves represented by coordinates (X' and X2). Copyright © 2009 Praise Worthy Prize S.r.l. - All rights reserved Keywords: Gears, Contact, Coefficient of offset, Interference, Correction.
Vol. 3. n. 3, pp. 275-283
Abstract - This paper presents analyse of crack origin and stress distribution of bonded steel-concrete composite beam by numerical method. A three-dimensional finite element model has been developed in this work. Before the stress analysis, results obtained via finite element model on deflexion and strain evaluations with increase of applied load are compared with those obtained by experimental test. The numerical model developed allows knowing the crack origin of the composite beam and the direction of crack propagation. The results show that compared with the other kinds of stresses, the local tensile stress in the concrete slab is the closest to the ultimate strength and causes the initial cracking in the concrete slab. Particularly, it is found that the variation of applied load width plays an important role in the determination of location and value of the maximal tensile stress in the concrete slab. However, the effect of variation of the adhesive thickness, from 3mm to 15mm, on the deflexion and the shear stress is not important. Based on the obtained results, it is concluded that the ruin of the bonded steel-concrete composite beam is not situated at the steel-concrete interface and the bonded composite beam is applicable in practice. Copyright © 2009 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Steel, Concrete, Composite beam, Adhesive bonding, Finite element.
Vol. 3. n. 3, pp. 284-292
Abstract - The development of computational fluid dynamics has successfully contributed to the prediction of the flow field through pumps and the enhancement of their design. In the present analysis a double-arc synthetic blade design method is proposed for the optimum hydraulic performance of a centrifugal pump. The one-dimensional Pfleiderer’s approach based on empirical analytical equations is applied for the main geometrical characteristics of the pump impeller. The numerical solution of the discretized three-dimensional, incompressible Navier-Stokes equations over an unstructured grid is accomplished with a commercial CFD finite-volume code. The characteristic performance curves are resulted through the calculation of the internal flow field. For every double-arc blade design method, the pressure distribution of the pump is computed and the velocity field between the blades at the leading edge and in the region of the tongue is studied. Copyright © 2009 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Blade Impeller, Centrifugal Pump, CFD Numerical Analysis, Double-Arc Design, Optimum Performance.
Vol. 3. n. 3, pp. 293-305
Abstract -
The flow in
the near wake of a circular cylinder at high Reynolds numbers
contributes to many engineering applications, e.g. Heat exchanger design
and heat pipe flow. The study of in the near wake of a circular cylinder
at high Reynolds numbers spots the light on the mechanism of turbulence
transport as the vortices will not interact in the first few diameters
downstream of the cylinder. The new turbulence model extracts a pressure
equation as a function of Magnus forces of fluid flow as will as its
gradients. The model express the Reynolds stresses as a function of the
pressure gradients, Magnus forces of fluid flow and its gradients. The
momentum equations will be solved using the new generic equations of the
Reynolds stresses components with the aid of finite difference
technique. The good compatibility between the numerical solutions using
the new turbulence model and the experimental findings will be at the
near wake region as will as at the interacting zone behind the circular
cylinder where the most numerical techniques failed to predict the flow
behavior at this area.
Keywords: Turbulent flow, Flow around a circular pipe, Turbulence Model.
Vol. 3. n. 3, pp. 306-311
Abstract -
This paper is
the first part of a study on the effects of the incorporation of
additional heat exchangers on the performances of a Water/LiBr
absorption refrigeration system (ARS). A thermo-economic approach is
used to evaluate this effect. This first part presents the formulations
developed for such a comprehensive analysis while the second paper deals
with the application of the developed formulation to three
configurations of an air cooled gas-fired water bromide ARS. In this
paper mass, energy, and exergy balances are illustrated and applied to
components system. Also, a thermoeconomic methodology is established to
evaluate the economic costs of all internal flows and a product of
system by formulating thermoeconomic cost balances and variables. The
thermoeconomic cost balances and variables formulated here have
significant importance to carry out the effects of including of heat
exchangers on thermoeconomic analysis of the ARS and to determinate the
optimal performances of system accounting economic constraints.
Keywords: Absorption, Refrigeration, Exergy, Economic, Water/Lithium Bromide.
Vol. 3. n. 3, pp. 312-321
Abstract -
Wettability
is an important characteristic of solid surfaces and is controlled by
chemical composition and surface roughness. The creation of
superhydrophobic engineering surfaces has aroused great interest in
research and practical industrial applications in nano/micro electro
mechanical surfaces (NEMS/MEMS). The review presented in this article
covers the principles of hydrophobicity and various techniques which can
be used to fabricate these surfaces. The modern techniques of
characterization of superhydrophobic surfaces have also been included.
Keywords: Superhydrophobicity, Cassie Baxter and Wenzel, Roughness, Low surface energy, Characterization.
by Jan Trnka, Radek Kolman, Pavla Dvořáková, Eduard Veselý Vol. 3. n. 3, pp. 322-331
Abstract - The paper deals with the study of stress waves propagation in a thin steel plate. Impact loading was realized by means of loading element with the exploding wire. The full-field visualization of the displacements caused by the generated waves was carried out by double-pulse holointerferometry (DPHI) with the ruby laser as a source of light. The history of acceleration in different points on the plate surface was studied simultaneously by miniature accelerometers. It is shown that loading in such a way enables us to generate not only the perpendicular impact but also the oblique one as well. The experimental results are compared with numerical ones and their agreement is very good. It is shown that generation of oblique impact by loading elements with the exploding wires is reliable and promising for study of transient phenomena in thin-walled structures. Copyright © 2009 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Stress wave propagation; thin-wall structures; double-pulse holointerferometry; accelerometer; finite element method; impact generation; oblique impact.
by Aidy Ali, M. Hosseini, B. B. Sahari Vol. 3. n. 3, pp. 332-338
Abstract - In recent years, influence of elastomer and rubber has increased significantly in engineering applications. Many factors provide long term durability and mechanical fatigue including nucleation and growth of cracks in the rubber is the first attention. Fatigue life prediction on the rubber parts was essential in relation to the extension of warranty period of the automotive components. A design of rubber parts versus fatigue failure is one of the serious topics to check the failures during the operation. To describe the subject efficiently and commercially, engineers require to model and design for mechanical fatigue in the manufacture process. This study presents a review of fatigue life failure criteria, fatigue damage behavior for elastomers and results of the attempts on predicting the experimental results of fatigue life rubber components. Copyright © 2009 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Rubber, Elastomer, Fatigue life, Rubber failure criteria.
by Vassilis C. Samaras, Dionissios P. Margaris Vol. 3. n. 3, pp. 339-344
Abstract - A new two-phase correction factor CoSM was introduced by the authors, correlating the two well-known theories of homogeneous flow and drift-flux model with experimental results in the case of a two-phase air-lift pump. CoSM, expressed as an exponential function of the gas superficial velocity, could not only take similar values as other correlation models do, in a large range of void fraction ε, but was meaningful in the whole range of ε. The scope of this paper is to present an extension of the method for the prediction of the performance of a three-phase air-lift pump with the aid of the extended three-phase correction factor CoSM(3p). Copyright © 2009 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Fluid Mechanics, Mass Transfer, Multiphase Flow, Voidage, Drift-flux Model, Air-lift Pump, Three-phase flow, Regime map.
Vol. 3. n. 3, pp. 345-352
Abstract -
In this work,
The viscoplastic deformation behaviour of microalloyed CMn(V–Nb–Ti)
steel is investigated by means of compression tests under isothermal hot
working conditions at temperatures ranging from 700 to 1050°C and strain
rates of 1.46x10-2 s-1, 2.9x10-3 s-1, and 7.34x10-4 s-1. The flow stress
data are analysed in terms of strain rate and temperature sensitivities.
A constitutive equation that relates not only the dependence of the flow
stress on strain, strain rate and temperature, but also for the
transformation points AC1 and AC3 obtained by the results of dilatometry
tests are 710°C and 855°C respectively. These measurements results and
the rheological parameters calculated a global scale were used to
critical estimations of the viscosity coefficient of mixture and the
strains rates in the (α+γ) two-phase region by mechanical models self
consistent model and the uniform plastic energy model (Iso-Work) can be
considered like obedient to mixture of two phases viscoplastic by power-
law. The usual strain rate sensitivity and activation energy value of
microalloyed CMn (V–Nb–Ti) steel are obtained by fitting experimental
data. Furthermore, specific values of strain rate sensitivities and
activation energies are calculated in the (α+γ) two-phase region and γ
single-phase region. Copyright © 2009 Praise Worthy Prize S.r.l. - All rights reserved
Keywords:
Two-phase
region, Microalloyed CMn (V–Nb–Ti) steel, Laws of mixture, Viscoplastic
behavior.
Vol. 3. n. 3, pp. 353-357 Abstract -
In the
present study, a 2D axisymmetric fluid flow and solidification model was
developed to simulate the moving solid/melt interface problem in the
large diameter (300 mm) of the silicon single crystal growth in a
Czochralski process using a finite volume method. The thermo-elastic
stress is calculated from the temperature field by adopting the plane
strain model in an axi-symmetric geometry of a cylindrical crystal. The
effect of different pulling rates to the interface shape and thermal
stress distribution in the crystal are predicted. Results are compared
with numerical solutions given in the literature. A reasonable agreement
was obtained. Copyright © 2009 Praise Worthy Prize S.r.l. -
All rights reserved Keywords:
Czochralski,
Silicon, Interface shape, Pulling rate, Thermal stress.
Vol. 3. n. 3, pp. 358-362 Abstract -
Intensive
agricultural activities are a source of pollution and degradation of
groundwater quality, original use of fertilizers and pesticides.
Fertilizer applied at rates greater than the need of plants, or on dates
not suitable, may be transported to groundwater. Mathematical models can
contribute to understanding the physical processes involved in this
transport process and be integrated with tools for prediction and
decision support. Most of the process of moving water in the land under
cultivation takes place in conditions of non-saturation. The modeling of
the movement in saturated and non-saturated, is usually performed by the
equation of Richards [2], a differential equation partial differential
of parabolic type in non-elliptical in saturated and saturated. The
purpose of this work is two-dimensional modeling of pollutant transport
in porous media. For the numerical resolution, we use the finite volume
method and the ADI method. Copyright © 2009 Praise Worthy Prize S.r.l. -
All rights reserved Keywords:
Porous media modeling, Transport of Pollutants, Moisture content,
Unsaturated zone, Two-dimensional.
Vol. 3. n. 3, pp. 363-367 Abstract
-
The work
discussed here is part of a comprehensive study to develop tools for
characterization and modeling of pollutant flows transported by water
flowing in the unsaturated zone of an aquifer (quantitative approach).
In our study, we present a practical model for calculation of transfer
of pollutants emitted by a source of pollution in our case represented
by a production plant paintings located in the city of SOUK AHRA. Copyright © 2009 Praise Worthy Prize S.r.l. -
All rights reserved Keywords:
Mechanism of
transfer, Model, Modeling, Contaminated aquifer, Environment.
by Lau Hao Wen,
Patththil Madhav Menon, Ng Kim Choon
Vol. 3. n. 3, pp. 368-371 Abstract
-
In this
study, a novel physical separation method using a flotation system that
employs micron sized air and ozone bubbles is designed and tested to
replace conventional dissolved air flotation (DAF) or clarification of
water by settling. The bubbles produced are fine and turn the water
milky white. Micro air bubbles remove fine coagulated but suspended
particles from the waste water, achieving a separation efficiency of up
to 99% of oil and grease and suspended solids. The removal of fine
suspended particles from the water reduced Total Suspended Solids (TSS),
Bio-Oxygen demand (BOD) and Chemical-Oxygen Demand (COD) levels in the
water, requiring less chemicals in downstream processes. The water was
subsequently treated using high concentration and micron sized ozone.
Test results show that both micro air flotation and ozone treatment have
achieved high reduction of oil and grease, TSS, BOD and COD. The water
is then filtered using a micro-filtration membrane, and the water fouls
the membrane. The waste water was replaced with PUB tap water, and micro
air and ozone bubbles are backwashed separately through the membrane.
Significant increase in the permeate flow is observed, implying that the
micro air and ozone bubbles are effective for fouling removal. Copyright © 2009 Praise Worthy Prize S.r.l. -
All rights reserved Keywords:
Micro air
bubbles, Microfiltration, Micro ozone bubbles, Waste water treatment.
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