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Home>Products>Journal and Reviews>I.RE.M.E.>Latest issue
International Review of Mechanical Engineering - September 2009 - Papers
International Review of Mechanical Engineering - Papers
Vol. 3. n. 5, pp.510-520
Abstract - The
dynamic behaviour, therefore vibroacoustic, of the gears is requested by
the static error of transmission, which is the internal source of
excitation, generated on the level of the engaging, and whose physical
origins are the elastic strain of teeth due to the application of the
engine torque and the variations of geometry of the gears. The elastic
joining induced by engaging is described by the parametric stiffness of
engaging k (t) along to the line of action. Their modelling requires the
placement of tools making it possible to characterize this source of
excitation and the resolution of contact equations between teeth in
catch. Copyright © 2009 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Gears, Toothed wheels, Transmission of power, Modelling, Static error of transmission, Stiffness of engaging, Static analysis, Modal analysis, Dynamic response.
Vol. 3. n. 5, pp.521-528
Abstract - In this paper we attempt to carry out the dynamic analysis of the guiding - suspension system of a motor vehicle using the testing in virtual environment. The model is realized using a virtual prototyping platform, which has as main component the MBS (Multi-Body Systems) package ADAMS. The model contains the front & rear suspensions, the steering and the car body, and it is analyzed in passing over bumps regime, simulating an experimental lab test. Each wheel is anchored on a sustaining plate which executes vertical motion relative to the fixed structure. The motion generators applied in the translational joints simulate the road profile. For controlling the motion of the input elements, the control system is developed using the C&C software EASY5, in mechatronic concept, by integrating the mechanical model and the control system at the virtual prototype level. One of the most important advantages of this kind of simulation consists in the possibility of make easy virtual measurements in any point and/or area and for any parameter. This is not always possible in the real case due to the lack of space for transducers placement, lack of appropriate transducers or high temperatures. This helps us to take quick decisions on any design changes without going through expensive hardware prototype building and testing. Copyright © 2009 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Motor Vehicle, Guiding - Suspension System, Dynamics, Virtual Prototype.
Vol. 3. n. 5, pp.529-537
Abstract - Practical applications of machine elements supported by flexible support are rotating shafts mounted on bearings. The bearings in general are sliding or rolling. Both types of bearings have stiffness and damping characteristics. The shaft itself has hysteric damping due to the deflection and whirling. The problem of journal bearings control is of great importance in whirling shafts. A very recent method for doing this is the creation of smart journal bearings using electro- rheological fluid. If such fluid is used to lubricate a journal bearing system it is expected that the application of an electric field between the rotor and stator will cause an alteration in the dynamic properties of the journal bearing. In this work a model of whirling flexible shaft supported by two identical electro – rheological (ER) journal bearings is introduced. The analysis here is based on linear and non – linear solution for the equations of motion about equilibrium position, and also applicable conditions for linearity of these equations was studied. The impedance of (ER) journal bearing is represented by four, linear springs and four electro - rheological (ER) dampers, using a Bingham plastic model of non- Newtonian fluid. The effect of Sommerfeld number and electric field inserted to ER fluid-film was studied. A dynamic response of the flexible shaft in the presence of classical and ER journal bearing was compared. A run - up and coast down was obtained at different values of electric field intensity for journal and at mid point of the shaft. Also the stability of journal bearing was studied for different values of rotor mass and radial clearance of the bearing. Copyright © 2009 Praise Worthy Prize S.r.l. - All rights reserved Keywords: Bearings, ER- Fluids, Vibrations, Linearization, Dynamic Models.
Vol. 3. n. 5, pp.538-546
Abstract - Under certain opening conditions and partial opening of control valves, the piping systems occasionally suffer large vibrations. To understand the valve instability that is responsible for such vibrations, experiments and CFD simulations were performed. As a result of the study of the turbulence flow through a single seat globe valve operating at small openings, it was found that a complex three-dimensional flow structure (valve attached flow) sets up in the valve region leading to high pressure variations in the valve trim region. CFD calculations showed how a jet may impinge on the roof of the valve body and cause a large-scale recirculation region in the pipe downstream of the valve. Moreover, it was found that the smaller valve opening, the larger the exciting force acting on the valve stem. The harmful effect of the fluid flow forces (exciting forces) is very much pronounced at relatively smaller valve opening. The simulation results for turbulent flow with k-ε model were more accurate than the k-ε model. In addition, k-ε model was simpler and faster in convergence than the k-ε model. Copyright © 2009 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Control valves, Turbulent, Simulation, Computational fluid dynamics.
Vol. 3. n. 5, pp. 547-552
Abstract - The following work presents the methodology used in order for develop a low cost Virtual Based Anthropomorphic Gripper application, for Automation Grasping Tasks of common object geometries in a robotics work-cell environment containing a six degrees of freedom Industrial Robot and an Anthropomorphic hand based device attached to it. In order to comply the low cost development requirement, a set of parameters are defined so the programming and editing of the virtual environment fulfills the specifications. Subsequently, the study of the human and mechanical hands kinematics allows the creation of virtual objects resembling their behavior and appearance. By studying human grasp postures it can be seen that each finger has a position from which a grasping table can be created, this information also works for an anthropomorphic gripper as they share similar anatomy. Based on these similarities, three basic shapes are chosen to test the application, a spherical, cylindrical and planar, which are available on the graphic user interface, so it can be executed on the defined virtual device. For testing purposes, a real anthropomorphic device is virtualized and from the virtual grasps performed, an information file is created for its execution on the workcell The developed application allows the virtualization of a six to nineteen degrees of freedom anthropomorphic hand, either using commercial or open source 3D modeling software, initial applications are on offline grasp task planning. The program execution is operating system independent, which makes it portable as well of the creation and edition of 3D geometries. Finally, future work can be aimed for training and educational purposes and the research expanded for improving the grasping technique using supervisory systems and shape recognition. Copyright © 2009 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Virtual, Grasp, Robotics gripper.
Vol. 3. n. 5, pp. 553-561
Abstract -
The great progress in computational fluid dynamics has sufficiently
contributed to the prediction of the flowfield through pumps and the
enhancement of their design. In the present analysis the influence of
blade design methods based on angle and velocity distribution is studied
in the flowfield and in the efficiency of a centrifugal pump. The
results are compared with the corresponding of the synthetic double-arc
blade design method for the same centrifugal pump geometry. 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 blade design method,
the pressure distribution inside the pump and around the impeller
periphery is computed. The velocity field between the blades at the
leading edge is examined.
Keywords: Angle Distribution Design, Blade Impeller, Centrifugal Pump, CFD Numerical Analysis, Double-Arc Design, Velocity Distribution Method.
Vol. 3. n. 5, pp. 562-565
Abstract -
Sulfates and chlorides are chemically aggressive environments for
reinforced concrete structures. Know the extent of the attacks caused by
these environments is required. These studies mainly attempted to
determine sodium sulfate solution influence on the mechanical properties
of normal strength concrete. In this paper we present results of an
experimental investigation on reinforced concrete beams (230×6×10 cm3).
The beams were loaded at the mid span following a two point loading
setup. Three kinds of environments were chosen for curing the beams
before testing: state temperature and humidity standard conditions,
water basin and sodium sulfate solution. The curing environments were
applied to the beams from three sides. The flexural strength, inelastic
strain in concrete, crack width and deflection were measured. The
experimental results show significant decrease of the flexural strength.
Moreover, the sulfate solution increases the width of flexural cracks
for the reinforced concrete beams.
Keywords: Reinforced concrete beam, Flexural strength, Crack, Deflection, Sulfate solution.
Vol. 3. n. 5, pp. 566-572
Abstract -
The surface quality of the orthopedic prostheses is a parameter
influencing in their life time. The wear of the parts in contact
generates particles of metal or plastic in the body of the person who
carries this prosthesis.
Keywords: End milling, Surface roughness, Ti-6Al-4V, Prosthesis.
Vol. 3. n. 5, pp. 573-578
Abstract - This article presents an analytical model that can simulate reinforced concrete beams in the post cracking phase of concrete. Analyses of reinforced concrete structures based on smeared crack approach generally include tensile softening relationships to estimate the average concrete tensile stress in the cracking range. In this procedure, the tension stiffening model is mainly inspired from the fracture energy concept applied for concrete. The proposed tension-stiffening law is formulated and integrated in the numerical program to quantify the tension stiffening contribution in the post-cracking array. Finite element model of the tension stiffening effect shows a well correlation between predicted results of this numerical simulation and available experimental data of idealized shear beams. Copyright © 2009 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Tension stiffening model, Shear failure, Reinforced concrete beams, Finite element method, Fracture energy concept, Smeared crack model, Post-cracking behavior.
Vol. 3. n. 5, pp. 579-587
Abstract - This paper presents an investigation into the application of a high gain feedback regulator for the problem of active vibration control (AVC) of a rectangular flexible plate structure. The plate system was first modeled using Finite Difference (FD) approach. Then, the validity of the obtained model was investigated through comparative studies between the plate natural frequencies predicted by the model and the exact values of resonance modes. A simple regulator with high feedback gain was employed to reduce the unwanted vibration at an observation point. An appropriate value of the feedback gain was acquired through a simulation study. Different types of disturbances were applied to excite the plate system at different excitation points so that the robustness of the proposed control algorithm can be evaluated in terms of its performance in reducing the vibration at observation point. Results of the study clearly demonstrate the effectiveness of the proposed control strategy to attenuate the unwanted vibrations of the flexible thin plate system. Copyright © 2009 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Feedback regulator, Finite difference, Flexible plate, Vibration.
by S.–P. Edwards, A.J. den Bakker, J. Zhou, L. Katgerman Vol. 3. n. 5, pp. 588-608
Abstract - This review presents the current state of the understanding of the phenomena associated with the formation of longitudinal weld seams during the extrusion of complex hollow aluminum profiles. The subject is of critical importance for the manufacturing aluminum extrusions, because a defective weld seam can introduce an inherent weakness into extruded product, which may make this product unsuitable for certain structural applications. It discusses the factors that determine the quality of weld seams including extrusion process parameters, thermal history and die design. In addition, it introduces assessment methods and criteria that can be used to discriminate between a defective weld seam and a sound weld seam. Copyright © 2009 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Extrusion, Weld Seam, Aluminum.
by A. Brahimi, M. Keddam, M.Sidi Moussa Vol. 3. n. 5, pp. 609-612
Abstract - In this study, the paste boriding treatment was carried out at 900 °C for 4 h on the surface of XC38 steel. The composition of the applied paste consisting of B4C, Al and SiC was taken as variable parameter. The generated boride layers were characterized by hardness measurements, optical microscopy examinations and XRD analysis. It is shown that the interface morphology of the borided layers and their properties such as wear resistance depend strongly on the paste composition. Furthermore, an optimization method was applied on the basis of experimental results to find an optimal value of the resistance against wear as a function of the paste composition. Copyright © 2009 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Boriding, Multi–element paste, Diffusion, Wear resistance, Optimization.
Vol. 3. n. 5, pp. 613-618
Abstract - This study was carried out to determine the correlations between percentage increases in local Nusselt number at different radial distance between steady and pulsating flow of circular air jet. A heat transfer of heated steady and pulsating air jet at frequencies between 10 to 80 Hz was measured in the study. The set-up was used to measure the heat flux at the stagnation point and the local Nusselt number at different radial distance. The radial distance is at 2, 4, 6, 8, 10 and 12 cm away from stagnation point. Measurement of the heat flux using a RdF heat flux microsensor was used to calculate the local heat transfer coefficient and local Nusselt number for steady air jet and for pulsating jet at Reynolds number of 32000. Results obtained show that the stagnation point Nusselt number is higher for steady jet compared to pulsating jet at all frequencies except at 70 Hz. At pulsating frequency of 70 Hz, the local Nusselt number is higher than the steady jet at all local positions. Percentage increases in local Nusselt number calculated for pulsating jet were higher than the local Nusselt number for steady jet starting from radial distance of 1 cm and above for pulsating frequencies of 20, 30 and 60 Hz. For pulsating frequency of 40, 50 and 80 Hz, the increases starts at radial distance of 2 cm. The relationship between the Nusselt number and the radial distance for each of the pulsating frequencies were determined for each pulsating frequency. Copyright © 2009 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Pulsating air jet, jet frequency, Nusselt number, Reynolds number, heat transfer coefficient.
Vol. 3. n. 5, pp. 619-626
Abstract - The paper deals with the lubrication of the human ankle joint in steady running. A biphasic mixture model is considered for articular cartilage (interstitial fluid and elastic porous matrix). The cartilage matrix is anisotropic and inhomogeneous. Synovial fluid is considered Newtonian. The fluid phase passes through the matrix pores and articular surfaces. An induced viscosity change of the synovial film due to the filtration of synovial fluid by articular cartilage is neglected in the numerical calculation. The model indicates that during running, similarly to walking, the joint operates in a mixed lubrication mode (a combination of the boundary and fluid film lubrication), but as compared to walking, with a major emphasis on the fluid film mode. Copyright © 2009 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Articular Cartilage, Human Ankle Joint, Lubrication Mode, Running, Synovial fluid Filtration.
Vol. 3. n. 5, pp. 627-631
Abstract - Rheology is known to have a strong impact on the flow behavior and the power consumption of mechanically agitated vessels. The laminar 2D agitation flow and power consumption of viscoplastic fluids with an anchor, gate and two blades impellers in a stirring tank is studied by using computational fluid dynamics (CFD). The objective of this paper is: to evaluate the power consumption for yield stress fluids in tree standard mixing systems. The power consumption is calculated for the different types of impeller configurations and an optimum configuration is proposed. Copyright © 2009 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Agitated tank, Anchor, Gate, Two blades agitator, Viscoplastic fluid, Finite volume method, CFD.
Vol. 3. n. 5, pp. 632-639
Abstract - Functionally Graded Materials (FGMs) are the emerging materials in which material properties vary continuously with position, in one direction. The present study is to fabricate a Functionally Graded Al/Si in situ material and to characterize it. Al /17wt.%Si alloy has been used to fabricate Al/Si FGM by centrifuge casting process specially designed for the purpose. The microstructural characteristic and hardness profile of these FGMs have been evaluated. The study shows the structure of this Al/Si alloy produced by this method changes from Hyper-Eutectic through to Hypoeutectic, with later having primary Al dendrites. It also reveals that hardness and the primary Si particles vary along the length of the sample. Copyright © 2009 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Centrifuge, Functionally Graded Material (FGM), G force, Hardness.
Vol. 3. n. 5, pp. 640-645
Abstract - Welding
residual stress is one of the most important factors of stress corrosion
cracking (SCC) growth in pressure boundary piping. A probabilistic
fracture mechanics model of structural reliability is described that
considers failure to occur as the result of subcritical and catastrophic
growth of pre-existing cracks that escape detection. The model considers
cracks to be two-dimensional and is capable of treating many of the
input parameters as random variables and can consider arbitrary
inspection schedules. Copyright © 2009 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Probabilistic fracture mechanics, Structural reliability, In-service inspection, Residual stresses, BWR piping.
by R. Mehdaoui, M. Elmir, T.Ghomri Vol. 3. n. 5, pp. 646-652
Abstract - The objective of this work is to study the thermal conductivity ratio (kr) effect on the structure of natural convection flow in a partially porous cavity. A cylindrical heat source maintained at a uniform temperature is introduced into a porous portion. The equations which describe the thermal transfer and the hydrodynamic flow are described by the Navier-Stokes equations modified by the extension of Darcy-Brinkman model and the energy equation. The results obtained are in the form of isotherm distribution, streamlines, the average Nusselt numbers and pressure. Correlations between these parameters and the thermal conductivity ratio are considered. This study is the one application object to the creation of a climate favorable to pushed plants in an agricultural greenhouse in an arid region. Copyright © 2009 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Natural convection, Porous, Saturated, Cavity, Fluid, Darcy, Brinkman.
by S. E. Razavi, M. Tabatabaei Vol. 3. n. 5, pp. 653-659
Abstract - A novel approach for the solution of two-dimensional flow over a backward-facing step at low Reynolds numbers with heat transfer is presented. For convective flux modeling an upwind-biased method is used. This type of flux treatment takes into account the pressure as a driving force between the cell faces. The incompressible Navier-Stokes equations along with artificial compressibility are marched in time by a fifth-order Runge-Kutta scheme. Applying the convective flux model led to accurate solutions and faster convergence rates. The obtained numerical results are compared with the available experimental and numerical data, in the technical literature. Copyright © 2009 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Incompressible flow, Heat transfer, Backward-facing step, Artificial compressibility, Finite-volume, Upwind-biased flux.
Vol. 3. n. 5, pp. 660-664
Abstract - An exact solution is given for the flow of a Maxwell fluid between two parallel disks rotating about non-coincident axes normal to the disks. Since the motion in an orthogonal rheometer used for determining the complex dynamic viscosity of a viscoelastic fluid corresponds to the category of “pseudo-plane motions”, the locus of stagnation points that shed light on the flow is carefully delineated. It is pointed out that the results observed by the space curves which reveal the stagnation points in the flow exhibit strong boundary layer development when the Reynolds and Deborah numbers increase. Copyright © 2009 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Maxwell Fluid, Orthogonal Rheometer, Stagnation Points.
by Lazarus Teneketzis Tenek Vol. 3. n. 5, pp. 665-669
Abstract - A solid element is developed for the force method. Using complementary work and the stress vector the element force matrix is derived. The global force matrix is then conceived by relating in a discrete sense the stress vector with nodal forces which through a direction cosine matrix relate to the global coordinate. The element has 8 nodes and accepts applied displacements, or applied forces as a boundary condition. The solution provides the nodal forces and in a second step the element deformation. A numerical example of a square plate discretized with solid elements is furnished. Copyright © 2009 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Complementary Work, Force Method EFM, Solid element, Force matrix.
Vol. 3. n. 5, pp. 670-673
Abstract - Springback or elastic recovery refers to the shape discrepancy between the fully loaded and unloaded configurations. Springback causes changes in shape and dimensions that can create major problems in the assembly. Hence, prediction of the springback is an important issue in sheet metal forming. Various investigations of springback prediction show that process parameters such as bend radius, sheet thickness, tool geometries, punch speeds, and material properties have considerable influence on springback. In the present paper, the effect of sheet thickness, punch speed and material properties on the springback angle has been discussed. Two different approaches, implicit and explicit are considered. A strain rate dependent plasticity model has been used to determine the effect of punch speed on the springback angle. Copyright © 2009 Praise Worthy Prize S.r.l. - All rights reserved
Keywords:
Springback,
Explicit, Implicit, Strain rate dependent.
Vol. 3. n. 5, pp. 674-678 Abstract - In this
paper, the finite element method is used to compute the deflection of a
single pile, placed in a soil layer and subjected to static lateral
loadings. The soil behavior is modeled as Mohr-Coulomb elastoplastic
model, while the pile material behavior is modelled as linear elastic
model. The main objective of this analysis is to determine the maximum
deflection of the pile. In order to characterize the effect of the soil
nature on the response of pile, sandy and clayey soils are considered.
For both soils, the influence on the pile response of the soil
nonlinearity pile dimensions has been analyzed and some concluded
remarks are presented. Numerical results obtained from the present
study, have been compared against published results and have shown a
good correlation. Copyright © 2009 Praise Worthy Prize S.r.l. -
All rights reserved Keywords:
Clay, Deflection, Finite Elements, Lateral loads, Pile, Sand.
Vol. 3. n. 5, pp. 679-686 Abstract - Nowadays,
the new and emerging concept of seismic structural design, the so-called
performance-based design, requires careful consideration of all aspects
involved in structural analysis. One of the most important aspects of
structural analysis is Soil-Structure Interaction (SSI). Such
interaction may alter the dynamic characteristics of structures and
consequently may be beneficial or detrimental to the performance of
structures. In order to observe such effects we study the seismic
response of an idealized small city composed of five equally spaced,
five storey reinforced concrete buildings anchored in a soft soil layer
overlaid by a rock half-space. Our results show response amplification
of the buildings in the near field in accordance with the results
observed in similar cases. Copyright © 2009 Praise Worthy Prize S.r.l. -
All rights reserved Keywords:
Soil-structure interaction, Wave based methods, Site effect, seismic
response, Response amplification.
Vol. 3. n. 5, pp. 687-693 Abstract - The high
performance of geared servomechanisms is strongly affected by the
dynamic characteristics of their mechanical systems. The paper presents
an analytical and computer-aided procedure for minimizing the dynamic
transmission error of spur gear mechanisms by using a
single-degree-of-freedom model. The relationships between time-varying
mesh stiffness and profile modifications are investigated. The amount of
optimum profile modifications is depended upon the magnitude of the
variable mesh stiffness of contacting tooth pairs and the applied load.
An accurate model and the variation of the gear mesh stiffness as a
function of the contact point along the contact line are presented in
the paper. The effect of the amount of the tooth tip relief on the
dynamic transmission error are studied at various loading conditions. Copyright © 2009 Praise Worthy Prize S.r.l. -
All rights reserved Keywords:
Spur gear, Profile modification, Mesh stiffness, Dynamic transmission
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