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Issue 1, Volume 4,
January 2009
Title of the Paper: Experimental
Visualization of Gas-Assisted Injection Long Bubble in a Tube
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Authors: Cheng-Hsing
Hsu, Kuang-Yuan Kung, Po-Chuang Chen, Shu-Yu Hu
Abstract: A long bubble-driven fluid flow in a circular tube is visualized by
an optical method. A pressurized airflow was injected into an 8 mm I.D. and
1,500 mm long horizontally placed glass tube filled with silicon oil to
produce a long bubble in the tube. The images were analyzed by two-value
calculation and a thinning process to extract the contour of the bubble front.
Data points on the contour were then deduced to undergo a regression curve
fitting. The results show a good verification of the theoretically derived
non-dimensional contour equation. The deduced penetration speed indicates that
the speed is increasing downstream due to the decreasing fluid slug in the
tube. The experimental results shows the theoretical bubble profile can be
introduced to the simulation study to reduce the calculating time, the ratio
(λ) of the bubble width to the diameter of the circular tube. The theoretical
bubble profile is more precise in a lower λ value than in a higher one.
Keywords: Long bubble,
Contour equation, Two-phase flow, Correlated number, Optical method
Title of the Paper: The Gas-assisted
Expelled Fluid Flow in the Front of a Long Bubble in a Channel
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Authors: C. H. Hsu, P.
C. Chen, K. Y. Kung, G. C. Kuo
Abstract: Investigated in this study is the steady-state flow field of a long
bubble penetrating into a region filled with a viscous fluid confined by two
closely located parallel plates. Instead of using the complicated procedure
for iteratively computing the free surface and flow patterns, we simply use a
theoretical profile of the bubble so that the influence of bubble shape on the
flow field can be examined directly. Due to the simplification, flow fields
with higher Reynolds number are easier to be included and different flow
phenomenon is found. The numerical techniques employed are finite difference
method (FDM) with successive over-relaxation (SOR). The simulation results
show coincidently with others the two typical flow patterns (complete bypass
flow and recirculation flow). The gradually moving of the stagnation point in
the front of the bubble tip between two typical flow patterns is clearly
presented and explainable. Both of the position of the stagnation point
parallel and perpendicular to the flow, *spx and*spy, depends on Reynolds
number, Re, andλ, the ratio of asymptotic bubble width to the distance between
two parallel plates. As λ or Re increases, *spy increases too, but*spx
decreases. A quasi-linear relationship between λ and *spx is found in a
recirculation flow region. Be ware that the stagnation point is very sensitive
with λ for Re>100. As Re increases, the maximum value of stream function
increases, and the recirculation zone near the bubble tip becomes bigger too.
Keywords: Long bubble,
expelled fluid flow, stagnation point, two-phase flow, inertia forces
Title of the Paper: Numerical Simulation
of Forging Process Using the Hybrid PCM/FEM
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Authors: Yong-Ming Guo
Abstract: In this paper, for analyses of metal forming problems, a point
collocation method (PCM) with a boundary layer of finite element is developed.
PCMs have some advantages such as no mesh, no integration. While, the
robustness of the PCMs is an issue especially when scattered and random points
are used. To improve the robustness, some studies suggest that the positivity
conditions can be important when using the PCMs. For boundary points, however,
the positivity conditions cannot be satisfied, so that it is possible to get
large numerical errors from the boundary points when using the PCMs.
Specifically, the errors could arise in point collocation analyses with
complicated boundary conditions. In this paper, by introducing a boundary
layer of finite element in boundary domain of workpiece, unsatisfactory issue
of the positivity conditions of boundary points can be avoided, and the
complicated boundary conditions can be easily imposed with the boundary layer
of finite element. A forging process is analyzed by using the hybrid PCM/FEM.
Keywords: Meshless method,
Point collocation method, Positivity conditions, FEM, Hybrid method, Forging
Title of the Paper: Comparison of the
Grey Theory with Neural Network in the Rigidity Prediction of Linear Motion
Guide
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Authors: Y. F. Hsiao, Y.
S. Tarng, K. Y. Kung
Abstract: The purpose of this paper is to compare the prediction models
constructed through neural network and grey theory, and to apply the
prediction model established to study of correlation between linear motion
guide rigidity under the stress of tension and compression. Strain data of
tension and compression are simultaneously obtained by the computer that is
linked with the Universal testing machine and translated into rigidity values
through the formula of δkF=. Through this study we can understand the
differences in prediction of rigidity between neural network and grey theory.
Experiment results will serve as reference for manufacturers and users, with
the hope that based on fewer measurement data testing time can be reduced and
the outcome can be more accurately predicted. Based on fewer measurement data,
the outcome can be more accurately predicted, and that with a nondestructive
test can accurately predict the rigidity of the linear motion guide. The
outcome indicates that the prediction model established through neural network
is superior to the prediction model established through the grey theory, and
that the neural network model can accurately predict the result.
Keywords: Grey prediction
model, rigidity, linear motion guide, neural network, tension, compression
Title of the Paper: Study of the
Lubrication Oil Consumption Prediction of Linear Motion Guide through the Grey
Theory and the Neural Network
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Authors: Y. F. Hsiao, Y.
S. Tarng
Abstract: To determine the lubrication oil consumption change of linear motion
guide under some mileage, this study designs a test machine to fasten the
linear motion guide. The grey prediction model GM(1,1) and neural network are
employed for comparison and exploration. Through this study we can understand
the differences in prediction of lubrication oil consumption between neural
network and grey theory. Experiment results will serve as reference for
manufacturers and users for the purpose of quality improvement and selection
of better linear motion guides. Based on fewer measurement data, the outcome
can be more accurately predicted, and that with a nondestructive test can
accurately predict the lubrication oil consumption of the linear motion guide.
The outcome indicates that the prediction model of neural network is superior
to the grey theory model GM(1,1). The average prediction error of neural
network prediction is around 2% - showing a very high accuracy level.
Keywords: Neural network,
grey theory, linear motion guide, lubrication oil, prediction, GM(1,1)
Issue 2, Volume 4,
April 2009
Title of the Paper: Measuring Full
Displacement Fields on Scattering Surfaces by a Portable Low-Cost
Interferometer
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Authors: M. Bova, L.
Bruno, L. Pagnotta, A. Poggialini
Abstract: The paper presents a device for measuring full displacement fields
working on the principle of speckle interferometry. The proposed
interferometer was designed with the aim of obtaining a lightweight
selfcontained device, easy to assemble with cheap and standard equipment. The
investigated area is illuminated by three laser diodes emitting 50 mW at 660
nm, and observed by a B&W firewire CCD camera. The accuracy of the
measurements is improved by means of a PZT actuator realized on purpose and
driven by a control electronics able to provide a very accurate supply
voltage. Furthermore by the control electronics it is possible to turn on and
off the diodes and to control the single light intensity of each laser. The
paper describes in details all the parts of the interferometer and the systems
implemented for optimizing the working conditions of the device. Furthermore
all the steps necessary for performing the measurements are reported, and
typical sets of experimental data are shown.
Keywords: Speckle
interferometry, laser diode, phase-shifting, low-cost, 3D deformation,
portable equipment
Title of the Paper: Application of
Finite Element Method to an Overhead Crane Bridge
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Authors: Camelia
Bretotean Pinca, Gelu Ovidiu Tirian, Ana Josan
Abstract: This paperwork analyses the tension and deformation state of the
resistance structure of an overhead crane bridge which used for all the
processes performed in the hall of a continuous casting department of an iron
and steel plant in order to find out the best sizes. This analysis is made up
with the help of the COSMOS software who enables us to make evolved finite
items – shell-type with three or four nodes per element. The shell-type finite
items belong to the C1–class items, and they have a field variable and the
I-type derivates working continuously alongside the frontier, meanwhile the
II-type continuous derivates per item are not continuous alongside the
frontier. These finite items allow us to design some complex structures more
accurately, such as the resistance structure of the crane bridge. This example
is not intended to be the only solution when designing symilar structures, but
the authors of this paperwork believe that it is providing enough information
and useful solutions for the analysis of the tension and deformation state in
case of finite items.
Keywords: Crane bridge,
analysis, model, resistance, overhead, finite elements, shell
Title of the Paper: 3D Shape of Specular
Surface Measurement Using Five Degrees of Freedom Camera System
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Authors: Khairi Yusuf,
Prasetyo Edi, Amir Radzi Abdul Ghani
Abstract: In this report, we describe a new method in obtaining a 3D shape of
specular surface by using five degrees of freedom (5-DOF) camera. We use the
principle that the normal vectors of the surface are extracted by aligning the
camera axis and the surface normal vector. From the normal vector data, the
shape of the surface is reconstructed. After the flat and the ball surface,
the objects of the research are continued to convex and concave specular
surface. The convex object is an automobile glass window, where in this object
we show that the back reflection of a parallel surface of a thin glass can be
eliminated. In the concave object we have a limitation that the radius of
object is not smaller than twice of the nearest distance from the camera to
the surface. The result shows that the methodology improves the 3-D shape of
object measurement with good accuracy.
Keywords: Shape
reconstruction, pattern recognition, computer vision, image processing, five
degrees of freedom camera, specular surface, normal vector, robotics
Title of the Paper: The Design of Light
Jet Aircraft
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Authors: Prasetyo Edi,
Khairi Yusuf, Amir Radzi Abdul Ghani, Hakim S. Sultan Aljibori
Abstract: This paper discusses the design of light jet aircraft (LJA) in the
university level. The design process that covers by this paper is just from
conceptual approach. Current technical information of the light jet aircraft
in the market will be studied for competitor analysis purpose. After that, the
calculation process will take part, like initial sizing, performance sizing,
initial sizing of main component, weight breakdown, cg (centre of gravity)
position and aircraft performance. It concludes with a discussion of the
results and recommendations for future work. This paper will only concentrate
on conceptual design, the next stage of design can be continuing in future
with the data from this paper.
Keywords: Conceptual
design, wing design, aircraft design, aerodynamic configuration, light jet
Issue 3, Volume 4,
July 2009
Title of the Paper: Impact Energy
Absorption of Concentric Circular Tubes
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Authors: Lion Kok Hao,
Amir Radzi Abdul Ghani, Prasetyo Edi, Khairi Yusuf
Abstract: Non-linear finite element code ABAQUS/Explicit was employed to
evaluate the energy absorption characteristics of concentric circular tubes
subjected to impact in the axial direction. Thin-walled circular tube plays a
vital role as energy absorber due to its high energy absorption capacity.
However, the main drawback of existing tube type energy absorber is the high
initial peak load. This work evaluates the capability of concentric circular
tubes in reducing the peak load that is exerted to the protected structures
and occupants during impact. Clearance and thickness of the structure were
varied and different materials such as aluminum alloy, high strength steel and
stainless steel were used. The study found that aluminum alloy has great
potential to be utilized as energy absorbing system due to its high specific
energy absorption capacity and long stroke. For all materials, increasing the
clearance between the inner and outer circular tubes resulted in a reduction
of peak load and a significant increase of specific energy absorption (SEA).
However, increasing the thickness adversely increased the initial peak load
and reduced the SEA. It can be deduced that concentric circular tubes could be
utilized as a safer design of energy absorber as it exhibited a lower initial
peak load during impact which is a desirable feature when designing for
occupant safety.
Keywords: Structural
crashworthiness, impact energy absorption, non-linear explicit finite element
Title of the Paper: Sensitivity Analysis
of Stability Problems of Steel Structures using Shell Finite Elements and
Nonlinear Computation Methods
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Authors: Zdenek Kala,
Jiri Kala
Abstract: The paper analyzes the influence of initial imperfections on the
ultimate limit state of a slender strut, applying the ANSYS programme. The
geometrical and material nonlinear finite element method was applied for the
theoretical analysis. Modelling of the steel structure was performed using
SHELL elements. The effect of input imperfections on the load-carrying
capacity is evaluated by sensitivity analysis. This paper is devoted to a
class of sensitivity analysis techniques that are known as the variance-based
methods. Input imperfections are of random origin. The Sobol’s sensitivity
analysis was used to determine the sensitivity of load-carrying capacity of a
strut with respect to the variance of initial imperfections. The sensitivity
analysis results identify the imperfections the variability of which can
influence the structure reliability. The Latin Hypercube Sampling method was
applied for the evaluation of sensitivity indices. The computation model
elaborated is unique with regard to its numerically demanding character.
Keywords: Reliability,
steel, structures, imperfections, stability, sensitivity analysis, shell
elements
Title of the Paper: Research on
Increasing the Lastingness of a Rolling Bridge
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Authors: Camelia
Bretotean Pinca, Gelu Ovidiu Tirian
Abstract: The paper’s purpose is to analysis the stresses and strains state in
the strength structure of a rolling bridge, presenting a fast and evaluated
computer aided solving method for complex static indeterminate structures. The
analysis of the stresses and strains state of the strength structure of a
rolling bridge for increasing its solidity in exploitation is made using the
calculation software with finite elements COSMOS/M. The research performed
allows the evaluation of the stresses state, pointing out the critical areas
and measures which are imposed in order to increase the solidity and bearing
capacity of the strength structure for the rolling bridge. The results we have
obtained allowed us to make up a study about the dimension optimization of the
strength structure in order to design the rolling bridge. Thus, the material
use could be reduced without exceeding the limits of the most appropriate
resistance.
Keywords: Stress, rolling
bridge, analysis, model, strength, finite elements, shell type
Title of the Paper: Optimal Trajectories
Towards Near-Earth-Objects using Solar Electric Propulsion (SEP) and Gravity
Assisted Maneuver
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Authors: Denilson Paulo
Souza dos Santos, Lorenzo Casalino, Guido Colasurdo, Antonio Fernando
Bertachini de Almeida Prado
Abstract: The solar electric propulsion could be the best option for the
transports of the future due to its high specific impulse when compared to the
chemical propulsion. Electric propellants are being extensively used to assist
the propulsion of terrestrial satellites for the maneuvers of orbit correction
and as primary propulsion in missions toward other bodies of the solar system.
In this work the optimization of interplanetary missions using solar electric
propulsion (SEP) and Gravity Assisted Maneuver to reduce the costs of the
mission, is considered. The high specific impulse of electric propulsion makes
a Gravity Assisted Maneuver 1 year after departure convenient. Missions for
several Near Earth Asteroids will be considered. The analysis suggests
criteria for the definition of initial solutions demanded for the process of
optimization of trajectories. Trajectories to the asteroid 2002TC70 are
analyzed. Direct trajectories, trajectories with 1 gravity assisted at the
Earth and with 2 gravity assisted with the Earth and either Mars are
presented. Shall be analyzed missions with thrusters PPS1350 and the Phall 1
for performance comparison. An indirect optimization method will be used in
the simulations.
Keywords: Astrodynamics,
Celestial Mechanics, Space Trajectories
Issue 4, Volume 4,
October 2009
Title of the Paper: Evaluation of the
Limit Load Capacity of Masonry Arch Bridges
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Authors: Amaryllis
Audenaert, Genserik Reniers, Wout Dullaert, Herbert Peremans
Abstract: Using a 2D decision support system based on a recent analytical
model, this paper is the first to demonstrate that bridge specific
characteristics require a detailed analysis to determine the collapse load. A
parameterized study of the limit load capacity is necessary to calculate the
worst case positioning of any kind of load. Because of the complexity of
finite element modeling and the computation time requirements of 3D finite
elements models for a large number of load positions, it is regularly assumed
that collapse positions are situated at the crown of the arc. Empirical
testing in this paper clearly demonstrates that this is not the case. The here
developed approach allows for a quick scan of any type of masonry arch bridge,
thus providing the necessary information on the critical range of load
positions to be analyzed in more detail by a 3D modeling approach.
Keywords: Arches, collapse
load, equilibrium,safety
Title of the Paper: Dimensional
Optimization for the Strength Structure of a Traveling Crane
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Authors: Camelia
Bretotean Pinca, Gelu Ovidiu Tirian, Ana Virginia Socalici, Erika Diana
Ardelean
Abstract: Most of the time, the strength structures who have not been
statically determined, cut to the right sized, and checked out by the classic
methods of the material strength cause the over sizing, because specialists
use approximate measurements in order to decrease the number of mathematical
calculation. This paper work describes the optimization of the main beam of a
strength structure of a traveling crane used in metallurgy – by using the
OPTSTAR mode that the COSMOS/M calculation software encloses which uses finite
elements. In order to accomplish the best suited size, we have to perform both
an analytic and experimental study about the performance of the traveling
crane. In order to do that, we analyze the state of the tensions and
deformation of the strength structure by using this calculation software based
on COSMOS finite elements. In order to validate the analytic study, we have
performed some industrial experiments by using specific devices for measuring
the resistance of the electrical tension. Both the analytic and experimental
studies have pointed out that we are able to come up with the best sizes in
order to reduce the material consumption we used during the production process
of the main beam within the strength structure of the traveling crane we have
analyzed.
Keywords: Tension,
traveling crane, optimization, deformation, over-sized, finite, elements
Title of the Paper: Non-linear Analysis
and Stability of the Automotive Suspensions with Neo–Hookean Elements
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Authors: Nicolae–Ddoru
Stanescu
Abstract: In this work we present two systems with non-linear neo–Hookean
components. In such systems there always exists an element with a non-linear
characteristic equation. This element can be considered to be a rubber or
another equivalent structure. We shall prove that the utilization of a neo–Hookean
element will not destroy the properties of the structure, but it riches these
properties and it could be a good solution in many cases. The first model
describes a quarter of an automobile and the second one is dedicated to a
half-automobile model. We obtain the equilibrium positions, study their
stability in the most general case and for the first model we also discuss the
stability of the motion. In the paper there are also numerical applications.
Keywords: Neo–Hookean,
stability, modeling, non-linear
Title of the Paper: Some Correlated
Factors Including Chip Surface of Bending Strength
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Authors: Aurel
Lunguleasa
Abstract: This scientific article presents some aspects referring to static
bending strength and its influencing factors. It is an exhaustive study of all
influencing factors but it only details the more important and known of these.
Only three wooden species are used, namely beech (Fagus silvatica L),
spruce-fir (Picea abies Karst) and poplar (Populus tremula L), for obtaining
chipboard. Main factors which are considered that they influence the bending
strength are: wooden specie, chip thickness, specific surface of chips,
percentage of resin, specifical consumption of adhesive and board density. All
of these are individually presented for finding the influence. Then, some of
these are extracted and try to find all the influences between them. Finally,
based on many rigorous experiments, a diagram for the grouped influence of
some correlated factors, were realized. The main influence of bending strength
that is found in this paper is chip thickness, but there are other hard points
such as specifically surface of chips or degree of compressin-compactation
Keywords: Chipboard,
bending strength, factors of influence, correlated factors, chip thickness,
resin percentage, specifical surface
Title of the Paper: Determining the
Optimal Build Directions in Layered Manufacturing
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Authors: A. Sanati
Nezhad, M. Vatani, F. Barazandeh, A. R. Rahimi
Abstract: Determining the optimal build directions is one of the most critical
factors in RP processes because it affects on the build time, support
structure, surface quality as well as the cost. The previous methods could
handle simple parts or limited objective functions. Moreover the methods with
multiple objective functions, had abstracted them into a single fitness
function in which the characteristics of individual objectives could not be
reflected properly. In the present work a new algorithm is presented to
determine the optimal build-up directions of the part in Stereolithography
systems. The algorithm can help RP users select among the optimal build-up
directions.The optimization is done using Multi-Objective Genetic Algorithm (MOGA).
The method proposed here handles build time, support volume and surface finish
as objective functions individually. At each GA step, the surface finish is
achieved applying adaptive layer thickness method and optimization algorithm
finds the optimal build directions with minimum build time and volume support.
The algorithm is developed by MATLAB. To evaluate the algorithm, several
sample parts are checked.
Keywords:
Stereolithography- Optimal Build Direction- Multi Objective Optimization -
Genetic Algorithm
Title of the Paper: Chaos in Grinding
Process
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Authors: Nicolae–Doru
Stanescu
Abstract: This paper presents a non-linear model for the external grinding of
a cylindrical work-piece. A system of non-linear differential equations for
the vibrations of the tool and the work-piece is obtained. Non-linearity comes
from the cutting force dependence on the feeding velocity and depth of cut. We
determine the number of the equilibrium positions, we proved that there exists
only one equilibrium position and we study its stability. Results of
simulation are discussed. A chaotic regime is found for realistic values of
the grinding parameters.
Keywords: Grinding,
equilibrium, stability, chaos
Title of the Paper: Sommerfeld and Mass
Parameter Identification of Lubricated Journal Bearings
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Authors: Domenico Guida,
Carmine M. Pappalardo
Abstract: In this paper we propose a method for identification of two
parameters that define the structure of lubricated journal bearings. In
rotordynamics literature these parameters are named Sommerfeld number and Mass
Number, respectively. The system analyzed belongs to the class of systems that
are described by n nonlinear second order differential equations. We have
obtained the analytical solutions of these equations using Lie series
expansion. This method can be applied to a vast class of dynamical systems,
provided that they are described by smooth equations. Lie series expansion is
a mathematical tool that allows us to obtain the system response in recursive
way using symbolic PC-codes. Besides, this procedure involves only a few
experimental data and makes the identification process very quick. It is worth
noting that the application that we propose does not take into account neither
the issue connected to experimental data noise nor the unavoidable
disturbances that occurs in measurement process. Actually, in applied system
identification one must always pay attention to the signal noise and to the
robustness of the solution with respect to disturbances, but these issues are
over the goal of this paper.
Keywords: Nonlinear System
Identification, Parameter Identification, Lubricated Journal Bearings
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