Abstract: In the present work, the performance of the particle
swarm optimization and the genetic algorithm compared as a typical
geometry design problem. The design maximizes the heat transfer
rate from a given fin volume. The analysis presumes that a linear
temperature distribution along the fin. The fin profile generated using
the B-spline curves and controlled by the change of control point
coordinates. An inverse method applied to find the appropriate fin
geometry yield the linear temperature distribution along the fin
corresponds to optimum design. The numbers of the populations, the
count of iterations and time to convergence measure efficiency.
Results show that the particle swarm optimization is most efficient
for geometry optimization.
Abstract: Control of commutation of switched reluctance (SR)
motor has been an area of interest for researchers for sometime now
with mixed successes in addressing the inherent challenges. New
technologies, processing schemes and methods have been adopted to
make sensorless SR drive a reality. There are a number of
conceptual, offline, analytical and online solutions in literature that
have varying complexities and achieved equally varying degree of
robustness and accuracies depending on the method used to address
the challenges and the SR drive application. Magnetic coupling is
one such challenge when using active probing techniques to
determine rotor position of a SR motor from stator winding. This
paper studies the effect of back-of-core saturation on the detected
rotor position and presents results on measurement made on a 4-
phase SR motor. The results shows that even for a four phase motor
which is excited one phase at a time and using the electrically
opposite phase for active position probing, the back-of-core
saturation effects should not be ignored.
Abstract: Thermally insulating ceramic coatings also known as
thermal barrier coatings (TBCs) have been essential technologies to
improve the performance and efficiency of advanced gas turbines in
service at extremely high temperatures. The damage mechanisms of
air-plasma sprayed YSZ thermal barrier coatings (TBC) with various
microstructures were studied by microscopic techniques after thermal
cycling. The typical degradation of plasma TBCs that occurs during
cyclic furnace testing of an YSZ and alumina coating on a Titanium
alloy are analyzed. During the present investigation the effects of
topcoat thickness, bond coat oxidation, thermal cycle lengths and test
temperature are investigated using thermal cycling. These results
were correlated with stresses measured by a spectroscopic technique
in order to understand specific damage mechanism. The failure
mechanism of former bond coats was found to involve fracture
initiation at the thermally grown oxide (TGO) interface and at the
TGO bond coat interface. The failure mechanism of the YZ was
found to involve combination of fracture along the interface between
TGO and bond coat.
Abstract: Today air-core coils (ACC) are a viable alternative to
ferrite-core coils in a range of applications due to their low induction
effect. An analytical study was carried out and the results were used as
a guide to understand the relationship between the magnet-coil
distance and the resulting attractive magnetic force. Four different
ACC models were fabricated for experimental study. The variation in
the models included the dimensions, the number of coil turns and the
current supply to the coil. Comparison between the analytical and
experimental results for all the models shows an average discrepancy
of less than 10%. An optimized ACC design was selected for the
scanner which can provide maximum magnetic force.
Abstract: Tip vortex cavitation is one of well known patterns of
cavitation phenomenon which occurs in axial pumps. This pattern of
cavitation occurs due to pressure difference between the pressure and
suction sides of blades of an axial pump. Since the pressure in the
pressure side of the blade is higher than the pressure in its suction
side, thus a very small portion of liquid flow flows back from
pressure side to the suction side. This fact is cause of tip vortex
cavitation and gap cavitation that may occur in axial pumps. In this
paper the results of our experimental investigation about movement
of tip vortex cavitation along blade edge due to reduction of pump
flow rate in an axial pump is reported. Results show that reduction of
pump flow rate in conjunction with increasing of outlet pressure
causes movement of tip vortex cavitation along blade edge towards
the blade tip. Results also show that by approaching tip vortex
cavitation to the blade tip, vortex tip pattern of cavitation replaces
with a cavitation phenomenon on the blade tip. Furthermore by
further reduction of pump flow rate and increasing of outlet pressure,
an unstable cavitation phenomenon occurs between each blade
leading edge and the next blade trailing edge.
Abstract: The decision to recruit manpower in an organization
requires clear identification of the criteria (attributes) that distinguish
successful from unsuccessful performance. The choice of appropriate
attributes or criteria in different levels of hierarchy in an organization
is a multi-criteria decision problem and therefore multi-criteria
decision making (MCDM) techniques can be used for prioritization
of such attributes. Analytic Hierarchy Process (AHP) is one such
technique that is widely used for deciding among the complex criteria
structure in different levels. In real applications, conventional AHP
still cannot reflect the human thinking style as precise data
concerning human attributes are quite hard to be extracted. Fuzzy
logic offers a systematic base in dealing with situations, which are
ambiguous or not well defined. This study aims at defining a
methodology to improve the quality of prioritization of an
employee-s performance measurement attributes under fuzziness. To
do so, a methodology based on the Extent Fuzzy Analytic Hierarchy
Process is proposed. Within the model, four main attributes such as
Subject knowledge and achievements, Research aptitude, Personal
qualities and strengths and Management skills with their subattributes
are defined. The two approaches conventional AHP
approach and the Extent Fuzzy Analytic Hierarchy Process approach
have been compared on the same hierarchy structure and criteria set.
Abstract: When a high DC voltage is applied to a capacitor with
strongly asymmetrical electrodes, it generates a mechanical force that
affects the whole capacitor. This phenomenon is most likely to be
caused by the motion of ions generated around the smaller of the two
electrodes and their subsequent interaction with the surrounding
medium. A method to measure this force has been devised and used.
A formula describing the force has also been derived. After
comparing the data gained through experiments with those acquired
using the theoretical formula, a difference was found above a certain
value of current. This paper also gives reasons for this difference.
Abstract: Korea Train eXpress (KTX) is now being operated,
which allows Korea being one of the countries that operates the
high-speed rail system. The high-speed rail has its advantage of short
time transportation of population and materials, which lead to many
researches performed in this matter. In the case of high speed classical
trackbed system, the maintenance and usability of gravel ballast
system is costly. Recently, the concrete trackbed structure has been
introduced as a replacement of classical trackbed system. In this case,
the sleeper plays a critical role. Current study investigated to develop
the track sleepers readily applicable to the top of the asphalt trackbed,
as part of the trcakbed study utilizing the asphalt material. Among
many possible shapes and design of sleepers, current study proposed
two types of wide-sleepers according to the shear-key installation
method. The structural behavior analysis and safety evaluation on each
case was conducted using Korean design standard.
Abstract: Metal matrix composites (MMC) are generating
extensive interest in diverse fields like defense, aerospace, electronics
and automotive industries. In this present investigation, material
removal rate (MRR) modeling has been carried out using an
axisymmetric model of Al-SiC composite during electrical discharge
machining (EDM). A FEA model of single spark EDM was
developed to calculate the temperature distribution.Further, single
spark model was extended to simulate the second discharge. For
multi-discharge machining material removal was calculated by
calculating the number of pulses. Validation of model has been done
by comparing the experimental results obtained under the same
process parameters with the analytical results. A good agreement was
found between the experimental results and the theoretical value.
Abstract: Aluminum/Copper clad sheet has been fabricated using
asymmetric extrusion method, which caused severe shear deformation
between Al and Cu plate to easily bond to each other. Interfacial
microstructure and mechanical properties of Al/Cu clad were studied
by scanning electron microscope equipped with energy dispersive
X-ray detector, micro-hardness, and tension tests. The asymmetric
extrusion bonding was very effective to provide a good interface for
atoms diffusion during subsequent annealing. The strength of bonding
was higher with the increasing extrusion ratio.
Abstract: Carbon steel is used in boilers, pressure vessels, heat
exchangers, piping, structural elements and other moderatetemperature
service systems in which good strength and ductility are
desired. ASME Boiler and Pressure Vessel Code, Section II Part A
(2004) provides specifications of ferrous materials for construction of
pressure equipment, covering wide range of mechanical properties
including high strength materials for power plants application.
However, increased level of springback is one of the major problems
in fabricating components of high strength steel using bending.
Presented work discuss the springback simulations for five different
steels (i.e. SA-36, SA-299, SA-515 grade 70, SA-612 and SA-724
grade B) using finite element analysis of air V-bending. Analytical
springback simulations of hypothetical layered materials are
presented. Result shows that; (i) combination of the material property
parameters controls the springback, (ii) layer of the high ductility
steel on the high strength steel greatly suppresses the springback.
Abstract: In this paper static and dynamic response of a
varactor of a micro-phase shifter to DC, step DC and AC
voltages have been studied. By presenting a mathematical
modeling Galerkin-based step by step linearization method
(SSLM) and Galerkin-based reduced order model have been
used to solve the governing static and dynamic equations,
respectively. The calculated static and dynamic pull-in
voltages have been validated by previous experimental and
theoretical results and a good agreement has been achieved.
Then the frequency response and phase diagram of the system
has been studied. It has been shown that applying the DC
voltage shifts down the phase diagram and frequency
response. Also increasing the damping ratio shifts up the
phase diagram.
Abstract: In this experimental study, performance of a counter
flow Ranque-Hilsch vortex tube (RHVT) with threads cut on its inner
surface was investigated experimentally (pitch is 1 and 2 mm). The
inner diameter of the vortex tube used was D=9 mm and the ratio of
the tube’s length to diameter was L/D=12. The experimental system
was a thermodynamic open system. Flow was controlled by a valve
on the hot outlet side, where the valve was changed from a nearly
closed position to its nearly open position. Fraction of cold flow (ξ) =
0.1-0.9, was determined under 300 and 350 kPa pressurized air. All
experimental data were compared with each other, the maximum
heating performance of the RHVT system was found to be 38.2 oC
and the maximum cooling performance of the RHVT in this study
was found to be -30.9 oC at pitch 1 mm.
Abstract: Tubular process equipment is often damaged in
industrial processes. The damage occurs both on devices working at
high temperatures and also on less exposed devices. In case of sudden
damage of key equipment a shutdown of the whole production unit
and resulting significant economic losses are imminent. This paper
presents a solution of several types of tubular process equipment. The
causes of damage and suggestions of correction actions are discussed
in all cases. Very important part is the analysis of operational
conditions, determination of unfavourable working states decreasing
lifetime of devices and suggestions of correction actions. Lately very
popular numerical methods are used for analysis of the equipment.
Abstract: The aim of this paper is to introduce a parametric
distribution model in fatigue life reliability analysis dealing with
variation in material properties. Service loads in terms of responsetime
history signal of Belgian pave were replicated on a multi-axial
spindle coupled road simulator and stress-life method was used to
estimate the fatigue life of automotive stub axle. A PSN curve was
obtained by monotonic tension test and two-parameter Weibull
distribution function was used to acquire the mean life of the
component. A Pearson system was developed to evaluate the fatigue
life reliability by considering stress range intercept and slope of the
PSN curve as random variables. Considering normal distribution of
fatigue strength, it is found that the fatigue life of the stub axle to
have the highest reliability between 10000 – 15000 cycles. Taking
into account the variation of material properties associated with the
size effect, machining and manufacturing conditions, the method
described in this study can be effectively applied in determination of
probability of failure of mass-produced parts.
Abstract: In industry, on of the most important subjects is die
and it's characteristics in which for cutting and forming different
mechanical pieces, various punch and matrix metal die are used.
whereas the common parts which form the main frame die are not
often proportion with pieces and dies therefore using a part as socalled
common part for frames in specified dimension ranges can
decrease the time of designing, occupied space of warehouse and
manufacturing costs. Parts in dies with getting uniform in their shape
and dimension make common parts of dies. Common parts of punch
and matrix metal die are as bolster, guide bush, guide pillar and
shank. In this paper the common parts and effective parameters in
selecting each of them as the primary information are studied,
afterward for selection and design of mechanical parts an
introduction and investigation based on the Mech. Desk. software is
done hence with developing this software can standardize the metal
common parts of punch and matrix. These studies will be so useful
for designer in their designing and also using it has with very much
advantage for manufactures of products in decreasing occupied
spaces by dies.
Abstract: This paper deals with the design of a moving sliding
surface in a variable structure plant for a second order system. The
chattering phenomena is also dealt with during the switching process
for an unstable sliding surface condition. The simulation examples
considered in this paper shows the effectiveness of the sliding mode
control method used for the design of the moving sliding surfaces. A
simulink model of the continuous system was also developed in
MATLAB-SIMULINK for the design and hence demonstrated. The
phase portraits and the state plots shows the demonstration of
the powerful control technique which can be applied for second
order systems.
Abstract: Modularized design approach can facilitate the
modeling of complex systems and support behavior analysis and
simulation in an iterative and thus complex engineering process, by
using encapsulated submodels of components and of their interfaces.
Therefore it can improve the design efficiency and simplify the
solving complicated problem. Multi-drivers off-road vehicle is
comparatively complicated. Driving-line is an important core part to a
vehicle; it has a significant contribution to the performance of a
vehicle. Multi-driver off-road vehicles have complex driving-line, so
its performance is heavily dependent on the driving-line. A typical
off-road vehicle-s driving-line system consists of torque converter,
transmission, transfer case and driving-axles, which transfer the
power, generated by the engine and distribute it effectively to the
driving wheels according to the road condition. According to its main
function, this paper puts forward a modularized approach for
designing and evaluation of vehicle-s driving-line. It can be used to
effectively estimate the performance of driving-line during concept
design stage. Through appropriate analysis and assessment method, an
optimal design can be reached. This method has been applied to the
practical vehicle design, it can improve the design efficiency and is
convenient to assess and validate the performance of a vehicle,
especially of multi-drivers off-road vehicle.
Abstract: A new technique of topological multi-scale analysis is
introduced. By performing a clustering recursively to build a
hierarchy, and analyzing the co-scale and intra-scale similarities, an
Iterated Function System can be extracted from any data set. The study
of fractals shows that this method is efficient to extract
self-similarities, and can find elegant solutions the inverse problem of
building fractals. The theoretical aspects and practical
implementations are discussed, together with examples of analyses of
simple fractals.
Abstract: The objective of this study is to investigate the
combustion in a pilot-ignited supercharged dual-fuel engine, fueled
with different types of gaseous fuels under various equivalence ratios.
It is found that if certain operating conditions are maintained,
conventional dual-fuel engine combustion mode can be transformed to
the combustion mode with the two-stage heat release. This mode of
combustion was called the PREMIER (PREmixed Mixture Ignition in
the End-gas Region) combustion. During PREMIER combustion,
initially, the combustion progresses as the premixed flame
propagation and then, due to the mixture autoignition in the end-gas
region, ahead of the propagating flame front, the transition occurs with
the rapid increase in the heat release rate.