Abstract: This paper presents the design, fabrication and
evaluation of magneto-rheological damper. Semi-active control
devices have received significant attention in recent years because
they offer the adaptability of active control devices without requiring
the associated large power sources. Magneto-Rheological (MR)
dampers are semi- active control devices that use MR fluids to
produce controllable dampers. They potentially offer highly reliable
operation and can be viewed as fail-safe in that they become passive
dampers if the control hardware malfunction. The advantage of MR
dampers over conventional dampers are that they are simple in
construction, compromise between high frequency isolation and
natural frequency isolation, they offer semi-active control, use very
little power, have very quick response, has few moving parts, have a
relax tolerances and direct interfacing with electronics. Magneto-
Rheological (MR) fluids are Controllable fluids belonging to the
class of active materials that have the unique ability to change
dynamic yield stress when acted upon by an electric or magnetic
field, while maintaining viscosity relatively constant. This property
can be utilized in MR damper where the damping force is changed by
changing the rheological properties of the fluid magnetically. MR
fluids have a dynamic yield stress over Electro-Rheological fluids
(ER) and a broader operational temperature range. The objective of
this papert was to study the application of an MR damper to vibration
control, design the vibration damper using MR fluids, test and
evaluate its performance. In this paper the Rheology and the theory
behind MR fluids and their use on vibration control were studied.
Then a MR vibration damper suitable for vehicle suspension was
designed and fabricated using the MR fluid. The MR damper was
tested using a dynamic test rig and the results were obtained in the
form of force vs velocity and the force vs displacement plots. The
results were encouraging and greatly inspire further research on the
topic.
Abstract: In this study, effects of EGR on CO and HC emissions
of a dual fuel HCCI-DI engine are investigated. Tests were
conducted on a single-cylinder variable compression ratio (VCR)
diesel engine with compression ratio of 17.5. Premixed gasoline is
provided by a carburetor connected to intake manifold and equipped
with a screw to adjust premixed air-fuel ratio, and diesel fuel is
injected directly into the cylinder through an injector at pressure of
250 bars. A heater placed at inlet manifold is used to control the
intake charge temperature. Optimal intake charge temperature was
110-115ºC due to better formation of a homogeneous mixture
causing HCCI combustion. Timing of diesel fuel injection has a great
effect on stratification of in-cylinder charge in HCCI combustion.
Experiments indicated 35 BTDC as the optimum injection timing.
Coolant temperature was maintained 50ºC during the tests. Results
show that increasing engine speed at a constant EGR rate leads to
increase in CO and UHC emissions due to the incomplete
combustion caused by shorter combustion duration and less
homogeneous mixture. Results also show that increasing EGR
reduces the amount of oxygen and leads to incomplete combustion
and therefore increases CO emission due to lower combustion
temperature. HC emission also increases as a result of lower
combustion temperatures.
Abstract: A two dimensional numerical simulation has been
performed for incompressible and compressible fluid flow through
microchannels in slip flow regime. The Navier-Stokes equations have
been solved in conjunction with Maxwell slip conditions for
modeling flow field associated with slip flow regime. The wall
roughness is simulated with triangular microelements distributed on
wall surfaces to study the effects of roughness on fluid flow. Various
Mach and Knudsen numbers are used to investigate the effects of
rarefaction as well as compressibility. It is found that rarefaction has
more significant effect on flow field in microchannels with higher
relative roughness. It is also found that compressibility has more
significant effects on Poiseuille number when relative roughness
increases. In addition, similar to incompressible models the increase
in average fRe is more significant at low Knudsen number flows but
the increase of Poiseuille number duo to relative roughness is sharper
for compressible models. The numerical results have also validated
with some available theoretical and experimental relations and good
agreements have been seen.
Abstract: Due to heightened concerns over environmental and economic issues the growing important of air pollution, and the importance of conserving fossil fuel resources in the world, the automotive industry is now forced to produce more fuel efficient, low emission vehicles and new drive system technologies. One of the most promising technologies to receive attention is the hybrid electric vehicle (HEV), which consists of two or more energy sources that supply energy to electric traction motors that in turn drive the wheels. This paper presents the various structures of HEV systems, the basic theoretical knowledge for describing their operation and the general behaviour of the HEV in acceleration, cruise and deceleration phases. The conventional design and sizing of a series HEV is studied. A conventional bus and its series configuration are defined and evaluated using the ADVISOR. In this section the simulation of a standard driving cycle and prediction of its fuel consumption and emissions of the HEV are discussed. Finally the bus performance is investigated to establish whether it can satisfy the performance, fuel consumption and emissions requested. The validity of the simulation has been established by the close conformity between the fuel consumption of the conventional bus reported by the manufacturer to what has achieved from the simulation.
Abstract: This paper describes the modeling and simulation of an
underwater robot glider used in the shallow-water environment. We
followed the Equations of motion derived by [2] and simplified
dynamic Equations of motion of an underwater glider according to our
underwater glider. A simulation code is built and operated in the
MATLAB Simulink environment so that we can make improvements
to our testing glider design. It may be also used to validate a robot
glider design.
Abstract: This paper reviews the major contributions to the Motion Planning (MP) field throughout a 35-year period, from classic approaches to heuristic algorithms. Due to the NP-Hardness of the MP problem, heuristic methods have outperformed the classic approaches and have gained wide popularity. After surveying around 1400 papers in the field, the amount of existing works for each method is identified and classified. Especially, the history and applications of numerous heuristic methods in MP is investigated. The paper concludes with comparative tables and graphs demonstrating the frequency of each MP method's application, and so can be used as a guideline for MP researchers.
Abstract: Accumulation of dust from the outdoor environment
on the panels of solar photovoltaic (PV) system is natural. There
were studies that showed that the accumulated dust can reduce the
performance of solar panels, but the results were not clearly
quantified. The objective of this research was to study the effects of
dust accumulation on the performance of solar PV panels.
Experiments were conducted using dust particles on solar panels with
a constant-power light source, to determine the resulting electrical
power generated and efficiency. It was found from the study that the
accumulated dust on the surface of photovoltaic solar panel can
reduce the system-s efficiency by up to 50%.
Abstract: To simulate heating systems in buildings, a research oriented computer code has been developed in Sharif University of Technology in Iran where the climate, existing heating equipment in buildings, consumer behavior and their interactions are considered for simulating energy consumption in conventional systems such as heaters, radiators and fan-coils. In order to validate the computer code, the available data of five buildings was used and the computed consumed energy was compared with the estimated energy extracted from monthly bills. The initial heating system was replaced by the alternative system and the effect of this change was observed on the energy consumption. As a result, the effect of changing heating equipment on energy consumption was investigated in different climates. Changing heater to radiator renders energy conservation up to 50% in all climates and changing radiator to fan-coil decreases energy consumption in climates with cold and dry winter.
Abstract: This study offers a new simple method for assessing
an axial part-through crack in a pipe wall. The method utilizes simple
approximate expressions for determining the fracture parameters K,
J, and employs these parameters to determine critical dimensions of a
crack on the basis of equality between the J-integral and the J-based
fracture toughness of the pipe steel. The crack tip constraint is taken
into account by the so-called plastic constraint factor C, by which the
uniaxial yield stress in the J-integral equation is multiplied. The
results of the prediction of the fracture condition are verified by burst
tests on test pipes.
Abstract: Equal Channel Angular Pressing (ECAP) is currently
being widely investigated because of its potential to produce ultrafine
grained microstructures in metals and alloys. A sound
knowledge of the plastic deformation and strain distribution is
necessary for understanding the relationships between strain
inhomogeneity and die geometry. Considerable research has been
reported on finite element analysis of this process, assuming threedimensional
plane strain condition. However, the two-dimensional
models are not suitable due to the geometry of the dies, especially in
cylindrical ones. In the present work, three-dimensional simulation of
ECAP process was carried out for six outer corner radii (sharp to 10
mm in steps of 2 mm), with channel angle 105¶Çü▒, for strain hardening
aluminium alloy (AA 6101) using ABAQUS/Standard software.
Strain inhomogeneity is presented and discussed for all cases. Pattern
of strain variation along selected radial lines in the body of the workpiece
is presented. It is found from the results that the outer corner
has a significant influence on the strain distribution in the body of
work-piece. Based on inhomogeneity and average strain criteria,
there is an optimum outer corner radius.
Abstract: In the various working field, vibration may cause injurious to human body. Especially, in case of the vibration which is constantly and repeatedly transferred to the human. That gives serious physical problem, so called, Reynaud phenomenon. In this paper, we propose a vibration transmissibility reduction module with flexure mechanism for personal tools. At first, we select a target personal tool, grass cutter, and measure the level of vibration transmissibility on the hand. And then, we develop the concept design of the module that has stiffness for reduction the vibration transmissibility more than 20%, where the vibration transmissibility is measured with an accelerometer. In addition, the vibration reduction can be enhanced when the interior gap between inner and outer body is filled with silicone gel. This will be verified by the further experiment.
Abstract: Current air conditioning system is using refrigerant as
the cooling medium. The main purpose of this study is to develop an
air conditioning system using chill water as the cooling medium. In
this system, chill water used to replace refrigerant as the cooling
medium. This study is focus on the split type unit air conditioning
system only. It will be involving some renovation on the indoor unit
and freezer. The cooling capability of this system was validate by few
series of testing, which conducted at standard 36m3 office room.
Result of the testing found that 0.1 m3 of chill water is able to
maintain the room temperature within standard up to 4 ~ 8 hours. It
expected able to maintain room temperature up to 10 hour with some
improvement.
Abstract: In this paper, a new cooling system using a nacelle duct
is proposed for the mechanical room in the household refrigerator. The
conventional mechanical room consists of a condenser, a compressor
and an axial fan. The axial fan is mainly responsible for cooling the
condenser and the compressor. The new cooling system is developed
by replacing the axial fan with the nacelle duct including the small
centrifugal fan. The parametric study is carried out to find the optimum
designs of the nacelle duct in terms of performance and efficiency.
Through this study, it is revealed that the new system can reduce the
space, electrical power and noise compared with the conventional
system
Abstract: Study of the vibration cylindrical shells made of
a functionally gradient material (FGM) composed of stainless
steel and nickel is important. Material properties are graded in
the thickness direction of the shell according to volume
fraction power law distribution. The objective is to study the
natural frequencies, the influence of constituent volume
fractions and the effects of boundary conditions on the natural
frequencies of the FG cylindrical shell. The study is carried
out using third order shear deformation shell theory. The
governing equations of motion of FG cylindrical shells are
derived based on shear deformation theory. Results are
presented on the frequency characteristics, influence of
constituent volume fractions and the effects of clampedclamped
boundary conditions.
Abstract: An experimental study is realized in order to verify the
Mini Heat Pipe (MHP) concept for cooling high power dissipation
electronic components and determines the potential advantages of
constructing mini channels as an integrated part of a flat heat pipe. A
Flat Mini Heat Pipe (FMHP) prototype including a capillary structure
composed of parallel rectangular microchannels is manufactured and
a filling apparatus is developed in order to charge the FMHP. The
heat transfer improvement obtained by comparing the heat pipe
thermal resistance to the heat conduction thermal resistance of a
copper plate having the same dimensions as the tested FMHP is
demonstrated for different heat input flux rates. Moreover, the heat
transfer in the evaporator and condenser sections are analyzed, and
heat transfer laws are proposed. In the theoretical part of this work, a
detailed mathematical model of a FMHP with axial microchannels is
developed in which the fluid flow is considered along with the heat
and mass transfer processes during evaporation and condensation.
The model is based on the equations for the mass, momentum and
energy conservation, which are written for the evaporator, adiabatic,
and condenser zones. The model, which permits to simulate several
shapes of microchannels, can predict the maximum heat transfer
capacity of FMHP, the optimal fluid mass, and the flow and thermal
parameters along the FMHP. The comparison between experimental
and model results shows the good ability of the numerical model to
predict the axial temperature distribution along the FMHP.
Abstract: In this study acoustic emission (AE) signals obtained during deformation and fracture of two types of ferrite-martensite dual phase steels (DPS) specimens have been analyzed in frequency domain. For this reason two low carbon steels with various amounts of carbon were chosen, and intercritically heat treated. In the introduced method, identifying the mechanisms of failure in the various phases of DPS is done. For this aim, AE monitoring has been used during tensile test of several DPS with various volume fraction of the martensite (VM) and attempted to relate the AE signals and failure mechanisms in these steels. Different signals, which referred to 2-3 micro-mechanisms of failure due to amount of carbon and also VM have been seen. By Fast Fourier Transformation (FFT) of signals in distinct locations, an excellent relationship between peak frequencies in these areas and micro-mechanisms of failure were seen. The results were verified by microscopic observations (SEM).
Abstract: In order to meet the limits imposed on automotive
emissions, engine control systems are required to constrain air/fuel
ratio (AFR) in a narrow band around the stoichiometric value, due to
the strong decay of catalyst efficiency in case of rich or lean mixture.
This paper presents a model of a sample spark ignition engine and
demonstrates Simulink-s capabilities to model an internal combustion
engine from the throttle to the crankshaft output. We used welldefined
physical principles supplemented, where appropriate, with
empirical relationships that describe the system-s dynamic behavior
without introducing unnecessary complexity. We also presents a PID
tuning method that uses an adaptive fuzzy system to model the
relationship between the controller gains and the target output
response, with the response specification set by desired percent
overshoot and settling time. The adaptive fuzzy based input-output
model is then used to tune on-line the PID gains for different
response specifications. Experimental results demonstrate that better
performance can be achieved with adaptive fuzzy tuning relative to
similar alternative control strategies. The actual response
specifications with adaptive fuzzy matched the desired response
specifications.
Abstract: Among all mechanical joining processes, welding has
been employed for its advantage in design flexibility, cost saving,
reduced overall weight and enhanced structural performance.
However, for structures made of relatively thin components, welding
can introduce significant buckling distortion which causes loss of
dimensional control, structural integrity and increased fabrication
costs. Different parameters can affect buckling behavior of welded
thin structures such as, heat input, welding sequence, dimension of
structure. In this work, a 3-D thermo elastic-viscoplastic finite
element analysis technique is applied to evaluate the effect of shell
dimensions on buckling behavior and entropy generation of welded
thin shells. Also, in the present work, the approximated longitudinal
transient stresses which produced in each time step, is applied to the
3D-eigenvalue analysis to ratify predicted buckling time and
corresponding eigenmode. Besides, the possibility of buckling
prediction by entropy generation at each time is investigated and it is
found that one can predict time of buckling with drawing entropy
generation versus out of plane deformation. The results of finite
element analysis show that the length, span and thickness of welded
thin shells affect the number of local buckling, mode shape of global
buckling and post-buckling behavior of welded thin shells.
Abstract: This paper presents a solution for ceramic cutting tools availability in interrupted machining. Experiments were performed on a special fixture – the interrupted cut simulator. This fixture was constructed at our Department of Machining and Assembly within the scope of a project by the Czech Science Foundation. The goals of the tests were to contribute to the wider usage of these cutting materials in machining, especially in interrupted machining. Through the centuries, producers of ceramic cutting tools have taken big steps forward. Namely, increasing durability in maintaining high levels of strength and hardness lends an advantage. Some producers of these materials advise cutting inserts for interrupted machining at the present time [1, 2].
Abstract: The problem of controlling a two link robotic manipulator, consisting of a rotating and a prismatic links, is addressed. The actuations of both links are assumed to have unknown dead zone nonlinearities and friction torques modeled by LuGre friction model. Because of the existence of the unknown dead zone and friction torque at the actuations, unknown parameters and unmeasured states would appear to be part of the overall system dynamics that need for estimation. Unmeasured states observer, unknown parameters estimators, and robust adaptive control laws have been derived such that closed loop global stability is achieved. Simulation results have been performed to show the efficacy of the suggested approach.