Abstract: Centrifugal-casting machine is used in manufacturing
special machine components like multi-layer journal bearing used in
all internal combustion engine, steam, gas turbine and air craft turboengine
where isotropic properties and high precisions are desired.
Moreover, this machine can be used in manufacturing thin wall hightech
machine components like cylinder liners and piston rings of IC
engine and other machine parts like sleeves, and bushes. Heavy-duty
machine component like railway wheel can also be prepared by
centrifugal casting. A lot of technological developments are required
in casting process for production of good casted machine body and
machine parts. Usually defects like blowholes, surface roughness,
chilled surface etc. are found in sand casted machine parts. But these
can be removed by centrifugal casting machine using rotating
metallic die. Moreover, die rotation, its temperature control, and good
pouring practice can contribute to the quality of casting because of
the fact that the soundness of a casting in large part depends upon
how the metal enters into the mold or dies and solidifies. Poor
pouring practice leads to variety of casting defects such as
temperature loss, low quality casting, excessive turbulence, over
pouring etc. Besides these, handling of molten metal is very
unsecured and dangerous for the workers. In order to get rid of all
these problems, the need of an automatic pouring device arises. In
this research work, a robot assisted pouring device and a centrifugal
casting machine are designed, developed constructed and tested
experimentally which are found to work satisfactorily. The robot
assisted pouring device is further modified and developed for using it
in actual metal casting process. Lot of settings and tests are required
to control the system and ultimately it can be used in automation of
centrifugal casting machine to produce high-tech machine parts with
desired precision.
Abstract: In this paper, we investigate the low-lying energy
levels of the two-dimensional parabolic graphene quantum dots
(GQDs) in the presence of topological defects with long range
Coulomb impurity and subjected to an external uniform magnetic
field. The low-lying energy levels of the system are obtained within
the framework of the perturbation theory. We theoretically
demonstrate that a valley splitting can be controlled by geometrical
parameters of the graphene quantum dots and/or by tuning a uniform
magnetic field, as well as topological defects. It is found that, for
parabolic graphene dots, the valley splitting occurs due to the
introduction of spatial confinement. The corresponding splitting is
enhanced by the introduction of a uniform magnetic field and it
increases by increasing the angle of the cone in subcritical regime.
Abstract: Maintenance and design engineers have great concern
for the functioning of rotating machineries due to the vibration
phenomenon. Improper functioning in rotating machinery originates
from the damage to rolling element bearings. The status of rolling
element bearings require advanced technologies to monitor their
health status efficiently and effectively. Avoiding vibration during
machine running conditions is a complicated process. Vibration
simulation should be carried out using suitable sensors/ transducers to
recognize the level of damage on bearing during machine operating
conditions. Various issues arising in rotating systems are interlinked
with bearing faults. This paper presents an approach for fault
diagnosis of bearings using neural networks and time/frequencydomain
vibration analysis.
Abstract: This paper focuses on the mathematical modeling for
solidification of Al alloy in a cube mold cavity to study the
solidification behavior of casting process. The parametric
investigation of solidification process inside the cavity was
performed by using computational solidification/melting model
coupled with Volume of fluid (VOF) model. The implicit filling
algorithm is used in this study to understand the overall process from
the filling stage to solidification in a model metal casting process.
The model is validated with past studied at same conditions. The
solidification process is analyzed by including the effect of pouring
velocity as well as natural convection from the wall and geometry of
the cavity. These studies show the possibility of various defects
during solidification process.
Abstract: In this paper, the experimental study for the instability
of a separator rotor is presented, under dynamic loading response in
the harmonic analysis condition. The global measurement and
analysis of vibration on the cement separator RC500 is carried, the
points of measurement used are radial dots, vertical, horizontal and
oblique. The measures of trends and spectral analysis for
reconnaissance of the main anomalies, the main defects in the
separator and manifestation, the results prove that the defects effect
has a negative effect on the stability of the rotor. Experimentally the
study of the rotor in transient system allowed to determine the
vibratory responses due to the unbalances and various excitations.
Abstract: Software quality issues require special attention
especially in view of the demands of quality software product to meet
customer satisfaction. Software development projects in most
organisations need proper defect management process in order to
produce high quality software product and reduce the number of
defects. The research question of this study is how to produce high
quality software and reducing the number of defects. Therefore, the
objective of this paper is to provide a framework for managing
software defects by following defined life cycle processes. The
methodology starts by reviewing defects, defect models, best
practices, and standards. A framework for defect management life
cycle is proposed. The major contribution of this study is to define a
defect management roadmap in software development. The adoption
of an effective defect management process helps to achieve the
ultimate goal of producing high quality software products and
contributes towards continuous software process improvement.
Abstract: Monitoring the conditions of rotating machinery, such
as bearings, is important in order to improve the stability of work.
Acoustic Emission (AE) and vibration analysis are some of the most
accomplished techniques used for this purpose. Acoustic emission
has the ability to detect the initial phase of component degradation.
Moreover, it has been observed that vibration analysis is not as
successful at low rotational speeds (below 100 rpm). This because the
energy generated within this speed region is not detectable using
conventional vibration. From this perspective, this paper has
presented a brief review of using acoustic emission techniques for
monitoring bearing conditions.
Abstract: It is quite essential to investigate the causes of
pavement deterioration in order to select the proper maintenance
technique. The objective of this study was to identify factors cause
deterioration of recently constructed roads in Khartoum state. A
comprehensive literature concerning the factors of road deterioration,
common road defects and their causes were reviewed. Three major
road projects with different deterioration reasons were selected for
this study. The investigation involved field survey and laboratory
testing on those projects to examine the existing pavement
conditions. The results revealed that the roads investigated
experienced severe failures in the forms of cracks, potholes, and
rutting in the wheel path. The causes of those failures were found
mainly linked to poor drainage, traffic overloading, expansive
subgrade soils, and the use of low quality materials in construction.
Based on the results, recommendations were provided to help
highway engineers in selecting the most effective repair techniques
for specific kinds of distresses.
Abstract: The purposes of hydraulic gate are to maintain the
functions of storing and draining water. It bears long-term hydraulic
pressure and earthquake force and is very important for reservoir and
waterpower plant. The high tensile strength of steel plate is used as
constructional material of hydraulic gate. The cracks and rusts,
induced by the defects of material, bad construction and seismic
excitation and under water respectively, thus, the mechanics
phenomena of gate with crack are probing into the cause of stress
concentration, induced high crack increase rate, affect the safety and
usage of hydroelectric power plant. Stress distribution analysis is a
very important and essential surveying technique to analyze
bi-material and singular point problems. The finite difference
infinitely small element method has been demonstrated, suitable for
analyzing the buckling phenomena of welding seam and steel plate
with crack. Especially, this method can easily analyze the singularity
of kink crack. Nevertheless, the construction form and deformation
shape of some gates are three-dimensional system. Therefore, the
three-dimensional Digital Image Correlation (DIC) has been
developed and applied to analyze the strain variation of steel plate with
crack at weld joint. The proposed Digital image correlation (DIC)
technique is an only non-contact method for measuring the variation of
test object. According to rapid development of digital camera, the cost
of this digital image correlation technique has been reduced.
Otherwise, this DIC method provides with the advantages of widely
practical application of indoor test and field test without the restriction
on the size of test object. Thus, the research purpose of this research is
to develop and apply this technique to monitor mechanics crack
variations of weld steel hydraulic gate and its conformation under
action of loading. The imagines can be picked from real time
monitoring process to analyze the strain change of each loading stage.
The proposed 3-Dimensional digital image correlation method,
developed in the study, is applied to analyze the post-buckling
phenomenon and buckling tendency of welded steel plate with crack.
Then, the stress intensity of 3-dimensional analysis of different
materials and enhanced materials in steel plate has been analyzed in
this paper. The test results show that this proposed three-dimensional
DIC method can precisely detect the crack variation of welded steel
plate under different loading stages. Especially, this proposed DIC
method can detect and identify the crack position and the other flaws
of the welded steel plate that the traditional test methods hardly detect
these kind phenomena. Therefore, this proposed three-dimensional
DIC method can apply to observe the mechanics phenomena of
composite materials subjected to loading and operating.
Abstract: Background: To compare the thinning patterns of the
ganglion cell-inner plexiform layer (GCIPL) and peripapillary retinal
nerve fiber layer (pRNFL) as measured using Cirrus high-definition
optical coherence tomography (HD-OCT) in patients with visual field
(VF) defects that respect the vertical meridian. Methods: Twenty eyes of eleven patients with VF defects that
respect the vertical meridian were enrolled retrospectively. The
thicknesses of the macular GCIPL and pRNFL were measured using
Cirrus HD-OCT. The 5% and 1% thinning area index (TAI) was
calculated as the proportion of abnormally thin sectors at the 5% and
1% probability level within the area corresponding to the affected VF.
The 5% and 1% TAI were compared between the GCIPL and pRNFL
measurements. Results: The color-coded GCIPL deviation map showed a
characteristic vertical thinning pattern of the GCIPL, which is also
seen in the VF of patients with brain lesions. The 5% and 1% TAI
were significantly higher in the GCIPL measurements than in the
pRNFL measurements (all P < 0.01). Conclusions: Macular GCIPL analysis clearly visualized a
characteristic topographic pattern of retinal ganglion cell (RGC) loss
in patients with VF defects that respect the vertical meridian, unlike
pRNFL measurements. Macular GCIPL measurements provide more
valuable information than pRNFL measurements for detecting the
loss of RGCs in patients with retrograde degeneration of the optic
nerve fibers.
Abstract: Manufacturing tolerancing is intended to determine
the intermediate geometrical and dimensional states of the part during
its manufacturing process. These manufacturing dimensions also
serve to satisfy not only the functional requirements given in the
definition drawing, but also the manufacturing constraints, for
example geometrical defects of the machine, vibration and the wear
of the cutting tool. The choice of positioning has an important influence on the cost
and quality of manufacture. To avoid this problem, a two-step
approach has been developed. The first step is dedicated to the
determination of the optimum position. As for the second step, a
study was carried out for the tightening effect on the tolerance
interval.
Abstract: Government reports and published research have
flagged and brought to public attention the deteriorating condition of
a large percentage of bridges in Canada and the United States. With
the increasing number of deteriorated bridges in the US, Canada, and
around the globe, condition assessment techniques of concrete
bridges are evolving. Investigation for bridges’ defects such as
cracks, spalls, and delamination and their level of severity are the
main objectives of condition assessment. Inspection and
rehabilitation programs are being implemented to monitor and
maintain deteriorated bridge infrastructure. This paper highlights the
state-of-the art of current practices being performed for concrete
bridge inspection. The information is gathered from the literature and
through a distributed questionnaire. The current practices in concrete
bridge inspection rely on the use of hummer sounding and chain
dragging tests. Non-Destructive Testing (NDT) techniques are not
being utilized fully in the process. Nonetheless, they are being
partially utilized by the recommendation of the bridge inspector after
conducting visual inspection. Lanes are usually closed during the
performance of visual inspection and bridge inspection in general.
Abstract: Nonlinear evolution of broadband ultrasonic pulses
passed through the rock specimens is studied using the apparatus
“GEOSCAN-02M”. Ultrasonic pulses are excited by the pulses of Qswitched
Nd:YAG laser with the time duration of 10 ns and with the
energy of 260 mJ. This energy can be reduced to 20 mJ by some light
filters. The laser beam radius did not exceed 5 mm. As a result of the
absorption of the laser pulse in the special material – the optoacoustic
generator–the pulses of longitudinal ultrasonic waves are excited with
the time duration of 100 ns and with the maximum pressure
amplitude of 10 MPa. The immersion technique is used to measure
the parameters of these ultrasonic pulses passed through a specimen,
the immersion liquid is distilled water. The reference pulse passed
through the cell with water has the compression and the rarefaction
phases. The amplitude of the rarefaction phase is five times lower
than that of the compression phase. The spectral range of the
reference pulse reaches 10 MHz. The cubic-shaped specimens of the
Karelian gabbro are studied with the rib length 3 cm. The ultimate
strength of the specimens by the uniaxial compression is (300±10)
MPa. As the reference pulse passes through the area of the specimen
without cracks the compression phase decreases and the rarefaction
one increases due to diffraction and scattering of ultrasound, so the
ratio of these phases becomes 2.3:1. After preloading some horizontal
cracks appear in the specimens. Their location is found by one-sided
scanning of the specimen using the backward mode detection of the
ultrasonic pulses reflected from the structure defects. Using the
computer processing of these signals the images are obtained of the
cross-sections of the specimens with cracks. By the increase of the
reference pulse amplitude from 0.1 MPa to 5 MPa the nonlinear
transformation of the ultrasonic pulse passed through the specimen
with horizontal cracks results in the decrease by 2.5 times of the
amplitude of the rarefaction phase and in the increase of its duration
by 2.1 times. By the increase of the reference pulse amplitude from 5
MPa to 10 MPa the time splitting of the phases is observed for the
bipolar pulse passed through the specimen. The compression and
rarefaction phases propagate with different velocities. These features
of the powerful broadband ultrasonic pulses passed through the rock
specimens can be described by the hysteresis model of Preisach-
Mayergoyz and can be used for the location of cracks in the optically
opaque materials.
Abstract: Si-Ge solid solutions (bulk poly- and mono-crystalline
samples, thin films) are characterized by high perspectives for
application in semiconductor devices, in particular, optoelectronics
and microelectronics. From this point of view, complex studying of
structural state of the defects and structural-sensitive physical
properties of Si-Ge solid solutions depending on the contents of Si
and Ge components is very important. Present work deals with the
investigations of microstructure, microhardness, internal friction and
shear modulus of Si1-xGex(x≤0,02) bulk monocrystals conducted at
room temperature. Si-Ge bulk crystals were obtained by Czochralski
method in [111] crystallographic direction. Investigated
monocrystalline Si-Ge samples are characterized by p-type
conductivity and carriers’ concentration 5.1014-1.1015cm-3.
Microhardness was studied on Dynamic Ultra Micro hardness Tester
DUH-201S with Berkovich indenter. Investigate samples are characterized with 0,5x0,5x(10-15)mm3
sizes, oriented along [111] direction at torsion oscillations ≈1Hz,
multistage changing of internal friction and shear modulus has been
revealed in an interval of strain amplitude of 10-5-5.10-3. Critical
values of strain amplitude have been determined at which hysteretic
changes of inelastic characteristics and microplasticity are observed. The critical strain amplitude and elasticity limit values are also
determined. Dynamic mechanical characteristics decreasing trend is
shown with increasing Ge content in Si-Ge solid solutions. Observed
changes are discussed from the point of view of interaction of various
dislocations with point defects and their complexes in a real structure
of Si-Ge solid solutions.
Abstract: This study intends to show the influence of the
hydrolytic degradation on the properties of the e-PTFE/NOMEX®
membranes used in fire-protective clothing. The modification of
water vapour permeability, morphology and chemical structure was
examined by MOCON Permatran, electron microscopy scanning
(SEM), and ATR-FTIR, respectively. A decrease in permeability to
water vapour of the aged samples was observed following closure of
transpiration pores. Analysis of fiber morphology indicates the
appearance of defects at the fibers surface with the presence of micro
cavities. ATR-FTIR analysis reveals the presence of a new absorption
band attributed to carboxylic acid terminal groups generated during
the amide bond hydrolysis.
Abstract: Effect of sprue/metal head height on mould filling,
microstructure and mechanical properties of TWDI casting is studied.
Results show that metal/sprue height of 50 mm is not sufficient to
push the melt through the gating channel, but as it is increased from
100-350 mm, proper mould filling is achieved. However at higher
heights between 200 mm and 350 mm, defects associated with
incomplete solidification, carbide precipitation and turbulent flow are
evident. This research shows that superior UTS, hardness, nodularity
and nodule count are obtained at 100 mm sprue height.
Abstract: Due to today’s globalization as well as outsourcing
practices of the companies, the Supply Chain (SC) performances
have become more dependent on the efficient movement of material
among places that are geographically dispersed, where there is more
chance for disruptions. One such disruption is the quality and
delivery uncertainties of outsourcing. These uncertainties could lead
the products to be unsafe and, as is the case in a number of recent
examples, companies may have to end up in recalling their products.
As a result of these problems, there is a need to develop a
methodology for selecting suppliers globally in view of risks
associated with low quality and late delivery. Accordingly, we
developed a two-stage stochastic model that captures the risks
associated with uncertainty in quality and delivery as well as a
solution procedure for the model. The stochastic model developed
simultaneously optimizes supplier selection and purchase quantities
under price discounts over a time horizon. In particular, our target is
the study of global organizations with multiple sites and multiple
overseas suppliers, where the pricing is offered in suppliers’ local
currencies. Our proposed methodology is applied to a case study for a
US automotive company having two assembly plants and four
potential global suppliers to illustrate how the proposed model works
in practice.
Abstract: Atmospheric carbon dioxide emissions are considered
as the greatest environmental challenge the world is facing today.
The tasks to control the emissions include the recovery of CO2 from
flue gas. This concern has been improved due to recent advances in
materials process engineering resulting in the development of
inorganic gas separation membranes with excellent thermal and
mechanical stability required for most gas separations. This paper,
therefore, evaluates the performance of a highly selective inorganic
membrane for CO2 recovery applications. Analysis of results
obtained is in agreement with experimental literature data. Further
results show the prediction performance of the membranes for gas
separation and the future direction of research. The materials
selection and the membrane preparation techniques are discussed.
Method of improving the interface defects in the membrane and its
effect on the separation performance has also been reviewed and in
addition advances to totally exploit the potential usage of this
innovative membrane.
Abstract: The paper presents a novel screening method to
indicate congenital heart diseases (CHD), which otherwise could
remain undetected because of their low level. Therefore, not
belonging to the high-risk population, the pregnancies are not subject
to the regular fetal monitoring with ultrasound echocardiography.
Based on the fact that CHD is a morphological defect of the heart
causing turbulent blood flow, the turbulence appears as a murmur,
which can be detected by fetal phonocardiography (fPCG). The
proposed method applies measurements on the maternal abdomen
and from the recorded sound signal a sophisticated processing
determines the fetal heart murmur. The paper describes the problems
and the additional advantages of the fPCG method including the
possibility of measurements at home and its combination with the
prescribed regular cardiotocographic (CTG) monitoring. The
proposed screening process implemented on a telemedicine system
provides an enhanced safety against hidden cardiac diseases.
Abstract: The aim of this study is to investigate formability of
Al based closed cell metallic foams at high temperature. The foam
specimens with rectangular section were produced from
AlMg1Si0.6TiH20.8 alloy preform material. Bending and free
bending tests based on gravity effect were applied to foam specimens
at high temperatures. During the tests, the time-angular deformation
relationships with various temperatures were determined.
Deformation types formed in cell walls were investigated by means
of Scanning Electron Microscopy (SEM) and optical microscopy.
Bending deformation about 90° was achieved without any defect at
high temperatures. The importance of a critical temperature and
deformation rate was emphasized in maintaining the deformation.
Significant slip lines on surface of cell walls at tensile zones of
bending specimen were observed. At high strain rates, the microcrack
formation in boundaries of elongated grains was determined.