Engineering and Technology Journal

The manufacturing of electrical converter using powder-metallurgy can be
considered as acomplex-subject due to the several variables which include
for examples, selection of raw materials, purity, and grain size. There are
many researches that have been used to study iron-nickel, iron-silicon, and
so on, but the research on iron-cobalt in our country is limited and due to
the significance of core-industrial in electrical converters, barometer and
computer devices…….etc, this work has included:
1. Preparing compacted-materials of (Fe1-xCox) by using powdermetallurgy
at different weight ratios (x=15, 25, 35, 50).
2. studying the effect of time and temperature of sintering on magnetic
properties ( permeability, coercivity force, and hystersis loop) for
materials prepared by using powder-metallurgy.
3. studying the effect of different ratios of pure cobalt-powder added on
magnetic properties and microstructure of prepared materials.
4. produceing different shapes and sizes of electrical-core

This research devoted to studying the properties of sliding wear of
three groups of copper alloys chosen to this study. They are Brass (70/30),
Silicon bronze and Silicon-Brass. These three groups have been examined
by using (pin on Disc) apparatus under different wear conditions including
applied loads and disc hardness is constant (35HRC). This study was
concluded that the wear rate was increased as the applied load and the wear
behavior was changed from mild wear into transition wear as the applied
load is increased. This research concludes that the alloy of Silicon-brass was
the best alloy due to high wear resistance in comparison with the other
alloys.

This research work presents a nonlinear fini te element
investigation on the behavior of high strength fiber reinforced concrete
corbels. This investigation is carried out in order to get a better
understanding of their behavior throughout the entire loading history.
The three- dimensional 20-node brick elements are used to
model the concrete, while the reinforcing bars are modeled as axial
members embedded within the concrete brick elements. The
compressive behavior of concrete is simulated by an elastic-plastic
work-hardening model followed by a perfectly plastic response,
which terminate at the onset of crushing. In tension, a fixed smeared
crack model has been used.

Two methods of forming, namely, semi-dry press and slip casting were used to
fabricate porous ceramics from local raw materials, kaolin and silica. Different
wt.% of aluminum-zinc mixture powders were used as gas creative agent in
chemical swelling method to create porosity in ceramic slurry before forming.
Dried formed ceramics were fired at four
different firing temperatures of (900, 1000, 1100 and 1200)°C.
It was found that the forming technique has a great effect on the properties of
the fabricated porous ceramics. From porosity point of view, slip casting is better
technique to produce high porous ceramics, but semi-dry pressing seems to be
good for other physical properties and mechanical properties.

In this research an analysis of multi-stage deep drawing process is carried out
for process design of cylindrical cup drawing with large drawing ratio ( β = 3.416).
A three stage deep drawing tooling was designed and constructed to carry out the
experimental work required to produce a cylindrical cup of (25mm outer diameter)
formed from a circular flat blank (82 mm diameter) comprised of mild steel of
(0.15%) carbon content, without any intermediate annealing. The difference in the
drawing ratio between the neighboring stages was reduced so as to achieve more
uniform deformation in the cross-section. The study confirms the real deformation
mechanism and inspects the contact conditions at the tool-blank interface. In the
second and third stage of drawing, three direct re-drawing methods were used to
re-draw the cup produced from the first stage (By using internal blank holder, with
out blank holder, and by using centering block method).
The analysis reveals that the difference in the drawing ratio, and the irregular
contact condition between the blank and die (which occur when using second and
third method of re-drawing), induces non-uniform metal flow, which cause
wrinkling, tearing, and severe extension of metal during the re-drawing process. for
There the first method (By using internal blank holder) was chosen for detailed
analysis because it ensures reduction in wrinkling and tearing of the cup wall.
From the comparison between the results of the three stages of drawing, it has
been found that the drawing force decrease for each successive stage of drawing
process, increasing the value of effective strain distribution over the cup wall with
die nose radius, the radial and hoop strain increases remarkably for each successive
stage of drawing, while the thickness strain increases slightly, which lead to
produce a uniform wall thickness of the re-draw cup. It was found that, the use of
internal blank holder in re-drawing process, increases cup formability, extends tool
life by eliminating wrinkling and tearing, reduces the possibility of failures,
improves part quality and increase production speed.

A mathematical model to predict the stress–strain behavior of fibrous concrete composites
under random cyclic compressive loadings is developed. The envelope
unloading strain is used as an index of load history, while the plastic strain and
reloading strain are predicted as functions of the envelope unloading strain for both
full and partial unloading and reloading. The model is independent of the expression
used for the envelope curve. Comparison with cyclic data shows good agreement.
The model can be used for completely random loadings, in both the pre–peak and
post–peak ranges. It is suitable for both plain and fibrous concrete composites. The
model has been built using MATLAB language computer program facilitating the
advanced mathematical
difficulties of solving and differentiating complex expressions.
In this paper, the monotonic stress–strain curves of Al-Sulayfani model [1] for fibrous
concrete had been adopted.

This work aims to study the effect of varying punch nose radius used in deep
drawing operation, on produced cup wall thickness, stress and strain distribution
across the wall of the drawn part, hydrostatic pressure ,residual stress developed in
the drawing part after drawing, and the value of work done to form the required
shape of drawn part.
In this work, six types of punches with various nose radii have been used to
form a cylindrical cup of (44mm) outer diameter,(28mm) height, and
(0.5mm)sheet thickness of mild steel of (0.15%) carbon content. A commercially
finite element program code (ANSYS 5.4), was used to perform the numerical
simulation of the deep drawing operation, and the numerical results were
compared with the experimental work.
The results show that, the value of work required to form parts with large nose
radii ismuch more than the value required to form parts with small punch nose
radii. An increase in the punch nose radius, results in an insignificant increase in
shear stress and shear strain. These values are very small which can be ignored.
The greatest thinning is seen to occur with hemispherical punch (Dome shaped
punch) due to great stretching of the metal over the punch head. The maximum
tensile stresses and the maximum thinning of the dome wall occur nearly at the
apex of the dome (a friction coefficient nearly equal to zero). In the presence of
friction, the position of maximum strain, which corresponds to the location of
maximum thinning point, moves away from the apex. The larger the friction is,
the larger is the distance between the apex and the point of maximum thinning.
The frictional force is applied to the metal largely by the edge of the punch and
not by its flat section. Maximum thickening of the cup wall occurs at the flange
rim, and this thickening increases with punch stroke.

In this investigation, steady two – dimensional natural convection heat
transfer of Newtonian and non-Newtonian fluids inside square enclosure has been
analyzed numerically for a wide range of the modified Rayleigh number of (103 ≤
Ra ≤ 105), with non-dimensional parameter(NE) of Prandtl – Eyring model ranging
from (0 to 10), and modified Prandtl number in the range (Pr* =1,10, and 100).
Two types of boundary conditions have been considered. The first,is when the side
walls are heated at different uniform temperatures and the horizontal walls are
insulated. The second, when the bottom wall is heated by applying a uniform heat
flux while the other walls are at the constant cold temperature. Also, the non-
Newtonian fluids under consideration were assumed to obey the Prandtl – Eyring
model. The numerical results of the values of average Nusselt number have been
confirmed by comparing them to similar known yeslts of previous works using the
same boundary conditions. Good agreement was obtained. The results are
presented in terms of isotherms and streamlines to show the behavior of the fluid
flow and temperature fields. In addition, some graphics represent the relation
between average Nusselt number and the parameters that are mentioned
previously. The results show the effect of non – dimensional parameter (NE) on the
velocity and temperature profiles. It also shows that the average Nusselt number is
a strong function of modified Rayleigh number, modified Prandtl number, nondimensional
parameter, and the boundary conditions. Four different correlations
have been made to show the dependence of the average Nusselt number on the
non-dimensional parameter, the modified Rayleigh and Prandtl numbers.

In this work, many techniques are suggested and analyses for
rectangular microstrip antenna (RMSA) operating in X-band for 10 GHz
center frequency. These approaches are: lowering quality factor, shifting
feeding point , using reactive loading and modification of the patch shape.
The design of a RMSA is made to several dielectric materials, and the
selection is based upon which material gives a better antenna performance
with reduced surface wave loss. Duroid 5880 and Quartz are the best materials
for proposed design to achieve a broader Bandwidth (BW) and better
mechanical characteristics than using air. The overall antenna BW for RMSA
is increased by 11.6 % with Duroid 5880 with shifted feeding point and with
central shorting pin (Reactive loading) while that for Quartz is 17.4 %.
Modification of patch shape with similar improving techniques gives an
overall increasing VSWR bandwidth of 26.2 % for Duroid 5880 and a
bandwidth of 30.9 % for Quartz. These results are simulated using Microwave
Office package version 3.22, 2000.