Print ISSN: 1681-6900

Online ISSN: 2412-0758

Volume 25, Issue 7

Volume 25, Issue 7, September 2007, Page 256-949


Mathematical Model of Autoclave Curing of Epoxy Resin Based Composite Materials

Adnan A. Abdul Razak; Najat J. Salah; Hassen Sh. Majdi

Engineering and Technology Journal, 2007, Volume 25, Issue 7, Pages 828-835

Polymer matrix composites using thermosetting resins as the matrix are
increasingly finding use in several applications. Process modeling
describing the governing curing has played an important role, in
improving the fundamental understanding and development of
composite fabrication techniques. In present work, the thermokinetic
involved in the autoclave curing of fiber-reinforced epoxy has been
studied by means of a computer program, using the transient heat
conduction equation coupled with kinetic equation, and the initial and
boundary conditions. In the analysis the cure assembly is assumed to
consist of a tool plate, composite laminate. The temperature distribution
and the degree of reaction are obtained as a function of position and
time.

Improvement of Thermal Properties for Binary Systems PVFPh, PVF-B by Addition of Silicon Carbide

Mohammed A. Abbas

Engineering and Technology Journal, 2007, Volume 25, Issue 7, Pages 836-848

Two binary systems of (PVF-Ph and PVF-B) were prepared at specific
conditions, and then thermal properties were improved by addition of a ceramic
material (SiC).
A different mixing ratio of ceramic material (SiC) powder was added to a
prepared binaries (PVF-Ph, PVF-B) at (polyvinyl formal-phenol, and polyvinyl
formal-bitumen) with a range (0.1-1)gm varied with (1-0.1)gm addition from both
phenol (Ph) and bitumen ( B ).
The thermal properties (thermal conductivity, stability) were measured for
both improved binary systems (PVF-Ph, and PVF-B), and the results proved that:
All thermal properties of two binaries (PVF-Ph, PVF-B) are modified with
excellent properties of bitumen that will be raised from (50˚C to 250˚C) and other
system (PVF-Ph) improved from (120˚C to 200˚C). Also the thermal conductivity
is modified at a wide range from (0.0999 w/m˚C to 0.000477 w/m˚C.).
A home made thermogravimetric system was designed to give TG-analysis
curve and check the stability of composite prepared system, where the results
proved that the optimum mixing ratio of composite system gives high stability
from (100˚C to 315˚C) with excess of ( 215˚C) than base one (PVF-B).

Effect of Zn % and Thermomechanical Treatments on the Mechanical Properties of Al-Zn-Mg Alloys

Ali H. Ataiwi

Engineering and Technology Journal, 2007, Volume 25, Issue 7, Pages 849-862

The aging kinetics and the coupling between plastic deformation and
subsequent aging on a set of Al-Zn-Mg alloys having different Zn-content
(6.33%, 7%, 7.5% and 8%) are investigated. These alloys are produced with
an extreme care during melting, alloying and sampling where the best
conditions of alloying are adopted .The response to multi thermomechanical
treatments practices are reported, where the combination between rolling
practice and aging is monitored by hardness measurements, tensile, impact
toughness measurements in addition to x-ray diffraction testing. The study
proves that, the zinc percent has a very important role in the precipitation
hardening sequence of tested alloy; this effect is concentrated on the speeding
up the kinetics of hardening by increasing the density and stability of GP
zones and μ'-phase.

Computer Aided Design and Modeling of FCCU Processing Iraqi Feed Stock

Neran K. Ibrahim; Shayma H. Khazaal

Engineering and Technology Journal, 2007, Volume 25, Issue 7, Pages 863-878

The relationships between the process variables for a Fluid Catalytic
Cracking unit (FCCU), processing vacuum gas oil (VGO) feedstock from
Kirkuk crude oil, were studied depending on material and energy balance
calculations. Computer programs written in Visual Basic (6.0) are developed
to evaluate all the process variables. The steady state models is used to design
the reactor, regenerator, fractionator and slurry settler. A hydrodynamic
model for the complete description of the FCCU is developed. The model
simulates the riser and the regenerator and incorporates operating conditions,
feed properties and catalyst effects. The effect of the selection of the input
(manipulated variables) on the output (measured variables) for the reactor
and regenerator is also studied.

The Effect of Cutting Tool Vibration on Surface Roughness of Workpiece in Dry Turning Operation

Safeen Y. Kassab; Younis K. Khoshnaw

Engineering and Technology Journal, 2007, Volume 25, Issue 7, Pages 879-889

This study is to find a correlation between surface roughness and cutting tool vibration
in turning. The ranges of process cutting parameters in the present study are limited:
cutting speed (34, 70, 130 m/min), depth of cut (0.1, 0.2mm), feed rate (0.07, 0.13,
0.17mm/rev) and tool overhanging (25, 30, 35, 40mm). The data are generated by lathe
dry turning of medium carbon steel samples at different levels of the mentioned above
parameters. Dry cutting tests (without using cutting fluid) are conducted to simulate a
good turning, the dry turning provided a clean environment to obtain undisturbed
clear cutting vibration, which results in more accurate and clear correlation between
cutting vibrations and roughness. The analysis of variance reveale in this study is that
the best surface roughness condition is achieved at a low (feed rate less and equal
0.13mm/rev), and with smaller tool overhang less and equal 30mm). The results also
show that the cutting speed has small effect on surface roughness than feed rate and
tool overhang. The depth of cut has not a significant effect on surface roughness in this
study.
Above results can be obtained when there is no built up edge and no damage
of the tool tip. Finally experimental results have shown good correlation between the
cutting tool vibration and surface roughness which can be used to control the finish
surface of the workpieces during the mass production.

Gain Characteristics of Silicon Transistor Treated by Laser

Rana O. Mahdi

Engineering and Technology Journal, 2007, Volume 25, Issue 7, Pages 890-896

In this work, profiles of laser-induced diffusion of arsenic in silicon are
presented. These profiles are considered to attempt increasing of the current
gain of silicon transistors. The current gain is well enhanced. This
enhancement is attributed to the increase achieved in the diffusion length
within a certain layer of emitter region. Laser-induced diffusion is a perfect
technique for improving the characteristics of electronic devices since it is
flexible, contactless, clean and well controlled.

Cumulative Damage in Fatigue of a Structure Subjected to Random Loading

Kadhim Karim Muhsin

Engineering and Technology Journal, 2007, Volume 25, Issue 7, Pages 897-917

When a structure is subjected to a random loading, its dynamic response
changes, characterized by shifts in the eigenvalues and modification of eigenvectors.
The peaks in the dynamic response spectrum will give indications of the natural
frequencies of the structure. Any damage in the structure will be reflected in the
spectrum as a shift in natural frequencies.
Crack initiation and early growth of fatigue cracks in 0.4% carbon steel and
2024-T4 aluminum are investigated using spectral density approach for applied
random loading. Energetic consideration and spectral density approach lead to the
formulation of a model used to predict the behavior of short and long cracks
initiation, propagation, and paths taking into account the microstructural variables
relevant to fatigue crack initiation and early crack growth.
The model indicates that crack arrest occurs when crack-tip is blocked by a
grain boundary. In the short crack region, propagation and non-propagation occurs
depending on random loading stress level and slip band energy released. The
application of the present model to cumulative damage is compared with the
experimental data and a reasonable agreement is found. The introduction of material
specification shows a quantitative description of the parameters which affect the
reliability of a structural component subjected to random loading. The power of the
analytic model and the simulation analysis in the present work give some insight to
the behavior of the structure under random loading showing the different mode
shapes, eigenvalues/vectors, deformation, propagation and non-propagation of cracks,
and the stresses caused by such random loading that can lead to fatigue failure. A life
predication model is presented for long-life fatigue , to control the hardware design
and to find a proper combination of random load and life .

Improving Oxidation Resistance of Stainless Steel (AISI 316L) by Pack Cementation

Ahmad Ali Moosa; Muna Khedeir Abbas; Rajab Mohammed

Engineering and Technology Journal, 2007, Volume 25, Issue 7, Pages 918-939

The cyclic oxidation resistance of austenitic stainless steel (AISI 316L) can be
improved by enriching the surface composition in Al and Si using pack cementation
process. In this work, stainless steel is coated with two different types of coatings,
the first one is Si-modified aluminide coating and the second is the Ce-doped silicon
modified aluminide coating. Aluminum, silicon with and without cerium were
simultaneously deposited by diffusion into St.St.316L substrate by the packcementation
process, using a pack mixture containing (18%A1, 7%Si, 2%NH4C1
and 73%Al2O3) and 0.5% Ce (wt %) when required.
Microstructure and chemical composition of the coated specimens were
analyzed using electron microscopy (SEM) with energy dispersive spectroscopy
(EDS). X-Ray diffraction (XRD) was used to identify phase formed in the surface
layer of as-coated specimens. The coating time was changed, and it was found that
diffusion coating time of 3h at 970C° produces coating thickness of 160-180μm and
consist mainly of FeAl and (Cr4Si4Al13) phases. Also, the surface morphology for the
coated samples after 3h coating time at 970C° are dense, smooth and homogeneous.
Cyclic oxidation tests were conducted on the uncoated St.St.316L , Si-modified
aluminide coating and on Ce-doped silicon modified aluminide coating at a
temperature range between (700-900)C° in (air and H2O) for 120h at 10 h cycle.
The oxidation kinetics for uncoated St.St.316L in air environment are found
to be linear, while the oxidation kinetics at water vapor environment are found to
be nearly parabolic. The linear rate constant (KL) and the parabolic rate constant
(Kp) values obtained at 800C° in air and water vapor are –2.77*10-7(mg/cm2)/s and
2.18*10-5(mg2/cm4)/s respectively. The phases present on the cyclic oxidation of
uncoated St.St.316L surface under most test conditions as revealed by XRD analysis
are chromium (III) oxide, NiFe2O4, NiCr2O4 and iron oxide. Oxide phases that were
formed on coated systems during air and H2O oxidation exposure condition are
FeAl2O4, Fe(Al,Cr)2O4 and Fe2O3. The oxidation kinetics for both coated systems in
air and water vapor are found to be linear and parabolic respectively.

Effect of window over-hang in Iraqi Building on Cooling Load

Nazar Farag Antwan

Engineering and Technology Journal, 2007, Volume 25, Issue 7, Pages 940-949

A study is done on an Iraqi building to estimate and show how the use of
over hang reduces the cooling load. The study shows how the effectiveness of
over hang is affected by the orientation and the area (height) of the windows.
This study shows that limit width of over hang on south window reduces the
cooling load by (9%), and when using the over hang on the east or west
window we need a large width over hang to reduce the cooling load by the
same percentage. Also this study shows that using over hang and increasing
the area of south windows allow us to receive a wide range of solar radiation
in winter and use it in heating and lighting and the cooling load does not
increase by the same percentage when using west or east windows. The results
show that the using of over hang in Iraq is important especially for south
windows.