Iraqi journal of mechanical and material engineering

This paper discusses the dynamic behavior (natural frequencies, modes shapes) of the axial fan. The fan blade stagger angle is adjustable. Three angles 20o, 35o and 60o are studied. Three dimensional finite elements with six degrees of freedom per node are employed to idealize the axial fan. ANSYS12 program is performed that takes the variables of the fan blade system. The obtained results reported the tenth structural natural frequencies and mode shapes which are based upon the behavior of fan, it can be shown that the natural frequency of the fan increased with increasing mode number and the amplitude decreases as the stagger angle increases. The results shows that the maximum amplitude occurred at stagger angle of 20° and have less error ratio.

In this research the effect of the die geometry in the compound extrusion (forward –
backward) process on the distribution of temperature and effective stresses is
investigated; Effect of the geometrical shape of extrusion process on the power
required for the forming process was also investigated. The flat surface for the punch
is chosen and two types of die shape (flat and arc) are studied. The analysis of
temperature and stresses distribution in the die and billet is studied using finite
element method via ANSYS software. The contact region was taken into
consideration. From the results, it was noted that there a tiny changes in the pattern of
temperature distribution and also a huge changes in the equivalent stress levels due to
the changing in die geometry. In the backward extrusion process, a significant effect
on the stress levels was also noticed due to changing in die geometry. At last, the
results show that the best results of was achieved at arc die geometry.

This research represents a theoretical study which deals with the developing steady, laminar, Newtonian and incompressible fluid flow and heat transfer through circular tube. The effects of heat conduction, body force, free convection, heat generation and viscous dissipation within the fluid are neglected. A computer program was built by using Gaussian elimination method to perform the numerical marching technique solution with finite difference method for two case of heating, constant wall temperature and constant wall heat flux boundary conditions for different values of Reynolds number (500,1000,2000) and Prandtl number (1, 2.5, 5). This approach provides a picture of the variation of the velocity and temperature profiles through the tube. The computational algorithm is able to calculate all the hydrodynamic properties such as velocities and pressure drop. Also, it is able to predict all the thermal properties such as the temperature, bulk temperature, and local Nusselt number. The velocity profile becomes fully developed at approximately Re05.02aLe, and the temperature distribution becomes fully developed at approximately Pr. Re05.02aLet, as expected

In this study, composite materials of an aluminum alloy(Al – 12 % Si) matrix
reinforced with 5wt% SiC particles were prepared by gravity die casting and squeeze
casting under casting pressure of ( 38MPa) and mold preheating at temperature (200
oC).
Microstructure and hardness for prepared base alloy and composite materials were
carried ou. Dry sliding wear type (pin–on-Disc) with variation in applied load was
carried out under a constant steel hardness (35 HRC), sliding speed (2.7 m / sec) and
sliding time (20 min).
It has been found that prepared base alloy(Al – 12 % Si) and composite materials
produced by squeeze casting have wear resistance better than that of base alloy and
composite materials produced by gravity die casting.

Al-alloy type 7020 was heated at different temperature (from 100 to 500) ºc to
observed the shape of precipitated phases. Pitting corrosion of this alloy was also
study by using immersion in 3.5% NaCl and polarization techniques. The aim of this
paper is to find the dependence of pitting corrosion morphology on the precipitated
phases for 7020 Al-alloy.
The results are confirmed that, at low heating temperatures between (100-200)
°C dendrite structures were observed. These zones suffered dendrite pitting corrosion,
when the alloy was exposed to corrosive medium of 3.5% NaCl.
At the intermediate temperatures range (250-350) °C, different shapes precipitated
phases are obtained. As heating temperature was increased these shapes converted
from dendrite to spherical shapes. This transition in shapes was also observed for
developed pit. At heating temperature up to 500 °C most of the formed pitting has the
spherical overall shapes corresponded with the phases shape, precipitated at these
range of temperatures.

In this paper, the viscoelastic and viscoplastic behavior of polyethylene (PE)
pipe is studied and analyzed using Space-time finite element method (FEM). The
(FEM) is achieved for Maxwell model and then the program is developed in three
dimensions (two-dimension in space and one dimension in time) and applied to (PE)
pipe under pressure loading. The time dependent partial differential equations
describing the viscoelastic deformation of (PE) pipe under pressure loading for
Maxwell element is solved using variational Galerkin continuous method in an
integral process using time slabs. As a result of this study, the FEM in viscoelastic
Maxwell model used to predict the relaxation modulus give accurate result compared
to analytical which used Prony series. The stress increases to large values at the first
stage of applied pressure loading and then decrease with increasing time. The
viscoelastic surface density of micro crack is increasing function with increasing
plastic strain.

In this research an attempt to introduce an additional improvement on the
properties of (Zn-Ni) electroplated layer. In this work electrodeposited layer of
different thickness of (Zn-Ni) from an alkaline solution is performed on samples of
low carbon steel. X-ray fluorescent (XRF) used to determine the chemical
composition of (Zn-Ni) deposited layer as well as x-ray diffraction (XRD) technique
is used to determine the phases of the electrodeposits layer.

This study explains the relationship between friction coefficient and pressure
change at a range of Reynolds (21056 - 32033) and (0 -1.4) solid loading ratio of two
phase flow (Gas-solid) inside a circular copper pipe of (63mm) inside diameter and
(2m) length by using laboratory apparatus and solving the equations mathematically.
An experimentally relationships of friction coefficient and pressure change with
Reynolds number and flow velocity one obtained also the relationship between the
solid loading ratio with friction coefficient and pressure change has been done for a
limit range of Reynolds number. It is noticed that the increasing in friction coefficient
and pressure change for two phase flow occurred when solid loading ratio
increasing. Also, the relationship between pressure changes and Reynolds number was
direct proportion while the relationship between friction coefficient and Reynolds
number was inversely related.

A numerical method was used for calculation the pressure distribution and
then finding aerodynamic forces to give an estimation for the high- lift systems effect
on two-dimensional airfoil for an inviscid incompressible flow (panel method), the
computational method investigated experimentally. The study focused on flap and slat
effects on the aerodynamic forces at the wings as two of the important items of the
high lift systems.
Experimental study was made with suction type low-speed wind tunnel for an
airfoil of (NACA 0015) supported with leading edge slat and trailing edge flap. The
effective forces of lift and drag were measured by two components balance. Different
angles of attack (-4, 0, 4, 8 & 12) o and different flap angles (0, 10, 20 & 30) o were
chosen with and without slat, variable air velocities (8, 12, 16 & 20) m/s were applied.
The computational results compared with experimentally measured data.

In this paper we studied the effect of fins length of heatsink on the performance of
the processor type Athlon XP+ 1.73GHz. First a common heat sink had been used,
then the reads of the processor it's temperature and heat emission at three conditions
were taken, the 1st one at minimum uses of performance just opening windows, the
2nd one at the average use of performance opening word document with some wrights
while the 3rd one is the maximum use of performance of the processor and this occurs
when we run a huge software or a complicated high graphics big game. Many
programs give us a full condition for any part of the computer especially the
processor such as (Norton System Work, Sandra SIS, Windows Vista Task Manager
(WVTM)…etc). In this research we used (WVTM) because it's part of the OS vista which will not apply another load upon the processor, also the (WVTM) contains great
tools of operations. Also we calculate the time requiring for the OS to boot at this type
of heatsink and other applications like office and others. Then we changed the heatsink
with another one with fins length twice than the old one. A model of the heatsink were
built for both cases by the package (AutoCAD 2008) and analyzed it in the package
(FLUENT 6.3) to show the thermal emission inside both heatsinks and the experimental
and theoretical results were acceptable.

The inhibitive effect of the aqueous extract of Ziziphus leaves on the corrosion
of mild steel in drinking water have been investigated by using an electrochemical
polarization and weight loss method. The obtained shows shows, that, the extract of
leaves of Ziziphus could work as an effective inhibitor against the corrosion of
steel in drinking water network. The inhibition percentage increases with the
increasing of the leaves of Ziziphus concentration at 30°C. The inhibitor percentage
efficiency above (98 %) was attained at extract of Ziziphus leaves concentration
(1% v/v). The inhibition efficiencies of the extract of leaves of Ziziphus obtained
from weight loss method and polarization measurements were in good agreement.
electrochemical polarization studies clearly reveal that the extract of leaves of
Ziziphus behaves predominantly as an anodic inhibitor. The study also shows that the
inhibition efficiency was insignificantly affected by the temperature rise of the
medium.

This paper proposed a computerized methodology of spur gears reconstruction
and feature extraction using image processing technique. The methodology was
prepared, by building a suitable logical program in Matlab environment, to process
the captured gear image using mathematical and logical relationships for the purpose
of spur gear data extraction required for 3D spur gear modeling which is include No.
of teeth, tooth height, Pitch circle, … etc.
The proposed system has been tested on different spur gears, and the extracted
data shows reliable spur gear modeling, which generates accurate and efficient model
and provides substantial saving in time and cost of production.

This research is intended to study the preparation of heat mirror by spray pyrolysis
method. Un-doped tin oxide (SnO2) and doped with 0.09%, 0.9%, and 9%, titanium
dioxide heat mirror films were deposited on pre-cleaned substrates. The
microstructure characterizations were carried out by x-ray diffraction technique. The
optical properties were obtained by UV-Visible spectrophotometer. The un-doped
samples have displayed average transmittance value of 73% in the visible region.
Whereas, the doped samples of 0.09 and 0.9 mol% TiO2 show a good reflectance
values of 76% and 80% respectively in the wavelength of 2700 nm.

In this research a flame of CNC cutting machine was used. It works manually
only in straight line cut. All experiments had been done to reach a proper ultimate
processing conditions for clean cut. The dwell time of preheating, piercing and the
speed of cutting are variables - in addition to gas pressure - control the cutting
process. The target was to improve cutting conditions of carbon steel metal of
thickness arranged from (10–15) mm, then to design a written program to be fed with
the final readings to the CNC machine to produce a complex frame having sections of
straight lines, curves and right angles with tolerance of 0.1mm. The value of cut
width which was (2) mm would be shifted toward the core dimensions according to
the program. By this technique, it is capable to produce complex shapes such as
gears, in particular big components having a clean and even cut for applications
require less accuracy.

This paper presents work in progress, concerning the reducing of stress
intensity factor values for finite width plates by using auxiliary circular holes, the
analysis is done by using the finite element method. To find the stress intensity factor
“SIF”, the ANSYS packages was implemented to evaluate the SIF by using th Finite
Element of Fracture Mechanic. It had found out that the SIF is reduced to 56% by
using the auxiliary hole in the plate, the dynamic load of unit step input had been test
to show the validity of this method, which is better to prevent crack from propagation.