Iraqi journal of mechanical and material engineering

The important role in the performance of machined parts and structures is residual stresses,
namely, in the following aspects corrosion resistance, fatigue life and part distortion. The
aim of this research was to predict the residual stresses in aluminum alloy Al-6061
workpiece after machining; this prediction of residual stresses was applied with different
value of cutting speed, feed rate and depth of cut using Taguchi method.
The model is verified with experimental measurements of residual stresses. With the
analytical model presented in this work, Feed rate is the most important variable that affect
on maximum residual stress after that cutting depth and rotational speed substantial
reduction in computational time is achieved in the predictions of residual stresses. The result
of this research is the contribution of depth of cut, rotational speed and feed with respect to
residual stress is (67.07, 24.8 and8.13) % respectively.

Mixed convection heat transfer in a horizontal channel supplied with metal foam blocks
and partially heated at a constant heat flux is numerically investigated with air as the
working fluid. The Brinkman-Forchheimer extended Darcy model is utilized to simulate the
flow in the porous medium and the Navier-Stokes equation in the fluid region. The
numerical investigations cover the Reynolds number range from 500 to 2000, heat fluxes
varied from 500 to 6000 W/m2, and Darcy number 5 x10-2 to 1x10-3. Results show that
the wall temperatures at each heated section are affected by the imposed heat flux variation,
Darcy and Reynolds numbers variation. The variations of the local heat transfer coefficient
and the mean Nusselt number are presented and analysed. The mean Nusselt number
enhancement was found to be more than 85% for all the studied cases from the fluid case.

The nanofibers of nickel ferrite (NiFe2O4) was prepared by electrospinning technique.
Nickel nitrate hexahydrate, iron nitrate nonahydrate, Polyvinylpyrrolidone (PVP) and Ndimethylformamide
(DMF) were used as precursor materials. Crystallization behavior of the
nanofibers was studied by X-ray diffraction (XRD). Nanofibers phases can change from
amorphous to spinel ferrite depending on the calcination temperature at (500°C, 600°C, 700
°C) and crystallite size by Scherrer’s formula about (18.26 – 28.10) nm, while
morphological and structural properties were investigated by scanning electron microscopy
(SEM). Magnetization measurements were carried out on a vibrating sample magenometer
(VSM), which revealed saturation magnetization of the samples were strongly dependent on
the calcination temperature. Finally, our results showed that the electrospinning method
leads to obtain nanofibers of nickel ferrite with good controllable stoichiometry at low
temperature.

The present work is a design and implementation of a compact single-axes solar
tracking system. The hybrid system a combination from mechanical and the electronic parts.
A tracking system are used to track the sun position and let the solar collector facing the sun
as long as possible. The single axis tracking system has the ability to rotate the solar
collector in horizontal axis and in both clockwise and anticlockwise .The electronic system
contains a microcontroller board connected to dual sensors and the output signal from the
microcontroller will be input to one-axis motor. The experiments conduct for flat plate solar
water collector in the first case non-tracking system and secondly case using tracking
system. The experimentally results that the average obtained falling solar radiation on solar
collector in the first case and the second case during the same time is (616 watt/m2, 725
watt/m2) respectively .This means an increase about 17.7 % at using tracking system and the
average useful heat gain output of solar collector during the same time is (65.8 watt, 85.5
watt) respectively it mean increased about 30.4 % at using tracking system.

In this work, preparation ternary polymer blends, by addition PMMA to the two groups of
binary polymer blends (98%Epoxy: 2%NR) and (95%Epoxy: 5%NR). Mechanical
properties for all prepared samples were studied. The results of this research showed that the
ternary polymer blends which have the ratios (93%Epoxy: 2 %NR: 5%PMMA) or
(90%Epoxy: 5 %NR: 5%PMMA) have the best results in fracture strength, young modulus,
compressive strength, and hardness and the maximum values were at 5%PMMA, while
elongation decreases with the addition PMMA to the blends. Moreover flexural properties
values, impact strength and fracture toughness decrease with increasing in PMMA
percentage for both groups, these polymer blends were characterized for morphology using
scanning electron microscopy (SEM).

The current paper presents a new construction of an Electro-Pneumatic (EP) elevator
system fully automated with Programmable Logic Controller (PLC) technology. This
elevator represents as a new concept derived and evolved from the pneumatic-vacuum
elevator as the idea of vacuum air is changed by the pressed air. The elector-pneumatic
elevator is capable of transporting people between floors without using any cables, counter
weight, or pulleys. An elevator system prototype constructed with three floors to elevate a
5kg payload with 1bar pressure had been proposed and controlled via a PLC controller of
(LS-GLOFA-G7M-DR20A), 8 inputs, and 12 outputs. The PLC was programmed with
Ladder diagram software. The idea of the proposed elevator system may be predicted to be
widely spread in the low-rise residential buildings .

An investigation has been made to study numerically the effect of wavy wall locations on
natural convection flow in a two dimensional enclosure filled with air containing a
concentric heated circular cylinder. The external walls of the considered enclosure are
maintained at a constant cold temperature (Tc) while the surface of the circular cylinder is
kept at a constant hot temperature (Th). The numerical simulation, based on a finite element
approach, is performed using program ANSYS version 11. The governing equations with
boundary conditions are solved iteratively using the Tri-Diagonal Matrix Algorithm
(TDMA). The current work is validated with previous numerical results available in the
literature. The study aims to determine the effect of wavy wall location which is
represented by varying the inclination angle (∅=0°, 90° and 180°), and undulation numbers
(n=1 and 2) on flow field and heat transfer for four selected Rayleigh numbers (Ra=103, 104,
105 and 106). Streamline and isotherm contours are determined. The effect local Nusselt
number along the hot surface of the circular cylinder is also examined in this study. The
results indicated that the average Nusselt number at the hot surface of the cylinder increases
with increasing the Rayleigh numbers and reduces when undulation number increases from
one to two.

Ventilation is the main performance requirement in laboratory design as it has to
guarantee a safe and comfortable indoor environment. standards and guidelines on laboratory
ventilation often impose high ventilation rates, increasing the energy need for ventilation.
This research focuses on the steady-state distribution of temperature and contaminate
concentrations in a real environment which was a function of several factors such as the
position of air exhausts. Here several different exhaust locations were investigated to
determine the optimum exhaust positions. In this study, CO2 is used as an indicator of the
concentration of pollutants inside tested room.
Room concentration patterns for a laboratory were simulated with computational fluid
dynamics (CFD) simulations by using (FLUINT6.3.26) and (GAMBIT V.2.4.6) computer
programs for various exhaust locations. The computational results were validated with design
data due to Iraqi cooling code (setup temperature and temperature difference from head to
foot level). The numerical results showed that the exhaust grills located near the ceiling
resulted in lower pollutant concentrations than the corresponding exhausts near the floor.

The present work deal with the effect of corrosion-mud on constant fatigue and
accumulated using 7049 aluminum alloy. Experimental results observed that fatigue life and
strength strongly effect by corrosion-mud treatment. The (fatigue life reduction factor
percentage) FLRF% can empirically expressed by the equation
The fatigue strength was reduced to 10% due to mud corrosion fatigue interaction. It was
indicated that Miner rule underestimated the mud corrosion fatigue life interaction.

Nonlinear free vibration analysis of composite laminated composite thin plate is
studied in present work. Numerical solution using Ansys finite element program
(Mechanical APDL 15.0) is used to investigate the effect of strain nonlinearity on the
natural frequency of these plates. Design parameter is changed to investigate their effect on
natural frequency of the plate such as lamination, aspect ratio, lamination angle and number
of plies. An experimental work is programed to manufacture and test the mechanical
properties and natural frequency of the plate for two boundary conditions (CCCC) and
(CFCF) to compare the results with those obtained from numerical analysis. Numerical
results are close to those obtained experimentally; maximum discrepancy is 4.04% for
symmetric (CFCF) boundary condition and 5.08 % for an-symmetric (CFCF) boundary
condition .

The application of optimization techniques is essential for a manufacturing unit to
respond effectively to ruthless competitiveness and increasing demand of quality product in
the market. In this study, multi-objective optimization on the basis of ratio analysis
(MOORA) technique was used to solve different decision-making problems and optimize
the machining parameters in the wire electrical discharge machining processes for different
materials. Five decision making problems requiring determination of optimum machining
parameters using different techniques are considered in this paper. In all these cases, the
obtained results using the MOORA technique compared with those suggested by the past
investigators and the results demonstrate the simplicity, suitability, possibility, and
flexibility of this technique when finding the solution for different complex decision-making
problems during machining setting.

Buoyancy-driven heat transfer convection enhancement in a two-dimensional
enclosure, for two cases boundary conditions: (isothermal and linearly varying) temperature
differential heated walls utilizing Nano fluid is studied numerically. In this study, three
various base fluids (water, ethylene glycol, or oil) based with (CuO) nanoparticles are
tested. Calculations of heat transfer rates were accomplished for a range of Rayleigh number
(103 ≤Ra≤106), Prandtl number is taken as (Pr = 6.7, 204, and 10959), and solid volume
fraction (0 % ≤ϕ≤ 10 %). Numerical computations are carried out for different combinations
of relevant parameters involved in the study. Results showed that the heat transfer rate
increases by increasing the volume fraction of the Nano fluid for all types of base Nano
fluid considered. The increment in average Nusselt number is strongly dependent on the
basic fluid and boundary condition chosen. The heat transfer rate also increases with
increases of Rayleigh number, and Prandtl number. Based on the present results, oil-base
nanoparticle in an enclosure with the isothermal temperature walls is preferable to attain
overall heat transfer enhancement. Also, the enhancement in heat transfer with (0.1) solid
volume fraction of (CuO) particles based with different basic fluids such as (water, EG, or
oil) increases (26.7%, 28.8%, and 32.94%) respectively for low (Ra) as compared to the
base fluid. For verification of current study, the results have been compared with the recent
studies at the same boundary conditions and are a good agreement.

In this study pitting corrosion is investigated in hypereutectic Al- 17wt% Si alloy
bearing magnesium . Many alloys were prepared by die casting with adding different
percentages of magnesium : 1 wt%, 4wt% & 9 wt% to the Al-17%Si alloy in order to study
the influence of magnesium addition on the corrosion behavior and pitting properties in
3.5% NaCl solution. Results of microstructure examination show that primary silicon (Si)
and eutectic silicon in base alloy was more susceptible to pitting corrosion compared to the
other alloys containing magnesium . It was found that the corrosion rate of alloy Al-17%Si
bearing Mg (in all percentages) was lower than that of base alloy. The corrosion potential
shifts to less negative value ( to more noble direction) and Epit to more positive value with
increasing Mg content to 9%wt. It means that the addition of Mg to Al-17% Si alloy
improves resistance to pitting corrosion and that no pitting appears in passive region during
the cyclic polarization test.