Iraqi journal of mechanical and material engineering

This work aims to study the effect of sintering temperatures on physical properties
(density and porosity) and corrosion behavior of compact(Al-4.5%Cu-1.5%Mg) alloy in
3.5% NaCl solution at room temperature using cyclic polarization method. Powder
technology was used to prepare this alloy by mechanical mixing of Al, Cu and Mg powders
in a ball mill for 6 hours to ensure a homogenous distribution of powders in the mixture.
Mixed powder was compacted by using single action pressing at (450 MPa) then followed
directly by sintering process at different temperatures (520,540,560,580 and 600ºC) for one
hour in vacuum furnace under the effect of inert gas condition. Density ,porosity and
microhardness measurements were performed to find the best sintering temperature. Tafel
extrapolation method and cyclic polarization tests were conducted for all sintered samples.
It was shown that the highest density and micro hardness were at sintering temperature
560ºC. It was found that the pitting corrosion resistance enhances with increasing sintering
temperature up to 560ºC and afterword it drops again at higher temperatures (580 and
600ºC).

In the present research, study the effect of adding two different types of reinforcing
particles, which included: nano-alumina (nano-Al2O3) and nano-silica (nano-SiO2), that
added with different volume fractions of (1%, 2% and 3%), on the some mechanical
properties of composite prosthesis complete denture base materials by using self (cold) cure
poly methyl methacrylate (PMMA) resin as new fluid resin matrix . In this research the
composite prosthetic dentures specimens consist of from two groups were prepared by using
casting methods, type (Hand Lay-Up) method according to the types of reinforced particles
which includes: the first group consists of PMMA resin reinforced by nano-alumina
particles, and the second group consists of PMMA resin reinforced by nano-silica particles.
The mechanical tests were performed on these specimens include compression test, impact
test, and hardness test . The result of this study showed the values of (compression strength
and hardness) properties increased with increasing the volume fraction of both (nano-Al2O3
and nano-SiO2) particles in PMMA complete denture base materials. While, the values of
(impact strength) property decreased . Also the addition of (nano-Al2O3) particles has a
noticeable effect on the most properties of composite material for prosthetic denture base
specimens more than the (nano-SiO2) particles, except the impact strength property .

The sudden stop of rotating shafts for any external & arbitrary reason due to
develop of circumference distortions because of dynamic angular displacement & by
dividing on static angular displacement produce ratio called ( SSRSR ) to undesired
elevations . The response according to \" Bernoli – Euler \" theory in undamped torsional
vibration , one – dimension bars & homogenous , continuous material of bars , hence
,derived response for time & pointed position (furrier functions ) , the result depend on
shaft engineering directory & modulus rigidity of shaft material & which is get convergence
for theory & practical results.

The purpose of this paper is to study the two-phase flow around hydrofoil. Experimental
studies have been conducted in a channel with air-water flow for different angles of
hydrofoil with different air and water discharges. The paper describes experiments carried
out in the channel with the rectangular test section of 100 x 30 x 800 mm. The maximum
inlet velocity at the test section for air is 1.115 m/s and for water is 0.022 m/s. These
experiments have been aimed to visualize the two phase flow phenomena as well as to
studies effect of pressure difference through channel with hydrofoil. All sets of flow data in
this study were obtained using pressure transducer and visualization by video camera and
recorded at multiple angles of attack (0o,15o and 25o) and different Water discharge (l/min)
(20, 25, 35 and 45) and different air discharge (l/min) (10, 20, 30 and 40). When (α=0°) the
flow is parallel to the hydrofoil surface and there is no vortex shedding behind the hydrofoil.
When (α=15°) the flow separates from the upper-surface and the separation point moves
towards the leading edge of the hydrofoil as the air water discharges increases. When the
angle of hydrofoil (α=25°), the flow separates near the leading edge of the upper surface and
large eddies are shed from both the upper and lower surfaces. For constant water discharge,
the pressure difference increased with increased air discharge with the same angle of
hydrofoil

In this paper, both experimental and numerical studies were performed in a fully
developed turbulent region heat transfer of the CuO-water nanofluid in a horizontal 0.019m
diameter, 1.5m long copper tube that subjected to a uniform heat flux at its outer surface. An
experimental investigation was done to evaluate the heat transfer characteristics, friction
factor and the pressure drop of the CuO-water nanofluid are conducted in the particle
volume concentration range of 0.01% < ِ < 2%, and Reynolds number range of 5020< Re <
19985. The thermal conductivity, specific heat, density and viscosity of the nanofluids were
measured. In numerical study, the finite volume method using Ansys R.15, standard ê – ه
turbulence model employed to solve the continuity, momentum, energy and turbulence
equations in three-dimensional domains. The experimental and numerical results showing
that the data were satisfied within a 1.7% maximum difference. The effects of the
nanoparticle concentration with uniform heat flux on the enhancement of the heat transfer
turbulent flow condition were presented. The Nusselt number (Nu) of the CuO-water
nanofluid case was higher than that the base fluid by approximately 48.7%. However, the
increase in the pressure drop ranged is about 18%. Finally, the results reveals that the CuOwater
nanofluids could be considered as a good and alternative conventional working fluid
in heat transfer applications.

Laser shock peening (LSP) is a technical method for generation the compressive
residual stress. LSP has been shown to greatly improve fatigue strength and lifetime. A
study of fatigue under a constant repeating bending stress has been conducted on AL-alloy
7075 alloy at a stress ratio (R= -1) and room temperature using laser peening technique with
overlay hydrofluoric acid (HF) as a confinement acid layer and as a media to increase the
penetration of laser pulses. Two groups of test have been considered. The first group (15
specimens) was examined under unpeened situation. The second group (15 specimens) was
examined under acid laser peening (ACLP). All mentioned groups were tested to generate
the S - N curve. hydrofluoric acid (HF) coating was used as a new technique to improve the
properties of the AL-alloy 7075. The experimental data showed that the use of (HF) acid, as
a coating material, largely increased the compressive residual stress at the surface. The
results provided a substantial improvement in fatigue life improvement factor reaching to
80% for this new coating.

An extended element free Galerkin method (XEFGM) has been adopted for crack
propagation of for graded glass/epoxy beams (along X1) subjected to non-proportional four
point bending. The incompatible interaction integral method and the sub-triangle technique
for enhancing the gauss quadrature accuracy near the crack are employed to calculate the
stress intensity factors. Numerical simulations have proved that XEFGM provides accurate
results by less number of nodes (DOFs) in comparison with the conventional FEM under
mixed-mode and non-proportional loading. MATLAB codes are used in obtaining the
results of this research. The results have shown good the reliability, stability, and efficiency
of present XEFGM and good agreements with the experimental works of crack propagation
with using less nodes in compare with the relevant references.

Dissimilar welding of austenitic stainless steel AISI 304L to shape memory alloy SMA
NiTi was conducted by utilized Nd: YAG laser beam welding technique. Both AISI 304ASS
and SMA have the same dimension (80*20*0.5) mm. The experimental investigation
included tensile shear test and microstructure. The results demonstrate that the maximum
shear force found in the sample (No/10) reach (2552 N) which has the better laser
parameters in this research (peak power of (2.25 KW), pulse duration of (2.4 ms), pulse
repetition rate of (40 Hz), and welding speed of (8 mm/Sec). SEM with optical microscope
demonstrate the solidification method along the fusion area various in different joints, where
they become the planer shape to cellular and transformed the last to dendritic from intrafusion
welding area toward the center because towards weld area interface to weld
centerline cooling rate will be rise in all SMA (NiTi) and Austenite stainless steel (ASS)
sides.

In the present work a theoretical analysis depends on the new higher order element
in shear deformation theory for simply supported cross-ply laminated plate is developed.
The new displacement field of the middle surface expanded as a combination of exponential
and trigonometric function of thickness coordinate with the transverse displacement taken to
be constant through the thickness. The governing equations are derived using Hamilton’s
principle and solved using Navier solution method to obtain the natural frequency. The
effect of many design parameters such as number of laminates, aspect ratio and thickness
ratio on dynamic behavior of the laminated composite plate have been studied. The modal
of the present work has been verified by comparing the results of shape functions with that
obtained by other worker. Result shows the good agreement with 3D elasticity solution and
that published by other researcher.

The research presents an experimental investigation on the steady state natural
convection heat transfer for helical coiled pipes with a vertical orientation. Water is used as
the working fluid for both the target fluid and the bath medium. The heat transfer
characteristics have been studied for three helical coils that having three curvature ratio
(0.056, 0.0625, and 0.115) and three coil pitches (12.5, 25, and 37.5)mm with a volume flow
rate of the target fluid ranges (10-25)L/min and two constant bath water temperatures (70
and 90)oC. All the experiments were performed for Rayleigh number range (1.76*109 –
1.15*1012). The experimental data have been used in SPSS software to predicted the
empirical correlation of outside Nusselt number as a function of Rayleigh number by using
height of the coil as a characteristic length then using this empirical relation in a computer
program that have written in Fortran 90 to predict the outlet temperature and compared with
the measured one. The results show that the inner and outer heat transfer coefficients
increase with increasing of curvature ratio (d/D) and the mass flow rate. Also the results
show that the difference between the measured and predicted outlet temperature equal to
1.5oC.

This article includes the design and improvement of the performance of V trough tube
collector in solar heating systems by using hybrid nanofluids, when hybrid metal (Cu
(20nm) +Al (20nm) +DW), hybrid metal oxide (CuO (50nm) +Al2O3 (50nm) +DW) and
distilled water are taken as the working fluids. The effects of metal and metal oxides hybrid
nanoparticles are taken into consideration on solar hybrid nanofluid heating system. In
experiments two types of hybrid nanoparticles are used with volume flow rate (20 and 40
lit/hr) and four hybrid nanoparticles concentration ratios (i.e. 1, 2, 3 and 5 % vol). The
distilled water used as base fluid. The working fluid with the higher thermal conductivity in
V – trough tube solar collector could improve heat transfer compared with that of distilled
water. The hybrid nanofluids (Cu (20nm) +Al (20nm) +DW) at 5 % vol and volume flow
rate (20, and 40 lit/hr) indicated significant effects through the thermal solar characteristics
values of FR(τα), – F RUL
were 0.524, – 7. 276 W/m2. K, 0.551 and – 7.423 W/m2.k, while
the hybrid nanofluids (CuO (50nm) +Al2O3 (50nm) +DW) were 0.473, – 6.183 W/m2. K,
0.492 and – 6.224 W/m2. K. The synergistic between nanoparticles and type of hybrid
nanofluid are a key factor for heat transfer improvement, and improve performance of (V)
trough tube solar collector. Use of hybrid nanofluids (Cu (20nm) +Al (20nm) +DW) and
(CuO (50nm) +Al2O3 (50nm) +DW) as a working fluid could improve thermal performance
due to high thermal conductivity for copper and aluminum. At high inlet temperature, this
kind (V trough tube) of solar furnace could improve the thermal performance by hybrid
nanofluids compared with distilled water.

Conventional and ultrasonic fatigue testing is usually conducted under axial or
rotating- bending loading. In spite of the differences in shape and design of the fatigue
specimens, the stressed volume plays a mutual role in assessing the fatigue life. This is due
to the fact that the probability of finding voids or inclusions, which are the sources of
cracks, increases as the stressed volume increases. The fatigue life of bearing steel generally
extends to the Giga cycle regime so conducting such fatigue testing in the laboratory is time
consuming and costly. In this work, a model based on neural network techniques has been
suggested to predict the fatigue strength of bearing steel. The input data for this model
includes hardness, the stressed volume, stress ratio and number of cycles. The model
captures reasonable trends and is able to estimate unseen experimental results on high
strength bearing steel AISI 52100. Extrapolation has been conducted for the rolling contact
fatigue life and the results show good agreement with the experimental data.

In this paper, (Nylon-6) spider-net containing (dioxide titanium) nanoparticles were
electro spun to produce nanofiber membrane with (TiO2 NPs). Characterization of the
nanofiber membrane containing (TiO2 NPs) were done by (SEM) and (EDX) analyses.
Pure (Nylon-6) nanofibers with an average diameter of (139 nm) were produced while
(TiO2) additive gives membrane (Nylon/TiO2) with an average nanofibers diameter of
(123 nm). (TiO2 NPs) with small amounts in (Nylon-6) solution were found which
improve the hydrophilicity (antifouling effect) with water contact angle (5.7؛), pure water
flux (4800.45 Lm-2h-1) and mechanical strength (7.075 MPa). It was concluded that
(Nylon-6/TiO2) antimicrobial (spider-net) which considered as a composite membrane
with antifouling effect can be used in water filter applications. An improvement in the
produced membrane mechanical strength was reached, also, rejection test of salt was
achieved with rejection percentage of (76) and (71) for (Pb(NO3)2) and (NaCl)
respectively.

A theoretical analysis of a proposed variable stiffness model of the suspension system is
studied to improve the traditional suspension system. The fundamental idea of system
focused on variable stiffness mechanism by added subsystem to suspension system
depended on control rotating arm balancing the force between sides, it consists of a vertical
control strut. The variation of the load transfer by rotate arm has spring and damper at
another side of it where the point of rotation is supplement the body of car by sup-system
as vertical support. The investigations of the variable by addition stiffness to the suspension
system for improvement of performance better than the variable stiffness systems for
equivalent or traditional. The expending principles to described the performance of the
characteristic behavior of system are fewer car body acceleration to ride comfort and lower
suspension and tire deflection for road holding considered.