Iraqi journal of mechanical and material engineering

This work aims to prepare a composite material based on epoxy resin reinforced by fiber
and dust particle from low carbon steel with various volume fractions and so, studying their effect
on tensile and flexural strength.
Fibers from low carbon steel, with 0.20 mm in diameter and low carbon steel dust particles
were used as reinforcement with a volume fraction of (0.8, 2.4, 4.0, 6.2, and 8.3 %).
The results showed that the tensile strength increases as volume fraction increases, for both
cases. But the reinforcement by dust particles has more tensile strength than fiber reinforcement.
For example, at volume fraction 0.8 %, the tensile strength of fiber composite was 135 MPa,
whereas tensile strength of dust particles was 158 MPa.
Also the results of flexural test show that the flexural strength increases as volume fraction
increases, for both cases, but in low carbon steel dust particles / epoxy composite, the flexural
strength reaches a maximum value 417.23 MPa at volume fraction 8.3 %. This value is higher than
that of low carbon steel fiber / epoxy composite.

The solution of Composite Spherical Shells subjected to different external loading and boundary
condition are investigation and analysis by the application of the classical composite-material
theory. In this research are used Chebyshev series in matrix form to reformulate the differential
equations of equilibrium of a composite spherical shell . Two problem are solved by using
Chebyshev theory, the first problem are solved laminated spherical shell under uniform external
pressure with open ( o=10o) , the results obtained for maximum stress is (5.298-5.563 N/m) and
maximum moment is (1.189-1.99 N.m/m).The results are compared with available published results
and confirmed mach well. The second problem is solved for a supported shells under unite edge
line load with different ( o=30o and 80o ), the results is seen the stress for laminated composite
shells concreted near the pole or near the equator and the bending is localized around the edges.

This research is concerned with the study of the effect of tempering on the fatigue strength of
medium carbon steel (CK 45), by using different heat treatments including quenching in water and
oil followed by tempering at (250, 450 & 650) oC comparisons between the effects of two mediums
on microstructure, mechanical properties and fatigue strength for each quenching media . The
fatigue tests have been done under constant amplitude stresses with a stress ratio (R=-1). The
experimental results reveal that water quenching followed by tempering at 250 oC (1 hr) gives
maximum fatigue strength for steel, and this is due to the formation of tempered martensite. Long
fatigue cracks have been measured and studied from using fractography of fatigue specimens
(SEM). Two models have been to proposed to assess fatigue lives of quenched and tempered
medium carbon steel at different tempering temperature . The first model was derived from the
fatigue crack growth rate equation (da/dN) while the second model was extracted from the stress
intensity factor equation ( ) K .

This research deals with the effect of using additional boundary conditions as well as
the eccentricity ratio on the axisymmetric free vibrational characteristics of thin isotropic
oblate spheroid shells. The formulation depends on the boundary matching method using
the non – shallow shell theory. The oblate shell was assumed to be constructed from two
spherical elements matched along the continuous boundaries. The additional boundary
conditions under construction were clamped – clamped, clamped – free and pined – pined. It
was found that the natural frequency of the shell with clamped – clamped additional
boundaries was greater than other two types of the additional boundaries. On the other hand it
was found that in the case of clamped – clamped boundary condition, the eccentricity ratio
has an effect on the natural frequency greater than the other two cases, i.e, clamped – free and
pined - pined cases, respectively.

This work represents an attempt to decrease manufacturing cost and to increase thermal
stability and fatigue life of (8009) aluminum base alloy. The alloys were prepared by a single step
die casting followed by rapid cooling (instead of the usual five stages forming). A microalloying
element (Zr) was added. The study adopted several techniques to improve properties including
certain metallurgical variables and mechanical treatments of surfaces. Several tests were carried out
to evaluate the performance of alloys, such as thermal stability, and fatigue strength tests before and
after surface mechanical treatments (shot peening by ceramic balls), density measurement and
metallographic examination.
Results showed that the prepared alloys are thermally stable. The addition of (0.2% Zr)
was associated with an increase in fatigue strength by (147%) corresponding to the base alloy at
low stress cycles (140 MPa) and (93%) at high stress cycles (300 MPa). Results also showed that a
period of (180) seconds for shot peening by ceramic balls gives the best surface mechanical
treatments. An improvement of (150%) and (124%) in fatigue life of (AlFeVSiZr) and (AlFe
VSi) alloys was observed after the surface treatment, when, subjected to low stresses (140 MPa).
At high stresses (300 MPa), however, the improvement was (139%) and (118%) in fatigue life of
the alloys respectively.

In this paper the bending behavior of composite plates manufactured from polyester
reinforced with fiberglass, jute fiber and eggshell powder is studied .The moisture effect on the
plate bending behavior is investigated by immersing the specimens in salt water and distilled water
for 7 days. Also the effect of type of edges fixture on the central displacement of the plate is
investigated. The results showed that for the fiberglass composite plates the central displacement for
the moist specimens is 3-4 times as that for dry specimens. For the eggshell powder composite
plates, it is found that the stiffness of the dry specimens is greater than that of moist specimens by
about three times. The moisture absorption shows no significant effect on the stiffness of the jute
composite plate.

This work deals with the preparing of composite materials based on aluminum alloy (2024)
and reinforcement materials particles of silicon carbide and graphite powder . Silicon carbide are
(3,5,7 wt%), whereas the proportion of the graphite was certified at (3wt%) . All samples
adopted in this work are prepared by stir casting The results have shown an increasing in mechanical properties such as ultimate tensile strength , Yield strength, Hardness and compressive strength at the expense of ductility for composite material with increasing reinforcement materials content.

Laminar natural convection heat transfer and fluid flow due to heating element inserted at
different positions over the inclined side wall of equilateral triangle enclosure has been analyzed
numerically in this study. The enclosure has filled with air as a working fluid with Pr=0.71. The
walls of the enclosure are insulated except an element on one side where the heat flux are applied.
The value of heat flux ( q" ) are 10, 30, 70 and 100 Watt with corresponding Rayleigh number of
105, 106, 107, 108 respectively. The length of the heating element was taken as 10% of the triangular
enclosure side wall length where the length of the wall equals to 10 cm. The governing mass,
momentum and energy equations are applied to the enclosure and solved by finite element using
commercial code (ANSYS 5.4) based on TDMA method. Three different situations (normal, side
and inverse) of the triangular enclosure with different positions of heating element are examined in
this study to obtain the maximum stream function. The results show that the maximum value of
stream function and high rate of heat transfer occur for normal situation of the enclosure and when
the heating element is applied at position2 (Po.2 is a distance over the inclined side wall which
takes a position limited between 0.2L to 0.3L from the edge of the triangle enclosure).

An investigation was carried out to study the effect of various parameters on crevice corrosion of
two different type geometry of ( rod, square) 304L stainless steel in 3.4% NaCl solution under static
conditions at different temperatures (25, 50) C°, rotation cylinder electrode was used for 100, 200
rpm at the same temperatures. It was found the maximum attack was in square 304L SS at 50 C°
under static conditions in account of geometric of specimen whereas slightly effect as the velocity
increases due to the passive film is formed on the steel surface. In contrast, the results show the
effect of temperature changes and velocity on corrosion rate in rod 304LSS is more pronounced as
temperatures and velocities rises enable the migration of chloride ions into the crevice.

The basic goal of fracture fixation is to stabilize the fractured bone, to enable fast healing of
the injured bone, and to return early mobility and full function of the injured extremity [1]. The
computerized tomography scan slices of the femur bone of one patient were translated to the
ANSYS V.(10) program and then the solid model (3D) model was built and analysed by the finite
element method under different loading conditions for each method of fixation. Finite element
analysis would help to reveal stress pathways across the shaft of the femur bone and the sites of the
8 screws or pins fixed at the shaft of the femur above and below the fracture site.
In the internal fixation method two types of screws' materials can be studied. Firstly
stainless steel and secondly cobalt chromium. The stress distributions were studied for each screw
material for different body weights. While in the external fixation method the stress distributions for
only stainless steel pins were studied.
The stress distributions for six pins or screws fixed at the fractured bone above and below
the fracture site for each method of fixation were studied.
The von mises stresses of the cobalt chromium screws fixed internally are less than the von
mises stresses of the stainless steel for each of the body weight. The stresses of the pins fixed
externally are greater than the stresses of the same screws fixed internally.
When decreasing the number of the screws or the pins the stress values will increase;
therefore when using eight screws or pins the stresses are less than those when used six screws or
pins for each method of fixation (internal and external).

Magnesium oxide with (5 µm) particle size with different Weight percentages (5%,15%,25%)
was added to conbextra epoxy (EP10) resin and measured the changing in thermal insulation to
this resin . Fourier equation was used to calculate the changing in coefficient of thermal
conductivity (k) for conbextra epoxy (EP10) before and after addition of magnesium oxide ,where
the results show improved thermal insulation of the resin by reduced in thermal conductivity
coefficient value after oxide addition , and the value of thermal insulation will increased with
increasing of additive percentage of magnesium oxide ,where it change from(0.24 W/m.ºC) before
added oxide to (0.16 W/m.ºC) after addition (25%) from oxide at temperature (40 ºC) which the
best value from oxide additive.

Samples of FRP prepared by applied unsaturated polyester resin as matrix reinforced by one layer
woven glass fiber( 0º/90º), using hand lay up method. The prepared samples are subjected to
thermal aging at 85 º C for different time in dryer oven up to 1200 hrs time and tested by
unnotched sample impact tester to obtained the fracture toughness , polynomial relationshape of
order 5 found between Gc and Aging time decreasing Gc strongly to lower value .The Stress strain
tests for aged to specific time and without aging samples by tensile test show that sample aged
thermally tend to brittle behavior and lost its mechanical properties as aging time increase, while
sample without aging show ductile behavior . FTIR analysis show decomposition of the polyester
by creating new free radical and observed new peak wave number in Transmation spectra due to
fiber crystallization.

The yield strength of Low/Medium Cr- Mo ferritic steels has been analyzed by a well selected
artificial neural networks (ANN) model using data sets obtained from ASTM publications. The
qualitative and quantitative effects of chemical composition, heat treatment and test temperature
have been studied. The proposed ANN model was obtained by applying averaging process to the
first best three models. The first one consists of 24 input nodes (the input variables), 23 hidden
nodes and the output node which is the target for the required yield strength. Among the previous
variables, it was found that the heat treatment ones have the greatest contribution to the yield
strength especially the tempering one i.e. the average contribution of about 15% was obtained.

In this work, simulation of fusion welding technique to estimate the cooling curves and
temperature distribution in submerged Arc (SA) welded workpiece was assessed. Numerical
analysis by using Finite Volume Method (FVM), applied to three-dimensional heat transfer model
to determine the cooling curve in weld metal zone. There is no reliable method for calculation such
cooling rate as a function of welding current, voltage speed and arc transfer efficiency in metal
joint geometry. Cooling rates are determined by affected of weld metal deposition in the fusion
zone at different welding speeds (22, 23 and 25) cm/min, with constant welding current at 500 Amp
and 40 voltages. The joint geometry of single-V- butt joint with one pass are used for half plate
dimensions (150×150×18) mm, fixed with standard geometry of (ISO-2560). Cooling curves
model which is confirming the capability and reliability of weld metal deposition in fusion zone
with different welding speeds. The optimization of filling area (weld metal deposition) by FVM is
determined in each welding speed having correct welding current to filling cell of weld area.