Iraqi journal of mechanical and material engineering

The research treats the problem of slump(as a type of creep) under self weight, that thermostone suffers during manufacturing process because the large dimensions and viscoelastic properties that the material has. Chemical composition and the percentage of added elements, especially the Gypsum and their effect on slump problem are studied using a practical method. The viscoelastic solution is applied here by Finite Element Method using the suitable model and taking with care the phenomena of aging. The viscoelastic solution is compared with the practical results for several stages of adding Gypsum.

A porous bearing with misaligned journal and non uniform permeability has
been investigated through the present work. The Reynolds' boundary condition has
been used to determine the boundary of the effective oil film. Two types of
misalignment, axial (vertical displacement) and twisting (horizontal displacement)
with different values have been adopted. Two models are considered to analyze a
finite porous bearing with misaligned shaft and non uniform permeability. In the first
model the permeability a cross the radial direction has been varied, while in the other
model the axial permeability has been varied. Effect of different supply pressure and
misalignment are investigated for a particular bearing permeability. It was found that
there is a slight effect to the supply pressure on the performance parameters of the
porous bearing. Varying the permeability in radial and axial direction cause an
increase of load carrying capacity with slight increase in coefficient of friction. It is
also noticed that the journal misalignment has a considerable effect on the bearing
performance.

Electrodeposited metal matrix/metal particle composite coatings (EMMC’s) were deposited, heat treated and characterized. Nickel matrix/ antimony particulate coatings deposited on Inconel 600 substrate (Ni-base superalloy) was chosen as a model system. The microstructure of the plated and heat treated coatings was characterized using light optical microscope (LOM) and X-ray diffraction analysis (XRD).
Results showed that Ni5Sb2, Ni3Sb, and NiSb phases are presented in the coated layer. Further NiSb is a good source for Sb2O4 compound formation under open heating. This oxide has good stability at high temperatures

The effects of variations in the thermomechanical treatments parameters on the microstructure and mechanical properties of Al-Cu-Mg alloy plates used in aircraft structure subjected to a post heat treatments have been conducted. It was confirmed that a large gain in fracture toughness combined with a good mechanical properties could be achieved by choice of the correct initial condition, amount and temperature of deformation, and the time temperature of the final age hardening sequence. In general, it was found that the material should be age hardened to the peak hardness conditions before deformation at an elevated temperature (warm rolling at 200°C) in order to prompt homogeneous slip. Room temperature deformation resulted in planar slip at the peak hardness conditions non uniform response on subsequent aging and give lower fracture toughness.

Due to increasing the importance of search about materials which have the
capability to resistance generated flame from fires and in the same time acts as an
insulator material so, this research introduced a material combined between these
characteristics.
In the present research, the preparation method of an insulator material, which
composed of phenol – formaldehyde reinforced by carbon fibers up to 40% weight
percentages, was expressed, as well as described thermal and mechanical properties.
Thermal erosion test was indicated the performance of the insulator material
efficiency to thermal insulation and flame retardancy. Thermal Erosion rate is
0.166mm /Sec.
Mechanical properties (compression test, impact test, flexural test) indicated high
toughness of insulator material.

The present work is a theoretical macro mechanics study, which concentrates
on linear viscoelastic creep behavior of short fiber reinforced polymeric composite
materials to estimate their flexural creep modulus at constant room temperature and at
a time range of 1 to 109 seconds. The loading cases are concentrated and the
deformations have been limited with small strains without permanent deformation. A
three-parameter model is used as a mathematical viscoelastic model. A finite element
program in Quick Basic had been designed to obtain the flexural creep modulus.
Halpin-Tsai equation shows an improvement in the modulus values for composite
materials reinforced with short fibers in both aligned and random reinforcement
through flexural creep estimations. On the other hand, the modified rule of mixtures
shows a slight effect of reinforcement on this property.

This study is used to compute the primitive variables of moderate supersonic flow
based on finite difference computational fluid dynamic methods. The problem
considered deals with a three-dimensional external, inviscid ,compressible supersonic
flow over a three-dimensional arc circular bump. In this work, Euler equation was
solved using time-marching MacCormack’s explicit technique. The flow conditions
are taken at sea level and Mach number at 1.97. To deal with complex shape of arc
circular bump the so-called “body fitted coordinate system” were considered and the
algebraic methods were used to generate grids over an arc circular bump. The results
showed a good agreement with other published results.

The dynamic behavior of a two phase (gas-solid) flow in a horizontal pipe is
studied in this work. The experimental and theoretical methods are set to examine the
effects of inlet velocity, loading ratio for different sizes of solid particles on the
pressure, velocity and the volume phase fraction along the pipe .The range of
velocities used in this work are between (12-42 m/s) and the loading ratios are
between (2-12) as mass of solid to mass of air. The solid is the sand at four groups of
particle size (150-300 m ), (300-425 m ), (425-600  m )and (600-850 m ).
The experimental rig is constructed to measure the inlet velocity and pressure along
(3.175cm) diameter (6m) long horizontal pipe. The results show that the loading ratio
(LR) and Reynolds number (Re) are the main parameters that control the pressure
drop along the pipe. The pressure drop increases as both Reynolds number and
loading ratio increase whereas the effect of particle size is opposite to that effect. The
pressure drop for a small particle is less than for the larger one. The empirical
correlation that relates the friction coefficient (Cf) through the pipe is represented
by the dimensionless groups (Re), (volume fraction, ) and (Froude number, Fr).
-1.356 -.809 0.125
exp  9.737  Re Fr Cf
The theoretical analysis consists of the solution of the steady state and the
unsteady state of the differential equations using the boundary conditions that govern
the two phase (gas-solid) flow GSVF is the computer program that was build to
simulate the dynamic behavior of the flow involved in the semi-empirical correlation
for (gas–solid) interaction (Sa). The dimensionless number (SR) suggested in this
work indicates that the volume fraction is the most effective parameter than Re and
Fr.
-3 0.848 -0.004 0.008
R S  5.310  Re Fr
The volume fraction, velocity and pressure profiles are evaluated as the output of
the computer program, only the pressure profiles are compared with the experimental
values. The pressure drop and the friction coefficients produced from the theoretical
analysis show that the theoretical values are (24%) higher than the experimental one.
-1.368 -0.681 0.077
Cf theo.  7.207 Re Fr

The research devoted the possibility of soft soldering ferritic nodular cast iron to
aluminum - zinc alloy, by using filler metals ASTM 60A, 40A & 70A. Cast iron was
electroplated with iron and tin, while aluminum was coated with different layers of
zinc, zinc-copper, zinc-copper-tin, zinc-copper-nickel and zinc-copper-nickel-tin. The
specimens were fixed in the overlap position, and heated in a furnace to temperatures
suitable to the soldering alloy in different holding times 5, 10, 15, 20, 25, 30 & 40min.
The bond on the aluminum side could not be achieved when it was immersion coating
with zinc while electroplating aluminum with copper over the zinc gave shear strength
of 7MPa at 30min. holding time, using 60A as soldering alloy. Electroplating another
layer of tin on aluminum increased shear strength to 11MPa at the same holding time
and soldering alloy. While electroplating with nickel layer on the aluminum after
zinc and copper layers gave shear strength of 10MPa. Adding fourth layer of tin on
aluminum helped increasing shear strength to 23MPa . Using 40A as a solder alloy
with the same two plated layers on cast iron and the four layers on aluminum gave
shear strength of 14MPa while 70A solder achieved 13MPa at holding time 25min.
The microstructure examinations show the formation of intermetallic compounds on
both metals while the X-ray diffraction test shows the formation of FeSn and FeSn2
phases on the cast iron, and ε-Cu3Sn, η-Cu6Sn5 and γ-NiSn, δ-Ni3Sn4 on the
aluminum, which are responsible for the bond.