Engineering and Technology Journal

The aim of the research is to study the influence of heat treatment temperature on
mechanical properties and limit fatigue of steel CK35. Tensile, impact and fatigue
rotating bending tests with the mean stress estimated to zero. All the tests of heat
treatment were conducted which include heating the steel to 840 ºC and then quenching
by water and after that tempering at temperature of (200, 400, 600) ºC and then cooling in
air, show that the temperatures of heat treatment improve the mechanical properties and
fatigue limit before and after heat treatment. The change in microstructure of steel before
heat treatment (ferrite and pearlite) and after quenching martensite and martempering
(Trostite or Sorbite) microstructures. Shown that structural barriers that may help in
depriving the growth of the crack. The mechanical properties and fatigue limit were
improved. The electronic microscope slides-scanner (SEM) of the fractured surface
showed the fatigue cracks growth which may be formed under the hard phases and then
reduction in growth in the plasticity region

Dielectric constant (εr ) and dielectric strength (Ebr) of composite materials that
consist of Novolak reinforced with glass fiber, Novolak reinforced with asbestos
fiber and Novolak reinforced with (60%) ratio of glass fiber and asbestos have
been Studied. The specimens were made in different ratios of
Hexamethylenetetramine (HMTA) content of (10%) and (14%), Then a study
was made on influence of (HMTA) on dielectric constant (εr ) and dielectric
strength ( Ebr) of these speciments. It was found that permittivity (εr ) and
dielectric strength (Ebr) for composite materials are dependent matrix the types
and properties of reinforcing materials.
Then relation between dielectric constant (ε
r) and frequency and temperature
and percentage moisture absorption was studied. It was found that dielectric
constant increases when the temperature and percentage moisture absorption
increase, whereas dielectric constant (ε
r) is dependent on capacity of composite
materials

In this work, an optical method was used for the determination of the
crystalline orientation of the chemically etched silicon surfaces in the (111),
(110) and (100) planes. This method depends on the light patterns of laser
beam reflected from the monocrystalline surfaces. The optical method submits
acceptable measuring accuracy and well-distinguished folded patterns

In the present work, the electrical and photovoltaic properties of Sb-pSi
contact were investigated for the first time. Two creditable methods were used
to determine the value of barrier height for this contact. Experimental results
showed a reasonable agreement with the simple Schottcky-Mott theory. The
contact showed good response to white light when it works under bias
condition.

The paper presents a newly developed method depending on trace
polynomial with new algorithm which has been written in Matlab language to
modify the Gordon, Mills and Welch generator by increasing the complexity
of the output sequence to increase the security of this generator concerning
the designed feature that limits the ability of anti-jammer. Good results are
obtained compared with Gordon, Mills and Welch generator using
Berlekamp-Massey method for determining the complexity of the output
sequences. Moreover, this paper has the useful properties of the trace
function. Some examples are given of show conciliated the results of this
proposed method.

The spectral density analysis of the articulated vehicles is a subject of great
importance and it is widely applied in the area of vehicles design and safety.
So the vehicles when ride over rough roads, respond dynamically and
inadequate road holding may arise .This paper examines the ride safety of an
articulated vehicle over irregular roads through an analytical study .The
vehicle responses to road surface undulations are studied using spectral
density approach which is reviewed and then applied on a vehicle model to
obtain the dynamic wheel loads a the results are drawn from the classical
system and conclusions are drawn as to the applicability of this approach. For
loaded and unloaded articulated vehicles, it may be concluded that for
unloaded vehicle the danger of the departure of the wheel from the road is
higher than with the loaded vehicles

Tensile strength and hardness property were studied in an epoxy (DGEBA)
resin as a matrix reinforced with glass fibers for different volume fraction as
layers.
A comparison was done between woven roven samples, random layers
samples and sandwich composite samples which consists of (woven roven and
random). Finally the results show that the sandwich composite gives higher
tensile strength, while the composite reinforced with woven roven fiber has
maximum hardness values

The critical speed of hyperbolic disks for the selected model is calculated
in three different cases, anisotropic material and thermal case, isotropic
material and thermal case finally isotropic material and thermal with
generated heat case. The second case is found to be the best because the
critical speed occurs above maximum speed values.
For recognition of the eccentricity (e) effects on the stability, the original
bearings of the selected model were tilting pads bearing replaced by
adjustable hydrodynamic pads bearing. The results proved that stability
criteria (Sc), critical mass (Mc), whirling frequency ratio ( - 2
fn ) of variable
rotational speed of the adjustable hydrodynamic pads bearing are stable for
the range of eccentricity (e) about 0.02 mm to 0.09 mm. Finally the
thermohydrodynamic (THD) analysis of eccentricity ratio (e) has effects on
the stability of the rotor-bearing system

Glascrete" is known as a concrete in which the aggregates wholly or partially
consist of crushed glass, where the glass is a unique material that could be
recycled many times without changing its chemical or mechanical properties. It
has been used for certain purposes where the aesthetical aspect is one of the main
considerations.
This experimental work aims to evaluate the possibility of incorporating waste
glass in glascrete tiles, as partial replacement for the fine aggregate. Two
replacements were investigated, those are 20 and 40% by volume of fine
aggregate.
The tiles are assessed with regard to the requirements of the Iraqi Standard
Specification No.1042/1987, by investigating their modules of rupture and total
water absorption.
The results prove that glascrete tiles with 20% and 40%of glass aggregate as
partial volume replacement of natural fine aggregate are found to be acceptable
with regard to the requirements of the Iraqi Standard Specification
No.1042/1987.

In this paper, a porous silicon (PS) layer is investigated as a sensing material
to detect the organic vapors with low concentration. The structure of the
prepared sensor consists of thin Au /PS/n-Si/Au thick where the PS is etched
photo -chemically. The current response of the sensor is governed by the
partial depletion of silicon located between two adjacent (porous
regions).This depletion is due to the charges trapped on dangling bonds
associated with the silicon – porous silicon interface