locomotive wheel slip in railway transport is a very actual problem for operation
process especially on the main tracks and tracks between industrial oil company and
power- generating stations, which always need to supply by oil products.
This res
earch included the conclusion of the reasons leading to the occurrence of the
event wheel slip as well as study the technical reality of the work of sand management
system in the locomotives and conduct analyzes and assessments of the substance sand
used to overcome such situation with the suggestion of suitable alternatives to raise the
adhesion coefficient between the railway wheels and improve an operating circumstances
animation tools Line.
Other causes include the contact of oil with the flanges and rims of wheels, which
reduces adhesion with the surface of the rails, and a general loss of traction on steep
gradients when pulling heavy loads.
In This research a surface hardening process by Ni coating and
subsequent diffusion heat treatments was studied at Al7075 alloy.
Nickel coatings with different thickness were obtained.
Introduction :The demand for posterior aesthetic restorations has dramatically
increased in recent years. Several new materials have been developed with improved
aesthetic, adhesive and mechanical properties.
Theoretically, nano-structured dental
resin omposites are purported to have increased
wear and hardness resistance compared with hybrid composites and may favor the
achievement of restoratives with better long-term performance.
Aim: The wear resistance of different types of resin composites were evaluated in
the in vitro study.
Material and methods :Two nanohybrid restorative composites -Tetric®EvoCeram
(Ivoclar-Vivadent) and CeramXTM(Dentsply) - were compared with a microhybrid
material - Tetric®Ceram (Ivoclar-Vivadent) and hybrid material Spectrom (Dentsply) .
wear resistance : fifteen specimens (3x3 mm) of each material were subjected to
wear tests .
The data were analyzed by 1-way ANOVA(<=0.5).
Results :
The Tetric®EvoCeram composite resin exhibited significantly less wear than the
CeramX and Tetric®Ceram material .
Conclusions :In terms of wear resistance, nano-structured composites may perform
either similarly or comparatively
better than a microfilled and hyprid composite .
nanohybrid restorative composites can thus be considered as a good restorative
material.
The main goal of maintaining and repairing equipment and machines during the
investment stages is to reduce the amount of money spent in order to maintain the validity
of their operation and the quality of their reliability under the different give
n investing
conditions (type of manufacturing materials, methods used, temperatures, nature of
investment, …. etc).
This goal can be achieved if we are able to control changes in the technical
conditions of equipment and the frictional parts during the investment stages, besides
knowing the physical laws/rules that govern the technical changes properly. Therefore, we
carried out a study on the theoretical plans of physical wear of brakes and the frictional
parts in means of transportation. This is done starting from wet (oily) wear plans of the
frictional parts in machines. Then, based on these plans we studied physical laws/rules
determining the intensity of dry wear of brakes, along with its speed and acceleration
during the investment and the unreliable, uneconomical (unsafe) operation stages, taking
into consideration the methods used in periodical technical maintenance, ways of driving,
and the average number of times brakes are used…etc .
Based on these formulas obtained, we can estimate/predict the start of ineffectiveness
of brakes and friction linings, in addition to the inception time of risky (unreliable)
operation stage. Consequently, this stage gives us indications for replacement or treating
with the traditional (known) mechanical and chemical ways, in light of the soaring prices
of materials in the Syrian Arab Republic.
A new group of Z n - Al alloys suitable for casting was developed in the late sixties, These alloys are
ZA - 8 , ZA - 12 and ZA – 27, where the numbers represent the approximate percentage of aluminum in the alloy. These alloys compete with cast iro
n and copper alloys and aluminum alloys. ZA – 27 alloy is characterized by the biggest strength and lowest density alloy from the rest of ZA alloys. It has
good physical and mechanical properties (good strength, good cast ability, ease of machining, good wear properties and high corrosion resistance).
This research is aimed to study the effect of heat treatment on mechanical properties as well as to improve the wear properties of ZA-27alloy.
Heat treatment of type T4 was applied on ZA-27 alloy (This treatment was done by heating the alloy
to a temperature equal to 370 oC for a period of 3 or 5 hours and then immersion in water followed by
natural aging for 30 days).
Wear testing has been made by using dry sliding test of pin samples on the disk - ZA – 27 alloy after
casting without any treatment and wear tests were performed on heat treated ZA – 27 alloy samples.
The microstructure of the alloy after casting and after heat treatment was examined and the effect of
the microstructure on the wear behavior was studied.
The hardness and tensile strength of heat treated samples were reduced while elongation was increased
compared with alloy after casting. The rate of decrease of hardness was equal to 34.7 %, which is
consistent with solutionizing period. On the contrary, the increase in the solutionizing period decreases strength and increases elongation. The study shows also that the heat treated samples have achieved a significant improvement on wear properties compared to the samples after casting without heat treatment
This study includes an experimental work to determine the effect of ultraviolet radiation (uv-rays) on the mechanical behavior of the conveyor rubber vulcanizing, which used in various transport operations, and in the cement plant Tartus. In this wor
k, it has been prepared different samples of belts, and they were exposed to uv radiation at differente times, then they were tested to know its wear and tensile strength.
The results were compared with samples similar to the samples tested, which was not exposed to the rays of UV, and with other samples exposed to temperatures, and that in order to reach the ideal conditions for the use of these belts, which ensures longer period of use and safe conditions. This study showed that uv-rays increase the average of wear and the tensile strength of belts.
This study deals with the friction and wear behavior of coating layers (fluoride and Graphite).The coatings are thermally sprayed on cast iron disks. Sliding is performed between cylindrical pins manufactured from organic brake linings and the coated
and uncoated disks. The coatings are characterized by measuring their hardness, porosity, and corrosion resistance. The corrosion resistance of the coating is tested by exposure to Nacl for 150 hours; the coating layer has had the best corrosion resistance. The friction and wear tests are conducted under contact pressures of (1.5 MPa to 7 MPa) and sliding speeds of 1 and 3 m/sec.
This research is aimed to verify the statement of pavement structural design and construction of bituminous concrete mixture which is used on wearing layers in roads and highways in Damascus city.
It's clearly found that many of these bituminous con
crete mixtures were far - away from standards and specifications regards to flexible pavements such as aggregate gradations, Marshall Stability, bitumen content and Marshall flow. The role of highway statements authorities who deal with pavement
design and supervise the construction is quit necessity.
Finally test results of cores taken from several roads in Damascus city were analyzed and compared with the designed mix «original» test results which was done in Damascus University labs.
