Design of experiments (DOE)
had been used in the study, and the results had been evaluated by the
surface response method. The results showed that the welding
current is the main parameter by its effect on the mechanical studied
properties and the parameters values which give the best responses
had been determined.
As a result of the industrial progress absolved by the world in all
fields, new materials have been produced that have excellent
engineering properties at low economical cost. Therefore, we have
done this research by greening a composite material with a metal
base (aluminum 6061) reinforced with stainless steel wire A304.
Aim: to compare NiTi hand instruments with Stainless- steel instruments according to separation, deformation and changing of working length during preparation of curved root canal in extracted teeth.
Materials and Methods: 24 of curved root canal we
re randomly divided into two groups. One group was prepared using stainless steel instruments and the other prepared by NiTi instruments. Separation and deformation of the two hand instrument systems were determined and the changing of working length during preparation were registered and compared. Data were collected and stastical analysis were conducted.
Results: Stainless steel system showed more separated and deformed instruments, but there were no significant differences between two systems. Also, change of working length was happened with stainless steel only but without significant differences with NiTi.
Conclusion: under the conditions of this study, it can be concluded that two hand instrumentation systems separated and deformed with no differences . However, working length was changed during use stainless steel but without differences between two system.
The aim of this work is to study the effect of the aging heat treatment on the pitting corrosion resistance of martensitic stainless steel. In this research a number of specimens from martensitic stainless steel were subjected to solution treatment a
t 1050 for one hour followed by water quenching then aging in the temperatures range (400-750) for different holding times (1-16 hrs).
After heat treatment, two types of corrosion tests (accelerated test and immersion test) were conducted. The results obtained in this research showed that the pitting corrosion resistance was
affected by Aging temperature and three critical temperatures were found in corrosion test: the
specimens aged at 475 0C had maximum corrosion rate. This may be due to the presence of stringer δ-
ferrite and precipitation of very fine precipitates which precipitated heterogeneously in the martensitic
matrix, which led to an increase in corrosion rate. The specimens aged at temperatures range (550 – 625) 0C had minimum values of corrosion rate, this is attributed to the high volume fraction of retained austenite. The specimens aged at temperatures above 625 had intermediate corrosion rate.
The type of pits, which resulted from two pitting corrosion tests, was independent form the form of δ-ferrite and carbides which presence in microstructure.
Aim: to compare the shaping ability of NiTi hand instruments with Stainless- steel instruments in preparation of curved root canal in extracted teeth.
Materials and Methods: a total of 24 of curved root canal were randomly divided into two groups. O
ne group was prepared using stainless steel instruments and the other prepared NiTi instruments. Curvatures pre-and post instrumentation were registered and compared. And straightening of the canals were determined by autocad analysis system.
Results: two systems were significantly changed the original canal curvature with no differences between both systems. However, the time required to finish preparation was significantly less with NiTi system.
Conclusion: under the conditions of this study, it can be concluded that two hand instrumentation system changed the original canal curvature, but the time consuming to finish the preparation was less with NiTi hand system.
When we visited the United Arab Company for Spinning and Weaving In the capital, Damascus, we found
a lot of problems in the units of feeding steam, and the most prominent of these problems occur corrosion
in the pipe of steam boilers, And the coll
apse in the heat exchanger on the thread dyeing machine (the
collapse of the body and pipes), so we took a group of samples in the places that suffer problems in order
to determine the mechanical and chemical properties, we found through analysis that the boiler tubes
were made of carbon steel, while the tubes and the body of heat exchanger was made of stainless steel, has
been shown through research that pipe boilers of carbon steel suffers of problems as a result overheating,
hydrogen damage and an attack Oxide, And the body of heat exchanger was suffering from an corrosion
Cracking result of the high proportion of chromium in it (chromium ratio up to 17%), has been
developing a set of solutions represented to be the metal surfaces clean and homogeneous, and must be
feed water free of salts, suspended solids, and gases
Welded joints corrosion phenomena for some kinds of stainless steels and nickel alloy was studied in
polluted phosphoric acid 37.7%H3Po4 using electrochemical techniques like Tafel polarization. Corrosion
rate of base metal and weld metal had calcu
lated & compared among these alloys.
Laboratory Test results showed the change in both corrosion rate and corrosion current densities (Icorr)
for tested alloys, and there is a clear difference between base metal and weld metal in most of tested alloys
, which lead to high corrosion rates of welded joint, and change in its properties then gets out of service in
some service conditions. The stainless steel 904L has low corrosion rates and low difference in corrosion
rates between base metal and weld metal, so it may be the most suitable alloy, among all the studied
alloys, for exploitation in polluted phosphoric acid 37.7%H3Po4 produced at the General Fertilizer
Company in Homs city.
This research showed the great importance for following studies of the effect of polluted phosphoric acid,
produced in General Fertilizer Company, on the high corrosion resisting alloys, to reach suitable alloys
for equipments and machines used for
its production, because of its high corrosion rates that create many
corrosion problems in these equipments and machines.
Ligating between brackets and orthodontic wire is considered
one of the important factor affecting the frictional resistance during sliding
movements.
Aim of study: For these reasons this investigation aimed to compare the
friction associating wi
th sliding movement for two types of brackets : selfligating
brackets and conventional brackets ; along stainless steel arch
wires.
