Due to a combination of optimal properties such as great strength, high hardness, good process ability, and good mechanical properties, AISI 4340 steel is widely used in many critical industrial applications such as nuclear, military, defense, and aerospace. It is also widely used in hydraulic forged machine tools, forged automotive crankshaft systems, shafts and gears, because of their improved characteristics, and its good tribological properties. The purpose regarding this work is to check the tribological characteristics of austempered AISI 4340 steel while dry and lubricated with machinery oil of SAE 30 grade as base oil. As received, AISI 4340 steel samples have been austempered to four definitely austenitic phase temperatures (850℃, 900℃, 1000℃, and 1050℃) for 90 minutes before being immersed in a mixture of potassium nitrite and sodium nitrite at 400℃ for 45 minutes. Friction and wear tests were then performed on austempered samples. Multi-walled carbon nanotube particles were blended at weight concentrations of 0.055, 0.1, 0.15, 0.20, 0.25, 0.30, 0.35, 0.40, and 0.45 with typical machinery oil of 30 grade as base lubricant oil. A pin on the disc wear configuration was used in the experimental investigation. The use of Multi-Walled Carbon Nanotube (MWCNTs) additives in the base oil resulted in a decrease in both friction coefficients and wear rates values when compared to typical base oil lubricant. The results also showed a reduction in both friction coefficients and wear rates as the sample's austempering temperatures were raised. Sliding surfaces were also photo micro graphed, and when the volume concentrations of Multi-Walled Carbon Nanotube particles in the normal base oil lubricant were increased, smoother surfaces with less damage were shown.

In this research, three mathematical models were designed, the first consisting of concrete, the second from carbon fiber, and the third from s-glass fiber, in order to compare the strength of composite materials to different stresses and deformations, because composite materials are better than concrete in terms of weight and shape and do not need to be applied to painting operations in addition to the fact that their thermal insulation is higher than Concrete in high proportions. From the results of the comparison, it was found that the second model was the best model in terms of bearing deformations, as the deformation percentage in it did not exceed the deformation of concrete a lot, reaching (17%), which is a very small percentage, and the stresses towards pregnancy for the second and third models were much better than the bearing of the first model, but the results indicate that the Von Mises Stress in the second model is higher than the first model by a percentage (57%), while the comparison of the third model with the first was the rate of increase percentage (47%).

Many mechanical parts are exposed to failure as a result of mechanical stresses for design or metallurgical reasons, and the phenomenon of fatigue represents the largest area and reaches (90%) of the faults of engineering parts that are subject to periodic stresses. The risk of fatigue failure occurs without warning, so the phenomenon of fatigue resistance has taken up a large part of the research and studies concerned with the dissolution of metals. This article aims to study the effect of fatigue resistance of ASTM 1050 steel. Carbonation, repeated quenching at different temperatures (780 & 770℃) using seven different solutions, and tempering at repeated tempering after each quenching at temperatures (230 & 250℃). The stress resistance of all the studied samples decreases after the second cooling in distilled water, with the exception of the samples that were initially quenched with the same solution and then quenched again. This is one of the most significant findings. Another finding is that following a second chilling in distilled water-based solution, the resistance to fatigue stress rises, increasing by up to (8.5%) in comparison to samples that were first quenched in the same solution then diluted.

The following chapter study the friction stir processes (FSP) is used to improve the surface characteristics of the alloy AA6061-T6 on the surface topography, hardness, tension mechanical characteristics, and microstructures of aluminum alloy, the impacts of friction stir process tool travel and rotation speeds were investigated. All friction stir processes (FSW) in this investigation used a cylindrical tool without a pin that had a 20 mm diameter, rotated at different rotating speeds 800, 1000, 1250, and 1600 rpm, and at different travel speeds 32, 63, and 80 mm per minute. The examination of the current study’s data and the test results showed that in stir friction processes, hardness rises with cutting depth. The study of the crystal structure showed that the hardness increased by twice as much for two stages as it did for one stage. Additionally, it was observed that as cutting depth increased, the size of the granules representing engineering defects grew smaller. Additionally, in the case of two stages, the ratio of granule size to friction was twice as high as in the case of one step. According to the results, using a single-stage friction stir process increased yield strength by 18% and tensile strength by 9.5%, while using a two-stage friction stir process increased yield strength by 20.4% and tensile strength by 11.5% when compared to metal basis.

The beams are frequently utilized in construction as well as in the fabrication of vehicles like as trains, ships, and airplanes. Depending on the necessary working circumstances, several materials may have been utilized in the production of these beams, from high fatigue resistance, high corrosion resistance, strong earthquake resistance, and other aspects. As a result, composite beams made of glass or carbon fibers are increasingly commonly employed. This is a result of its strong collapse resistance, light weight, and strong fatigue stress resistance. In order to compare the models' resistance to deformations, stresses, and strains that they are exposed to during loading, this article focuses on constructing a variety of models using a variety of composite materials and shapes. The outcomes demonstrate a rise in the rate of deformation. against beams with linear shapes in those with non-linear shapes. Additionally, the findings demonstrate an increase in stresses and strains in regions with curves (i.e., areas that are nonlinear).