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In this paper try with use of cryogenic cooling by liquid nitrogen damage such as surface roughness¡ micro cracks¡ surface oxidation and burns¡ as well as control the grinding force in grinding titanium alloy to get their minimum. In addition to the latest statistical techniques appropriate to the nature and effect of each of the grinding parameters (cutting speed¡ work speed and depth of cut) and the interaction effect of surface roughness on the output power of vertical and tangential force put to their optimal levels has identified. This paper demonstrates the use of liquid nitrogen as a coolant has a positive effect on reducing surface roughness and grinding forces¡ the surface also reduces the damages of the work piece and the titanium alloy surface oxidation during grinding to prevent. In addition¡ each of the parameters including¡ cutting speed¡ work speed and depth of the outputs of the paper¡ to be effective¡ for example by increasing shear rate increases the surface roughness and grinding forces are reduced¡ as well as increased depth of cut increases the surface roughness and forces.

Ti-6Al-4V titanium alloy has great application in medicine and military industries due to its capabilities, namely high strength to weight ratio and corrosion resistance. In the current research, the effect of aging treatment on microstructure and wear behavior of Ti-6Al-4V titanium alloy was investigated. Pin on disk wear test was applied to assess the wear behavior. Specimens were first solution treated at 950C and 1050C and then were quenched and aged. Some specimens were annealed before aging at 700C. The results showed that aging treatment resulted in the hardness increase and the wear resistance decrease. It was also observed that annealing treatment before aging, enhanced the martensite decomposition and the formation of α2 particles, and correspondingly resulted in more hardness and lower wear resistance. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) analyses confirmed that presence of hard phase α2 particles within soft beta phase was the main reason for wear resistance decrease.

Residual stresses and distortion are of the main disadvantages of welding process which determining the amount and distribution of them have great importance in the design of structures, especially in the space industry. In this study, a finite element method is used to analyze the thermo- mechanical behavior of a spherical shell due to TIG welding. The spherical shell is made of titanium alloy (Ti-6Al-4V) with 2 mm thickness. The modeling of welding process is based on an uncoupled thermo- mechanical coupling. TIG welding is examined for six cases based on current intensity and welding progress speed setting the voltage on 12 V in all cases. Distribution of temperature and residual stresses caused by TIG welding of the titanium spherical shell have been extracted and compared among the six different cases. The effects of current intensity and welding progress speed on shell distortion and residual stress have been investigated. The results showed that increasing the current intensity and decreasing the welding progress speed have the most effects on longitudinal residual stresses which the amount of this increasing reached to %44 for decreasing the welding progress speed. Welding distortion increases to maximum %132 by increasing current and decreasing welding progress speed.

Friction stir welding (FSW) has many advantages in welding dissimilar joints in comparison with fusion welding methods. In this study, weld ability of butt joint of 5052 aluminum alloy and Ti-6Al-4V titanium alloy by FSW process has been studied and discussed. The welding was successfully performed by using a tool with frustum pin. The influences of both rotational and traverse speed of welding tool on mechanical properties are investigated. The results show that the metallurgical and mechanical properties improve by choosing appropriate parameters. The highest tensile strength of 260 MPa was obtained at rotational speed of 500 rpm and a 40 mm/min traverse speed, which was ~ 94% of the aluminum base metal tensile strength. As a result of increasing the rotational speed from 500 to 1000 rpm, high heat input can forms cracks at joint area. In rotational speed of 1000 rpm, increasing traverse speed from 40 to 56 mm/min leads to a sound joint with 192 MPa of tensile strength. This decreasing in tensile strength can be related to the formation of intermetallic compounds such as TiAl3, along the entire interface between the two alloys

Ultimate surface quality in machining process has a great effect on the workpiece performance and is the most important characteristic of machined surface. Using cutting fluid, as an effective factor on surface integrity improvement, has environmental problems and is harmful for operator’s health. As a result, using minimum quantity lubrication (MQL) is considered as an alternative method. In this study, surface roughness of Ti-6Al-4V alloy workpieces were investigated in high speed milling process and using MQL method. Full factorial experiments including 5 levels of cutting speed and 2 levels of feed rate were implemented. Results revealed that a surface roughness of 0.2 µm could be achieved in high speed milling of Ti-6Al-4V alloy in proper cutting conditions and in presence of MQL method. Furthermore, minimum surface roughness was reported in cutting conditions of Vc=450 m/min and fz=0.08 mm/tooth.

"DEFORM" three-dimensional finite element software is used to describe the behavior of plastic deformation of Ti-6Al-4V workpiece during blade preform extrusion process. Under different conditions of extrusion, numerical analysis of the process force parameter during extrusion process is presented. The relative effects of billet temperature, friction coefficient and die temperature on process force were investigated. To determine the process friction coefficient, the ring compression test of Ti-6Al-4V alloy with glass lubrication was performed. Also experimental tests were successfully done in order to manufacture blade preform. It was observed that billet temperature has much effect on force of Ti-6Al-4V alloy blade preform extrusion process. Die temperature has effect on the process force but its effect is not as much as the effect of the billet temperature. By increasing of the die temperature, the process force decreases. Experimental tests showed that the billet transfer process from the furnace to die has important effect on done or not done of the extrusion process because the billet transfer process from the furnace to die is cause of alters the billet initial temperature just before extrusion process. By reducing of the placing and transfer time of billet from the furnace to die, due to the vicinity of the billet and air, billet temperature have less reduction and therefore it becomes easier to shape. Also by increasing the friction coefficient, the force required for extrusion of Ti-6Al-4V alloy blades preform increased.

Abrasive water jet cutting process can produce tapered edges on cutting kerf. This problem can limit the applications of abrasive water jet cutting process and in some cases it is necessary another edge preparation process. In this paper, an experimental investigation kerf characteristics of Ti-6Al-4V titanium alloy under abrasive water jet cutting is presented. In this regards, it is shown how to use the hybrid approach of Taguchi method and principal component analysis to optimize abrasive water jet cutting are used in this paper. The abrasive water jet cutting process input parameters effect on material removal rate and the characteristics of the surface. A considerable effort was made in understanding the influence of the system operational process parameters such as water jet pressure, traverse speed, abrasive flow rate, and standoff distance. Due to appropriate selecting abrasive water jet cutting process parameters leads to optimizing of kerf characteristics include top kerf width, kerf tapper and kerf deviation, therefore it is important to select appropriate input parameters. The obtained results from this method show that the hybrid approach of Taguchi method and principal component analysis is a suitable solution for optimizing of abrasive water jet cutting process.

Hot forging of the aerofoil blades has complicated mechanical and metallurgical characteristics therefore; it needs numerical and experimental investigations. In this research, hot forging process of a titanium alloy aerofoil blade has been analyzed by finite element method. Then experimental tests have executed. For the numerical simulation, first material behavior of the titanium alloy has been investigated then friction factor has been obtained by ring test. Using the process simulation, material flow, die cavity filling, strain and temperature distribution, forging load and lateral forces applied the dies during the forging process have been investigated. In the next stage, trial tests have been executed. At last, numerical results have been compared with the experimental results. Results show that the forging process has been done successfully and simulation results have a good agreement with the experimental results.