الفهرس 
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Abstract
Friction welding is considered as one of the welding techniques used in many industrial applications (e.g. pipe and tube welding). The heat is generated for the welding process as a result of frictional between the welding area and the welding tool. In friction welding, the welding process generated without the melting of the base metal. Regarding the pipes or tubes welding by traditional/normal method of friction welding, the friction welding process creates an internal and external flash defect. The external flash is easy to remove by machining processes while the internal flash is difficult to remove, thus the presence of these flash is an obstacle to move fluids or gases inside the welded pipes or tubes lines. In this study, the conventional/normal friction welding process is developed by using crush and friction to produce welded tubes without internal flash defect using a new technique called orbital friction crush welding (OFCW). This type of welding is a technique based on combining the orbital friction stir welding (OFSW) and friction crush welding (FCW). The laboratory equipment is prepared on a turning machine besides using it as a tube welding machine with the OFCW technique. A new welding tool of OFCW is employed for this purpose. The welding tool has a disk geometry with a special groove circumference of the disk. The welding tool was rotated and managed by an electric motor while both ends of the joint were installed on a mandrel between the lathe chuck and its tailstock, so that, the rotation of the welded joint occurs at the same speed as the turning of the lathe. The OFCW process is accomplished by converging the welding tool from both ends of the joint during rotation where the contact of the welding tool occurs with the joint, which leads to severe friction that is caused by high temperature, so the welding tool crushes the tube flanges thus, made a welded joint. Experiments were carried out on commercial aluminum tubes with an external diameter of 60 mm and the tube wall thickness of 3 mm with lengths of 150 mm, beside heat treatment process (annealing) of the tubes that was performed before the welding. The joint ends are prepared as flanges from the welding side by a simple spinning tool. Experiments were conducted to study the effect of welding process parameters on the quality of welding as well as the heat generated during the welding process in addition to study the mechanical properties of the welded joints. The welding process variables are the rotational speeds, the flange diameter ratio, and the welding tool profiles. Four-speed values were chosen; 500, 630, 800, 1000 rpm, three values of flange ratio were chosen, which is 1.25,1.35,1.45, also, three different tool profiles/ grooves were used. The first profile has V-profile, the second has an isosceles trapezoidal and the last has a concave profile shape. The effect of these variables on the temperature during the welding process, the maximum stress of the welded joint, and the mechanical properties of the welded joints were studied. The results also showed the success of a new tool in the welding process of aluminum tubes. The results also showed that, by increasing the rotational speed, the temperature and the tensile strength of the welded joints will be increased, and that the best welding tool is the tool that has the isosceles trapezoidal groove. As for the ratio of the flange diameter, the results showed that the highest values of tensile stress were achieved at the ratio of the flange diameter of 1.25. The results showed that the maximum tensile strength of the welded joint up to 40% compared with the base metal strength.