فهرست مطالب موسی ساجد

Additive manufacturing is a set of modern manufacturing technologies with a novel revolutionary point of view that addresses most of limitations that were around due to using conventional manufacturing methods. Due to the lack of references for additive friction stir manufacturing, in the present paper the new developments in friction stir additive manufacturing of metals, alloys, and metal matrix composites are presented and summarized. Friction stir additive manufacturing is a solid-state process that yields a dense and homogeneous structure with a significant microstructural refinement with no fusion defects such as shrinkage cavities, porosity, and cracks. The rest of the paper was arranged as follows: friction stir welding is discussed as the base technology. Then, the two additive manufacturing methods that are based on friction stir welding, i.e. additive friction stir manufacturing and additive friction stir deposition are presented.

In friction stir welding process, a non-consumable rotary tool is used which consists of a pin and a shoulder. The tool/workpiece friction results in stirring, plastic deformation, and joining. It is the shoulder penetration which leads to thinning of the upper sheet and remaining of a hole. In this study, a stationary shoulder was used to investigate the spot welding of a non-alloyed aluminium sheet to address the mentioned drawback. The aim was to investigate the effects of tool rotational speed with two levels of 1000 and 2000 rpm, tool shoulder diameter with two levels of 20 and 24 mm, and plunge depth with two levels of 3 and 3.5 mm on the microhardness, strength, and microstructure of the welded samples. Feed rate and dwell time were constantly set to 20 mm/s and 10s, respectively. Optimization was carried out in three modes including maximum strength, maximum hardness, and a combination of the maximum strength and hardness. In the first mode, the maximum strength was 1389.51 N in the specimen welded with a tool rotational speed of 2000 rpm, plunge depth of 3 mm, and tool shoulder diameter of 24 mm. In the second mode, the highest micro-hardness value was 91.33 HV in the specimen that was welded with a tool rotational speed of 1000 rpm, plunge depth of 3.5 mm, and tool shoulder diameter of 20 mm. Finally, in the third mode, the combination of the highest strength and micro-hardness values were 1389.51 N and 85.66 HV, respectively.

Solid-state welding and processing methods will be an alternative to joining lightweight metals that cannot be welded using conventional fusion welding processes. After three decades after its invention, FSW is the first choice in joining high-strength aluminum alloys with an application in automotive and aerospace. The process is also capable of joining other alloys too. Due to the success of FSW, it was considered for more complicated applications and joining high-strength alloys. It should be noted that FSW is not the only successful rotary friction-based solid-state welding process. In recent years, friction hydro-pillar processing (FHPP) which is successful in repairing surface and body cracks and defects of different steel grades is also very interesting. In the present study, main rotary friction-based welding and processing methods are introduced and discussed in two major classes including friction stir welding and friction hydro-pillar processing.

Metal sandwiches are a new class of ultra-lightweight materials made from a porous metal core and two outer metal plates. High strength and high energy absorption capacity, resistance to heat, and also fast and inexpensive recyclability make these materials ideal for use in many industries including automotive, aerospace, oil, energy and construction industries. Considering the advantages of friction stir welding, the connection of these plates using this welding technology can be used industries for welding of bimetal sandwiches. In this research, feasibility of using frictional stir welding to prepare metal sandwiches with a core of aluminum foams and copper covers was investigated. The investigated parameters were tool rotational speed, in three levels of 2000, 2500 and 3000 rpm, and tilt angle in two levels of 5 and 7 degree. The cross-sections of the joints were investigated for weld quality which confirmed a successful joining. Tensile tests were carried out to evaluate the joint strength. It was concluded that the effect of tool rotational speed on the weld strength is much higher than the effect of tilt angle and has a reverse relation with tensile strength. The best strength which was 18.8 MPa was obtained with a tool rotational speed of 2000 rpm and a tilt angle of 5 degree.

Nowadays traditional manufacturing technologies are being substituted by nontraditional ones. Recent advances in physics like ability to control of ultra-sonic waves, laser beam, electron beam, electrical discharge and plasma arc have interested mechanical engineers to utilize these advanced technics as manufacturing technologies. Among these technologies plasma is an outstanding technic, plasma arc not only is used directly for welding and cutting procedures but also has the main role in controlling of other nontraditional manufacturing technologies like laser beam welding and machining, and electron discharge machining. The recent advances in plasma utilization for manufacturing technologies are summarized in this article.