---

Single point incremental forming is a sheet metal forming process that has more flexibility than another methods. This process don't require to die and could formed various shape white use the simple tool and CNC machine. In this paper the influence of process parameters on the forces and dimensional accuracy and thickness distribution in single point incremental forming is investigated. These parameters include the feed rate, tool rotation, vertical step, movement strategy of tool and lubrication. Beginning with the design and construction of the fixture and clamping it on the dynamometer and create of tool (tungsten carbide), the preparation process was done on a CNC milling machine. Then, the experimental tests were carried out on Aluminum alloy sheets (Al-1200) with creation of pyramid frustum; after the measuring of force in different directions, the influence of parameters on the forming force was investigated. Also parts were measured with CMM devices and compared. The results showed that with increasing the feed rate, the vertical force decreases and with increasing tool rotation speed, horizontal force decreases. The use of lubricant, is effective on the improvement of process.

---

Friction stir welded butt joints were performed on sheets made of AA2024-T351 aluminum alloy at tool rotational speeds of 400, 630, 800 rpm and traverse speeds of 8, 16, 25 mm/min. The fatigue crack propagation rate was investigated according to standard ASTM-E647 in CT specimens. FE simulation of FSW process was implemented for different welding conditions and next the fatigue crack propagation was simulated using XFEM method. In this analysis, to assess the damage in the joints, maximum stress criterion is used. The maximum principal stress in element was the fracture criterion. Numerical results are in good agreement with the experiments so the simulation is reliable. The obtained results show that the tool rotational and traverse speed affect the fatigues crack growth rate. For all welded specimens crack propagation rate was slower than that of the base metal for low values of ∆K (∆K≤13 Mpa) but is much faster at high values of ∆K. Furthermore fatigue properties of specimens that welded with lower speeds are better than base metal and increase in rotational or traverse speeds of the tool will increase the crack propagation rate of the welded specimens.

---

Single point incremental forming is a new and flexible method for 3D parts production of sheet metal. In this way, a hemispherical tool forms incrementally the sheet being clamped in perimeter. Because of the nature of localized deformation in this process, the formability is higher and forming forces are lower as compared to traditional sheet metal forming process. However, in this method dimensional accuracy is somewhat low due to spring back and bending occurred in boundaries. Recently, the incremental forming process using frictional heat has been developed. In this research, the experimental effect of generated heat by friction stir of the tool on dimensional accuracy in components of AA3105 sheet has been studied at high rotational speeds. By this method, due to friction movements of tool, the temperature of formation area rises while fixing the general temperature of sheet by spraying cooling liquid. Then, the sheet has low strength in contact region with tool while it has high strength in other areas. As a result, the force imposed on the sheet as well as the undesirable plastic deformation will decrease. Also, by decreasing the yielding stress, elastic strain and spring back decreases as well. An increase in formability because of softening of forming area is another contribution of this strategy. This idea has been studied by production of some parts of truncated-pyramid geometry and changing rotational speed from 1000 to 7000 RPM. The results show that at speed higher than 3000 RPM, formability and dimensional accuracy of the parts increase.

---