Tilt angles used in the FSW process: (a) travel angle, (b) work angle. 

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Context 1

... traditional FSW process consists of the insertion of a rotational tool, formed by a pin and a shoulder, into the abutting surfaces of pieces to be welded and moved along the weld joint, as illustrated in Fig. 1. During the process, the pin located inside the weld joint, generating heat through both friction and plastic deformation softens the material and enables plastic flow, causing the mixture of materials. At the same time, the shoulder placed on the surface of the seam heats and drags material from the front to the back side of the tool, preventing leakage of material out of the welding joint and forming a smooth surface. Dur- ing the welding process the FSW tool can be tilted backward (travel angle) and sideways (work angle), Fig. 2. While travel angles different from zero are mainly applied when a rotational shoulder tool is used, work angles different from zero are applied in dissimilar-thickness butt weld applications. This process is applied mainly to butt, lap and T-butt weld joints but other joint geometries can be ...