A Contemporary Review on Friction Stir Welding of Circular Pipe Joints and the Influence of Fixtures on This Process

Figure 9

The welding system: (a) the setting for pipe welding; a schematic diagram of the welding parameters showing O1 and O2. (b) Hardness distributions at the middle thickness along the horizontal dash lines in the cross-sections shown as insets for each region: overlap of all distributions; distribution for FR, MR, and LR. (c) Tensile curves of 4 regions; traverse cross-sections of fractured joints after tensile test showing two fracture modes. (PRS stands for pipe rotation rate; TRR for tool rotation rate; O1 stands for offset1; O2 stands for offset2; ID stands for insertion depth); FR: former region; MR: middle region; LR: later region; OR: overlap region. [114].