raise the interface temperature of the two parts being joined, thereby reducing the process forces required to make a solid-state weld compared to traditional friction welding". The process applies to both linear and rotary friction welding. Today, the friction welding research materials comes from many places around the world, including Africa, South America, North America, Europe and Asia, and Australia. Metal techniques Rotary friction welding Rotary friction welding (RFW) is one of the methods of friction welding. One welded element is rotated to the other and pressed down. The heating of the material is caused by friction work and created not separable weld. Linear friction welding Linear friction welding (LFW) is similar to spin welding, except that the moving chuck oscillates laterally instead of spinning. Friction stir welding Friction stir welding (FSW) is a solid-state joining process that uses a non-consumable tool to join two facing workpieces without melting the workpiece material. Heat is generated by friction between the rotating tool and the workpiece material, which leads to a softened region near the FSW tool. While the tool is traversed along the joint line, it mechanically intermixes the two pieces of metal, and forges the hot and softened metal by the mechanical pressure, which is applied by the tool, much like joining clay, or dough. Friction surfacing Friction surfacing is a process derived from friction welding where a coating material is applied to a substrate. A rod composed of the coating material (called a mechtrode) is rotated under pressure, generating a plasticized layer in the rod at the interface with the substrate. Thermoplastic technique Linear vibration welding In linear vibration welding the materials are placed in contact and put under pressure. An external vibration force is then applied to slip the pieces relative to each other, perpendicular to the pressure being applied. Orbital friction welding Orbital friction welding is similar to spin welding, but uses a more complex machine to produce an orbital motion in which the moving part rotates in a small circle, much smaller than the size of the joint as a whole. Method list connected to friction welding Forge welding Friction stir welding (FSW) Friction stir spot welding (FSSW) Linear friction welding (LFW) Friction welding of pipeline girth welds (FRIEX) Friction hydro pillar overlap processing (FHPPOW) Friction hydro pillar processing (FHHP) Linear vibration welding Spin welding of polymers Low Force Friction Welding Other information Welds tests for