Linear friction welding is similar to direct drive rotary friction welding since both are a constant energy input process. But unlike rotary, linear friction welding uses linear oscillation (a repeated back and forth motion) to create a solid state weld.
The linear process can be altered to accommodate different incoming part geometries. We can decrease the amount of forge force, which changes the rate of power input going into the weld, resulting in slower rate of upset. To achieve the desired amount of upset, the part will need to be oscillated for a longer period of time.