Friction Stir Processing (FSP)
Friction Stir Processing to Improve Formability & Fatigue Life
How it works
Presently, prevailing ship construction is limited aluminum plates or sheets to be formed to a minimum of a 2.5T bend radius through an angle of 90° degrees in a press brake. Cracking is more prevalent when formed parallel to the rolling direction; therefore, press brake forming of the flange is usually done transversely to the direction of rolling. To obtain long length flange members several sheets must be joined to honor the forming of the sheet transverse to the rolling direction. This results in extra cost and distortion from the weld seams by joining standard width sheets for transverse bending to obtain long flange member lengths. Cracking nevertheless occurs, unless the part is pre-annealed by heating. If there is cracking it is repaired by arc welding which also anneals the part.
FSP will prevent cracked flanges on formed members and improve material utilization.
To avoid temper loss from repairs or preheating as required by current process development of this technique may allow smaller bend radii to be employed resulting in additional cost and weight reductions.