TWI

With regard to the use of friction pull plug welding to close out the termination hole associated with pin tool retraction during friction stir welding of circumferential welds in pressurised cryogenic propellant tanks, an investigation is presented into test data relating residual strength capability to flaw size in two aluminium alloy plug weld configurations. Experiments were conducted in laboratory air and in liquid nitrogen on welds between two differing Al-Cu alloys and on Al-Li alloy. Critical flaw size was estimated from residual strength testing at -196 and +20 deg.C of surface crack tension samples with fatigue pre-cracks grown from electric discharge machined notches. Plug weld fracture surfaces were photographed. The relevance of the results with respect to the efficacy of nondestructive inspection and proof testing of mission critical defects is discussed.

9th International Symposium, 15-17 May 2012, Session 6A: Applications II, Paper 03