Fracture Assessment of Welded Aerospace Aluminium Alloys using SINTAP Route

Analytical assessment levels of the Structural Integrity Assessment Procedure (SINTAP) were applied to middle cracked thin Al 6013 T6 base material and friction stir welded (FSW) wide plates to predict their residual strength. The welded joints exhibit strength undermatching and, hence, plastic strain localization occurs within the lower strength FSW weld region which requires special considerations when applying the SINTAP based failure assessment route. Two R-curve types were used in the analysis: in terms of the J-integral obtained from the load-CMOD (Crack Mouth Opening Displacement) test record and in terms of directly measured crack tip opening displacement (CTOD) δ5 at the crack tip. The SINTAP estimations of maximum load level for the base material panels were remarkably accurate predicting almost exactly the experimental residual strength value in the highest analysis level. The weld strength mismatch analysis level applied to the FSW wide plates has successfully provided a conservative estimate of the maximum load (being 16% lower then the experimental value).