Challenges in the detection of weld-defects in friction-stir-welding (FSW)

Abstract

ABSTRACTFriction-Stir-Welding (FSW) involves many critical process variables that affect the overall quality of the weld produced; consequently, it is difficult to accurately predict the most favourable process parameters to acquire high-quality defect-free welds. Quality of an FSW joint is influenced by several crucial factors including welding process parameters, and many others. Since the new invention of FSW process, investigators have researched the influence of process parameters and pin tool profiles on microstructures and mechanical properties with a view to optimise FSW process, thereby keeping the degradation of the weld strength to a minimum. In this study weld defects in Friction-Stir (FS) welded thick (8.13 mm) aerospace grade aluminium alloy (AA 2219-T87) are correlated with weld process parameters from an assortment of a large matrix of weld schedules. In this investigation, a novel FSW process parameter window was established for the effective joining of aerospace grade aluminium which could successfully distinguish several types of weld schedules with characteristic and intrinsic weld-defects. Using experimental results obtained from various schedules, an empirical force index (Effective Force Index), which is a function of the critical weld process parameters is proposed to identify regions of weld schedules.