Quantitative Weld Quality Acceptance Criteria: An Enabler for Structural Lightweighting and Additive Manufacturing Recent developments in fracture-mechanics based defect acceptance criteria, as well as robust computational techniques, are higlighted

Most of the existing weld quality acceptance criteria stipulated in various codes and standards, as well as in recommended practices, are empirical in nature. Historically, these workmanship-based criterias have been adequate for quality control purposes in construction of welded structures. However, as the competition for achieving structural lightweighting intensifies, more quantitative quality acceptance (also known as fitness-for-purpose based) criteria are increasingly called for. This is because various new forms of discontinuities and joint configurations (e.g., dissimilar materials joints) cannot be readily related to existing acceptance criteria. Even if existing criteria can be made applicable, recent research findings have shown that existing criteria can be excessively conservative for some and unconservative for others when dealing with thin gauge and lightweight construction. A similar situation exists for additively manufactured metallic components, which can be viewed as "all weld metal" components containing randomly distributed discontinuities over the entire component volume. In this paper, some of the recent developments in quantitative weld quality acceptance criteria will be first highlighted, some of which are made possible by advanced fracture mechanics analysis techniques. Applications in structural lightweighting and additive manufacturing will then be demonstrated with some real-world examples. Finally, implications on a broader application of the methodologies presented for ensuring both structural integrity and cost-effectiveness in construction will be discussed in light of these developments.