A New Burn-Through Criterion Derived From In-Service Welding Mechanism: Radial Stress Burn-Through Criterion

Abstract

Abstract. Since the 1970s, various burn-through criteria have been proposed by numerous research institutions regarding in-service welding phenomenon. However, no widely recognized criterion has emerged to date due to the ambiguity of the burn-through mechanism, which lacks a scientific explanation and hinders the formulation of a definitive criterion. This study independently established an in-service welding test device based on the ABB automatic welding system and conducted burn-through experiments utilizing digital image correlation (DIC), high-speed photography technique, and other methods to identify critical conditions for burn-through. The reliability of numerical simulation models for in-service welding was validated through DIC strain measurements. Both experiments and numerical simulations revealed that radial deformation represents the primary mode of deformation preceding burn-through. It was indicated that the welding thermal stress would significantly weaken the influence of the medium pressure. The overall stress evolution behavior during in-service welding was mainly dominated by the welding stress. The critical condition for burn-through occurs when radial deformation transitions from an inward-convex form to an outward-convex form. Radial stress is identified as the key stress driving burn-through, with its absolute value exceeding yield strength being a critical condition for it to occur. This study elucidates mechanisms behind burn-through and develops a radial stress burn-through criterion that aligns closely with experimental values while clarifying mechanisms behind maximum inner-wall temperature criterion.