Experimental and Numerical Investigation of Localised Corrosion-Driven Brittle Failure in Welded Metallic Joints under Cyclic Loading Conditions

Abstract

Localized corrosion is one of the most critical degradation mechanisms affecting the structural integrity of welded metallic joints operating under cyclic loading conditions, particularly in aggressive environments. The interaction between corrosion-induced material loss, stress concentration, and cyclic loading significantly accelerates crack initiation and promotes brittle failure modes, yet the underlying mechanisms remain insufficiently quantified. This study presents a comprehensive experimental and numerical investigation into corrosion-driven brittle failure in welded metallic joints subjected to cyclic loading. A series of corrosion–fatigue experiments were conducted on welded structural steel joints exposed to chloride-rich environments, focusing on the development of localized corrosion pits and their evolution into dominant cracks. Mechanical cyclic loading was applied under controlled stress ratios to replicate service-like conditions. Crack initiation sites, fracture morphologies, and failure modes were systematically characterized using optical microscopy and scanning electron microscopy. The experimental results reveal that localized corrosion significantly alters stress distribution near the weld toe and heat-affected zone, promoting premature crack initiation and brittle fracture behavior. To complement the experimental observations, a finite element-based numerical framework was developed to simulate corrosion-induced damage accumulation and crack propagation under cyclic loading. The numerical model explicitly incorporates pit geometry, localized material degradation, and cyclic stress–strain response. Model predictions show strong agreement with experimental crack growth trends and fracture locations. Parametric analyses further demonstrate that pit depth-to-width ratio and cyclic load amplitude are the dominant parameters governing the transition from ductile to brittle failure. The combined experimental–numerical approach provides new insight into the coupled effects of localized corrosion and cyclic loading on welded joints. The results highlight critical thresholds beyond which corrosion pits act as dominant crack nucleation sites, leading to accelerated brittle failure. The findings of this study contribute to improved life prediction models for welded metallic structures and support the development of more reliable design and inspection strategies for corrosion-prone structural systems