EFFECT OF CORROSION ON FATIGUE PERFORMANCE OF STEEL ROBOTIC WELDS FOR UNDERWATER MARINE COMPONENTS

Oikonomou, Alexandros and Aggidis, George (2026) EFFECT OF CORROSION ON FATIGUE PERFORMANCE OF STEEL ROBOTIC WELDS FOR UNDERWATER MARINE COMPONENTS. PhD thesis, Lancaster University.

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Abstract

Corrosion is a critical factor that significantly impacts the fatigue performance of welded structures subjected to marine environments. Investigations into corrosion fatigue typically involve deriving S-N curves through testing of specimens that have undergone varying degrees of corrosion. However, there is a paucity of research specifically addressing the comparative fatigue behavior of pre-corroded and non-corroded specimens. This study aims to bridge this gap by conducting systematic fatigue tests on pre-corroded specimens alongside their non-corroded counterparts. This dual approach facilitates a more comprehensive understanding of the effects of corrosion on both the initiation and propagation of fatigue cracks. A key innovation in the current research is the use of state-of-the-art robotic welding, specifically employing the FCAW process, for specimen preparation. Robotic integration in welding processes offers several advantages, including enhanced consistency in weld quality and improved repeatability over extended durations. This method also introduces flexibility, allowing for more complex welding geometries to be achieved with precision. These benefits are particularly critical for fatigue testing, where weld consistency is paramount to ensure reliable results. The literature review highlights a scarcity of data on the fatigue performance of HY100 steel and 316Ti stainless steel in corroded conditions, despite their extensive use in marine and demanding environments. This contrasts with the relatively well-documented fatigue behavior of S355 steel welds, which, however, have seldom been studied using robotic welding technologies. By focusing on HY100 and 316Ti weldments and employing robotic FCAW, this study fills a significant research gap and contributes new insights into the corrosion fatigue performance of these materials. The anticipated outcomes—derived from fatigue experiments, fractographic analyses, and metallographic studies—are expected to substantially enhance the existing knowledge base. By exploring under-studied materials and methods, particularly the implications of robotic FCAW on corrosion fatigue, this research provides novel findings that can inform both academic research and industrial practices. These contributions are especially relevant given the lack of comparable data, emphasizing the importance of this study in advancing the understanding of corrosion fatigue mechanisms in marine structural applications.