Fatigue behavior of FSW high-yield strength steel welds for shipbuilding application

摘要

Ship building industry is looking for new welding techniques to increase the cost-effectiveness of their production. With the help of previous study dedicated to aeronautical issues, friction stir welding (FSW) seems to be a new opportunity to optimize welding for metallic materials. This study deals with the mechanical behavior of the FSW steel assemblies and in particular fatigue behavior. To demonstrate the reliability of this process, two different steels are joined: DH36 (conventional steel for naval construction) and S690QL (high-strength steel). Assemblies are, on one hand, characterized with conventional tests used to validate welding-operating procedure and on the other hand, investigations are focused on the cyclic behavior of the structure to go forward in the knowledge of this technique. The main goal of this approach is to check the relevance of the fabrication process applied to naval steels. Furthermore, this study contributes to give more experimental results describing the fatigue life of FSW structures. To our best knowledge, this is the first time that full S/N curves are plotted for two different steels such as S690QL or DH36. Results are very encouraging and indicate that the FSW process is relevant for naval applications especially for DH36 and need few improvements for S690QL.