Development of Weld Quality Criteria Based on Fatigue Performance

Historically, production technology researchers and structural design researchers have had only limited dialogue and each group has focused on their own narrow field of interest. This has led to inconsistencies in the definition of so-called “weld class systems” which have been primarily developed based on concepts related to good workmanship but have little or no relation to the actual performance of the welded structure. Additionally, some of the quality measures in existing systems are qualitative and, thus, subjective. In recent years, Commission XIII of the International Institute of Welding (IIW) has been promoting research and developing the technical background needed to develop a weld quality guideline which quantitatively relates weld acceptance criteria to the expected structural performance (primarily fatigue strength). A new weld class system with this same objective has recently been developed as a Volvo Group Standard. This system is described in this paper. The new standard has three quality levels for fatigue; as-welded normal quality, as-welded high quality and post-weld treated quality. It contains acceptance limits which are consistent with the expected fatigue strength and which can more objectively handle revisions. This new system will help in the development of new structures with lower weight and increased reliability.