Fatigue strength assessment of Invar alloy weld joints using the notch stress approach

The aim of this study investigated the fatigue strength of Invar alloy weld joints. Invar steel (Fe-Ni 36%) is widely used in the primary and secondary barriers of membrane-type liquified natural gas (LNG) containment vessels. The fatigue test was carried out for two different types of welded joints with raised edge specimens and with overlap joint specimens based on the nominal and notch stress approaches. The thickness of the Invar plate is less than 1.5 mm, so the notch stress approach with rref = 0.05 mm was applied. Our evaluation of the results in terms of the FAT value and the slopes of the design curves are compared with steel, aluminum, and magnesium weld joints in accordance with International Institute of Welding (IIW) recommendations.