Fatigue strength assessment of MARK-III type LNG cargo containment system

The aim of this paper is to investigate the fatigue strength of the GTT Mark-III type LNG insulation system. The LNG insulation system consists of several composite layers with various connections; plywood, triplex, reinforced polyurethane foam and mastic. Consequently, the LNG insulation system may include mechanical failures such as cracks as well as delaminations within the layers due to sloshing impact loads and fatigue loadings. In addition, these failures may cause a significant decrease of structural integrity. In this study, a series of fatigue tests have been carried out for Mark-III type LNGC insulation systems at room temperature considering the effect of sloshing impact. The load levels have been determined based on the ultimate strength of reinforced polyurethane foam. The aim of the study is to investigate the typical failure characteristics of the MARK-III LNG insulation system and to obtain the S–N data under fatigue loading. A consolidated single S–N curve is obtained based on a systematic finite element procedure. Future use of the S–N data in fatigue analysis requires that the response analysis is carried out using a finite element model with the same mesh density and material properties. This study can be used as a fundamental study for the fatigue assessment of the LNGC insulation system as well as a design guideline.