The Marine Environmental Protection Committee (MEPC) of the International Maritime Organization (IMO) agreed upon progressively stricter limitations for Nitrogen Oxide (NOx) emissions for vessels. This latest trend has led to increased demand for liquefied natural gas (LNG) and ethane gas carriers. One of the most important issues in the design of LNG and ethane carriers is structural integrity of storage tanks. Considering the operation temperature of LNG and ethane gas carriers, storage tanks are typically manufactured with low temperature materials, such as Al-5083, SUS 304, Invar and nickel steels. In particular, nickel steels are used in demanding good strength and heat-resistant applications. In this regard, this study evaluated fatigue crack propagation characteristics of nickel steels with various Ni contents between 3.5 wt% and 9 wt% both at room and cryogenic temperatures. Fatigue crack growth rate (FCGR) characteristics of 3.5 and 7% nickel steel are obtained by testing according to ASTM E647. Moreover, FCGR of nickel steels are compared with those of other low temperature materials. For room temperature, test results showed that fatigue crack propagation rate increased with the increase of nickel contents. The value m at cryogenic temperature is higher than that of room temperature. In addition, the value C at cryogenic temperature is lower than that of room temperature when the FCGR characteristics are presented by Paris’ law.
Effect of Residual Stresses on Fatigue Crack Propagation at Room Temperature in a Ferritic-Austenitic Welded Joint
