Effects of low temperature overload and cycling temperature on fatigue crack growth behavior of ship steels in Arctic environments

The mechanical and fatigue performance of ship steels at low temperature are critical to ensure the safety of polar ships in Arctic areas. In this paper, the fatigue crack growth (FCG) behaviors of high-strength steel EH36 and Ultra-high strength steel EQ70 under low temperature overload were studied by experiments. The experimental results show the tensile and yield strength of two steels increase as the temperature decreases, and the influence of the temperature on the strength is bigger for EH36 steel. Within the toughness state, low temperature or overload can extend the fatigue life of both steels. As the temperature decreases, the FCG life increment of EQ70 is bigger. When overload rate is 1.5, the temperature has a more significant impact on the fatigue crack growth rate (FCGR) before overload. When overload rate is 2.5, the influence of temperature on the FCGR before and after overload is essentially the same. The retardation effect on the FCG life caused by overload diminishes as the temperature decreases. Furthermore, the FCGR fluctuates under cyclic temperature and the FCG life is similar to that at 0 degrees C, which can be considered in the safety assessment of polar ships in the Arctic.