## 1 Introduction
Taking the elevator as an example, it consists of rudder blades, a rudder stock, a rudder handle, a guide rod, a guide device, a transmission rod, an implementing press, a hydraulic steering system, etc. At present, research on the fatigue of polar ships by scholars both domestically and internationally mainly focuses on the fatigue problems of ship materials under ice-induced loads and low-temperature conditions. The analysis methods mainly include theoretical analysis and experimental research. In terms of theoretical analysis, the fatigue life of different materials and structures is mainly predicted and evaluated by finite element analysis and other methods (numerical simulation and experimental analysis). In terms of experimental research, fatigue life is mainly studied and verified through experimental testing and data collection. [PERSON] [7] carried out Charpy impact and low-temperature fatigue crack growth tests on S460 structural steel and concluded that the fatigue of the material at the ductile-brittle transition temperature has a very different fatigue crack growth rate than the fatigue above this temperature. [PERSON] [8] reviewed the fatigue properties of steels at low temperatures, noted the effects of low temperatures on different aspects of the fatigue life of steels and their weldments, and verified the necessity of low-temperature fatigue testing of materials. Subsequently, [PERSON] [9] conducted experimental research on the fatigue behavior of Q420 high-strength steel under different stress amplitudes and temperatures through impact and strength tests. The results showed that Q420B steel met the requirements of impact and strength tests, and low temperatures improved the fatigue performance of the material to a certain extent. Fatigue fracture occurred at higher stress amplitudes and decreased with decreasing temperature. [PERSON] [10] discussed the effects of the sea state, environmental conditions, and materials on the fatigue performance of ships, emphasizing that fatigue analysis and life cycle prediction are critical for structural integrity calculations of naval ships and vessels. The study focused on fatigue calculations and life prediction using the Palmgren-Miner method, and it concluded that consideration of the fatigue life prediction in the early design stage can help identify the critical locations of potential fatigue cracks. [PERSON] [11] emphasized that predicting the fatigue life of the rudder bar of a ship is critical, and his study was conducted on an LCT ship for the transverse rocking motion of the ship. Numerical simulation, calculation of rudder bar bending stresses, and application of the Palmgren-Miner formula were used to predict the fatigue life, and the fatigue life of the rudder bar was predicted to be 1.8 years. [PERSON] et al. [12; 13] comprehensively reviewed the current state-of-the-art methods for evaluating the high period fatigue strength of steel structures at subzero temperatures, outlined how the effect of temperature on fatigue strength is taken into account when designing steel structures, and experimentally analyzed the effect of subzero temperatures on the fatigue strength of ordinary and high-strength steel structures. [PERSON] et al. [14] studied the low-temperature fatigue properties of EH36 steel used in polar icebreakers, and their experimental results showed that EH36 steel has good impact toughness and low-temperature resistance and that the fatigue crack growth rate of EH36 steel at low temperatures is low compared with that at room temperature, which suggests that it has good resistance to crack initiation and growth at low temperatures. [PERSON] [15] analyzed the cause of rudder tie rod fracture at room temperature of a certain type of ship. Figure 1 shows a schematic diagram of a tie rod fracture, and the analysis results show that there is a foreign object between the tie rod and the rudder rod mechanism, resulting in the rudder movement process of the tie rod exhibiting localized larger displacement changes, which ultimately caused the fracture.