## 1 Introduction  
Fatigue is a common failure mode of ship structures [1]. The widespread use of high-strength steel in recent years has directed the attention of researchers to the fatigue failure of ship structures. [PERSON] investigated the fatigue properties of two types of ship structure and observed that T-welded and cruciform welded joints are prone to fatigue resulting from high cyclic loads [2]. T-welded and cruciform welded joints are commonly-used welded joints in polar ships. Cruciform welded joints can simulate the intersections between longitudinal and transverse web frames in ships, and T-welded joints can simulate the intersections of longitudinal and transverse bulkheads in ships [3]. The fatigue properties of welded components have been studied by many researchers [4; 5]. However, most of these studies evaluated the fatigue properties of these welded components at room temperature, and the parameters obtained at room temperature are not appropriate for fatigue evaluation at low temperature [5]. For ships navigating in ice fields, low-temperature-induced fatigue damage is a highly relevant issue. [PERSON] and [PERSON] [6] studied the fatigue damage of icebreakers based on the ice-induced loads and found that the fatigue damage caused by ice-induced loads deserves attention, which means that extremely harsh environments and conditions will present new challenges to the fatigue properties of the structure [7]. According to the regulations published by the China Classification Society (CCS) [8], DH36 steel can be used in marine structural components at \(-\)60 \({}^{\circ}\)C environments. A similar description can also be found in the specification \"Ships for Navigation in Ice\", published by DNV GL [9]. Hence, the study of low temperature fatigue of DH36 steel at \(-\)60 \({}^{\circ}\)C has great practical significance for the evaluation of fatigue properties of polar ships. The fatigue properties of steel and its weld can be affected by ambient temperature [10; 11; 12; 13; 14]. For example, [PERSON] and [PERSON] carried out fatiguetests of metallic alloys S275 J2 and Al7075 T6 at low temperatures [10]. [PERSON] and [PERSON] found the fatigue crack behavior of DH36 steel and its butt weld is temperature-dependent [13; 14]. Although the effect on the fatigue properties of steels at low temperatures is well documented, there are few experimental data of fatigue properties of T-welded and cruciform welded joints of DH36 steel at low temperatures available. Therefore, the research on the fatigue properties of T-welded and cruciform welded joints of DH36 steel at \(-60\)\({}^{\circ}\)C deserves to be studied. The fatigue properties of welded joints can be analyzed by many factors, such as the stress concentration factor, microstructure, Vickers hardness, and fractography. These factors can be divided into structural perspective, material perspective, and fractography. From the structural perspective, the stress concentration factor plays an important role in determining the fatigue properties [15]. A structure with a higher stress concentration factor is more prone to crack, and the crack propagation rate is also higher [16]. From the material perspective, the microstructure can reflect the fatigue properties of the structure [17]. [PERSON] proposed a method to predict the fatigue limit using Vickers hardness measurements and verified the good correlation between Vickers hardness and fatigue properties [18]. [PERSON] developed a new short-time procedure named PHYBAL\({}_{\text{CHT}}\) which can evaluate fatigue properties of metallic materials based on cyclic hardness indentation tests [19], [PERSON] investigated the fatigue properties and associated crack growth behaviors of as-hot-rolled and solution-treated Fe-30 Mn-3 Si-3 Al twinning-induced plasticity (TWIP) steels. His results showed that fatigue crack behavior of this TWIP steel is related to the hardness [20]. These researchers observed that the Vickers hardness affects the fatigue properties.