ABSTRACT The mechanical properties and fatigue behavior of welded joints are key factors affecting the safe operation of polar equipment. In this study, fatigue tests were conducted on three types of EH36 welded joints, namely T‐welded, cruciform welded, and butt‐welded joints, at 20°C and −60°C. Mean S‐N curves and P‐S‐N curves with a 97.5% survival probability were obtained for these joints. The experimental results showed that low temperature significantly increased the yield strength σ s and ultimate tensile strength σ b of both EH36 base metal and weld metal. The EH36 weld metal exhibited higher σ s than the base metal, whereas its total tensile strain at fracture (TTSF) was lower. In addition, the difference in TTSF between the weld metal and base metal decreased as the temperature decreased. Low temperature significantly extended the fatigue lives of the welded joints. Among the three joint types, the butt‐welded joints exhibited the best fatigue performance, whereas the cruciform welded joints exhibited the worst. All tested joints showed similar failure characteristics, involving the growth of semi‐elliptical surface cracks or multiple semi‐elliptical cracks leading to through‐thickness fracture. Compared with the DNV‐GL design S‐N curve, all experimentally fitted P‐S‐N curves were located above the design curve. These results provide experimental support for the safety assessment of welded structures in polar equipment.
Qiao et al. (Mon,) studied this question.