Abstract: 5059 aluminum alloy has become the preferred choice for the ship structure due to its excellent mechanical properties and corrosion resistance. However, the current code lacks the S-N fatigue curve of the 5059 aluminum alloy, imposing difficulties on the fatigue evaluation of the 5059 aluminum alloy ship structure. The 5059 aluminum alloy and a typical marine welded joint are designed to carry out the fatigue tests at the room temperature and the low temperature (-35℃). The corresponding fatigue S-N curve is fitted by the least square method based on the test data. A finite element model of the specimen for fatigue test is established, and the stress obtained by the finite element analysis is extrapolated to obtain the hot spot stress. The fatigue life of the fatigue specimen is predicted by using the fitted S-N curve and compared with the result from the fatigue test. The results show that the proposed S-N curve of the 5059 aluminum alloy material and the welded joint can be used to predict the fatigue life of the ship structure under the low temperature environment.

Key words: aluminum alloy, fatigue test, S-N curve, low-temperature fatigue, hotspot stress

摘要： 5059铝合金具有很好的力学性能和耐腐蚀性,已成为船体结构的首选,然而现行规范缺乏5059铝合金材料的疲劳S-N曲线,难以进行对使用该铝合金材料船舶结构的疲劳评估。该文设计了5059铝合金材料及1个典型的船用焊接接头,进行了室温和低温（-35 ℃）疲劳试验,结合试验数据使用最小二乘法拟合出相应的疲劳S-N曲线。建立了疲劳试验试件的有限元模型,将有限元分析得到的应力通过外推法插值得到热点应力,代入拟合的S-N曲线预测疲劳试件寿命,并与疲劳试验结果比较。结果表明,所提出的5059铝合金材料和焊接接头S-N曲线可用于低温环境下船舶结构的疲劳寿命评估。

关键词: 铝合金, 疲劳试验, S-N曲线, 低温疲劳, 热点应力