船用铝合金5059的典型焊接节点疲劳试验和寿命预报方法研究

Fatigue Test and Life Prediction Method of Typical Welded Joints for Marine Aluminum Alloy 5059

与传统的5083或6082系列铝合金相比,5059铝合金材料具有更好的力学性能和耐腐蚀性。但目前的焊接规范或船级社规范缺少相应的疲劳等级曲线,不利于船用铝合金5059结构的疲劳评估。同时,薄板铝合金的焊接结构存在较大的初始焊接缺陷,导致焊接拐角处的应力集中效应更加明显。较大的焊接变形给拐角附近应力集中效应和疲劳强度的精确评估带来了较大挑战。本文设计了四种典型的船用焊接接头开展疲劳试验,并将获得的疲劳数据用于拟合得到相应的疲劳等级曲线。在此基础上,进一步验证了名义应力、热点应力、有效缺口应力和缺口应力强度因子法评估对接、十字、T型焊接接头疲劳寿命的准确性和可靠性。此外,一些量化的结论可以用于指导船用铝合金5059焊接结构的应力场和疲劳评估。

Compared with the traditional 5083 or 6082 series aluminum alloy,5059 aluminum alloy material has better mechanical properties and corrosion resistance.However,the current welding code or classification society code lacks the corresponding fatigue class curve,which is not convenient for fatigue assessment of 5059 aluminum alloy marine structure.Meanwhile,the welding structure of thin aluminum alloy has bigger initial welding defects,resulting in more obvious stress concentration effect at the welding corners.Large welding deformation brings great challenges to the precision evaluation of stress concentration effect and fatigue strength near corners.In this paper,four typical marine welded joints were designed to carry out fatigue tests,and the fatigue data obtained were used to fit the corresponding fatigue class curves.On this base,the accuracy and reliability of nominal stress,hot spot stress,effective notch stresses and notch-stress intensity factor(N-SIF)method in estimating fatigue lifetime of butt,cruciform,T welded joints were further verified.Moreover,some quantitative recommendations are given for use in situations of practical interest of the design techniques being considered.