大型集装箱船高强度厚钢甲板安全寿命评估方法

Safety Life Assessment of Thick High Tensile Steel Plates on Large Container Ships

疲劳是船舶与海洋工程结构破坏的主要模式之一。高强度钢的应用使得结构的疲劳问题更加突出。对于采用以高强度厚钢板为甲板的大型集装箱船来说,有必要进行高强度厚钢板的焊接缺陷部位安全寿命评估方法研究。以应力范围的长期分布服从两参数Weibull分布的随机载荷为疲劳载荷,裂纹扩展率采用单一曲线模型预报裂纹在任意时刻的尺寸,结合应力强度因子并参考应力计算方法和失效评估图技术提出一套计算集装箱船高强度钢厚钢板安全寿命评估的方法。通过编制计算程序,对某集装箱船甲板进行安全寿命计算。最后,分析疲劳载荷谱对安全寿命的影响。计算结果表明:载荷回复期的长短和Weibull分布的形状参数的取值都会极大影响结构疲劳安全寿命。

Fatigue is one of the main damage modes of ships and ocean engineering structures. The appli-cation of high tensile steel makes the fatigue problem in ship hulls even more severe. For large containerships whose decks are constructed with thick high tensile steel plates,it is essential to study the safety lifeassessment of those parts with welding defects. In this paper,the fatigue loading spectrum is generatedfrom a long-term distribution which obeys the two-parameter Weibull distribution,and the unique crackgrowth rate model is adopted to predict the crack size at a certain given time. By combining the predictedcrack size,the calculation of stress intensity factor,and the reference stress in Failure Assessment Dia-gram（FAD）,a procedure to estimate the safety life of a cracked thick high tensile steel plate is presented.The corresponding problem in a container ship is then investigated via a calculation program. Finally,theinfluences of the fatigue loading spectrum on damage tolerance and fatigue life are analyzed. Results indi-cate that both the length of the fatigue load repetition period as well as the shape parameter of Weibull dis-tribution greatly affect the fatigue safety life.