考虑载荷流泄时盾构机T形焊接结构疲劳可靠性分析

T形焊接结构是盾构机刀盘的关键结构之一，焊接处裂纹在亚临界的扩展是其疲劳失效的关键因素。文章考虑载荷流泄情况下，基于概率断裂力学的一次二阶矩方法提出了一种新的结构疲劳可靠性分析方法。将该方法应用到某盾构机T形焊接结构，给出了考虑与不考虑载荷流泄两种情况下结构疲劳可靠性计算结果，并用Monte Carlo方法验证了文章方法的有效性；利用最小二乘法拟合出了载荷流泄系数对该T形焊接结构疲劳可靠性的影响曲线，将该曲线划分了三个区域：即高、中、低疲劳失效区。结果表明在考虑和不考虑载荷流泄时，T形焊接结构的疲劳失效概率分别是8.2644e-05和3.4314e-04，即载荷流泄能一定程度上提高了结构的疲劳可靠度；实际工程在盾构机T形焊接结构疲劳可靠性设计时，T形焊接结构的厚度作为一个设计变量，而低失效区可以作为一个可靠度约束条件。研究成果为实际工程上盾构机刀盘的维修、检验计划和设计都有一定的理论指导意义。

Fatigue Reliability Study on T-welded Component of Shiled Machine Considering Load Shedding

T-welded component is one of the key structures of the shield machine cutterhead, and sub-critical crack in the weld extensions is a key factor in its fatigue faliure. A new structural fatigue reliability analysis method is proposed, considering load shedding, by the use of probablistic fracture mechinics based on FORM method. The method is applied to a T-welded shield structure, and results of structural fatigue reliability are gotten at the cases of with and without considering load shedding. The method’s validity is verified using Monte Carlo method. And a curve that load shedding impacts on the T-welded structure fatigue reliability is fitted via least square method, which is divided in three regions: the high, medium and low fatigue failure zone. The results showed that the fatigue failure probabilities were 8.2644e-05 and 3.4314e-04 when with and without considering load shedding, which load shedding improved the structure fatigue reliability was reputed. The thickness of T-welded structure was thought as a design variable in the practical project design of fatigue reliability, in which low fatigue failure zone may be used as a reliability constraint. The results have a certain theoretical guidance for the maintenance, inspection plan and design of shield machine cutterhead in the practical project.