航空发动机限寿件表面特征概率损伤容限评估

为满足航空发动机适航规章(FAR/CCAR33.70)限寿件安全性评估要求,系统总结了基于特殊材料数据库、线弹性断裂力学分析与表面特征失效概率分析的表面特征概率损伤容限评估方法。以表面孔特征为例,总结分析符合适航规章要求的孔特征概率损伤容限评估流程,描述优化的孔特征评估方法,根据咨询通告AC33.70-2中带孔特征轮盘算例完成概率损伤容限评估模型的验证。结果表明:20 000循环寿命期内,不进行无损检测和在4 000及8 000循环对相互独立的90%部件进行两次无损检测的失效概率分别为2.677×10-4和1.514×10-4,符合适航算例校准要求。基于优化评估方法计算的失效概率为3.406×10-4,可初步判定表面特征适航符合性。该评估方法为限寿件表面孔特征评估提供技术支持,并对其他表面特征的评估具有一定的指导意义。 

Probabilistic damage tolerance assessment of surface features of aero engine life limited parts

In order to meet the safety requirements of airworthiness regulations (FAR/CCAR33.70) on life limited parts (LLPs), a probabilistic surface damage tolerance method was summarized based on the special material data, linear elastic fracture mechanics analysis and damage risk analysis. The damage tolerance assessment for hole features was analyzed and a new modified method for evaluating the probability of failure (POF) was proposed with higher efficiency. This method was verified referring to the test case provided by AC33.70-2. The assessment result showed that the POF of the disk with hole features was 2.677×10-4 times (20 000 cycles) without any in-service inspection and 1.514×10-4 times (20 000 cycles) with two inspections at 4 000 and 8 000 cycles based on the assumption that 90% of the parts are inspected at 4 000 cycles and an independent 90% of the parts are inspected at 8 000 cycles. Based on the modified method, the conservative POF was 3.406×10-4, demonstrating the preliminary compliance of airworthiness regulations. The surface analysis of damage tolerance assessment provides a support for evaluating the safety of hole features, which is instructive to other surface features.