起落架调节接头开裂及安全评估方法分析

飞机在经历约1 000个起落后的大修时，磁粉检测发现约60%的起落架调节接头存在开裂现象。通过断口宏观观察、微观观察、硬度检测和组织分析，确定起落架调节接头开裂性质为疲劳开裂，开裂原因主要与调节接头转接处安全裕度不足有关。调节接头为寿命件，试验件存在90%以上的疲劳扩展区域，说明调节接头具有较强的抗裂纹扩展能力。基于损伤容限设计和断裂力学对起落架接头寿命反推方法进行分析和阐述，通过反推方法的实施可实现对带裂纹接头的安全使用性以及可维修性进行评价。

Analysis of Cracking and Safety Assessment of Adjusting Joint of Undercarriage

After about 1000 representative flights, about 60% of the adjusting joints of an aircraft undercarriage were found to have cracked during magnetic particle testing. In the present work, the crack mode and cause of the joints were analyzed by micro and macro observation, structure observation and hardness testing. The results show the failure mode of the joints is fatigue, and the main cause is that the joints have no sufficient safety margin. The fatigue area occupied more than 90% of the facture surface of the joint test specimen, so it can be assumed that the joint has a good cracking tolerance. Base on damage-tolerance design and fracture mechanics, a reverse deduction method for fatigue life was discussed, which can be used to assess the safety and maintenance of the joints.