TC2钛合金弹性片裂纹原因分析

Cracking Cause Analysis of TC2 Elastic Pieces

针对航空发动机尾喷管弹性片多次出现裂纹故障,利用视频显微镜、扫描电镜等设备,通过对弹性片进行外观检查、断口分析、能谱分析、金相检查以及流场和应力分析等方法,确定弹性片裂纹性质和产生原因。结果表明:故障弹性片裂纹性质为多源疲劳,起源于弹性片薄板间的焊缝位置;飞机垂直尾翼处流场异常,造成气动载荷较大,是弹性片产生裂纹的主要原因;同时,弹性片选用0.5 mm厚的TC2薄板强度储备不足,焊缝位置存在未焊合缺陷,形成较大的应力集中,降低了弹性片的抗疲劳性能,促进了疲劳裂纹的萌生。提出相应的改进建议,避免类似故障的发生。

Cracking occurred to the elastic pieces of tail nuzzles in aero engines for several times.The failure mode and cause were analyzed by visual inspection,fracture analysis,energy spectrum analysis,metallographic examination,flow field analysis and stress analysis.Results indicate that the cracks are multi-source fatigue cracks,initiating from the weld joints between the sheets of the elastic pieces.The larger aerodynamic load caused by abnormal flow field were the main reason for the fatigue cracking.Meanwhile,the safety margin of the 0.5 mm TC2 sheets is insufficient and there are incomplete fusion defects at the weld joints,resulting in stress concentration and reducing fatigue resistance.The two factors promoted the initiation of the fatigue cracks.Finally,some improvement measures were put forward to avoid similar failure.