航空发动机滑油箱支架断裂失效分析

Fracture Analysis of Bracket in an Aeroengine Lubricating Oil Tank

针对在某发动机试车过程中发生的滑油箱支架断裂故障,通过外观检查、断口分析、磨损痕迹对比分析、材质分析以及有限元分析计算等失效分析方法,确定了故障支架的断口性质以及断裂原因。分析结果表明:发动机滑油箱故障支架断口为起源于吊耳内弧表面的高周疲劳断口。故障支架存在悬臂结构,当对螺栓施加拧紧力矩时,支架的悬臂结构会产生明显的变形不协调,使支架的2个吊耳出现偏载,导致支架局部应力集中,是疲劳裂纹萌生的主要原因。在发动机试车过程中,支架在装配应力和振动应力综合作用下,裂纹在支架应力集中区域萌生并扩展导致支架最终断裂。提出了完善设计结构形式并减小拧紧力矩等改进建议,避免类似故障再次发生。

In order to analyze the fractured fault of the aeroengine lubricating oil tank’s bracket during a engine test,the fracture prop⁃erty and causes of the fractured bracket were determined by the fracture analysis methods of appearance inspection,fracture analysis,com⁃parative analysis of wear track,material analysis and stress distribution calculation.The analysis results shows that the fracture mode of the bracket is high-cycle fatigue fracture.The fatigue source is located in the surface of the inner arc of the bracket’s hook.The deviation load of bracket’s hooks appears because of the forced hooks’uncoordinated deformation caused by the cantilever structure when the tight⁃ening torque is applied at the bolt.The main cause for the fatigue crack initiation is the local stress concentration of the bracket due to the deviation load.Under the combined action of assembly stress and vibration stress during the engine test,the crack initiates and expands in the stress concentration area,leading to the the final fracture.The suggestions for improvement about perfecting design structure and reduc⁃ing the tightening torque are proposed to avoid similar events.