飞机方向舵液压载荷机构进油导管裂纹分析

Cracking Analysis on Oil Inlet Pipe of Hydraulic Load Unit of Aircraft Rudder

针对飞机方向舵液压载荷机构进油导管裂纹故障,采用宏微观观察、化学成分分析、金相组织检验等方法,结合导管的制备工艺过程,对失效原因进行分析。结果表明:进油导管的裂纹性质为疲劳开裂,开裂原因是导管在冷轧/拔过程中先产生原始裂纹,再经热处理及酸洗后形成无断裂特征区,疲劳从无断裂特征区边缘线性起始。导管内外表面还存在沿晶开裂,为导管在酸洗过程中酸洗过度产生。

The oil inlet pipe of the hydraulic load unit of an aircraft rudder cracked.In order to find out the cracking cause of the pipe,macroscopic and microscopic observation,chemical composition analysis,metallographic structure examination were carried out,and the preparation process of the pipe was analyzed.The results indicate that the failure mode of the oil inlet pipe is fatigue cracking.The reason for the fatigue cracking is that an original crack was formed in the cold rolling/pulling process,and then an area without fracture characteristics was formed after heat treatment and acid pickling process.The fatigue crack originated linearly from the edge of the area without fracture characteristics.In addition,there exist intergranular cracks both at the inner and outer surface of the oil inlet pipe,which were formed in the process of acid pickling of the pipe.