Reasons for cracking of the pressure supply pipe of the safety valve in the aircraft hydraulic system

The pressure supply pipe of the safety valve in the hydraulic system of a certain aircraft cracked. The causes of catheter cracking were analyzed using macroscopic observation, scanning electron microscopy analysis, metallographic examination, mechanical property testing, dynamic stress testing. The results show that the cracking property of the pressure supply conduit was high cycle fatigue cracking, and the reserve margin of pipeline stiffness was insufficient, resulted in excessive dynamic stress and ultimately led to fatigue cracking of the pipe.