When an airplane was inspected,the pipe linked to the hydraulic-pressure framework of the rudder was found to have fractured and the rotational joint was locked.

This paper contains a detailed experiment analysis on the fracture section characteristic,metallographic organization,chemical consists and mechanics property of the drill-stem subs,and performs a set of analysis calculation on the mutative load which putting on the drill-stem subs.

Study and Develop on the High-speed Multi-channels Rotary Joint;

Orthogonal test was performed to determine the laser phase-transformation hardening process suitable for a rotary joint made of 35CrMo alloy,which was aiming at increasing the wear-resistance of the rotary joint.