Multibody Dynamics Characteristics of Friction-welded Piston and Their Effect on Pump Cavitation Mitigation

This paper introduces the high-speed rotational friction welding process and control parameters for new-type pistons in heavy-duty pumps, focusing on the heavy-duty fluid power mechanical components manufactured by this process. Taking the hollow closed piston made by high-speed rotational friction welding as the research object, a coupled numerical model integrating computational fluid dynamics and rigid-flexible coupled tmultibody dynamics is established. The multibody dynamics characteristics of friction-welded pistons and their effects on the improvement of pump cavitation are analyzed through numerical simulation and experiment. The results show that the piston stress concentrates on the ball neck and the core rod near the ball head side during the suction stroke, the slipper is subjected by the squeezing force from the piston ball head and the cutting force from the return plate hole on the slipper rim, and the stress gradient direction at the slipper bottom is orthogonal to the velocity vector of slipper. Although the local stress in the friction-welded piston exceeds 250MPa during the discharge stroke, the distribution of stress concentration points is dispersed, ensuring the structural strength safety of the piston assembly. In terms of pressure and cavitation characteristics, compared with traditional large-cavity pistons, the friction-welded piston form the smallest dead volume with the cylinder block, achieving higher volumetric efficiency and faster response. The smaller dead volume avoids the medium-pressure impact caused by the oil inertia during oil suction, reduces the intensity of cavitating jets, and decreases the risk of cavitation erosion.