Evolution of friction couples in volume hydraulic machines due to achievements in material science and technology

Abstract

The article analyses modern achievements in the field of volumetric axial and radial piston hydraulic machines for the mobile sector of application in terms of using the latest design solutions, friction pair materials and technologies. Goal. The aim is to acquaint specialists with directions for creating hydraulic machines of a modern technical level due to increased pressure and rotation frequency. Methodology. The evolution of constructive decisions regarding the selection of pairs of rolling and sliding friction and their change depending on the achievements in materials science, tribology and increasing the accuracy of machines for the finishing of friction surfaces are consistently considered. Results. It is shown that in axial-piston hydraulic machines with an inclined disk, the transition to hydrostatic piston pairs with heel pads was made, which made it possible to increase the pressure up to 52 MPa. In radial-piston high-torque multi-cycle hydraulic motors, almost all manufacturers have replaced the rolling friction piston pairs with sliding pairs due to the latest anti-friction materials and precision processing. Thus, the ratio of mass to power decreased almost 6 times. For radial-piston hydraulic transmissions with ball-pistons, a failure analysis was performed, respectively, regarding the materials used, quality and control of heat treatment. Originality and practical value. For promising high-speed hydraulic transmissions with ball-pistons, recommendations have been developed for the selection of steels and control of their manufacture on the basis of taking into account materials science tools. The work in the production of piston balls from ceramic materials are offered. The given informative and practical research results are planned to be taught to master's students in the discipline of "Design and Testing of Hydraulic Drives of Construction and Road Vehicles" at KhNAHU.