Abstract
The lubricant film of hydrostatic circular pad in the heavy-duty rotary table is affected by the roughness, thermal and hydrodynamic effect, which can cut down the load-carrying capacity and machining accuracy of the heavy-duty machine tool. In this paper, a coupled energy equation with mean Reynolds equation based on the Christensen’s stochastic model of rough surfaces is presented to analyze the temperature rising, pressure distribution and load-carrying capacity of the hydrostatic circular pad. The mean Reynolds equation, momentum equation, continuity equation, and energy equation are coupled and solved using the finite difference method to obtain the characteristics of lubricant film. It is found that the uneven pressure distribution and the temperature rising of lubricant film in resistive oil edge of hydrostatic circular pad are related to the increase of dimensionless hydrodynamic parameter S due to the thermal and hydrodynamic coupling effect. The load-carrying capacity and stability of heavy-duty rotary table is weakened due to the thermal and hydrodynamic effects.
Highlights
Due to the high load-carrying capacity, small viscous dissipation, high stiffness, low running friction, long service life, and good resistance to vibration, the heavy-duty hydrostatic rotary table has been widely used to carry and machine the large workpiece in the heavy-duty machine tool
Considering the hydrodynamic pressure of lubricant film is caused by the hydrodynamic effect, we may assume the pressure of recess and resistive oil edge are all zero
The uneven pressure distribution is strengthened with the increase of hydrodynamic parameter
Summary
Due to the high load-carrying capacity, small viscous dissipation, high stiffness, low running friction, long service life, and good resistance to vibration, the heavy-duty hydrostatic rotary table has been widely used to carry and machine the large workpiece in the heavy-duty machine tool. Important aspects that determine the performance of a hydrostatic circular pad are the flow pattern, rough surface of resistive oil edge, heat generation as well as the hydrodynamic effect. The height of the roughness is generally of the same order as the mean asperities in a lubricated contact Under these situations, the influence of surface roughness on the characteristics of hydrostatic circular pads should be considered. Osterle and Hughes [10] and Dowson [11] analyzed the inertia effects in hydrostatic thrust bearings using the assumptions of the classical lubrication theory where they assumed that the term associated with the centripetal inertia cannot be neglected. The roughness, hydrodynamic and thermal coupled effect on the pressure distribution and load-carrying capacity of circular oil pad is analyzed based on the Christensen’s stochastic model of rough surfaces. The hydrodynamic and thermal effect rule of circular oil pad for the hydrostatic rotary table can be obtained, which will provide theoretical foundation for optimization of heavy-duty hydrostatic rotary table
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