Theoretical Disquisition on the Static and Dynamic Characteristics of an Adaptive Stepped Hydrostatic Thrust Bearing with a Displacement Compensator

Abstract

Stepped hydrostatic thrust bearings used in metal-cutting machines are characterized by high load capacity and damping, which ensure the stable operation of structures. However, in comparison with throttle thrust bearings, they have a high compliance. It is preferable that, in addition to the main bearing function, a modern hydrostatic bearing has the ability to provide low (including negative) compliance for the implementation of an adaptive function in order to actively compensate for the deformation of the machine resilient system, thereby increasing the accuracy of metalworking. This paper considers the design of a stepped hydrostatic thrust bearing, which, in order to reduce the compliance to negative values, features a technical improvement consisting of the use of an active displacement compensator on an elastic suspension. In this paper, the results of mathematical modeling and theoretical research of stationary and non-stationary modes of operation of the adaptive thrust bearing are presented. The possibility of a significant reduction in the static compliance of the structure, including the negative compliance values, is shown. It was found that negative compliance is provided in a wide range of loads, which can be up to 80% of the range of permissible bearing loads. The study of the dynamic characteristics showed that with a targeted selection of parameters that ensure optimal performance, the adaptive thrust bearing is able to operate stably in the entire range of permissible loads. It has been established that an adaptive stepped hydrostatic thrust bearing with a displacement compensator has a high stability margin, sufficient to ensure its operability when implementing the adaptive function.

Theoretical Study of the Static and Dynamic Characteristics of a Slotted Adaptive Hydrostatic Thrust Bearing with a Regulator of the Lubricant Output Flow

“…A particular case of a TF at s = 0 is the static compliance K(0) = b 0 /a 0 . Therefore, in this work and other works of the authors on the study of bearings with lubricant flow controllers and displacement compensators that provide the bearings with an adaptive function, the term "compliance" is used [4,5,10,11].…”

“…This allows us to significantly reduce the number of variable parameters that affect the characteristics of the thrust bearing. Following [4], we take the scales of values: p s for pressures, r 0 for radii, t 0 for the current time, h 0 for gaps and deformation e, πh 3 0 p s 6µ for volumetric lubricant flow rate, 2πr 2 0 p s for axial forces, where h 0 corresponds to the gap h in the bearing that carries the design load f 0 , and µ is the lubricant viscosity. Dimensionless quantities are signified by Greek and capital Latin letters.…”

“…Sliding bearings with hydrostatic lubrication (journal bearings, thrust bearings, and guides) used in modern metal-cutting machines usually work as passive supporting structures [1,2]. At the same time, these devices can act as adaptive units, which, in addition to their load-carrying function, are capable of performing the role of automatic deformation compensators of the technological system of the machine, thereby helping to reduce errors and, consequently, reduce the time of metalworking [3,4]. The adaptive function of such bearings arises only in those designs that are able to compensate for the positive compliance of the technological system of the machine, operating in the modes of negative compliance and thereby providing the total zero compliance of the machine [5,6].…”

“…In work [4], it is shown that the stability of a step hydrostatic thrust bearing with an LOFR can be provided without the use of an ECTS, which simplifies the design. The mathematical model of the bearing takes into account the compliance of the elastic displacement compensator, but what is not taken into account is that, at the same time, it can act as a damper, which improves the dynamics of the bearing.…”

Research on the dynamic pressure effect of clearance oil film of stepped hydrostatic thrust bearing

“…The combined bearing composed of the water-lubricated hydrostatic thrust bearing and two kinds of radial rolling bearings developed by Lin Shengye has the technical advantages of large axial bearing capacity, small friction power loss, and low-temperature rise [6]. Kodnyanko V has carried out mathematical modeling and theoretical research on the steady and unsteady working modes of adaptive thrust bearing [7]. Venerus DC analyzed the squeeze flow in the lubricating oil film between the porous disk and the impermeable disk of the bearing caused by the relative motion of the disk, and found the analytical solution of the coupling equations controlling the flow in the lubricating oil film and the porous disk [8].…”