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Article

Xibing Li, Tian Cheng, Ming Li, Mingjian Li, Ruren Wu and Yingsi Wan

This paper aims to research the lubrication performance of large-size rectangular oil pad in hydrostatic thrust bearing for heavy computer numerical control (CNC) vertical lathe.

Abstract

Purpose

This paper aims to research the lubrication performance of large-size rectangular oil pad in hydrostatic thrust bearing for heavy computer numerical control (CNC) vertical lathe.

Design/methodology/approach

The research establishes the mathematical models of velocity, flux and pressure fields, etc., for lubrication performance distribution, and analyzes its load-bearing behavior.

Findings

When hydrostatic thrust bearing’s rotating speed is within ω12, the oil flow generated by plate’s relative motion is greater than that generated by pressure difference and centrifugal force, and in the opposite direction, making it not easy to emit friction heat, so the rotating speed range ω12 should be avoided for bearing.

Originality/value

The research provides powerful theoretical basis for the structure design, operating reliability and practical application of large size rectangular oil pad hydrostatic thrust bearing, and realizing the prediction of its lubrication performance.

Details

Industrial Lubrication and Tribology, vol. 68 no. 3
Type: Research Article
ISSN: 0036-8792

Keywords

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Article

Chengpei Liu and Junping Hu

This paper aims to study the performance of hydrostatic turntables by using fluid structure interaction (FSI) and thermal effect coupled model.

Abstract

Purpose

This paper aims to study the performance of hydrostatic turntables by using fluid structure interaction (FSI) and thermal effect coupled model.

Design/methodology/approach

A novel fluid-structure-thermal coupled model is set up to study the problem. The FSI technique and computational fluid dynamics (CFD) method are used by this new model, and the thermal effects are also considered. Hydrostatic turntables with different system parameters (oil supply pressure, oil recess depth and surface roughness) are studied under different working conditions (rotational speeds of turntable and exerted external loads). Performance characteristics obtained from this FSI-thermal coupled model and conventional model are presented and compared.

Findings

Theoretical predictions are in good agreement with the experimental data. The results of new FSI-thermal coupled model are more accurate than those of the old conventional model. To acquire better performance of the system, the novel FSI-thermal model becomes necessary for different hydrostatic turntable systems.

Originality/value

This developed model is a useful tool for studying hydrostatic turntables. To get an improved performance, a proper selection of design parameters of the system based on FSI-thermal model is essential.

Details

Industrial Lubrication and Tribology, vol. 70 no. 9
Type: Research Article
ISSN: 0036-8792

Keywords

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Article

Zhifeng Liu, Junyuan Guo, Yumo Wang, Dong Xiangmin, Yue Wu, Zhijie Yan and Gong Jinlong

This paper aims to propose a method for finding the maximum rotational speed of an inclined turntable at which the stability of the bearing oil film is maintained.

Abstract

Purpose

This paper aims to propose a method for finding the maximum rotational speed of an inclined turntable at which the stability of the bearing oil film is maintained.

Design/methodology/approach

The finite difference method was used to solve the Reynolds equation. Variation of bearing capacity of a tilted hydrostatic turret over time was determined. The combined effect of tilt and rotational speed of the turret on the oil film stability was also analyzed.

Findings

When the turntable is operated at low speeds with only small angle of tilt, stability of the oil film is maintained. At lower rotational speeds, a smaller angle of tilt improves the bearing capacity and ensures stability of the oil film. Whereas, higher rotational speeds can have a considerable influence on the bearing capacity.

Originality/value

The results demonstrate that the inclination or tilt of the turntable significantly affects the stability of the oil film.

Details

Industrial Lubrication and Tribology, vol. 72 no. 5
Type: Research Article
ISSN: 0036-8792

Keywords

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Article

Xiaodong Yu, Xu Zuo, Chao Liu, Xuhang Zheng, Hang Qu and Tengfei Yuan

Hydrostatic thrust bearing is a key component of the vertical CNC machining equipment, and often results in friction failure under the working condition of high speed and…

Abstract

Purpose

Hydrostatic thrust bearing is a key component of the vertical CNC machining equipment, and often results in friction failure under the working condition of high speed and heavy load. The lubricating oil film becomes thin or breaks because of high speed and heavy load and it affects the high precision and stable operation of the vertical CNC machining equipment; hence, it is an effective way of avoiding friction failure for achieving the oil film shape prediction

Design/methodology/approach

For the hydrostatic thrust bearing with double rectangular cavities, researchers solve the deformation of the friction pairs in hydrostatic bearing by using the computation of hydrodynamics, elasticity theory, finite element method and fluid-thermal-mechanical coupled method. The deformation includes heat deformation and elasticity deformation, the shape of gap oil film is got according to the deformation of the friction pairs in hydrostatic bearing, and gets the shape of gap oil film, and determines the influencing factors and laws of the oil film shape, and achieves the prediction of oil film shape, and ascertains the mechanism of friction failure. An experimental verification is carried out.

Findings

Results show that the deformation of the rotational workbench is upturned along its radial direction under the working condition of high speed and heavy load. However, the deformation of the base is downturned along its radial direction and the deformation law of the gap oil film along the radius direction is estimated; the outer diameter is close but the inner diameter is divergent wedge.

Originality/value

The conclusion can provide a theoretical basis for the oil film control of hydrostatic thrust bearing and improve the stability of vertical CNC machining equipment.

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Article

Xiao-dong Yu, Lei Geng, Xiao-jun Zheng, Zi-xuan Wang and Xiao-gang Wu

Rotational speed and load-carrying capacity are two mutual coupling factors which affect high precision and stable operation of a hydrostatic thrust bearing. The purpose…

Abstract

Purpose

Rotational speed and load-carrying capacity are two mutual coupling factors which affect high precision and stable operation of a hydrostatic thrust bearing. The purpose of this paper is to study reasonable matching relationship between the rotational speed and the load-carrying capacity.

Design/methodology/approach

A mathematical model of relationship between the rotational speed and the load-carrying capacity of the hydrostatic bearing with double-rectangle recess is set up on the basis of the tribology theory and the lubrication theory, and the load and rotational speed characteristics of an oil film temperature field and a pressure field in the hydrostatic bearing are analyzed, reasonable matching relationship between the rotational speed and the load-carrying capacity is deduced and a verification experiment is conducted.

Findings

By increasing the rotational speed, the oil film temperature increases, the average pressure decreases and the load-carrying capacity decreases. By increasing the load-carrying capacity, the oil film temperature and the average pressure increases and the rotational speed decreases; corresponding certain reasonable matching values are available.

Originality/value

The load-carrying capacity can be increased and the rotational speed improved by means of reducing the friction area of the oil recess by using low-viscosity lubricating oil and adding more oil film clearance; but, the stiffness of the hydrostatic bearing decreases.

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Article

Yanqin Zhang, Jichang Sun, Pengrui Kong, Xiangbin Kong and Xiaodong Yu

The purpose of the paper is to analyze the bearing capacity of hydrostatic bearing during the change of film thickness under different working conditions and to improve…

Abstract

Purpose

The purpose of the paper is to analyze the bearing capacity of hydrostatic bearing during the change of film thickness under different working conditions and to improve the processing efficiency and precision of equipment.

Design/methodology/approach

In this study, Q1-205 double rectangular cavity hydrostatic thrust bearing is selected as the research object. The dynamic mesh method and ANSYS/FLUENT software are used to simulate the curves of oil film thickness and oil pressure under different operating conditions. Finally, the change of pressure in the oil cavity at different operating speeds under a certain inlet flow rate was tested through design experiments.

Findings

When the film thickness was thick, the maximum pressure in the oil cavity at different inlet velocities showed little difference. With a larger inlet flow, the maximum pressure in the oil cavity was higher. The pressure at the edge of the oil seal was linearly distributed. The oil pressure in the downstream side was greater than that in the counter flow side. When the working pressure was low, the pressure in the oil cavity slightly decreased with the increase of working speed. Moreover, the pressure loss at high speed was considerable.

Originality/value

Based on the lubrication theory, the mathematical model of the bearing oil film was set up. The bearing capacity equation of the hydrostatic cavity was derived. The double-rectangular-annular hydrostatic guides studied in this paper have not been reported in previous research literature and the method of dynamic mesh dynamic simulation of variable viscosity is seldom studied before. The bearing characteristics and the change of oil film thickness under different working conditions have been studied systematically and comprehensively. The theoretical analysis results are basically consistent with the experimental results.

Details

Industrial Lubrication and Tribology, vol. 71 no. 9
Type: Research Article
ISSN: 0036-8792

Keywords

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Article

Vijay Kumar Jadon and Madhvender Singh

Hybrid bearings have found increasing applications in various machines owing to their large number of favorable characteristics like high load carrying capacity, increased…

Abstract

Purpose

Hybrid bearings have found increasing applications in various machines owing to their large number of favorable characteristics like high load carrying capacity, increased minimum fluid film thickness, long life and increased damping making them attractive for various applications such as turbo machinery, machine tool spindles, precision grinder spindles, etc. A careful design of such bearing for optimum performance has always been among the key issues of the researchers. The present work has been carried out to study the effect of bearing geometric parameters on performance of hybrid journal bearing and supply cut‐off behavior has also been studied for the improved performance.

Design/methodology/approach

The generalized Reynold's equation governing the fluid flow in the clearance space between bearing and journal has been solved using finite element method to determine the pressure distribution, subsequently performance of hole‐entry hybrid journal bearing are computed. The journal centre equilibrium position for the given load is computed and the formulation is explained. The geometric parameters include aspect ratio, land width ratio, number of rows and number of holes per row. Further, performance of the bearing is computed with increasing the load, which induces negative pressure or the backpressure at the supply holes subsequently those are plugged to support the higher load.

Findings

The obtained results are presented in graphical form and logical conclusions are drawn and the modified configurations with reduced number of holes are suggested for higher load. It is observed that the bearing configuration with aspect ratio = 1.0 and land width ratio = 0.2 is best for high load support for low power requirement as less lubricant is required to be pumped in the bearing yet it provides sufficient fluid film thickness and lower values of maximum pressure. The load carrying capacity of the bearing can be further increased by plugging the holes on which backpressure is obtained for same bearing configuration. A feedback control with hybrid bearing system will sustain the sudden increase of load by shutting off the supply of the lubricant through supply hole where negative pressure is encountered.

Originality/value

The paper addresses the performance of non recessed hybrid journal bearings with wide range of geometric parameter. The results are quite useful for the bearing designer. The supply cut‐off is another aspect of originality of the paper as it provides the better load support.

Details

Industrial Lubrication and Tribology, vol. 59 no. 2
Type: Research Article
ISSN: 0036-8792

Keywords

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Abstract

Details

Aircraft Engineering and Aerospace Technology, vol. 80 no. 1
Type: Research Article
ISSN: 0002-2667

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Article

WHEN John I. Snyder Jr. flew over from the United States he probably did not relish the Cassandra rôle into which circumstances had forced him. As president of U.S…

Abstract

WHEN John I. Snyder Jr. flew over from the United States he probably did not relish the Cassandra rôle into which circumstances had forced him. As president of U.S. Industries he gave one of the most depressing addresses of modern times. Since his firm is a large manufacturer of automation machines it was probably natural that he should say: ‘Automation is inevitable. Its use is rapidly increasing. Positive action by the makers of automation machines must be taken now to preserve the human values which could otherwise become cannon fodder of the automation barrage.’

Details

Work Study, vol. 11 no. 7
Type: Research Article
ISSN: 0043-8022

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Article

TODAY the holding of seminars grows apace and threatens, if unchecked, to become a major industry, turning us into a nation of seminarians. The subjects discussed are…

Abstract

TODAY the holding of seminars grows apace and threatens, if unchecked, to become a major industry, turning us into a nation of seminarians. The subjects discussed are varied and the speakers, especially if imported from the United States, described with a wealth of hyperbole. The settings are often luxurious. The cost, when expressed in terms of the time that well‐paid executives are away from their offices, is considerable.

Details

Work Study, vol. 19 no. 8
Type: Research Article
ISSN: 0043-8022

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