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Book part
Publication date: 17 July 2007

Allen C. Bluedorn and Kimberly S. Jaussi

As part of the developing attention being paid to time in organization science, this chapter discusses two temporal dimensions – polychronicity and speed – and develops…

Abstract

As part of the developing attention being paid to time in organization science, this chapter discusses two temporal dimensions – polychronicity and speed – and develops propositions relating these two temporal dimensions to other organization science variables. The propositions are specified according to levels of analysis, at least three of which are considered in propositions presented for each dimension. Two other temporal dimensions – punctuality and temporal depth – are also described, albeit not as extensively as polychronicity and speed. A fifth temporal phenomenon, entrainment, provides insights into organizational processes as well as the four temporal dimensions. The chapter concludes by outlining some reasons for caution for both theory and practice.

Details

Multi-Level Issues in Organizations and Time
Type: Book
ISBN: 978-0-7623-1434-8

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Article
Publication date: 9 April 2019

Mohamed Abd Alsamieh

The purpose of this paper is to study the behavior of elastohydrodynamic contacts subjected to forced harmonic vibrations including the effect of changing various working…

Abstract

Purpose

The purpose of this paper is to study the behavior of elastohydrodynamic contacts subjected to forced harmonic vibrations including the effect of changing various working parameters such as frequency, load amplitude and entrainment speed.

Design/methodology/approach

The time-dependent Reynolds equation is solved using the Newton–Raphson technique. The film thickness and pressure distribution are obtained at every time step by simultaneous solution of the Reynolds equation and film thickness equation including elastic deformation.

Findings

The frequency of vibration, load amplitude and entrainment speed are directly related to the film thickness perturbation, which is formed during load increasing phase of the cycle. The film thickness formed during load increasing phase is larger than that formed during load decreasing phase with larger deviation at a higher frequency or load amplitude and vice versa for lower frequency or load amplitude. The entrainment speed of the contact has an opposite effect to that of the frequency of vibration or load amplitude.

Originality/value

Physical explanations for the behavior of elastohydrodynamic contact subjected to forced harmonic vibration are presented in this paper for various working parameters of frequency, load amplitude and entrainment speed.

Details

Industrial Lubrication and Tribology, vol. 71 no. 6
Type: Research Article
ISSN: 0036-8792

Keywords

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Article
Publication date: 4 September 2017

Xue-feng Wang, R.F. Hu, Weiyan Shang and Fuzhou Zhao

The dent is one of typical surface defects on the surfaces of the machine elements and it is not in fact inerratic. This work aims to investigate the effect of a single…

Abstract

Purpose

The dent is one of typical surface defects on the surfaces of the machine elements and it is not in fact inerratic. This work aims to investigate the effect of a single dent with a marginal bump on the film shape in elastohydrodynamic lubrication (EHL) point contacts.

Design/methodology/approach

The experimental investigations of a single dent with marginal bump were carried out using multi-beam interferometry in EHL point contacts. In the meantime, its numerical simulation was also finished using multi-level method and multilevel multi-integration method. The effects of the entrainment velocity and the applied load as well as the slide-roll ratio on the film were chiefly discussed. Meanwhile, the comparison of films between smooth and dented surfaces was conducted under simple sliding conditions.

Findings

Under pure sliding conditions, the minimum film thickness presents itself near the marginal bump at lower entrainment velocity. The inlet dimple before the marginal bump is subjected to the operating conditions. Under pure rolling conditions, the shape of the dent is almost unchanged when it is passing through the contact region at lower entrainment velocity. The dent depth hardly depends on the applied load under static conditions. However, larger load enhances the inlet dimple and the elastic deformation of the dent with the marginal bump under pure sliding conditions.

Originality/value

This work is helpful to understanding the effect of the marginal bump before the single dent on point contact EHL films.

Details

Industrial Lubrication and Tribology, vol. 69 no. 5
Type: Research Article
ISSN: 0036-8792

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Article
Publication date: 1 June 2002

M.F.J. Bohan, I.J. Fox, T.C. Claypole and D.T. Gethin

The paper focuses on the solution of a numerical model to explore the sliding and non‐Newtonian fluid behaviour in soft elastohydrodynamic nip contacts. The solution…

Abstract

The paper focuses on the solution of a numerical model to explore the sliding and non‐Newtonian fluid behaviour in soft elastohydrodynamic nip contacts. The solution required the coupling of the fluid and elastomer regimes, with the non‐Newtonian fluid properties being described using a power law relationship. The analysis showed that the fluid characteristics as defined by the power law relationship led to large differences in the film thickness and flow rate with a movement of the peak pressure within the nip contact. The viscosity coefficient, power law index and sliding ratio were shown to affect the nip performance in a non‐linear manner in terms of flow rate and film thickness. This was found to be controlled principally by the level of viscosity defined by the power law equation. The use of a speed differential to control nip pumping capacity was also explored and this was found to be most sensitive at lower entrainment speeds.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 12 no. 4
Type: Research Article
ISSN: 0961-5539

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Article
Publication date: 8 February 2021

Qiancheng Qin, Xue-Feng Wang, Rufu Hu and Xiaomin Cheng

This study aims to investigate the effects of single dent on the film thickness and pressure in elastohydrodynamically lubricated (EHL) point contacts by numerical analysis.

Abstract

Purpose

This study aims to investigate the effects of single dent on the film thickness and pressure in elastohydrodynamically lubricated (EHL) point contacts by numerical analysis.

Design/methodology/approach

The governing equations of single dent were established and then the variations of the film thickness and pressure induced by the applied load, the entrainment velocity and the ball radius were investigated. Meanwhile, the film thickness and pressure under smooth and dented surfaces were compared with each other.

Findings

The dent enhances both the maximum pressure and the second pressure peak. The minimum film thickness arises before the dent under certain conditions. In the meantime, the pressure decreases at the inside of the dent and the film thickness is just the reverse. The entrainment velocity remarkably affects the overall film thickness, whereas the rest of the input parameters mainly decides the details of the film curve. All input parameters remarkably affect the overall pressure, especially the maximum pressure.

Originality/value

This work is helpful to understanding the effect of the single dent on the lubricating properties of EHL point contacts.

Details

Industrial Lubrication and Tribology, vol. 73 no. 3
Type: Research Article
ISSN: 0036-8792

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Article
Publication date: 29 August 2019

Zhen Li, Yufan Lu, Chi Zhang, Jinlong Dong, Xiaoli Zhao and Liqin Wang

The traction behaviours of lubricating oil significantly affect the stability and lubrication regime of aviation high-speed ball bearings. Rolling elements will slide at a…

Abstract

Purpose

The traction behaviours of lubricating oil significantly affect the stability and lubrication regime of aviation high-speed ball bearings. Rolling elements will slide at a low traction force (TF). Therefore, traction behaviours need to be studied, and a fitting expression for traction curves to rapidly calculate the traction coefficient (TC) should be developed.

Design/methodology/approach

The traction behaviours of an aviation lubricating oil were studied in severe operating conditions with a self-designed two-disc testing rig. Based on the least squares method and the Levenberg–Marquardt theory, a rapid calculation expression was developed by fitting the obtained traction curves. The correction of this expression was experimentally verified by comparing the TCs under different operating conditions. This expression was also used to modify the commonly accepted quasi-dynamic model of rolling bearings.

Findings

An increase of the load led to an increase in the TC. In comparison, the temperature and entrainment speed showed inverse effects. The proposed expression exactly predicted the trend of the experimentally acquired traction curve. The calculation with the modified dynamic model showed that the action of the TF on a single rolling element varied and that the temperature increase of the outer raceway is higher than the inner raceway, which is caused by the TF and relative sliding speed between the elements and raceways.

Originality/value

The proposed fitting expression is able to simplify the TC calculation of synthetic aviation lubricating oil in practical engineering applications. This paper can provide an important reference for the traction behaviour of synthetic aviation lubricating oil under severe conditions and assist with its rapid calculation and practical application in engineering.

Details

Industrial Lubrication and Tribology, vol. 72 no. 1
Type: Research Article
ISSN: 0036-8792

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Article
Publication date: 12 March 2018

Wei Pu, Jiaxu Wang, Guangwu Zhou, Ke Xiao and Junyang Li

The purpose of this study is to describe and observe the effect of surface topography associated with arbitrary directions of rolling and sliding velocities on the…

Abstract

Purpose

The purpose of this study is to describe and observe the effect of surface topography associated with arbitrary directions of rolling and sliding velocities on the performance of lubricating films in elliptical contacts.

Design/methodology/approach

The most recently published mixed elastohydrodynamic (EHL) model by Pu and Zhu is used. Three different machined rough surfaces are discussed and the correlated inclined angle of surface velocity varies from 0° to 90° in the analyzed cases. These cases are carried out in a wide range of speeds (five orders of magnitude) while the simulated lubrication condition covers full-film and mixed EHL down to the boundary lubrication.

Findings

The results indicate that the variation of the average film thickness corresponding to different entrainment angles is distinct from those without considering surface roughness. In addition, the surface topography appears to have an immense effect on the lubrication film thickness in the exceptive situation.

Originality/value

This paper has not been published previously. Surface roughness has attracted much attention for many years owing to the significant influence on lubricating property. However, previous studies mainly focus on the counterformal contact with the same direction between surface velocity and principal axis of the contact zone. Little attention has been paid to the specific condition with the arbitrary direction of rolling and sliding velocities found in hypoid gears and worm, and some other components. The purpose of this study is to describe and observe the effect of surface topography associated with arbitrary directions of rolling and sliding velocities on the performance of lubricating films in elliptical contacts based on the most recently published mixed EHL model by Pu and Zhu.

Details

Industrial Lubrication and Tribology, vol. 70 no. 2
Type: Research Article
ISSN: 0036-8792

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Article
Publication date: 3 April 2019

Zhen Li, Xiaoli Zhao, Dezhi Zheng, Tingjian Wang, Le Gu and Liqin Wang

This study aims to evaluate the rheological properties of aviation lubricating oil under conditions of heavy load, high speed and high temperature and the applicability of…

Abstract

Purpose

This study aims to evaluate the rheological properties of aviation lubricating oil under conditions of heavy load, high speed and high temperature and the applicability of the classical rheological model under severe conditions.

Design/methodology/approach

A Chinese aviation lubricating oil was used and its traction curves were obtained using a new two-disk tribotester. Its rheological parameters were calculated based on empirical formulae. Moreover, the traction force was calculated based on the classical Eyring rheological model.

Findings

The traction curves are obtained with respect to contact pressure, temperature and rolling speed. The rheological parameters are significantly influenced by environmental factors, especially viscosity. The traction force calculated using the Eyring model is consistent with the experimental results.

Originality/value

A novel two-disk tribotester was designed using a gas bearing and speed–force closed-loop control to ensure measurement accuracy. The mechanism of rheological properties was analyzed and the applicability of the classical rheological model under severe conditions was verified. It provided an experimental and theoretical basis for expanding the application of classical rheological models under extreme conditions.

Details

Industrial Lubrication and Tribology, vol. 71 no. 4
Type: Research Article
ISSN: 0036-8792

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Article
Publication date: 17 January 2020

Jiaxing Pei, Xu Han and Yourui Tao

The purpose of this paper is to propose an simple and efficient stiffness model for line contact under elastohydrodynamic lubrication (EHL) and to investigate the gear…

Abstract

Purpose

The purpose of this paper is to propose an simple and efficient stiffness model for line contact under elastohydrodynamic lubrication (EHL) and to investigate the gear meshing stiffness by the proposed model.

Design/methodology/approach

The method combines the surface contact stiffness and film stiffness as EHL contact stiffness. The EHL contact stiffness can be calculated by the external load and displacement of the load action point. The displacement is the sum of deformation of the film and contact surface and is equal to the distance of the mutual approach of two contact bodies.

Findings

The conclusion is drawn that the contact stiffness calculated by the proposed model is smaller than that by the minimum film model and larger than that by the mean film model. It is also concluded that the gear meshing stiffness under EHL is slightly smaller than that under dry contact.

Originality/value

The EHL contact stiffness can be obtained by the increment of external load and mutual approach directly. The calculation of oil film stiffness and surface contact stiffness separately is avoided.

Peer review

The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-11-2019-0465

Details

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

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Article
Publication date: 10 August 2018

Xuefang Cui, Fanming Meng, Delong Kong and Zhitao Cheng

The purpose of this study is to investigate the thermal elastohydrodynamic lubrication (TEHL) analysis of a deep groove ball bearing.

Abstract

Purpose

The purpose of this study is to investigate the thermal elastohydrodynamic lubrication (TEHL) analysis of a deep groove ball bearing.

Design/methodology/approach

The TEHL model for the groove ball is first established, into which the elastic deformation is incorporated. In doing so, the elastic deformation is solved with the fast Fourier transform (FFT). And the bearing temperature rise is solved by the point heat source integration method. Then, effects of the applied load, relative velocity and the slide-roll ratio on the TEHL of the bearing are analyzed.

Findings

There exist the large pressure peaks at two edges of the raceway along its width direction and the increment in the relative velocity between the roller and the raceway, or one in the slide-roll ratio arguments the temperature rise.

Originality/value

This study conducts a detailed discussion of the TEHL analysis of deep groove ball bearing and gives a beneficial reference to the design and application of this kind of bearings.

Details

Industrial Lubrication and Tribology, vol. 70 no. 7
Type: Research Article
ISSN: 0036-8792

Keywords

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