The purpose of this paper is to investigate squeezing and rotating motions between two rough parallel circular discs lubricated by piezo – viscous couple stress lubricant with…
Abstract
Purpose
The purpose of this paper is to investigate squeezing and rotating motions between two rough parallel circular discs lubricated by piezo – viscous couple stress lubricant with pressure-dependent viscosity variation.
Design/methodology/approach
Based upon the Stokes couple stress theory, Barus viscosity-pressure dependency relation and Christensen rough surfaces model, squeeze film characteristics between two rough parallel circular discs are obtained.
Findings
According to the results, it is found that, the combined effects of couple stresses and viscosity-pressure dependency increases squeeze film performance with respect to the classical Newtonian iso-viscous (constant viscosity) lubricant. However, increasing the rotational inertia parameter reduces squeeze film characteristics. On the other hand, depending on the structure of surface roughness, the squeeze film characteristics can be increased or decreased. Furthermore, results show that the surface roughness with circular pattern increases squeeze film characteristics, while the surface roughness with radial pattern will decrease it.
Originality/value
This paper is relatively original and describes the squeeze film characteristics between two parallel circular discs with viscosity-pressure dependency, rotational inertia, couple stresses and surface roughness effects.
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Keywords
The purpose of this paper is to investigate squeezing and rotating motions between two rough parallel circular discs lubricated by ferro-fluid couple stress lubricant.
Abstract
Purpose
The purpose of this paper is to investigate squeezing and rotating motions between two rough parallel circular discs lubricated by ferro-fluid couple stress lubricant.
Design/methodology/approach
Based upon the Stokes couple stress theory, ferro-hydrodynamic model of Shliomis and Christensen rough surfaces model, squeeze-film characteristics between two rough parallel circular discs considering rotational inertia effects are obtained.
Findings
According to the results, it is found that the combined effects of couple stresses and ferro-fluid lubricants increases squeeze film performance with respect to the classical Newtonian lubricant. However, increasing the rotational inertia parameter reduces squeeze film characteristics. On the other hand, depending on the structure of surface roughness, the squeeze film characteristics can be increased or decreased. Furthermore, results show that the surface roughness with circular pattern increases squeeze film characteristics, while the surface roughness with radial pattern will decrease it.
Originality/value
This paper is relatively original and describes the squeeze film characteristics between two parallel circular discs with ferro- fluid, rotational inertia, couple stresses and surface roughness effects.
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Vishal Singh and Arvind K. Rajput
The present paper aims to analyse the synergistic effect of pocket orientation and piezo-viscous-polar (PVP) lubrication on the performance of multi-recessed hybrid journal…
Abstract
Purpose
The present paper aims to analyse the synergistic effect of pocket orientation and piezo-viscous-polar (PVP) lubrication on the performance of multi-recessed hybrid journal bearing (MHJB) system.
Design/methodology/approach
To simulate the behaviour of PVP lubricant in clearance space of the MHJB system, the modified form of Reynolds equation is numerically solved by using finite element method. Galerkin’s method is used to obtain the weak form of the governing equation. The system equation is solved by Gauss–Seidal iterative method to compute the unknown values of nodal oil film pressure. Subsequently, performance characteristics of bearing system are computed.
Findings
The simulated results reveal that the location of pressurised lubricant inlets significantly affects the oil film pressure distribution and may cause a significant effect on the characteristics of bearing system. Further, the use of PVP lubricant may significantly enhances the performance of the bearing system, namely.
Originality/value
The present work examines the influence of pocket orientation with respect to loading direction on the characteristics of PVP fluid lubricated MHJB system and provides vital information regarding the design of journal bearing system.
Peer review
The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-07-2023-0241/
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F. Stefani, A. Ferrari and D.T. Beruto
To propose a new numerical elastohydrodynamic (EHD) analysis method suited to cinematic pairs lubricated with aqueous dispersions of collagen gelled media.
Abstract
Purpose
To propose a new numerical elastohydrodynamic (EHD) analysis method suited to cinematic pairs lubricated with aqueous dispersions of collagen gelled media.
Design/methodology/approach
In comparison with traditional lubricants, these media are characterized by an apparent viscosity that increases with film thickness. Hence, the Reynolds equation has been numerically solved taking into account the new rheological law. The apparent viscosity of 4 percent collagen gel dispersions, as measured at a fixed shear rate of 100 l/s, is in the range 2‐5 Pa s, when film thickness varies between 20 and 200 μm. These experimental data have been fitted using a power law. The proposed analysis method has been applied to a 180° partial bearing, which rigid journal rotates in a flexible sleeve, made up by a resin shell.
Findings
The results of this tribological analysis have been compared with those concerning traditional isoviscous fluids which viscosity has been set equal to the viscosity of the gelled media when the film thickness is constant, i.e. in the unloaded bearing. The minimum film thickness calculated has been turned out equal to 66.8 μm in the former case, and 27.6 μm in the latter case. Furthermore, when the cinematic pair is lubricated with the aqueous gel media, film thickness distribution over the bearing surface is more uniform, active film region is wider and, consequently, peak pressure is lower than when the isoviscous lubricant is employed.
Research limitations/implications
For lightly loaded journal bearings, the dependence between apparent viscosity and the shear rate in the lubricant film has been neglected, so that the apparent viscosity has been considered changing only with the film thickness.
Originality/value
The paper introduces a new numerical EHD analysis method for use with cinematic pairs lubricated with aqueous dispersions of collagen gelled media.
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Lucian Capitanu, Virgil Florescu and Liliana-Laura Badita
The purpose of this study was to realize finite element simulation in order to dynamically determine the area of the contact, the contact pressure and the strain energy density…
Abstract
Purpose
The purpose of this study was to realize finite element simulation in order to dynamically determine the area of the contact, the contact pressure and the strain energy density (identified as a damage function) for three different activities – normal walking, ascending stairs and descending stairs – that could be considered to define the level of the activity of the patient.
Design/methodology/approach
The finite element model uses a modern contact mechanism that includes friction between the metallic femoral condyles or femoral head (considered rigid) and the tibial polyethylene insert or acetabular cup (considering a non-linear behaviour).
Findings
For all three activities, the finite element analyses were performed, and a damage score was computed. Finally, a cumulative damage score (that accounts for all three activities) was determined, and the areas where the fatigue wear is likely to occur were identified.
Originality/value
A closer look at the distribution of the damage score reveals that the maximum damage is likely to occur not at the contact surface, but in the subsurface.
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Xianghui Meng, Changya Yu, Youbai Xie and Benfu Mei
This paper aims to investigate the lubrication performance of cam/tappet contact during start up. Especially, the thermal insulation effects of coating on the lubrication…
Abstract
Purpose
This paper aims to investigate the lubrication performance of cam/tappet contact during start up. Especially, the thermal insulation effects of coating on the lubrication performance during cold start up process and warm start up process are studied.
Design/methodology/approach
A numerical model for the analysis of thermal elastohydrodynamic lubrication of coated cam/tappet contact is presented. In this model, the Reynolds equation and the energy equations are discretized by the finite difference method and solved jointly.
Findings
During start up, the contact force at cam nose-to-tappet contact decreases with increasing time, while the absolute entrainment velocity has the upward trend. The minimum film thickness, maximum average temperature and friction power loss increase with increasing time, while the coefficient of friction decreases during start up. Because of the thermal insulation effect, the coating can significantly increase the degree of temperature rise. Compared with the uncoated case, the coated cam/tappet results in a lower friction power loss. Generally, the friction power loss in the cold start up process is much higher than that in the warm start up process.
Originality/value
By this study, the lubrication performance and the kinematics and the dynamics of the cam/tappet during start up process are investigated. Meanwhile, the thermal insulation effect of coating is also illustrated. The difference of lubrication performance between cold start up process and warm start up process is analyzed. The results and thermal elastohydrodynamic lubrication method presented in this study can be a guidance in the design of the coated cam/tappet.
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This paper aims to investigate the effect of changing speed of the entraining motion on the formation of ultra-thin lubricating films under different elliptical ratios. The…
Abstract
Purpose
This paper aims to investigate the effect of changing speed of the entraining motion on the formation of ultra-thin lubricating films under different elliptical ratios. The ellipticity parameter (K) varied from 1 (a ball-on-plate configuration) to 6 (a configuration approaching line contact). The influence of the ellipticity parameters, the dimensionless speed and the effects of surface forces on the formation of the minimum film thickness has been demonstrated. The demarcation boundary between region dominated by elastohydrodynamic lubrication (EHL) and that by the surface force action has been demonstrated for different elliptical ratios.
Design/methodology/approach
The numerical solution has been carried out, using the Newton–Raphson iteration technique, applied for the convergence of the hydrodynamic pressure. The film thickness and pressure distribution are obtained by simultaneous solution of the Reynolds’ equation, the elastic deformation (caused by hydrodynamic pressure, surface force of solvation and Van der Waals force) and the load balance equation. The operating conditions, load and speed of entraining motion, promote formation of ultra-thin films that are formed under the combined action of EHL, surface contact force of solvation and molecular interactions due to presence of Van der Waals force.
Findings
The paper provides insights about the transition between region dominated by EHL and that by the surface force action for changing ellipticity ratio (K) from 1 (a ball-on-plate configuration) to 6 (a configuration approaching line contact).
Originality/value
This paper fulfils an identified need to study the effect of changing ellipticity ratio on the formation of ultra-thin films that are formed under the combined action of EHL, surface contact force of solvation and molecular interactions due to presence of Van der Waals force.
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X.F. Wang and D.G. Chang
The purpose of this paper is to understand the lubricating properties of the tripod sliding universal joint (TSUJ) in order to overcome its premature failures caused by the poor…
Abstract
Purpose
The purpose of this paper is to understand the lubricating properties of the tripod sliding universal joint (TSUJ) in order to overcome its premature failures caused by the poor lubricating regime.
Design/methodology/approach
A simplified geometrical model is derived from the main mating surfaces redesigned, and then the effects of the applied load and reduced elastic modulus, as well as the lubricant viscosity on the pressure and film thickness, are theoretically studied by using multi‐level methods.
Findings
The obtained results show that increasing applied load increases the overall pressure distribution and decreases the overall film thickness. Higher viscosity results in a thicker oil film and a remarkable second pressure peak even exceeding the central pressure. High‐reduced elastic modulus increases the overall pressure but hardly influences on the film thickness.
Research limitations/implications
Numerical analysis on the lubricating properties of TSUJ has been carried out on the basis of the simplified geometrical model. However, there are other factors affecting the lubricating performance such as temperature and surface roughness and so on. Besides, the corresponding experimental investigation should be conducted in the succeeding work.
Originality/value
This work is a new application of elastohydrodynamic lubrication in practical viewpoint and provide a new direction in designing futuristic tripod universal joints. Thus, the results are of great value for its design and application.
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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 performance of…
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.
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Nioosha Ghasemi Dolatsara, Maghsood Daliri and Moharram Shameli
The purpose of this paper is to investigate squeezing and rotating motions between two parallel annular discs lubricated by ferro-fluid couple stress lubricant in the presence of…
Abstract
Purpose
The purpose of this paper is to investigate squeezing and rotating motions between two parallel annular discs lubricated by ferro-fluid couple stress lubricant in the presence of a uniform magnetic field.
Design/methodology/approach
Based upon the Stokes couple stress theory and ferro-hydrodynamic model of Shliomis, squeeze film characteristics between two parallel annular discs are obtained.
Findings
According to the results, it is found that the combined effects of couple stress and ferro-fluid lubricant increase squeeze film performance with respect to the classical Newtonian lubricant. However, an increase in the rotational inertia parameter reduces squeeze film characteristics.
Originality/value
This paper is relatively original and describes the squeeze film characteristics between two parallel annular discs with rotational inertia, couple stress and ferro-fluid lubricant effects.