Effect of Rolling Velocity and Maximum Hertzian Pressure on Fluid Film in Steady State EHL Line Contact with Rough Surface and Linear Piezoviscosity

2014 ◽  
Vol 592-594 ◽  
pp. 1371-1375
Author(s):  
Nitesh Talekar ◽  
Punit Kumar
Keyword(s):  
Surface Roughness ◽  
Steady State ◽  
Film Thickness ◽  
Rough Surface ◽  
Computer Code ◽  
Fluid Film ◽  
Line Contact ◽  
Rolling Velocity ◽  
Load Carrying ◽  
Lubricated Contact

Consideration of surface roughness in steady state EHL line contact is the first step towards understanding the lubrication of rough surface problem. Current paper investigates the use of sinusoidal waviness in the contact; more precisely it gives performance of real fluid in EHL line contact. The effect of various parameters like rolling velocity (U) and maximum Hertzian pressure (ph) on surface roughness by using properties of linear and exponential piezo-viscosity is taken into consideration to evaluate behavior of pressure distribution of load carrying fluid film and film thickness. Full isothermal, Newtonian simulation of EHL problem gives described effects. Spiking or fluctuation of pressure and film thickness curves is expected to show presence of irregularities on the surface chosen and amount of fluctuation depends on certain parameters and intensity of irregularities present. Rolling side domain of-4.5 ≤ X ≤ 1.5 with grid size ∆X=0.01375 is selected. A computer code is developed to solve Reynolds equation, which governs the generation of pressure in the lubricated contact zone is discritized and solved along with load balance equation using Newton-Raphson technique.

The Effects of Surface Roughening and Protective Film Formation on Scuff Initiation in Boundary Lubrication

1991 ◽  
Vol 113 (2) ◽  
pp. 295-302 ◽  
Author(s):  
Young-ze Lee ◽  
K. C. Ludema
Keyword(s):  
Surface Roughness ◽  
Film Thickness ◽  
Carrying Capacity ◽  
Fluid Film ◽  
Surface Roughening ◽  
Protective Film ◽  
Load Carrying Capacity ◽  
Surface Failure ◽  
Load Carrying ◽  
Fluid Film Thickness

The mechanisms of failure of lubricated steel surfaces were investigated. The focus was on two phenomena, namely, the effects of lubricant reactivity and the effects of sliding speed. Experiments were performed with the ball-on-flat and the cylinder-on-flat geometries in the manner of the methods used to develop the failure maps of the (OECD) IRG. Contact resistance and coefficient of friction were measured during the tests and surface roughness was measured frequently during the tests. Surface failure could not be predicted by using the ratio λ (the ratio of fluid film thickness to composite surface roughness) except when chemically inert lubricants are used. Even then the adverse influence of temperature rise on fluid film thickness does not adequately explain the low load carrying capacity of lubricated surfaces at high sliding speeds. There is a separate effect, namely, a quicker and more severe surface roughening at high speeds than at low speeds, which causes surface failure. The protective layers on sliding surfaces that form by chemical reaction with the lubricant were found to reduce the surface roughening and increase the load carrying capacity of surfaces to values of λ as low as 0.03.

Surface Roughness Effects in an EHL Line Contact

1992 ◽  
Vol 114 (3) ◽  
pp. 616-622 ◽  
Author(s):  
C. H. Venner ◽  
W. E. ten Napel
Keyword(s):  
Surface Roughness ◽  
Steady State ◽  
Film Thickness ◽  
Pressure Profile ◽  
Line Contact ◽  
Roughness Effects ◽  
Misleading Information ◽  
Roughness Profile ◽  
Pressure Profiles ◽  
Load Conditions

In this paper the influence of surface roughness on the pressure profile and film thickness in a steady state EHL line contact is investigated using input from an actually measured roughness profile in the calculations. Pressure profiles and film shapes for different load conditions are shown. The presented results strongly indicate that in the steady state situation considered here a significant deformation of the roughness profile occurs. As a result the often used λ parameter being the ratio of film thickness and standard deviation of the roughness (h/σ) with σ based on the undeformed roughness profile may give misleading information as far as the effect of the roughness on pressure and film shape is concerned.

Performance analysis of rough surface hybrid thrust bearing with elliptical dimples

2020 ◽  
pp. 135065012093198
Author(s):  
Vivek Kumar ◽  
Satish C Sharma
Keyword(s):  
Surface Roughness ◽  
Carrying Capacity ◽  
Machining Process ◽  
Fluid Film ◽  
Textured Surface ◽  
Stiffness Coefficient ◽  
Load Carrying Capacity ◽  
Power Losses ◽  
Load Carrying ◽  
Film Stiffness

Surface roughness is inherent to all machining processes. Therefore, even a high precision machining process renders micro-roughness to some extent on the surface of conventional materials. The asperities height of many rough engineering surfaces follows Gaussian distribution. The surface roughness on the bearing surface may significantly affect the bearing performance. Surface texturing is emerging as a new technique to improve the tribological behavior of the mating surfaces. Usually dimensions/height of micro-roughness is of order of the depth of surface textures in fluid film bearings. Neglecting micro-roughness while numerically simulating a textured surface bearing may generate inaccurate bearing performance data. In presented work, finite element simulation of textured surface hybrid thrust bearings has been performed. Surface texture is provided over thrust pad in the form of regular arrays of elliptical dimples. A parametric optimization is carried out to determine optimum attributes of elliptical dimple (axis, depth, texture length and orientation) so that the load-carrying capacity and fluid film stiffness should be maximized and film frictional power losses should be minimized. Use of textured surface (with optimum elliptical dimple attributes) results into a significant enhancement in load-carrying capacity (91.3%), film stiffness coefficient (+98.8%) and reduction in frictional power losses (−48.3%). It is also observed that elliptical dimple and micro-roughness (transverse orientation) generate synergistic effects in further enhancing the load-carrying capacity (+101.4%) and film stiffness coefficient (+112%) of the bearing.

Computational analysis of the steady state performance of an adjustable/controllable multi-pad bearing profile under LBP orientations

2020 ◽  
pp. 095440622095770
Author(s):  
Girish Hariharan ◽  
Raghuvir Pai
Keyword(s):  
Steady State ◽  
Theoretical Model ◽  
Theoretical Analysis ◽  
Film Thickness ◽  
Computational Analysis ◽  
Fluid Film ◽  
Adjustable Mechanism ◽  
State Behaviour ◽  
Steady State Behaviour ◽  
Steady State Performance

A theoretical model of a four-pad bearing profile with unique adjustable or controllable features is simulated in the present study by considering load directed between the pads. Radial and tilt adjustable mechanism of the four bearing pads can effectively control and modify the rotor operating behaviour. Inward and outward motions of the bearing pads result in the generation of narrow and broader convergent regions, which directly influences the fluid film pressures. In the theoretical analysis, load-between-pad (LBP) orientations and pad adjustment configurations are taken account of by employing a modified film thickness equation. The effect of load position in influencing the steady state behaviour of the four-pad adjustable bearing under varied pad displaced conditions is analysed in this study. The outcome of the analysis highlighted the effectiveness of four-pad adjustable bearing in improving the steady state performance by operating under negative adjustment conditions and with load acting on the bearing pads.

scholarly journals Analysis of Line Contact Elastohydrodynamic Lubrication with the Particles under Rough Contact Surface

2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
Keying Chen ◽  
Liangcai Zeng ◽  
Juan Chen ◽  
Xianzhong Ding
Keyword(s):  
Film Thickness ◽  
Rough Surface ◽  
Thickness Distribution ◽  
Traction Force ◽  
Elastohydrodynamic Lubrication ◽  
Equation System ◽  
Line Contact ◽  
Equivalent Inclusion Method ◽  
Equivalent Inclusion ◽  
The Matrix

A numerical solution for line contact elastohydrodynamic lubrication (EHL) occurring on the rough surface of heterogeneous materials with a group of particles is presented in this study. The film thickness disturbance caused by particles and roughness is considered into the solution system, and the film pressure between the contact gap generated by the particles and the surface roughness is obtained through a unified Reynold equation system. The inclusions buried in the matrix are made equivalent to areas with the same material as that of the matrix through Eshelby’s equivalent inclusion method and the roughness is characterized by related functions. The results present the effects of different rough topographies combined with the related parameters of the particles on the EHL performance, and the minimum film thickness distribution under different loads, running speeds, and initial viscosities are also investigated. The results show that the roughness morphology and the particles can affect the behavior of the EHL, the traction force on a square rough surface is smaller, and the soft particles have more advantages for improving the EHL performance.

A Theory of Liquid-Solid Lubrication in Elastohydrodynamic Regime

1989 ◽  
Vol 111 (3) ◽  
pp. 440-444 ◽  
Author(s):  
M. M. Khonsari ◽  
S. H. Wang ◽  
Y. L. Qi
Keyword(s):  
Particle Size ◽  
Film Thickness ◽  
Carrying Capacity ◽  
Theoretical Study ◽  
Solid Particles ◽  
Solid Lubrication ◽  
Load Carrying Capacity ◽  
Line Contact ◽  
Load Carrying ◽  
Bounding Surfaces

A theoretical study of the effectiveness of solid particles dispersed in oil in the elastohydrodynamic line contact is presented. The analysis includes the variation of the viscosity and density of the lubricant as a function of pressure. The deformation of solid particles and that of the bounding surfaces are taken into consideration. Results are presented for the variation of the film thickness and the load carrying capacity as a function of the particle size, concentration, and properties of various types of particles.

scholarly journals A comparison of porous structures on the performance of slider bearing with surface roughness in micropolar fluid film lubrication

2019 ◽  
Vol 23 (3 Part B) ◽  
pp. 1813-1824 ◽  
Author(s):  
Pentyala Rao ◽  
Birendra Murmu ◽  
Santosh Agarwal
Keyword(s):  
Surface Roughness ◽  
Micropolar Fluid ◽  
Fluid Film ◽  
Porous Structures ◽  
Slider Bearing ◽  
Sphere Model ◽  
Load Carrying ◽  
Improved Performance ◽  
Film Lubrication ◽  
Fluid Film Lubrication

This paper presents the theoretical analysis of comparison of porous structures on the performance of a slider bearing with surface roughness in micropolar fluid film lubrication. The globular sphere model and Irmay?s capillary fissures model have been subject to investigations. The general Reynolds equation which incorporates randomized roughness structure with Stokes micropolar fluid is solved with suitable boundary conditions to get the pressure distribution, which is then used to obtain the load carrying capacity. The graphical representations suggest that the globular sphere model scores over the Irmay?s capillary fissures model for an overall improved performance. The numerical computations of the results show that, the act of the porous structures on the performance of a slider bearing is improved for the micropolar lubricants as compared to the corresponding Newtonian lubricants.

Effect of Liquid-Solid Lubricant on Mixed Lubrication in Line Contact

2011 ◽  
Vol 148-149 ◽  
pp. 778-784
Author(s):  
Rattapasakorn Sountaree ◽  
Panichakorn Jesda ◽  
Mongkolwongrojn Mongkol
Keyword(s):  
Friction Coefficient ◽  
Film Thickness ◽  
Solid Lubricant ◽  
Reynolds Equation ◽  
Contact Region ◽  
Mixed Lubrication ◽  
Line Contact ◽  
Load Carrying ◽  
Roughness Amplitude ◽  
Raphson Method

This paper presents the performance characteristics of two surfaces in line contact under isothermal mixed lubrication with non-Newtonian liquid–solid lubricant base on Power law viscosity model. The time dependent Reynolds equation, elastic equation and viscosity equation were formulated for compressible fluid. Newton-Raphson method and multigrid technique were implemented to obtain film thickness profiles, friction coefficient and load carrying in the contact region at various roughness amplitudes, applied loads, speeds and the concentration of solid lubricant. The simulation results showed that roughness amplitude has a significant effect on the film pressure, film thickness and surface contact pressure in the contact region. The film thickness decrease but friction coefficient and asperities load rapidly increases when surface roughness amplitude increases or surface speed decreases. When the concentration of solid lubricant increased, friction coefficient and asperities load decrease but traction and film thickness increase.

Film Thickness and Asperity Load Formulas for Line-Contact Elastohydrodynamic Lubrication With Provision for Surface Roughness

2012 ◽  
Vol 134 (1) ◽  
Author(s):  
M. Masjedi ◽  
M. M. Khonsari
Keyword(s):  
Surface Roughness ◽  
Film Thickness ◽  
Reynolds Equation ◽  
Surface Deformation ◽  
Elastohydrodynamic Lubrication ◽  
Load Ratio ◽  
Material Surface ◽  
Line Contact ◽  
Wide Range ◽  
Minimum Film Thickness

Three formulas are derived for predicting the central and the minimum film thickness as well as the asperity load ratio in line-contact EHL with provision for surface roughness. These expressions are based on the simultaneous solution to the modified Reynolds equation and surface deformation with consideration of elastic, plastic and elasto-plastic deformation of the surface asperities. The formulas cover a wide range of input and they are of the form f(W, U, G, σ¯, V), where the parameters represented are dimensionless load, speed, material, surface roughness and hardness, respectively.

A Study of Elastohydrodynamic Lubrication of Rough Surfaces

1991 ◽  
Vol 113 (1) ◽  
pp. 110-115 ◽  
Author(s):  
L. Chang ◽  
M. N. Webster
Keyword(s):  
Surface Roughness ◽  
Film Thickness ◽  
Rough Surface ◽  
Contact Zone ◽  
Elastohydrodynamic Lubrication ◽  
Operating Conditions ◽  
Micro Deformation ◽  
Sinusoidal Functions ◽  
Sensitive Parameters ◽  
Pressure Perturbations

This paper reports some results of rough-surface, elastohydrodynamically lubricated (EHD) contacts obtained using a previously developed transient EHD model. The surface roughness is modeled with sinusoidal functions of small wavelength compared to the contact zone. Results are presented showing how the operating conditions affect the film thickness, micro-deformation of the roughness, and the pressure perturbations due to motion and interaction of roughness within the contact. This preliminary work suggests that the entraining velocity and the slide-to-roll ratio are the most sensitive parameters influencing the lubrication process of rough-surface EHD contacts.

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