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.

scholarly journals Theoretical and experimental analysis of a partially textured thrust bearing with square dimples

2007 ◽  
Vol 221 (7) ◽  
pp. 771-778 ◽  
Author(s):  
V. G. Marian ◽  
M Kilian ◽  
W Scholz
Keyword(s):  
Film Thickness ◽  
Carrying Capacity ◽  
Thrust Bearing ◽  
Surface Texturing ◽  
Optimal Number ◽  
Friction Torque ◽  
Fluid Film ◽  
Load Carrying Capacity ◽  
Load Carrying ◽  
Fluid Film Thickness

Surface texturing has proved to be very efficient in full and mixed lubrication, reducing the friction coefficient and the wear rate of mating surfaces. By partially texturing the inlet zone of a thrust washer pad load carrying capacity is generated in the system. In the present paper, a partially textured thrust bearing with square dimples is analysed theoretically using a thermohydrodynamic model. The equations are solved numerically by the finite-difference method. The bearing was realized by the photolithographic method and the theoretical results (fluid film thickness and friction torque) were compared with the experimental data obtained on the test rig. It is found that an optimal number of 12 sectors maximize the load carrying capacity of the bearing. The optimal textured fraction, which maximizes the load carrying capacity is 0.5 on the circumferential direction and 0.9-1 on the radial direction. A good correlation was found between the theoretical and experimental results for the two measured parameters (fluid film thickness and friction torque).

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.

Influence of Surface Roughness on Non-Newtonian Thermohydrostatic Performance of a Hole-Entry Hybrid Journal Bearing

2007 ◽  
Vol 129 (3) ◽  
pp. 595-602 ◽  
Author(s):  
T. Nagaraju ◽  
Satish C. Sharma ◽  
S. C. Jain
Keyword(s):  
Surface Roughness ◽  
Thermal Effect ◽  
Carrying Capacity ◽  
Journal Bearing ◽  
Fluid Film ◽  
Load Carrying Capacity ◽  
Fluid Film Bearings ◽  
Load Carrying ◽  
Transverse Pattern ◽  
Newtonian Behavior

A general solution scheme to account the surface roughness and the cross-film viscosity variation of lubricant due to its non-Newtonian behavior and rise in fluid-film temperature for the analysis of fluid-film bearings is presented. The combined influence of surface roughness, non-Newtonian behavior of lubricant, and thermal effects on the performance of a hole-entry hybrid journal bearing system has been investigated. The surface roughness, especially stationary roughness (i.e., rough bearing and smooth journal) with a transverse pattern was found to partially compensate for the loss in load-carrying capacity due to the thermal and/or non-Newtonian behavior of lubricant effects. It limits 18.86% loss in load-carrying capacity due to the thermal effect to only 1.6% and 33.99% loss due to the combined influence of non-Newtonian lubricant and thermal effect to 16.76%.

scholarly journals Shear cutting induced residual stresses in involute gears and resulting tooth root bending strength of a fineblanked gear

2021 ◽  
Author(s):  
Daniel Müller ◽  
Jens Stahl ◽  
Anian Nürnberger ◽  
Roland Golle ◽  
Thomas Tobie ◽  
...  
Keyword(s):  
Surface Roughness ◽  
Residual Stresses ◽  
Carrying Capacity ◽  
Bending Strength ◽  
Tooth Root ◽  
Load Carrying Capacity ◽  
Near Surface ◽  
Load Carrying ◽  
Involute Gears ◽  
Cut Surface

AbstractThe manufacturing of case-hardened gears usually consists of several complex and expensive steps to ensure high load carrying capacity. The load carrying capacity for the main fatigue failure modes pitting and tooth root breakage can be increased significantly by increasing the near surface compressive residual stresses. In earlier publications, different shear cutting techniques, the near-net-shape-blanking processes (NNSBP’s), were investigated regarding a favorable residual stress state. The influence of the process parameters on the amount of clean cut, surface roughness, hardness and residual stresses was investigated. Furthermore, fatigue bending tests were carried out using C-shaped specimens. This paper reports about involute gears that are manufactured by fineblanking. This NNSBP was identified as suitable based on the previous research, because it led to a high amount of clean cut and favorable residual stresses. For the fineblanked gears of S355MC (1.0976), the die edge radii were varied and the effects on the cut surface geometry, hardness distribution, surface roughness and residual stresses are investigated. The accuracy of blanking the gear geometry is measured, and the tooth root bending strength is determined in a pulsating test rig according to standardized testing methods. It is shown that it is possible to manufacture gears by fineblanking with a high precision comparable to gear hobbing. Additionally, the cut surface properties lead to an increased tooth root bending strength.

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.

A Comparison of Porous Structures on the Performance of a Slider Bearing with Surface Roughness in Couple Stress Fluid Film Lubrication

2015 ◽  
Vol 813-814 ◽  
pp. 921-937
Author(s):  
P.S. Rao ◽  
Santosh Agarwal
Keyword(s):  
Surface Roughness ◽  
Carrying Capacity ◽  
Couple Stress ◽  
Type Equation ◽  
Random Variable ◽  
Couple Stress Fluid ◽  
Load Carrying Capacity ◽  
Porous Structures ◽  
Slider Bearing ◽  
Load Carrying

This paper presents the theoretical study and analyzes the comparison of porous structures on the performance of a couple stress fluid based on rough slider bearing. The globular sphere model of Kozeny-Carman and Irmay’s capillary fissures model have been subjected to investigations. A more general form of surface roughness is mathematically modeled by a stochastic random variable with non-zero mean, variance and skewness. The stochastically averaged Reynolds type equation has been solved under suitable boundary conditions to obtain the pressure distribution in turn which gives the expression for the load carrying capacity, frictional force and coefficient of friction. The results are illustrated by graphical representations which show that the introduction of combined porous structure with couple stress fluid results in an enhanced load carrying capacity more in the case of Kozeny-Carman model as compared to Irmay’s model.

The Performance of Hydrodynamic Lubricating Films With Viscosity Variations Perpendicular to the Direction of Motion

1972 ◽  
Vol 94 (1) ◽  
pp. 44-48 ◽  
Author(s):  
E. B. Qvale ◽  
F. R. Wiltshire
Keyword(s):  
Film Thickness ◽  
Carrying Capacity ◽  
Load Carrying Capacity ◽  
End Effects ◽  
Parametric Curves ◽  
One Dimensional ◽  
Lubricating Film ◽  
Families Of Curves ◽  
Load Carrying ◽  
The Coefficient Of Friction

The effects of prescribed viscosity variations across a hydrodynamic lubricating film are studied. The film is strictly one dimensional and end effects are neglected. The viscosity variations are given by three families of curves. The considerable decreases (in the limit 100 percent) and occasional increases in the coefficient of friction that can occur for constant film thickness and load-carrying capacity are evaluated and the results are presented in terms of parametric curves. Important physical situations where these viscosity variations may be observed or produced are described.

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.

Sign in / Sign up

Export Citation Format

Share Document