Elastohydrodynamic Lubrication by Powder Slurries

1996 ◽  
Vol 118 (1) ◽  
pp. 67-73 ◽  
Author(s):  
D. Y. Hua ◽  
M. M. Khonsari
Keyword(s):  
Elastohydrodynamic Lubrication ◽  
Pressure Profile ◽  
Load Carrying Capacity ◽  
Carrier Fluid ◽  
Shear Thinning Fluids ◽  
Contact Configuration ◽  
Load Carrying ◽  
Traction Coefficient ◽  
Higher Temperature ◽  
Performance Results

Thermoelastohydrodynamic analysis of a powder slurry containing a mixture of MoS2 particles and a carrier fluid is presented for a line-contact configuration. The constitutive equation of the slurry is a non-Newtonian formulation based on experimental data. The model includes provisions for elastic/plastic deformation of particles in the slurry. Through this deformation, particles are shown to contribute to the load-carrying capacity. The viscosity of the carrier fluid is shown to increase considerably as a result of adding a large amount of particles, thus appreciably affecting the EHL behavior of powder slurries. Performance results are presented for the pressure profile, film thickness, temperature distribution, and traction coefficient for a number of sliding/rolling ratios. The existence of particles in slurry is shown to give rise to a higher temperature field and tends to increase the traction coefficient compared to typical shear thinning fluids.

Deformation Effects on the Load Carrying Capacity of the Barrel Bearing in Axial Piston Pumps and Motors

2006 ◽  
Author(s):  
Peter A. J. Achten ◽  
Marc P. A. Schellekens
Keyword(s):  
Elastic Deformation ◽  
Carrying Capacity ◽  
Thrust Bearing ◽  
Pressure Profile ◽  
Load Carrying Capacity ◽  
Axial Piston Pumps ◽  
Load Carrying ◽  
Face Seals ◽  
Axial Piston Machine ◽  
Axial Piston

Most hydrostatic pumps and motors apply mechanical face seals, often also acting as a thrust bearing. The load carrying capacity of these bearings is very much dependent on the pressure profile generated in the sealing gap. Previous research, outside pumps and motors, has already shown that the gap pressure profile is largely influenced by small radial deformations of the seal lands. This paper discusses the elastic deformation of pump components and the effects of these deformations on the load carrying capacity of a barrel in an axial piston machine.

scholarly journals Understanding the Mechanism of Load-Carrying Capacity between Parallel Rough Surfaces through a Deterministic Mixed Lubrication Model

Lubricants ◽  
2022 ◽  
Vol 10 (1) ◽  
pp. 12
Author(s):  
Yuechang Wang ◽  
Abdullah Azam ◽  
Gaolong Zhang ◽  
Abdel Dorgham ◽  
Ying Liu ◽  
...  
Keyword(s):  
Carrying Capacity ◽  
Rough Surfaces ◽  
Elastohydrodynamic Lubrication ◽  
Mixed Lubrication ◽  
Stribeck Curve ◽  
Future Research ◽  
Load Carrying Capacity ◽  
Proposed Model ◽  
Load Carrying ◽  
Lift Off

Experimental results have confirmed that parallel rough surfaces can be separated by a full fluid film. However, such a lift-off effect is not expected by the traditional Reynolds theory. This paper proposes a deterministic mixed lubrication model to understand the mechanism of the lift-off effect. The proposed model considered the interaction between asperities and the micro-elastohydrodynamic lubrication (micro-EHL) at asperities within parallel rough surfaces for the first time. The proposed model is verified by predicting the measured Stribeck curve taken from literature and experiments conducted in this work. The simulation results highlight that the micro-EHL effect at the asperity scale is critical in building load-carrying capacity between parallel rough surfaces. Finally, the drawbacks of the proposed model are addressed and the directions of future research are pointed out.

Efficient running-in of gears and improved prediction of the tooth flank load carrying capacity

2019 ◽  
Vol 71 (3) ◽  
pp. 366-373
Author(s):  
Martin Zimmer ◽  
Dirk Bartel
Keyword(s):  
Carrying Capacity ◽  
Plastic Material ◽  
Rough Surfaces ◽  
Elastohydrodynamic Lubrication ◽  
Load Carrying Capacity ◽  
Content Type ◽  
Load Carrying ◽  
Life Model ◽  
Extended Life ◽  
Tooth Flank

Purpose The purpose of this paper is to determine parameters for an efficient running-in of gears and an improved method for the prediction of the tooth flank load carrying capacity. Design/methodology/approach In this contribution, a model for the calculation of the pitting life of involute spur gears is introduced, which is based on an extension of the life model according to Ioannides and Harris for rough surfaces. To achieve the most realistic thermal elastohydrodynamic lubrication simulation and stress calculation possible, measured real surfaces and elastic-plastic material properties of the area close to the surface are used. Special attention is paid to the compatibility of the fatigue life calculation for heterogeneous rough surfaces and their consistent consideration in the lifespan calculation. Findings A non-destructive running-in for twin-disc pairings can be performed using suitable operating parameters, which subsequently can be transferred to tooth flank tests. Using the extended life model according to Ioannides and Harris, an enhanced prediction of the tooth flank load carrying capacity is possible. Originality/value The developed extended life model includes a new numerical approach for calculating the tooth flank load carrying capacity. It has the potential to reliably support and hence to accelerate the design process of gears.

Improvement of Punch Profiles for Elastic Circular Contacts

2006 ◽  
Vol 128 (3) ◽  
pp. 486-492 ◽  
Author(s):  
Marilena Glovnea ◽  
Emanuel Diaconescu
Keyword(s):  
Carrying Capacity ◽  
Numerical Evaluation ◽  
Pressure Profile ◽  
Electrical Contacts ◽  
Machine Design ◽  
Load Carrying Capacity ◽  
Uniform Pressure ◽  
Pressure Distributions ◽  
Load Carrying ◽  
Double Integrals

Machine design and electrical contacts involve frequently elastic circular contacts subjected to normal loads. Depending on geometry, these may be Hertzian or surface contacts. Both possess highly nonuniform pressure distributions which diminish contact load carrying capacity. The achievement of a uniform pressure distribution would be ideal to improve the situation, but this violates stress continuity. Instead, the generation of a uniform pressure over most of contact area can be sought. Generally, equivalent punch profile which generates this pressure is found by numerical evaluation of double integrals. This paper simplifies the derivation of punch profile by using an existing correspondence between a polynomial punch surface and elastically generated pressure. First, an improved pressure profile is proposed seeking to avoid high Huber-Mises-Hencky stresses near contact surface. Then, this is approximated by the product between typical Hertz square root and an even polynomial, which yields directly the punch profile. Formulas for normal approach and central pressure are derived.

Steady-state performance of elliptical contact lubricated with micropolar fluids

2019 ◽  
Vol 234 (9) ◽  
pp. 1482-1499
Author(s):  
Dhanendra Dewangan ◽  
Mihir Sarangi
Keyword(s):  
Steady State ◽  
Reynolds Equation ◽  
Elastohydrodynamic Lubrication ◽  
Continuum Theory ◽  
Micropolar Fluids ◽  
Load Carrying ◽  
Molecular Length ◽  
Traction Coefficient ◽  
Modified Reynolds Equation ◽  
Steady State Performance

In this work, the numerical investigation is done for the steady-state performance of elliptical contacts lubricated with micropolar fluids. The Eringen’s micro-continuum theory is applied to deduce the modified Reynolds equation for micropolar fluids. The modified Reynolds equation is discretized by the finite difference technique and evaluated by a multigrid technique for finding the steady-state pressure distribution; simultaneously, the elasticity equation is solved with the multilevel multi-integration method. The numerical solution is achieved under isothermal conditions and considering the exponential variation of viscosity with pressure. The effect of micropolar parameters, i.e. nondimensional characteristics length defines the molecular length of the blended additives, and coupling number measures the coupling between the angular and linear momentum of molecules, and operating parameters are studied. Owing to the analysis, the pronounced effect of the micropolar parameters on the elastohydrodynamic lubrication of elliptical contacts is observed and which cannot be avoided. Lubricants added with solid additives and coupling between linear and angular momentum improved the overall film thickness and pressure and enhanced the load-carrying capacity. Also, a nominal rise in the traction coefficient is noticed, but this increase in the traction coefficient is quite less when compared to Newtonian fluids.

scholarly journals The Collapse of Titanium C-Column due to Thermal Compression

Materials ◽  
2020 ◽  
Vol 13 (18) ◽  
pp. 4193
Author(s):  
Leszek Czechowski ◽  
Adrian Gliszczyński ◽  
Nina Wiącek
Keyword(s):  
Carrying Capacity ◽  
Elevated Temperatures ◽  
Image Correlation ◽  
Linear Expansion Coefficient ◽  
Load Carrying Capacity ◽  
Lagrange Equations ◽  
Thermal Compression ◽  
Load Carrying ◽  
Higher Temperature ◽  
Thin Walled

The analysis of structures under higher temperature is important for predicting the ultimate strength of a structure. Therefore, many experimental tests on samples should be undertaken to observe their behaviour and to determine ultimate load. The present work includes the study on a thin-walled C-column made of titanium compressed in an elevated temperature. The phenomenon of buckling and the post-buckling state of columns were investigated during heating or compressing in higher temperature. The tests of compression were conducted for several temperature increments by assuming the same preload to determine the load-carrying capacity. The deformations of columns until total damage were measured by using the non-contact Digital Image Correlation Aramis® System (DICAS). The numerical calculations based on the finite element method (FEM) were performed to validate the empirical results. The full characteristics of one-directional tension tests were taken into account in order for them to be constant or dependent on the temperature change. Numerical computations were conducted by employing Green–Lagrange equations for large deflections and strains. Based on our own experiment, the thermal property of titanium as a linear expansion coefficient was stable up to 300 °C in contrast to its mechanical properties. The paper shows the influence of varying material properties as a function of temperature on the behaviour and load-carrying capacity of columns. These aspects cause thin-walled columns made of titanium to endure, in elevated temperatures, significantly smaller maximum loads. Moreover, the critical buckling loads for several types of stiff supports were compared to the maximum loads of columns. The results obtained indicate that the temperature rise in columns by 175 K with regard to ambient temperature brings about the decrease of the maximum load by a half.

Prevention of interfacial slippage in isothermal pure rolling line contact elastohydrodynamic lubrication under heavy loads

2003 ◽  
Vol 217 (4) ◽  
pp. 323-332 ◽  
Author(s):  
Yongbin Zhang
Keyword(s):  
Carrying Capacity ◽  
Elastohydrodynamic Lubrication ◽  
Load Carrying Capacity ◽  
Pure Rolling ◽  
Load Carrying ◽  
Rolling Line ◽  
Line Contacts ◽  
Heavy Loads ◽  
Inlet Zone ◽  
Interfacial Slippage

The contact-lubricant interfacial slippage, near and in the inlet zone, significantly reduces the load-carrying capacity of elastohydrodynamic lubrication (EHL) in isothermal pure rolling line contacts under heavy loads. The EHL load-carrying capacity can be significantly improved by the prevention of this interfacial slippage. Equations are derived for predicting the critical interfacial limiting shear stress, which is the least for preventing this interfacial slippage. These equations can be used for designing the EHL system of which the load-carrying capacity is not reduced by this slippage.

Hydrostatic Gas Bearings

1960 ◽  
Vol 82 (2) ◽  
pp. 276-285 ◽  
Author(s):  
John H. Laub
Keyword(s):  
Gas Flow ◽  
Pressure Profile ◽  
Load Carrying Capacity ◽  
Air Bearing ◽  
Gas Flow Rate ◽  
Test Fixture ◽  
Gas Bearings ◽  
Load Carrying ◽  
Gap Height ◽  
Starting Torque

Orifice-regulated hydrostatic gas bearings offer significant advantages for instrument applications. In particular, gimbal bearings for inertial guidance systems can be designed with negligible starting torque and high stiffness, and for operation at extreme temperatures. A literature search revealed the lack of convenient and accurate data for the design of hydrostatic gas bearings of various configurations, taking into consideration the effects of compressibility, which cannot be neglected at higher pressures. Based on Euler’s equation, expressions for the significant parameters, i.e., pressure profile, gas-flow rate, gap height, and load-carrying capacity of pad and step bearings, are developed. These parameters yield results which are in excellent agreement with experimental data. The test fixture incorporates pneumatic loading by means of a bellows-suspended piston which is prevented from cocking by an air bearing.

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