Partial EHL friction coefficient model to predict power losses in cylindrical gears

2018 ◽  
Vol 233 (2) ◽  
pp. 303-316 ◽  
Author(s):  
Aitor Arana ◽  
Jon Larrañaga ◽  
Ibai Ulacia
Keyword(s):  
Friction Coefficient ◽  
Operating Conditions ◽  
Power Losses ◽  
Gear Mesh ◽  
Numerical Predictions ◽  
Reference Stress ◽  
Fluid Load ◽  
Stress Behaviour ◽  
Good Agreement ◽  
Ehl Friction

The accurate prediction of friction coefficient and power losses in the gear mesh is a key subject to several gear-related fields of study. However, there is still not a unified method for large ranges of operating conditions, different gear geometries and lubricant types. The current paper meets this demand by modelling partial EHL friction with an asperity-fluid load sharing approach where fluid traction is calculated with the Ree-Eyring equation and the reference stress behaviour is predicted from piezoviscosity coefficient. It will be shown that only an accurate description of the lubricant’s viscosity behaviour is required to compute friction in gears. Finally, mesh power losses are predicted considering thermal effects and numerical predictions are compared to experimental results showing good agreement.

Analysis of the Oil Squeezing Power Losses of a Spur Gear Pair by Mean of CFD Simulations

2012 ◽  
Author(s):  
Franco Concli ◽  
Carlo Gorla
Keyword(s):  
High Efficiency ◽  
Fluid Dynamic ◽  
Axial Direction ◽  
Spur Gear ◽  
Operating Conditions ◽  
Pollutant Emissions ◽  
Main Concern ◽  
Power Losses ◽  
Dynamic Simulations ◽  
Gear Mesh

Efficiency is becoming more and more a main concern in the design of power transmissions and the demand for high efficiency gearboxes is continuously increasing. Also the new restrictive euro standards for the reduction of pollutant emissions from light vehicles impose to improve the efficiency of the engines but also of the gear transmissions. For this reason the resources dedicated to this goal are continuously increasing. The first step to improve efficiency is to have appropriate models to compare different design solutions. Even if the efficiency of transmissions is quit high if compared to the efficiency of the engines and appropriate models to predict the power losses due to gear meshing, to bearings and to seals already exist, in order to have a further improvement, some aspects like the power losses related to the oil churning, oil squeezing and windage are still to be investigated. These losses rise from the interaction between the moving or rotating elements of the transmission and the lubricant. In previous papers [39, 40, 41 43, 44], the authors have investigated the churning losses of planetary speed reducers (in which there is a relative motion between the “planets + planet carrier” and the lubricant). This report is focused on the oil squeezing power losses. This kind of losses is associated with the pumping of the oil at the gear mesh, where there is a contraction of the volume between the mating gears due to the rotation of them and a consequent overpressure. This overpressure implies a fluid flow primarily in the axial direction and this, for viscous fluids, means additional power losses and a decrease of the efficiency. In this work this phenomena has been studied by means of some CFD (computational fluid dynamic) simulations with a VOF (volume of fluid) approach. The influence of some operating conditions like the rotational speed and the lubricant temperature have been studied. The results of this study have been included in a model to predict the efficiency of the whole transmission.

A discussion of Arana, A., Larrañaga, J., & Ulacia, I. (2019). Partial EHL friction coefficient model to predict power losses in cylindrical gears. Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology, Vol. 233(2) 303–316

2019 ◽  
Vol 234 (7) ◽  
pp. 1168-1170 ◽  
Author(s):  
Scott Bair
Keyword(s):  
Friction Coefficient ◽  
Pressure Dependence ◽  
Elastohydrodynamic Lubrication ◽  
Power Losses ◽  
True Nature ◽  
The Real ◽  
Cylindrical Gears ◽  
Real Nature ◽  
Heated Debate ◽  
Ehl Friction

There is presently a heated debate within the field of elastohydrodynamic lubrication (EHL). Some have attributed this to a controversy regarding the shear dependence of viscosity. However, the real nature of the debate is, as it has been for more than 40 years, whether or not to correctly describe the piezoviscous effect. If real pressure dependence of viscosity were to be employed in all EHL analyses, then the true nature of shear dependence would become apparent and the debate would end.

Prediction of friction-related power losses of hypoid gear pairs

2007 ◽  
Vol 221 (3) ◽  
pp. 387-400 ◽  
Author(s):  
H Xu ◽  
A Kahraman
Keyword(s):  
Friction Coefficient ◽  
Linear Regression Analysis ◽  
Mechanical Efficiency ◽  
Friction Model ◽  
Operating Conditions ◽  
Hypoid Gear ◽  
Power Losses ◽  
Efficiency Losses ◽  
Gear Contact ◽  
Hypoid Gear Pairs

A model to predict friction-related mechanical efficiency losses of hypoid gear pairs is proposed in this study. The model includes a gear contact model, a friction prediction model, and a mechanical efficiency formulation. The friction model uses a friction coefficient formula obtained by applying multiple linear regression analysis to a large number of elastohydrodynamic lubrication analyses covering typical ranges of key parameters associated with surface roughness, geometry, load, kinematics, and the lubricant. Formulations regarding the kinematic and geometric properties of the hypoid gear contact are presented. The load and friction coefficient distribution predictions are used to compute instantaneous torque/power losses and the mechanical efficiency of a hypoid gear pair at any given position. Results of a parametric study are presented at the end to highlight the influence of key operating conditions, surface finish, and lubricant properties on mechanical efficiency losses of hypoid gears.

scholarly journals An Experimental Investigation of Churning Power Losses of a Gearbox

2018 ◽  
Vol 140 (3) ◽  
Author(s):  
J. Polly ◽  
D. Talbot ◽  
A. Kahraman ◽  
A. Singh ◽  
H. Xu
Keyword(s):  
Helical Gear ◽  
Operating Conditions ◽  
Gear Pair ◽  
Power Losses ◽  
Helical Gears ◽  
Gear Mesh ◽  
System A ◽  
Final Drive ◽  
Helical Gear Pair ◽  
Lubrication Conditions

In this study, load-independent (spin) power losses of a gearbox operating under dip-lubrication conditions are investigated experimentally using a final-drive helical gear pair from an automotive transmission as the example system. A dedicated gearbox is developed to operate a single gear or a gear pair under given speed and temperature conditions. A test matrix that consists of sets of tests with: (i) a single spur, helical gears, or disks with no teeth and (ii) helical gear pairs is executed at various temperatures, immersion depths, and pinion positions relative to its mating gear. Power losses from single gear and gear pair at identical operating conditions are compared to quantify the components of the total spin loss in the form of losses due to gear drag, gear mesh pocketing, and bearings and seals.

Measurements of Static Loading Versus Eccentricity in a Flexure-Pivot Tilting Pad Journal Bearing

1997 ◽  
Vol 119 (2) ◽  
pp. 297-304 ◽  
Author(s):  
Nick V. Walton ◽  
Luis San Andres
Keyword(s):  
Static Loading ◽  
Mechanical Energy ◽  
Operating Conditions ◽  
Good Prediction ◽  
Power Losses ◽  
Static Loads ◽  
Numerical Predictions ◽  
Tilting Pad ◽  
Bearing Assembly ◽  
Tilting Pad Journal Bearing

An experimental investigation examining the static loading characteristics of a four-pad, flexure-pivot tilting pad bearing is presented. Tests are conducted on a Fluid Film Bearing Element Test Rig for journal speeds ranging from 1800 to 4500 rpm, and applied static loads between pads to 1400 N. Results obtained from measurements of bearing eccentricities and bearing pad temperatures were compared to numerical predictions. Bearing power losses were also estimated using a simple thermal model for the bearing assembly. Comparisons between theory and experimental results indicate good correlation for measured eccentricities over the tested range of applied static loads and journal speeds. Negligible displacements in the direction orthogonal to the applied load verified the expected behavior of the test bearing over the range of operating conditions. Thermal analysis of the hearing system lead to good prediction of the bearing power losses, and indicated that the majority of the mechanical energy is transferred via convection.

Load-Independent Spin Power Losses of a Spur Gear Pair: Model Formulation

2009 ◽  
Vol 131 (2) ◽  
Author(s):  
S. Seetharaman ◽  
A. Kahraman
Keyword(s):  
Power Loss ◽  
Spur Gear ◽  
Companion Paper ◽  
Total Spin ◽  
Operating Conditions ◽  
Gear Pair ◽  
Power Losses ◽  
Gear Mesh ◽  
Drag Forces ◽  
Mechanics Model

A physics-based fluid mechanics model is proposed to predict spin power losses of gear pairs due to oil churning and windage. While the model is intended to simulate oil churning losses in dip-lubricated conditions, certain components of it apply to air windage losses as well. The total spin power loss is defined as the sum of (i) power losses associated with the interactions of individual gears with the fluid, and (ii) power losses due to pumping of the oil at the gear mesh. The power losses in the first group are modeled through individual formulations for drag forces induced by the fluid on a rotating gear body along its periphery and faces, as well as for eddies formed in the cavities between adjacent teeth. Gear mesh pumping losses will be predicted analytically as the power loss due to squeezing of the lubricant, as a consequence of volume contraction of the mesh space between mating gears as they rotate. The model is applied to a unity-ratio spur gear pair to quantify the individual contributions of each power loss component to the total spin power loss. The influence of operating conditions, gear geometry parameters, and lubricant properties on spin power loss are also quantified at the end. A companion paper (Seetharaman et al., 2009, “Oil Churning Power Losses of a Gear Pair: Experiments and Model Validation,” ASME J. Tribol., 131, p. 022202) provides comparisons to experiments for validation of the proposed model.

Lateral Motion of an Axially Moving Tape on a Cylindrical Guide Surface

2007 ◽  
Vol 74 (5) ◽  
pp. 1053-1056 ◽  
Author(s):  
Bart Raeymaekers ◽  
Frank E. Talke
Keyword(s):  
Friction Coefficient ◽  
Friction Force ◽  
Bending Stiffness ◽  
Experimental Results ◽  
Lateral Motion ◽  
Lateral Bending ◽  
Lateral Tape Motion ◽  
Numerical Predictions ◽  
Axially Moving ◽  
Good Agreement

The lateral motion of a tape moving axially over a cylindrical guide surface is investigated. The effects of lateral bending stiffness and friction force are studied and the attenuation of lateral tape motion as a function of the guide radius and friction coefficient is determined. Good agreement between numerical predictions and experimental results is observed.

scholarly journals An Experimental Investigation of Churning Power Losses of a Gearbox

2017 ◽  
Author(s):  
J. Polly ◽  
David Talbot ◽  
Ahmet Kahraman ◽  
Avinash Singh ◽  
Hai Xu
Keyword(s):  
Helical Gear ◽  
Operating Conditions ◽  
Gear Pair ◽  
Power Losses ◽  
Gear Mesh ◽  
System A ◽  
Automotive Transmission ◽  
Final Drive ◽  
Helical Gear Pair ◽  
Lubrication Conditions

In this study, load-independent (spin) power losses of a gearbox operating under dip-lubrication conditions are investigated experimentally using a final-drive helical gear pair from an automotive transmission as the example system. A dedicated gearbox is developed to operate a single gear or a gear pair under given speed and temperature conditions. A test matrix that consists of sets of tests with (i) single gears (spur, helical, or representative disks with no teeth), and (ii) helical gear pairs is executed at various temperatures, immersion depths and pinion positions relative to its mating gear. Power losses from single gears and gear pairs at identical operating conditions are compared to quantify the components of the total spin loss in the form of losses due to gear drag, gear mesh pocketing, and bearings and seals.

Dynamic analysis of a helical gear reduction by experimental and numerical methods

2020 ◽  
Vol 68 (1) ◽  
pp. 48-58
Author(s):  
Chao Liu ◽  
Zongde Fang ◽  
Fang Guo ◽  
Long Xiang ◽  
Yabin Guan ◽  
...  
Keyword(s):  
Numerical Methods ◽  
Dynamic Analysis ◽  
Dynamic Behavior ◽  
Fourth Order ◽  
Numerical Models ◽  
Helical Gear ◽  
Operating Conditions ◽  
Dynamic Responses ◽  
Lumped Mass ◽  
Gear Mesh

Presented in this study is investigation of dynamic behavior of a helical gear reduction by experimental and numerical methods. A closed-loop test rig is designed to measure vibrations of the example system, and the basic principle as well as relevant signal processing method is introduced. A hybrid user-defined element model is established to predict relative vibration acceleration at the gear mesh in a direction normal to contact surfaces. The other two numerical models are also constructed by lumped mass method and contact FEM to compare with the previous model in terms of dynamic responses of the system. First, the experiment data demonstrate that the loaded transmission error calculated by LTCA method is generally acceptable and that the assumption ignoring the tooth backlash is valid under the conditions of large loads. Second, under the common operating conditions, the system vibrations obtained by the experimental and numerical methods primarily occur at the first fourth-order meshing frequencies and that the maximum vibration amplitude, for each method, appears on the fourth-order meshing frequency. Moreover, root-mean-square (RMS) value of the acceleration increases with the increasing loads. Finally, according to the comparison of the simulation results, the variation tendencies of the RMS value along with input rotational speed agree well and that the frequencies where the resonances occur keep coincident generally. With summaries of merit and demerit, application of each numerical method is suggested for dynamic analysis of cylindrical gear system, which aids designers for desirable dynamic behavior of the system and better solutions to engineering problems.

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