scholarly journals Elastohydrodynamics of a Worm Gear Contact

2000 ◽  
Vol 123 (2) ◽  
pp. 268-275 ◽  
Author(s):  
S. Kong ◽  
K. Sharif ◽  
H. P. Evans ◽  
R. W. Snidle
Keyword(s):  
Film Thickness ◽  
Three Dimensional ◽  
Elastohydrodynamic Lubrication ◽  
Worm Gear ◽  
Simulation Technique ◽  
Elastic Contact ◽  
Gear Teeth ◽  
Film Forming ◽  
Worm Gears ◽  
Gear Contact

The paper is concerned with prediction of elastic contact and elastohydrodynamic film thickness in worm gears. Using the undeformed geometry of the gap between gear teeth in contact a three-dimensional elastic contact simulation technique has been developed for calculation of the true area of elastic contact under load relative to the wheel and worm surfaces. A parallel investigation of elastohydrodynamic lubrication effects has been carried out using a special non-Newtonian, thermal solver which takes account of the nonsymmetrical and spin aspects of worm contacts. An interesting feature of the results obtained is the discovery of regions of poor film forming due to entrainment failure at the edges of the contact.

Simulation of Wear in a Worm Gear Under Elastohydrodynamic Conditions

2005 ◽  
Author(s):  
K. J. Sharif ◽  
H. P. Evans ◽  
R. W. Snidle ◽  
I. M. Egorov
Keyword(s):  
Film Thickness ◽  
Iterative Process ◽  
Elastohydrodynamic Lubrication ◽  
Gear Wheel ◽  
Worm Gear ◽  
Wear Model ◽  
Gear Teeth ◽  
Practical Measure

The paper is concerned with the prediction of wear of worm gear wheel teeth. The wear model that has been developed is based upon a full elastohydrodynamic lubrication (EHL) analysis of the contact between the teeth at various stages of meshing. Wear over the contacting region on the wheel tooth is calculated from a modified Archard-type law, taking pressure, film thickness and sliding values from the EHL results. The development of wear is obtained by an iterative process in which the shape of the contacting surfaces, as modified by wear, is updated in the EHL solution. This process leads to the prediction of wear contours on the gear teeth from which the increase in backlash (a practical measure of worm gear wear) can be obtained.

A Three-Dimensional Model of Line-Contact Elastohydrodynamic Lubrication for Heterogeneous Materials with Inclusions

2016 ◽  
Vol 08 (02) ◽  
pp. 1650014 ◽  
Author(s):  
Kun Zhou ◽  
Qingbing Dong
Keyword(s):  
Film Thickness ◽  
Half Space ◽  
Surface Deformation ◽  
Three Dimensional ◽  
Elastohydrodynamic Lubrication ◽  
Lubricant Film ◽  
Line Contact ◽  
Lubricant Film Thickness ◽  
Equivalent Inclusion Method ◽  
Surface Contact

This paper develops a three-dimensional (3D) model for a heterogeneous half-space with inclusions distributed periodically beneath its surface subject to elastohydrodynamic lubrication (EHL) line-contact applied by a cylindrical loading body. The model takes into account the interactions between the loading body, the fluid lubricant and the heterogeneous half-space. In the absence of subsurface inclusions, the surface contact pressure distribution, the half-space surface deformation and the lubricant film thickness profile are obtained through solving a unified Reynolds equation system. The inclusions are homogenized according to Eshelby’s equivalent inclusion method (EIM) with unknown eigenstrains to be determined. The disturbed half-space surface deformations induced by the subsurface inclusions or eigenstrains are iteratively introduced into the lubricant film thickness until the surface deformation finally converges. Both time-independent smooth surface contact and time-dependent rough surface contact are considered for the lubricated contact problem.

Worm Gear Performance

1935 ◽  
Vol 129 (1) ◽  
pp. 127-194 ◽  
Author(s):  
Henry E. Merritt
Keyword(s):  
Comparative Method ◽  
Worm Gear ◽  
Line Contact ◽  
Simple Method ◽  
Geometrical Properties ◽  
Gear Teeth ◽  
Experimental Apparatus ◽  
Load Carrying ◽  
The Coefficient Of Friction ◽  
Worm Gears

The paper represents an attempt to establish a basis upon which the load-carrying capacity and efficiency of worm gears may be predicted. It forms a supplement to a forthcoming British Standard Specification. The requirements of a worm thread profile are briefly considered and the use of the involute helicoid as a basis of worm thread design is recommended. The geometrical properties of the involute helicoid are discussed and a simple method of determining the zone and lines of contact is given. On a theorem on the curvature of tooth profiles as basis, the relative curvature of worm threads and wheel teeth is determined. A method of comparing the stress conditions between lubricated surfaces making moving line-contact is presented and its application to the determination of the allowable loading on worm gear teeth results in simple formulæ. A comparative method of determining wheel tooth strength is also given. An experimental apparatus has been developed for investigating the friction between surfaces in lubricated line-contact, and some of the results obtained therefrom are described. The relation between the results obtained from rolling and sliding disks and from actual worm gears is discussed, and average values of the coefficient of friction which may be used in design are given.

Three-Dimensional Temperature Distribution in EHD Lubrication: Part II—Point Contact and Numerical Formulation

1993 ◽  
Vol 115 (1) ◽  
pp. 36-45 ◽  
Author(s):  
Kyung-Hoon Kim ◽  
Farshid Sadeghi
Keyword(s):  
Temperature Distribution ◽  
Film Thickness ◽  
Numerical Study ◽  
Control Volume ◽  
Three Dimensional ◽  
Point Contact ◽  
Elastohydrodynamic Lubrication ◽  
Lubricant Film ◽  
Numerical Formulation ◽  
Energy Equations

A numerical study of Newtonian thermal elastohydrodynamic lubrication (EHD) of rolling/sliding point contacts has been conducted. The two-dimensional Reynolds, elasticity and the three-dimensional energy equations were solved simultaneously to obtain the pressure, film thickness and temperature distribution within the lubricant film. The control volume approach was employed to discretize the differential equations and the multi-level multi-grid technique was used to simultaneously solve them. The discretized equations, as well as the nonorthogonal coordinate transformation used for the solution of the energy equation, are described. The pressure, film thickness and the temperature distributions, within the lubricant film at different loads, slip conditions and ellipticity parameters are presented.

Effects of Asperities in Elastohydrodynamic Lubrication

1980 ◽  
Vol 102 (3) ◽  
pp. 374-378 ◽  
Author(s):  
M. Kaneta ◽  
A. Cameron
Keyword(s):  
Film Thickness ◽  
Glass Plate ◽  
Three Dimensional ◽  
Point Contact ◽  
Elastohydrodynamic Lubrication ◽  
Critical Value ◽  
Optical Interferometry ◽  
Asperity Height ◽  
Height Ratio ◽  
Pure Rolling

Optical interferometry was used to study rough surfaces under lubricated point contact. Three dimensional “asperities” of chromium were sputtered onto a steel ball which was run against a smooth glass plate under both rolling and sliding. The experimental results were compared with the various published theories. The film thicknesses found in sliding are different from those observed in pure rolling, which are nearly equal to the theoretical values. Film thickness collapse occurred when the central film thickness/half asperity height ratio (λ ratio) reached a critical value.

Elastohydrodynamic Lubrication of Hypoid Gears

1981 ◽  
Vol 103 (1) ◽  
pp. 195-203 ◽  
Author(s):  
V. Simon
Keyword(s):  
Film Thickness ◽  
Numerical Solution ◽  
Elastohydrodynamic Lubrication ◽  
Operating Conditions ◽  
Performance Characteristics ◽  
Temperature Variations ◽  
Hypoid Gears ◽  
Oil Film ◽  
Gear Teeth ◽  
Energy Equations

The full thermal elastohydrodynamic analysis of the lubrication of hypoid gears is presented. A numerical solution of the coupled Reynolds, elasticity and energy equations for the pressure, temperature and film thickness is obtained. The temperature variations across the oil film and in the pinion and gear teeth are included. The real tooth geometry of the modified hypoid gears is treated. The effect of the operating conditions on the performance characteristics is discussed.

New equations for enhanced film thickness in line contacts under pressurized ambient conditions

2016 ◽  
Vol 231 (5) ◽  
pp. 616-622 ◽  
Author(s):  
Niraj Kumar ◽  
Punit Kumar
Keyword(s):  
Film Thickness ◽  
Ambient Pressure ◽  
Elastohydrodynamic Lubrication ◽  
Viscosity Coefficient ◽  
Ambient Conditions ◽  
Alternative Approach ◽  
Film Forming ◽  
Highly Sensitive ◽  
Minimum Film Thickness ◽  
Line Contacts

An elastohydrodynamic lubrication model is proposed for line contacts under pressurized ambient conditions often encountered in hydraulic pumps, submarine machinery and many other submerged systems. It has been demonstrated that the film forming behavior under such conditions is essentially different from that in conventional elastohydrodynamic lubrication contacts. The numerical simulation results are regressed to develop new central and minimum film thickness equations for Newtonian fluids as functions of ambient pressure, speed, load, and material parameters. An alternative approach is also discussed which involves the use of existing film thickness formulas with ambient viscosity and pressure–viscosity coefficient pertaining to the desired pressure range. A film thickness enhancement of more than 100% over conventional elastohydrodynamic lubrication case is observed. This enhancement is shown to be highly sensitive to the pressure–viscosity coefficient. Besides, the effect of shear-thinning behavior is also investigated and it is found to lower the film thickness enhancement, especially at high ambient pressures.

A Geometrical Model Producing a Surface Equivalent To the Working Surface of the Gear Tool «Hob»

2019 ◽  
Vol 7 (2) ◽  
pp. 56-60 ◽  
Author(s):  
С. Рязанов ◽  
S. Ryazanov
Keyword(s):  
Dimensional Space ◽  
Three Dimensional ◽  
Geometrical Model ◽  
Worm Gear ◽  
Analytic Description ◽  
Geometrical Parameters ◽  
Computer Algorithms ◽  
Kinematic Chains ◽  
Worm Wheel ◽  
Worm Gears

Existing mathematical models for calculating worm gearing [34; 38] are quite complex and do not always provide an opportunity to quickly and accurately obtain the desired result [1; 3; 24–26]. A simpler way to find a suitable gearing option that satisfies the task is using computer simulation methods and computer graphics, and in particular solid modeling algorithms [4; 5; 30–33; 36; 37]. This information can be entered into the computer in order to simulate control of the movement of the cutting tool. Ultimately, this boils down to the problem of analytic description and computer representation of curves and surfaces in three-dimensional space [18–20]. Despite the diversity and good development of the calculation methods, and the analysis of the geometrical parameters of the worm gear, there is a lack of means and methods for displaying the process of forming the working surfaces of the worm gear elements [28; 29; 41]. There are no computer algorithms for obtaining the producing surfaces of a worm cutter, which are obtained by a tool with a modified producing surface. A change in the geometric shape of the tool producing surface will lead to a change in the working surfaces of the worm wheel and turns of the worm, which may lead to an improvement in their contact. This article shows the application of the developed methods and algorithms of geometric and computer modeling, which are designed to form the helical surface of the turns of the worm and the teeth of the worm wheel. Their use will speed up the process of calculating intermediate adjustments of machines used for cutting worm gears, bypassing complex mathematical calculations that, under conditions of aging of the gear-cutting machine fleet, their wear and inevitable reduction in the accuracy of their kinematic chains. This can be achieved only by applying a deliberate modification of the contacting surfaces, which reduces the sensitivity of the worm gear to the manufacturing errors of its elements, which allows to maintain the quality of the gears produced at a sufficiently high level.

scholarly journals Elastohydrodynamic Lubrication Analysis of Gear Tooth Surfaces From Micropitting Tests

2003 ◽  
Vol 125 (2) ◽  
pp. 267-274 ◽  
Author(s):  
J. Tao ◽  
T. G. Hughes ◽  
H. P. Evans ◽  
R. W. Snidle ◽  
N. A. Hopkinson ◽  
...  
Keyword(s):  
Film Thickness ◽  
Gear Tooth ◽  
Testing Machine ◽  
Elastohydrodynamic Lubrication ◽  
Real Surface ◽  
Test Protocol ◽  
Contact Phase ◽  
Gear Teeth ◽  
Pressure Cycling ◽  
Tooth Surfaces

The paper presents numerical results for the elastohydrodynamic lubrication of gear teeth using real surface roughness data taken from micropitting tests carried out on an FZG gear testing machine. Profiles and load conditions corresponding to four load stages in the micropitting test protocol are considered. Elastohydrodynamic film thickness and pressure analyses are presented for conditions having a slide/roll ratio of 0.3 during the single tooth contact phase of the meshing cycle. Comparisons are also included showing the elastohydrodynamic response of the tooth contacts at different times in the meshing cycle for one of the load stages. The rheological model adopted is based on Ree-Eyring non-Newtonian shear thinning, and comparisons are also included of models having constant and different pressure-dependent specifications of the Eyring shear stress parameter τ0. Parameters obtained from the micro EHL analyses are presented that quantify the degree of adversity experienced by the surfaces in elastohydrodynamic contact. These quantify extreme pressure behavior, extreme proximity of surfaces, and pressure cycling within the overall contact and indicate that the different fluid models considered lead to significantly different pressure and film thickness behavior within the contact.

Numerical Solution of Mixed Thermal Elastohydrodynamic Lubrication in Point Contacts With Three-Dimensional Surface Roughness

2016 ◽  
Vol 139 (1) ◽  
Author(s):  
Xiaopeng Wang ◽  
Yuchuan Liu ◽  
Dong Zhu
Keyword(s):  
Surface Roughness ◽  
Film Thickness ◽  
Three Dimensional ◽  
Point Contact ◽  
Elastohydrodynamic Lubrication ◽  
Lubricant Film ◽  
Operating Conditions ◽  
Thickness Variation ◽  
Wide Range ◽  
Film Lubrication

Elastohydrodynamic lubrication (EHL) is a common mode of fluid-film lubrication in which many machine elements operate. Its thermal behavior is an important concern especially for components working under extreme conditions such as high speeds, heavy loads, and surfaces with significant roughness. Previous thermal EHL (TEHL) studies focused only on the cases with smooth surfaces under the full-film lubrication condition. The present study intends to develop a more realistic unified TEHL model for point contact problems that is capable of simulating the entire transition of lubrication status from the full-film and mixed lubrication all the way down to boundary lubrication with real machined roughness. The model consists of the generalized Reynolds equation, elasticity equation, film thickness equation, and those for lubricant rheology in combination with the energy equation for the lubricant film and the surface temperature equations. The solution algorithms based on the improved semi-system approach have demonstrated a good ability to achieve stable solutions with fast convergence under severe operating conditions. Lubricant film thickness variation and temperature rises in the lubricant film and on the surfaces during the entire transition have been investigated. It appears that this model can be used to predict mixed TEHL characteristics in a wide range of operating conditions with or without three-dimensional (3D) surface roughness involved. Therefore, it can be employed as a useful tool in engineering analyses.

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