Thermoelastic Effects in Lubricated Rolling/Sliding Line Contacts

1991 ◽  
Vol 113 (1) ◽  
pp. 174-181 ◽  
Author(s):  
P. C. Sui ◽  
F. Sadeghi
Keyword(s):  
Temperature Distribution ◽  
Numerical Model ◽  
Film Thickness ◽  
Thermal Stresses ◽  
Shear Stresses ◽  
Ehd Lubrication ◽  
Line Contacts ◽  
Thermoelastic Effects ◽  
Machine Elements ◽  
Thermoelastic Displacement

A numerical model was developed to investigate the subsurface mechanical and thermal stresses in rolling/sliding machine elements operating under elasto-hydrodynamic (EHD) lubrication of line contacts. A thermal non-Newtonian EHD lubrication model was modified to include the thermoelastic displacement of the solids. The pressure, film thickness, and temperature distribution obtained from the model were used to calculate the subsurface mechanical and thermal stresses within the rolling/sliding machine elements. The thermoelastic effects on the magnitude and location of the maximum shear stresses are presented.

Surface roughness modification in elastohydrodynamic line contacts operating in the elastic piezoviscous regime

1998 ◽  
Vol 212 (2) ◽  
pp. 145-162 ◽  
Author(s):  
C. J. Hooke
Keyword(s):  
Surface Roughness ◽  
Spatial Distribution ◽  
Analytical Solution ◽  
Film Thickness ◽  
Numerical Solutions ◽  
Entrainment Velocity ◽  
Original Surface ◽  
Ehd Lubrication ◽  
Line Contacts

In heavily loaded elastohydrodynamic (EHD) lubrication contacts operating in the piezoviscous regime, the original surface roughness is largely flattened as it enters the conjunction and is replaced by an inlet generated clearance variation. This clearance variation is convected through the contact at the entrainment velocity. It has a spatial distribution that differs (except for rolling without slip) from the original surface and a different amplitude. This amplitude may be smaller or greater than that of the original profile. An analytical solution of this behaviour is presented for contacts operating well inside the elastic piezoviscous regime for the situation where the roughness is relatively small compared with the film thickness. This solution allows the main features of surface roughness modification to be understood and produces results that compare well with the few numerical solutions available.

Thermoelastic Distortion of EHD Line Contacts During the Passage of Soft Debris Particles

1999 ◽  
Vol 121 (2) ◽  
pp. 265-271 ◽  
Author(s):  
G. K. Nikas ◽  
R. S. Sayles ◽  
E. Ioannides
Keyword(s):  
Thermal Stresses ◽  
Frictional Heating ◽  
Three Dimensional ◽  
Operational Parameters ◽  
Dimensional Solution ◽  
Debris Particle ◽  
Debris Particles ◽  
Line Contacts ◽  
Contact Mechanical ◽  
Thermoelastic Displacement

During the passage of a debris particle through an EHD contact, mechanical stresses due to particle compression and thermal stresses due to particle frictional heating produce a thermoelastic/plastic stress field, which governs the way a possible damage is generated. In the present paper, the complete three-dimensional solution of the thermoelastic distortion of surfaces due to the compression of a soft, ductile debris particle in an EHD line contact is presented both theoretically and through a realistic example. It is found that thermal stresses increase the likelihood of yielding and produce a characteristic “omega” shaped thermoelastic displacement. The important outcome of this work is the construction of a map which shows the critical particle size to cause damage (plastic deformations) in combination with operational parameters as the lubricant film thickness and relative sliding velocity of the contact.

The Effects of Surface Irregularities on the Elastohydrodynamic Lubrication of Sliding Line Contacts. Part I—Single Irregularities

1984 ◽  
Vol 106 (1) ◽  
pp. 104-112 ◽  
Author(s):  
P. R. Goglia ◽  
T. F. Conry ◽  
C. Cusano
Keyword(s):  
Shear Stress ◽  
Film Thickness ◽  
Smooth Surface ◽  
Maximum Stress ◽  
Elastohydrodynamic Lubrication ◽  
Maximum Value ◽  
Ehd Lubrication ◽  
Line Contacts ◽  
Surface Irregularities ◽  
Octahedral Shear Stress

A full line contact solution, under isothermal conditions, is obtained in which the effects of single stationary surface irregularities on the EHD lubrication process are studied under pure sliding conditions. The irregularities studied are furrows, furrows with built-up edges, and asperities. The effects of these irregularities on film thickness, pressure, and subsurface octahedral shear stress are presented. The pressure and film thickness resulting from such surface irregularities are significantly changed from their smooth surface values. These changes alter the state of stress in the subsurface region by increasing the maximum value of octahedral shear stress and bringing the location of this maximum stress closer to the surface. The film thickness in the contact is significantly changed from the smooth surface value only when the irregularities are located in the inlet region while the maximum value of the octahedral shear stress increases to the greatest extent when the irregularities are located in the outlet half of the contact.

Thermal Non-Newtonian Elastohydrodynamic Lubrication of Rolling Line Contacts

1991 ◽  
Vol 113 (3) ◽  
pp. 481-491 ◽  
Author(s):  
H. Salehizadeh ◽  
N. Saka
Keyword(s):  
Film Thickness ◽  
Contact Region ◽  
Elastohydrodynamic Lubrication ◽  
Pressure Profile ◽  
Shear Stresses ◽  
Hertz Contact ◽  
Minimum Film Thickness ◽  
Line Contacts ◽  
Pressure Spike ◽  
Heavy Loads

The two-dimensional thermal elastohydrodynamic equations were numerically solved for a Ree-Eyring type lubricant under pure rolling conditions. Profiles of lubricant pressure, film thickness, and temperature were obtained for medium to heavy loads and moderate to high rolling speeds. The pressure results generally show a small secondary peak near the outlet, but at the highest load considered no pressure spike is obtained and the pressure profile is almost Hertzian. The film thickness results show an increase in minimum film thickness with increasing rolling speeds, but at a lesser rate than those predicted for a Newtonian fluid under isothermal conditions. It is found that unless the lubricant becomes non-Newtonian in the inlet region, the reduction in minimum film thickness at high rolling speeds is completely due to thermal effect. The lubricant temperature profile and the amount of heat generated and dissipated in the contact region were also calculated. The lubricant temperature reaches a maximum just before the entrance to the Hertz contact region. Both shear and compression heating are found to be important in raising the lubricant temperature in the inlet. As the lubricant enters the Hertz contact zone, the temperature first drops rapidly, because of the rapid heat conduction to the rollers, and then remains almost constant for most of the Hertz contact. Near the exit where the pressure gradients are large, the lubricant temperature drops rapidly below the ambient because of lubricant expansion. The lubricant then heats up rapidly before leaving the contact area as a result of heat generated by shear stresses.

Effect of Surface Texturing on EHD Lubrication Films Under Transient Speed Condition

2011 ◽  
Author(s):  
Martin Zimmerman ◽  
Ivan Krupka ◽  
Martin Hartl ◽  
Pavel Houska
Keyword(s):  
Film Thickness ◽  
Flat Surface ◽  
Contact Point ◽  
Surface Texturing ◽  
Polished Surface ◽  
Speed Profile ◽  
Ehd Lubrication ◽  
Machine Elements ◽  
Contact Surfaces ◽  
Effect Of Surface

Transient EHD lubrication, where operating parameters such as speed, load and surface curvature vary over time, occurs in many machine elements such as cams, gears or roller bearings. The effect of transient speed and surface texturing on EHD lubrication films are investigated by the direct observation. For the purposes of the experiment the speed profile of contact point between cam and follower is used. Most critical part of the operation is when the contact surfaces are running in opposite directions. This effect can cause a lubricant film breakdown and in consequence also damage of contact surfaces. For this reason three types of experiments, for the same speed profile, are carried out for polished surface and for contact surfaces with and without surface texturing. It has enabled us to consider if the texture of micro-dents have any significant influence on film thickness especially in critical parts of the operation. To simplify the problem the concept of cam and follower contact was replaced by EHD contact of the flat surface of chromium coated glass disk and a steel ball. Also only transient speed was taken into account. The method used to measured film thickness was thin film colorimetric interferometry. The experimental results show that micro-dents could increase lubrication efficiency under rolling/sliding condition through the lubricant emitted from micro-dents. It was found that the lubricant emitted from micro-dents helps to separate contact surfaces especially in the case where the contact surfaces moves very slowly in the opposite direction.

Plane Thermal Stress Analysis of an Orthotropic Cylinder Subjected to an Arbitrary, Transient, Asymmetric Temperature Distribution

2002 ◽  
Vol 69 (5) ◽  
pp. 632-640 ◽  
Author(s):  
K.-C. Yee ◽  
T. J. Moon
Keyword(s):  
Temperature Field ◽  
Thermal Stress ◽  
Temperature Distribution ◽  
Analytical Solution ◽  
Stress Analysis ◽  
Stress Function ◽  
Thermal Stresses ◽  
Shear Stresses ◽  
Thermal Stress Analysis ◽  
Interlaminar Shear

A closed-form, analytical solution is presented for the transient, plane thermal stress analysis of a linearly elastic, homogeneously orthotropic hollow cylinder subjected to an arbitrary temperature distribution. The thermoelastic solution, obtained by a stress function approach, can be used as the basis for the corresponding thermoviscoelastic solution for thermorheologically simple viscoelastic materials by invoking the viscoelastic Correspondence Principle. This solution can also be directly extended to the class of weakly inhomogeneously orthotropic cylinders using perturbation methods. The transient asymmetric temperature field is characterized by Fourier-Bessel eigenfunction expansions. The analytically derived stress function satisfies a linear, fourth-order inhomogeneous partial differential equation and the Cesaro integral conditions, which assure the existence of a single-valued displacement field. The corresponding thermal stresses are then computed by the stress-stress function relations. A key feature of the analytical solution is that the hoop, radial, and shear stresses, due to the transient arbitrary temperature distribution, are expressed explicitly in terms of the scalar temperature field. A polymer composite example is presented to validate the current method and to qualitatively illustrate the distribution of thermal stresses due to an asymmetric temperature distribution. Numerical results are presented for the thermally driven hoop, radial and (interlaminar) shear stresses in a hollow, hoop-wound glass/epoxy cylinder. This analysis demonstrates that potentially debilitating interlaminar shear stresses can develop in laminated composites when subjected to an even modest transient asymmetric temperature distribution. Their magnitudes depend on the severity of the spatial and temporal thermal gradients in the circumferential direction. While still relatively low compared to the hoop stress, the shear stress may cause thermal failure due to the typically low interlaminar shear strengths of laminated composite materials.

scholarly journals Influence of thermal and flow conditions on the temperature distribution in the evaporator tubes

2019 ◽  
Vol 128 ◽  
pp. 01024 ◽  
Author(s):  
Marek Majdak
Keyword(s):  
Temperature Distribution ◽  
Numerical Model ◽  
Working Conditions ◽  
Thermal Stresses ◽  
Flow Analysis ◽  
Effect Of Temperature ◽  
Flow Conditions ◽  
Time Step ◽  
Thermophysical Parameters

The article presents the results of thermal and flow analysis of the working conditions of neighbouring waterwall tubes, loaded with heat streams of different values. The numerical model used for the analysis, allowing to calculate the temperature distribution of the tubes and the fluid flowing throughthem at each time step depending on the thermophysical parameters of the fluid and the material from which the tubes were made. By using the algorithm it is possible to precisely determine the temperaturedistribution for tubes, allowing to determine the places where the most divergent temperatures occur and in which thermal stresses of the highest value may occur. Analysis for several adjacent tubes willallow for the effect of temperature differences in the tubes to the temperature of the fin which is connecting them and to collect data that may be used for the determination of stress distribution in the tubes and fins.

Three-Dimensional Temperature Distribution in EHD Lubrication: Part I—Circular Contact

1992 ◽  
Vol 114 (1) ◽  
pp. 32-41 ◽  
Author(s):  
Kyung Hoon Kim ◽  
Farshid Sadeghi
Keyword(s):  
Temperature Distribution ◽  
Film Thickness ◽  
Temperature Rise ◽  
Thermal Effects ◽  
Three Dimensional ◽  
Elastohydrodynamic Lubrication ◽  
Simultaneous System ◽  
Ehd Lubrication ◽  
Energy Equations ◽  
Circular Contact

A complete numerical solution of Newtonian thermal compressible elastohydrodynamic lubrication of rolling/sliding point (circular) contact has been obtained. The multilevel multigrid technique was used to solve the simultaneous system of thermal Reynolds, elasticity and the energy equations with their boundary conditions. The effects of various loads, speeds, and slip conditions on the lubricant temperature, film thickness, and friction force have been investigated. The results indicate that the temperature rise in the contact is significant and thermal effects cannot be neglected.

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