An Advanced Model to Study the Possible Thermomechanical Damage of Lubricated Sliding-Rolling Line Contacts From Soft Particles

2000 ◽  
Vol 123 (4) ◽  
pp. 828-841 ◽  
Author(s):  
George K. Nikas
Keyword(s):  
Thermal Stresses ◽  
Frictional Heating ◽  
Influential Factors ◽  
Plastic Compression ◽  
Lubricated Contacts ◽  
Debris Particles ◽  
Line Contacts ◽  
Soft Particles ◽  
Thermomechanical Damage ◽  
Advanced Model

A model presented earlier by the author (Nikas et al., 1998, 1999) for the study of the possible risks associated with the entrapment of debris particles in lubricated contacts has been refined to account for additional influential factors that could affect the results obtained from the initial model. The new results showed that soft contaminants could indeed be very destructive and damage a concentrated sliding contact mainly due to the thermal stresses developed from the frictional heating of the contact during the plastic compression and shearing of a particle. This model yielded flash temperatures of the order of 100°C and up to 2000°C (or more, until local yield occurs). It also showed that it is often the thermal stresses which cause the problems, rather than the mechanical stresses from particles’ deformation.

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.

Thermal Modeling and Effects From Debris Particles in Sliding/Rolling EHD Line Contacts—A Possible Local Scuffing Mode

1999 ◽  
Vol 121 (2) ◽  
pp. 272-281 ◽  
Author(s):  
G. K. Nikas ◽  
E. loannides ◽  
R. S. Sayles
Keyword(s):  
Theoretical Studies ◽  
Third Body ◽  
The Past ◽  
Local Material ◽  
Debris Particles ◽  
Asperity Contacts ◽  
Line Contacts ◽  
Machine Elements ◽  
Soft Particles ◽  
Local Material Properties

The damage caused by debris particles in concentrated contacts has been studied extensively in the past, both theoretically and experimentally. Most of the theoretical studies, in which the damage on the surfaces was calculated in the form of dents, were performed isothermally. It is known that sliding asperity contacts, which resemble third body contacts, reach high local temperatures that can affect local material properties which, in turn, will affect the way damage is generated on the surfaces of machine elements. In the present work the heat transfer of lubricated, rolling/sliding line contacts in the presence of a ductile spherical particle is modeled. The particle is assumed to be significantly softer than the counterfaces that squash it. The local flash temperatures due to the combined sliding and squashing of a debris particle are calculated. It is found that high temperatures caused from small and soft particles are rather the rule than the exception.

Formulas for Entraining Velocity in Lubricated Line Contacts

2002 ◽  
Vol 124 (4) ◽  
pp. 856-858
Author(s):  
Enrico Ciulli
Keyword(s):  
Relative Motion ◽  
Physical Meaning ◽  
Point Of View ◽  
Lubricated Contacts ◽  
Line Contacts ◽  
Two Bodies

The knowledge of the entraining velocity is necessary for the investigation of lubricated contacts. The entraining velocity is the average of the surface velocities of the two bodies in contact relative to the contact itself; its estimation can be actually not always immediate. In this work the general case of two pairing cylindrical surfaces in planar relative motion is analyzed from a kinematical point of view. Formulas for the evaluation of the entraining velocity are presented that are directly applicable to any case of connected members of a mechanism. The physical meaning of the terms of the proposed formulas is also briefly investigated from a lubrication point of view.

scholarly journals Thermal Stresses Due to Frictional Heating with Time-Dependent Specific Power of Friction

2017 ◽  
Vol 11 (4) ◽  
pp. 280-284 ◽  
Author(s):  
Katarzyna Topczewska
Keyword(s):  
Thermal Stresses ◽  
Frictional Heating ◽  
Subsurface Layer ◽  
Specific Power ◽  
Dimensionless Temperature ◽  
Friction Element ◽  
Friction Power ◽  
Thermal Bending ◽  
The Coefficient Of Friction ◽  
Spatio Temporal

AbstractIn this paper influence of temporal profile of the specific friction power (i.e. the product of the coefficient of friction, sliding velocity and contact pressure) on thermal stresses in a friction element during braking was investigated. Spatio-temporal distributions of thermal stresses were analytically determined for a subsurface layer of the friction element, based on the model of thermal bending of a thick plate with unfixed edges (Timoshenko and Goodier, 1970). To conduct calculations, the fields of dimensionless temperature were used. These fields were received in the article (Topczewska, 2017) as solutions to a one-dimensional boundary-value problem of heat conduction for a semi-space heated on its outer surface by fictional heat flux with three, different time profiles of the friction power.

Uniform Equations in the Inlet and Exit Zones of Heavily Loaded Point and Line Elastohydrodynamically Lubricated Contacts Involved in Various Steady Motions

2015 ◽  
Vol 137 (2) ◽  
Author(s):  
Ilya I. Kudish
Keyword(s):  
Film Thickness ◽  
Point Contact ◽  
Elastohydrodynamic Lubrication ◽  
Point Contacts ◽  
Lubrication Film ◽  
Lubricated Contacts ◽  
Asymptotic Equations ◽  
Line Contacts ◽  
Steady Motions ◽  
Numerical Approaches

Heavily loaded point elastohydrodynamically lubricated (EHL) contacts involved in steady purely transitional, skewed transitional, and transitional with spinning motions are considered. It is shown that in the central parts of the inlet and exit zones of such heavily loaded point EHL contacts the asymptotic equations governing the EHL problem along the lubricant flow streamlines for the above types of contact motions can be reduced to two sets of asymptotic equations: one in the inlet and one in the exit zones. The latter sets of equations are identical to the asymptotic equations describing lubrication process in the inlet and exit zones of the corresponding heavily loaded line EHL contact (Kudish, I. I., 2013, Elastohydrodynamic Lubrication for Line and Point Contacts: Asymptotic and Numerical Approaches, Chapman and Hall/CRC). For each specific motion of a point contact, a separate set of formulas for the lubrication film thickness is obtained. For different types of contact motions, these film thickness formulas differ significantly (Kudish, I. I., 2013, Elastohydrodynamic Lubrication for Line and Point Contacts: Asymptotic and Numerical Approaches, Chapman and Hall/CRC). For heavily loaded contacts, the discovered relationship between point and line EHL problems allows to apply to point contacts most of the results obtained for line contacts (Kudish, I. I., 2013, Elastohydrodynamic Lubrication for Line and Point Contacts: Asymptotic and Numerical Approaches, Chapman and Hall/CRC; Kudish, I. I., and Covitch, M. J., 2010, Modeling and Analytical Methods in Tribology, Chapman and Hall/CRC).

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.

Residual Thermal Stresses Induced by Local Heat Treatment on Spherical Vessels and Their Influential Factors

2008 ◽  
Vol 130 (1) ◽  
Author(s):  
Wang Ze-jun ◽  
Jing Hong-yang
Keyword(s):  
Heat Treatment ◽  
Thermal Stress ◽  
Thermal Stresses ◽  
Small Region ◽  
Local Heat ◽  
Influential Factors ◽  
Residual Thermal Stress ◽  
Heated Region ◽  
Local Heat Treatment ◽  
Holding Temperature

For the purpose of finding a way to control effectively the residual thermal stresses induced by local heat treatment on spherical vessels, a thermal tracing program is developed successfully based on the transient thermal analysis and controlling method of average temperature of nodes located in an “observed region.” Typical calculation cases reveal that the local heat treatment process itself does cause obvious residual thermal stress that is high enough to cause yield when concentrated heating on small region is adopted, but decentralized heating on a larger region can lower effectively the residual thermal stresses to a rather desirable level. It can be found through a one by one analysis of ten factors, which are possibly influential on residual thermal stress: arc radius of heated region, holding temperature, volume, and wall thickness of the vessel are primary effective factors. The bandwidth of the annular insulated region, the heating rate, and the size of the observed region are secondary factors. Heating pattern, holding time, and cooling rate can hardly affect the residual thermal stress. Considering the primary factors except holding temperature, and taking 30% of yield stress as the expected residual thermal stress level, the recommended arc radius of heated region should be 2.2Rt in minimum.

scholarly journals Finite element modelling of the dynamics of groovy ball bearings

2018 ◽  
Vol 148 ◽  
pp. 16004
Author(s):  
Olamide Ajala ◽  
Ekaterina Pavlovskaia ◽  
Marian Weircigroch
Keyword(s):  
Finite Element ◽  
Numerical Analysis ◽  
Thermal Stresses ◽  
Frictional Heating ◽  
Element Model ◽  
Contact Theory ◽  
Ball Bearings ◽  
Relative Slip ◽  
Thrust Bearings ◽  
Plastic Strength

Geometry modified thrust bearings exposed to rolling and sliding contact are subjected to wear and localized frictional heating caused by relative slip between the two sliding surfaces. This leads to a rise in temperature, thermal stresses and changes in the elastic and plastic strength and physical properties of the material. The changes in the properties in turn alter the stress state, the displacement field, life and reliability of the bearing. Hence, a finite-element model is created to study the dynamics of groovy thrust bearing. In this paper, Hertz contact theory and numerical method are used to simulate the dynamics and kinematics of groovy ball bearings. The optimal loading parameters are identified in this study based on the analysis of the system responses and properties. The results of the numerical analysis and validation are presented. The numerical analysis proves the concept of transforming rotational motion into axial oscillation and demonstrates the capabilities of the numerical simulation to accurately model the dynamics of the groovy ball bearing.

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