Application of Kinematically Compatible Rolling-Contact Pairs to the Design of Low-Friction Rocker-Pivots

1985 ◽  
Vol 107 (3) ◽  
pp. 388-393 ◽  
Author(s):  
M. Chew
Keyword(s):  
Rolling Contact ◽  
Friction Reduction ◽  
Valve Train ◽  
Rolling Motion ◽  
Rolling Element Bearings ◽  
Low Friction ◽  
Rolling Element ◽  
Highly Loaded

The concept of rolling-contact has been applied to reduce friction at highly loaded rocker-pivots without the use of rolling element bearings. Various configurations for a rolling motion at the pivot are discussed. As an example, this rolling-contact concept is applied to the pivot of a valve-train rocker. Problems relating to stability and motion distortion of the rocker are addressed and solved, resulting in significant friction reduction at the pivot.

Analysis of the conditions for the occurrence of the effect of a minimum of friction in hybrid bearings based on the load separation principle

2018 ◽  
Vol 233 (2) ◽  
pp. 271-280
Author(s):  
Roman Polyakov ◽  
Leonid Savin ◽  
Alex Fetisov
Keyword(s):  
Rolling Contact ◽  
Friction Reduction ◽  
Fluid Film ◽  
Rolling Element Bearing ◽  
Contact Friction ◽  
Rolling Element Bearings ◽  
Operating Characteristics ◽  
Fluid Film Bearings ◽  
Friction Regime ◽  
Rolling Element

Reliability of rotating machinery is determined to a considerable degree by the bearing units. For several applications the requirements in rotational speed, bearing load and maximal vibration level are so extreme that neither rolling-element bearings nor fluid-film bearings could provide necessary operating characteristics during all regimes of operation. Hybrid bearings, which are a combination of rolling-element and fluid-film bearings, can improve performance characteristics and reliability of the rotor-bearing systems. A hybrid bearing, where a rolling-element bearing and a fluid-film bearing are positioned parallel to the vector of external load (PLEX), has the following advantages compared to a single bearing, whether rolling-element or fluid-film one: increase of life expectancy, load capacity increase, friction reduction, thermal regime enhancement, increase of stiffness, and damping properties. The present paper presents the results of theoretical and numerical research of friction characteristics of PLEX in mixed sliding and rolling friction, i.e. combination of viscous and rolling contact friction, regime. The conditions of minimum friction effect occurrence have been substantiated, and rational relations between characteristics of hybrid rolling-element bearings and fluid-film bearings needed for provision of such effect have been experimentally proven. Finally, the paper presents recommendations regarding design of such hybrid bearings for heavily loaded bearing nodes of rolling mills.

Effects of out-of-contact lubricant channeling on friction and film thickness in starved elastohydrodynamic lubrication point contacts

2016 ◽  
Vol 231 (4) ◽  
pp. 432-440 ◽  
Author(s):  
Fadi Ali ◽  
Ivan Křupka ◽  
Martin Hartl
Keyword(s):  
Film Thickness ◽  
Digital Camera ◽  
Elastohydrodynamic Lubrication ◽  
Contact Condition ◽  
Friction Reduction ◽  
Rolling Element Bearings ◽  
Point Contacts ◽  
Practical Applications ◽  
Rolling Element ◽  
Ball On Disc

This study presents experimental results on the effect of out-of-contact lubricant channeling on the tribological performance of nonconformal contacts under starved lubrication. Channeling of lubricant was carried out by adding a slider with a limited slot for scraping the displaced lubricant on one of mating surfaces (ball). Thus, the scraped lubricant is forced to flow back into the depleted track through the limited slot resulting in robust replenishment. The measurements have been conducted using optical tribometer (ball-on-disc) equipped with a digital camera and torque sensor. The effect of lubricant channeling was compared to the original contact condition by means of measuring friction and film thickness. The results show that the out-of-contact lubricant channeling leads to a significant enhancement of film thickness and friction reduction under starved conditions. Indeed, the starved elastohydrodynamic lubrication contacts transformed to the fully flooded regime after introducing the flow reconditioning. Moreover, the film thickness decay over time, which is common with starved elastohydrodynamic lubrication contacts, has not been observed in the case of lubricant channeling. However, the beneficial effect of lubricant channeling diminishes as the original contact condition tends to the fully flooded regime. The results of this study can be easily implemented in practical applications such as radial and thrust rolling-element bearings.

Some Effects of Lubricant Composition and Tappet Rotation on Cam/Tappet Friction

1989 ◽  
Vol 111 (4) ◽  
pp. 683-691 ◽  
Author(s):  
P. A. Willermet ◽  
J. Pieprzak
Keyword(s):  
Experimental Data ◽  
Frictional Contact ◽  
Angular Resolution ◽  
Friction Model ◽  
Journal Bearings ◽  
Valve Train ◽  
Wave Form ◽  
Rolling Element Bearings ◽  
Lubricant Composition ◽  
Rolling Element

A cam/tappet friction rig was constructed from a 1.6 L Ford valve train. The head casting and the camshaft were shortened so that only two journal bearings remained. Only one of the two remaining cam/tappet contacts was used as a frictional contact. All other contacts were equipped with rolling element bearings so that essentially all the turning torque came from cam/tappet friction and valve spring forces. The rig, together with a data acquisition/wave form analyzer system and a computer, was capable of measuring instantaneous torque with an angular resolution of less than one degree, and reducing the data to provide calculated values for parameters such as the friction coefficient. The experimental data were compared with results from a cam/tappet friction model to assist in interpretation. The data and model illustrated that lubricant composition and tappet rotation have important effects not only on overall friction, but also on the shape of friction versus cam angle curves.

scholarly journals Further understanding of rolling contact fatigue in rolling element bearings - A review

2019 ◽  
Vol 140 ◽  
pp. 105849 ◽  
Author(s):  
Mostafa El Laithy ◽  
Ling Wang ◽  
Terry J. Harvey ◽  
Bernd Vierneusel ◽  
Martin Correns ◽  
...  
Keyword(s):  
Rolling Contact Fatigue ◽  
Contact Fatigue ◽  
Rolling Contact ◽  
Rolling Element Bearings ◽  
Rolling Element

Low friction rolling element bearings

Wear ◽  
1985 ◽  
Vol 104 (4) ◽  
pp. 309-322 ◽  
Author(s):  
R. Gohar
Keyword(s):  
Rolling Element Bearings ◽  
Low Friction ◽  
Rolling Element

scholarly journals Forensic Engineering Analysis Of Failed Roller Bearings

1998 ◽  
Vol 15 (2) ◽  
Author(s):  
Olof H. Jacobson
Keyword(s):  
Case Studies ◽  
Forensic Analysis ◽  
Rolling Contact ◽  
Rolling Element Bearings ◽  
Bearing Failure ◽  
Engineering Analysis ◽  
Operating Characteristics ◽  
Bearing Failures ◽  
Rolling Element ◽  
Forensic Engineering

Failure Of Rolling Element Bearings Often Results In Damage To The Bearing Elements And Adjacent Components Such As Axles, Shafts, Gearboxes, Wheels, Etc. Forensic Analysis Of Rolling Contact Bearings Is Discussed In This Paper. A Review Of Bearing Types And Typical Operating Characteristics Is Presented. A Procedure For Systematic Examination And Analysis Of Bearing Failure Evidence Is Suggested, And Several Case Studies Are Presented Which Demonstrate The Types Of Evidence Typically Remaining And The Logic Which Leads To Engineering Conclusions Concerning The Cause Of Bearing Failures.

The Role of Hydrogen on Rolling Contact Fatigue Response of Rolling Element Bearings

2010 ◽  
Vol 7 (2) ◽  
pp. 102543 ◽  
Author(s):  
R. H. Vegter ◽  
J. T. Slycke ◽  
John Beswick ◽  
S. W. Dean
Keyword(s):  
Rolling Contact Fatigue ◽  
Contact Fatigue ◽  
Rolling Contact ◽  
Rolling Element Bearings ◽  
Rolling Element

A 3D Finite Element Study of Fatigue Life Dispersion in Rolling Line Contacts

2011 ◽  
Vol 133 (4) ◽  
Author(s):  
Nick Weinzapfel ◽  
Farshid Sadeghi ◽  
Vasilios Bakolas ◽  
Alexander Liebel
Keyword(s):  
Finite Element ◽  
Shear Stress ◽  
Material Properties ◽  
Rolling Contact Fatigue ◽  
Contact Fatigue ◽  
Critical Shear Stress ◽  
Rolling Contact ◽  
Shear Stresses ◽  
Rolling Element Bearings ◽  
Rolling Element

Rolling contact fatigue of rolling element bearings is a statistical phenomenon that is strongly affected by the heterogeneous nature of the material microstructure. Heterogeneity in the microstructure is accompanied by randomly distributed weak points in the material that lead to scatter in the fatigue lives of an otherwise identical lot of rolling element bearings. Many life models for rolling contact fatigue are empirical and rely upon correlation with fatigue test data to characterize the dispersion of fatigue lives. Recently developed computational models of rolling contact fatigue bypass this requirement by explicitly considering the microstructure as a source of the variability. This work utilizes a similar approach but extends the analysis into a 3D framework. The bearing steel microstructure is modeled as randomly generated Voronoi tessellations wherein each cell represents a material grain and the boundaries between them constitute the weak planes in the material. Fatigue cracks initiate on the weak planes where oscillating shear stresses are the strongest. Finite element analysis is performed to determine the magnitude of the critical shear stress range and the depth where it occurs. These quantities exhibit random variation due to the microstructure topology which in turn results in scatter in the predicted fatigue lives. The model is used to assess the influence of (1) topological randomness in the microstructure, (2) heterogeneity in the distribution of material properties, and (3) the presence of inherent material flaws on relative fatigue lives. Neither topological randomness nor heterogeneous material properties alone account for the dispersion seen in actual bearing fatigue tests. However, a combination of both or the consideration of material flaws brings the model’s predictions within empirically observed bounds. Examination of the critical shear stress ranges with respect to the grain boundaries where they occur reveals the orientation of weak planes most prone to failure in a three-dimensional sense that was not possible with previous models.

Nonlinear Mechanics of Rolling Contacts With Surface Defects

2010 ◽  
Author(s):  
Mohsen Nakhaeinejad ◽  
Jaewon Choi ◽  
Michael D. Bryant
Keyword(s):  
Surface Defects ◽  
Nonlinear Behavior ◽  
Rolling Contact ◽  
Rolling Element Bearing ◽  
Rolling Element Bearings ◽  
Detailed Model ◽  
Outer Race ◽  
Model Based ◽  
Rolling Contacts ◽  
Rolling Element

Nonlinear behavior of force and displacements in rolling contacts with the presence of surface defects are studied. Model-based fault assessments in rolling element bearings and gears require detailed modeling and dynamics of faults. A detailed model of rolling element bearings with direct correspondence between parameters of the model and physical components is developed. The model incorporates dynamics of faults, nonlinear contacts, slips and surface separations. Mechanics of contacts with inner race faults (IRF), ball faults (BF), and outer race faults (ORF) are studied using the developed model. Contacts force, displacement and impulse signals are studied for different size and types of surface defects. It is shown that impulse signals contain useful information about the severity of surface defects in rolling element bearing. Results provide model-based diagnostics a deep knowledge of rolling contact mechanics with surface defects to be used for fault assessments.

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