Friction coefficient between gear teeth in mixed film lubrication

2005 ◽  
pp. 525-533 ◽  
Author(s):  
J. Castro ◽  
A. Campos ◽  
A. Sottomayor ◽  
J. Seabra
Keyword(s):  
Friction Coefficient ◽  
Gear Teeth ◽  
Mixed Film ◽  
Film Lubrication

A Mixed-TEHL Analysis of Cam-Roller Contacts Considering Roller Slip: On the Influence of Roller-Pin Contact Friction

2018 ◽  
Vol 141 (1) ◽  
Author(s):  
Shivam S. Alakhramsing ◽  
Matthijn B. de Rooij ◽  
Aydar Akchurin ◽  
Dirk J. Schipper ◽  
Mark van Drogen
Keyword(s):  
Friction Coefficient ◽  
Thermal Effects ◽  
Mixed Lubrication ◽  
Contact Friction ◽  
Sudden Increase ◽  
Low Friction ◽  
Pure Rolling ◽  
Lubrication Performance ◽  
Cam Follower ◽  
Film Lubrication

In this work, a mixed lubrication model, applicable to cam-roller contacts, is presented. The model takes into account non-Newtonian, thermal effects, and variable roller angular velocity. Mixed lubrication is analyzed using the load sharing concept, using measured surface roughness. Using the model, a quasi-static analysis for a heavily loaded cam-roller follower contact is carried out. The results show that when the lubrication conditions in the roller-pin contact are satisfactory, i.e., low friction levels, then the nearly “pure rolling” condition at the cam-roller contact is maintained and lubrication performance is also satisfactory. Moreover, non-Newtonian and thermal effects are then negligible. Furthermore, the influence of roller-pin friction coefficient on the overall tribological behavior of the cam-roller contact is investigated. In this part, a parametric study is carried out in which the friction coefficient in the roller-pin contact is varied from values corresponding to full film lubrication to values corresponding to boundary lubrication. Main findings are that at increasing friction levels in the roller-pin contact, there is a sudden increase in the slide-to-roll ratio (SRR) in the cam-roller contact. The value of the roller-pin friction coefficient at which this sudden increase in SRR is noticed depends on the contact force, the non-Newtonian characteristics, and viscosity–pressure dependence. For roller-pin friction coefficient values higher than this critical value, inclusion of non-Newtonian and thermal effects becomes highly important. Furthermore, after this critical level of roller-pin friction, the lubrication regime rapidly shifts from full film to mixed lubrication. Based on the findings in this work, the importance of ensuring adequate lubrication in the roller-pin contact is highlighted as this appears to be the critical contact in the cam-follower unit.

Effect of Transfer Films on Friction of PTFE/PEEK Composite

2020 ◽  
Vol 143 (4) ◽  
Author(s):  
Shuren Qu ◽  
King Him Lo ◽  
Su Su Wang
Keyword(s):  
Solid State ◽  
Friction Coefficient ◽  
Friction Theory ◽  
Subsequent Investigation ◽  
Transfer Films ◽  
Constituent Material ◽  
Peek Composite ◽  
Theoretical Predictions ◽  
Film Development ◽  
Film Lubrication

Abstract This paper investigates the effect of transfer films on friction coefficient of polytetrafluoroethylene (PTFE)/polyetheretherketone (PEEK) composite. Friction experiments were carried out first to investigate transfer-film development during sliding contact of PTFE/PEEK composite with different PTFE volume fractions on a steel counterface. Quantitative relationships between PTFE/PEEK composite friction coefficient and constituent material mechanical properties are then established to facilitate the subsequent investigation of friction mechanisms and influence of transfer films on the composite friction. A micromechanics-based friction theory is developed for predicting PTFE/PEEK composite friction coefficient. The effect of transfer films on composite friction is accounted for based on two distinctly different mechanisms—one with solid-state film lubrication and the other with PTFE as a solid-state lubricant on the top surface of transfer films. The friction theory is first validated through the excellent agreement obtained between the theoretical predictions and the in-house experimental results on PTFE/PEEK composite with up to 20% PTFE (by volume). The validity of the theory is further demonstrated by comparing the theoretical predictions with the test data reported by other researchers in the literature.

Effect of Friction Coefficient on the Stiffness Excitation of Gear

2011 ◽  
Vol 86 ◽  
pp. 713-716 ◽  
Author(s):  
Yu Mei Hu ◽  
De Shuang Xue ◽  
Yang Jun Pi
Keyword(s):  
Friction Coefficient ◽  
Simulation Model ◽  
Normal Load ◽  
Single Pair ◽  
Friction Coefficients ◽  
Gear Teeth ◽  
Load Distributions ◽  
Single Tooth ◽  
Element Technique ◽  
Double Teeth

This study addresses the effect of different friction coefficients on the stiffness excitation of gear using finite element technique. Firstly, the simulation model of single pair of gear teeth mesh is established, and the effect of friction coefficient on the composite stiffness values of the teeth meshing is studied. After that, simulation model of multiple pairs of gear teeth meshing is created and the normal load distributions under different friction coefficients in a single meshing cycle are calculated using quasi-static calculation method. Finally, the relationship between friction coefficient and stiffness excitation of gear system is obtained. The investigation results indicate that at the alternation place of single tooth meshing and double teeth meshing, the stiffness excitation of the system is greater under larger friction coefficient when double teeth meshing change into single tooth meshing, while the opposite situation occur when single tooth meshing change into double teeth meshing. The amplitude value of stiffness variation for single pair of teeth meshing under different friction coefficients is 2.12%, while the amplitude value of teeth loads variation for multiple pairs of teeth meshing under different friction coefficients is 22.87%.

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