Gear Tribology Aspects in Aircraft High-Lift Actuation Systems

2011 ◽  
Author(s):  
Anngwo Wang ◽  
Lotfi El-Bayoumy
Keyword(s):  
Film Thickness ◽  
Boundary Lubrication ◽  
High Lift ◽  
Lubrication Film ◽  
Root Cause ◽  
Lubrication Regime ◽  
Rotary Actuator ◽  
Actuation Systems

Gears are extensively used in aircraft high-lift actuation systems in which the loading is high and the speed is relatively slow. The specific lubrication film thickness falls into the boundary lubrication regime. In case of lubrication failure, it will cause pitch-line pitting, scoring or micropitting. Many tests have been performed to examine the root cause of these problems. The sliding and rolling action between mating gears in a compound planetary rotary actuator is the source of variation in efficiency. This efficiency variation can be smooth or fluctuating depending on the combination and timing of ring, planet and sun gears. The instantaneous efficiency characteristics of synchronous and non-synchronous actuators under forward-driving with opposing load and reverse-driving with aiding load are investigated. These are some of the gear tribological topics discussed in this paper.

Stribeck Curve for Starved Line Contacts

2006 ◽  
Vol 129 (1) ◽  
pp. 181-187 ◽  
Author(s):  
I. C. Faraon ◽  
D. J. Schipper
Keyword(s):  
Film Thickness ◽  
Layer Thickness ◽  
Boundary Lubrication ◽  
Numerical Data ◽  
Contact Model ◽  
Stribeck Curve ◽  
Lubrication Regime ◽  
Straight Line ◽  
Line Contacts ◽  
Good Agreement

This paper discusses a mixed lubrication model in order to predict the Stribeck curve for starved lubricated line contacts. This model is based on a combination of the contact model of Greenwood and Williamson and the elastohydrodynamic (EHL) film thickness for starved line contacts. The starved solution to be implemented in the EHL component is obtained by using numerical data of Wolveridge, who computed the starved film thickness for smooth line contacts. Calculations are presented for different oil supply layer thickness over roughness values (hoil∕σs). For values of the oil layer thickness over roughness ratio larger than approximately 6, the Stribeck curve and separation between the rough surfaces do not change compared to the fully flooded situation. If the oil layer thickness over roughness ratio is in the range of 6 down to 0.7, friction starts to increase and the film thickness decreases. When the oil layer thickness over roughness ratio is less than approximately 0.7, the Stribeck curve tends to transform into a straight line and separation stays at the same value as in the boundary lubrication regime. Comparison between measurements and calculations is made and a good agreement is found.

The Film Thickness in Piezoviscous-Rigid Regime; Film Thickness Lubrication Regimes Transition Criteria

1984 ◽  
Vol 106 (3) ◽  
pp. 375-381 ◽  
Author(s):  
L. Houpert
Keyword(s):  
Film Thickness ◽  
General Formula ◽  
Lubricant Film ◽  
Lubricant Film Thickness ◽  
Dimensionless Parameters ◽  
Lubrication Regimes ◽  
Lubrication Film ◽  
Lubrication Regime ◽  
Transition Criteria

A new general formula is proposed to calculate the lubricant film thickness in the piezoviscous rigid lubrication regime. Equivalent radii ratio, load, speed, and material dimensionless parameters are included. New general criteria to decide whether piezoviscous rigid or EHD (elasto-hydrodynamic) or isoviscous elastic lubrication film thickness formulas have to be used are proposed. Comparisons with some other published results are made.

Robust Interfacial Tribofilms by Borate- and Polymer-Coated ZnO Nanoparticles Leading to Improved Wear Protection under a Boundary Lubrication Regime

Langmuir ◽  
2021 ◽  
Vol 37 (5) ◽  
pp. 1743-1759 ◽  
Author(s):  
Kimaya Vyavhare ◽  
Richard B. Timmons ◽  
Ali Erdemir ◽  
Brian L. Edwards ◽  
Pranesh B. Aswath
Keyword(s):  
Boundary Lubrication ◽  
Zno Nanoparticles ◽  
Wear Protection ◽  
Lubrication Regime

Analysis of the Contribution of Adhesion and Hysteresis to Shoe–Floor Lubricated Friction in the Boundary Lubrication Regime

2012 ◽  
Vol 47 (3) ◽  
pp. 341-347 ◽  
Author(s):  
Caitlin Moore Strobel ◽  
Pradeep L. Menezes ◽  
Michael R. Lovell ◽  
Kurt E. Beschorner
Keyword(s):  
Boundary Lubrication ◽  
Lubrication Regime

Synergistic Antiwear Effects of Zinc Dialkyl Dithiophosphate and Different Detergents

2008 ◽  
Author(s):  
G. Pennecot ◽  
K. Komvopoulos ◽  
E. S. Yamaguchi
Keyword(s):  
Wear Rate ◽  
Boundary Lubrication ◽  
Base Oil ◽  
Temperature Range ◽  
Zinc Dialkyl Dithiophosphate ◽  
Contact Voltage ◽  
Lubrication Regime ◽  
Steel Surfaces ◽  
Dialkyl Dithiophosphate ◽  
Insight Into

The effectiveness of blends consisting of base oil, some secondary zinc dialkyl dithiophosphate (ZDDP), and different detergents to form antiwear tribofilms on steel surfaces sliding in the boundary lubrication regime was investigated in the temperature range of 105–125°C. The efficacy of the tribofilms formed from these blends was evaluated in terms of contact voltage and wear rate measurements. The best antiwear performance was demonstrated by the tribofilm formed from the blend containing sulphonate detergent. The results of this study provide insight into competing effects between ZDDP and different detergents that affect significantly the antiwear performance of the formed tribofilms.

A New Postulation of Viscosity and Its Application in Computation of Film Thickness in TFL1

2002 ◽  
Vol 124 (4) ◽  
pp. 811-814 ◽  
Author(s):  
Chaohui Zhang ◽  
Jianbin Luo ◽  
Shizhu Wen
Keyword(s):  
Thin Film ◽  
Experimental Data ◽  
Film Thickness ◽  
Solid Surface ◽  
Contact Area ◽  
Elastohydrodynamic Lubrication ◽  
Thin Film Lubrication ◽  
Lubrication Film ◽  
Viscosity Modification ◽  
Film Lubrication

In this paper, a viscosity modification model is developed which can be applied to describe the thin film lubrication problems. The viscosity distribution along the direction normal to solid surface is approached by a function proposed in this paper. Based on the formula, lubricating problem of thin film lubrication (TFL) in isothermal and incompressible condition is solved and the outcome is compared to the experimental data. In thin film lubrication, according to the computation outcomes, the lubrication film thickness is much greater than that in elastohydrodynamic lubrication (EHL). When the velocity is adequately low (i.e., film thickness is thin enough), the pressure distribution in the contact area is close to Hertzian distribution in which the second ridge of pressure is not obvious enough. The film shape demonstrates the earlobe-like form in thin film lubrication, which is similar to EHL while the film is comparatively thicker. The transformation relationships between film thickness and loads, velocities or atmosphere viscosity in thin film lubrication differ from those in EHL so that the transition from thin film lubrication to EHL can be clearly seen.

Calculation of Elastohydrodynamic Lubrication Film Thickness for Hip Prostheses During Normal Walking

1990 ◽  
Vol 33 (2) ◽  
pp. 239-245 ◽  
Author(s):  
Cheng-Tao Wang ◽  
Yi-Ling Wang ◽  
Qing-Li Chen ◽  
Min-Run Yang
Keyword(s):  
Film Thickness ◽  
Elastohydrodynamic Lubrication ◽  
Normal Walking ◽  
Hip Prostheses ◽  
Lubrication Film
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