A computational model is proposed for the prediction of friction-related mechanical efficiency losses of parallel-axis gear pairs. The model incorporates a gear load distribution model, a friction model, and a mechanical efficiency formulation to predict the instantaneous mechanical efficiency of a gear pair under typical operating, surface, and lubrication conditions. The friction model uses a new friction coefficient formula obtained by using a validated non-Newtonian thermal elastohydrodynamic lubrication (EHL) model in conjunction with a multiple linear regression analysis. The load and friction coefficient, distribution predictions are used to compute instantaneous torque/ power losses and the mechanical efficiency of a gear pair at any given rotational position. Efficiency measurements from gear pairs having various gear designs and surface treatments are compared to model predictions. Mechanical efficiency predictions are shown to be within 0.1% of the measured values, indicating that the proposed efficiency model is accurate. Results of a parametric study are presented at the end to highlight the influence of key basic gear geometric parameters, tooth modifications, operating conditions, surface finish, and lubricant properties on mechanical efficiency losses.

Prediction of Mechanical Efficiency of Parallel-Axis Gear Pairs

https://deepblue.lib.umich.edu/bitstream/handle/2027.42/24617/0000027.pdf?sequence=1&isAllowed=y

A review of scuffing and running-in of lubricated surfaces, with asperities and oxides in perspective

https://www.nber.org/system/files/working_papers/w23991/w23991.pdf

Temperature Effects on Productivity and Factor Reallocation: Evidence from a Half Million Chinese Manufacturing Plants

Scuffing - a review

Thermoelastic instability of sliding contact in the absence of wear

Any rational approach to gear design must consider, as a minimum, the impact of the various modes of gear-tooth failure on gear performance; operating life and reliability; and size, weight, and cost. Gear teeth may fail basically by either strength-related or lubrication-related causes. However, many strength-related failures are influenced by lubrication, or may be induced by lubrication-related failures. This paper emphasizes the principal lubrication-related failure modes of gear teeth, and examines the complex interactions between gear mechanics and gear lubrication in affecting such failure modes. Presented at the 30th Annual Meeting in Atlanta, Georgia, May 5–8, 1975

Gear Failure Modes—Importance of Lubrication and Mechanics

Properties of inorganic energy-conversion and heat-transfer fluids for space applications

Mechanisms of Wear in Misaligned Splines

Sliding experiments from—195 to +200 C are reported for metals lubricated with thin films of hydrocarbons, fatty acids, and synthetic lubricants in helium and air. For copper and iron pairs lubricated with pure organic compounds, a marked rise in friction and wear is found to occur at the melting point of the film material. From just below the melting point down to —195 C, there is an increase in friction but negligible wear, indicating increased shear strength of the solid film. This is substantiated by contact resistance measurements. The behavior of fatty acids in dry air indicates that oxygen promotes the formation of higher-melting soap, and defers the above-noted friction rise to the melting point of the soap. Humidity serves to displace the friction rise to an even higher temperature. Presented as an American Society of Lubrication Engineers paper at the Lubrication Conference held in Washington, D.C., October 13–16, 1964

Boundary Lubrication Behavior of Organic Films at Low Temperatures

The current drop-weight test methods for evaluating the compatibility of materials with liquid oxygen under impact are briefly discussed, with particular emphasis upon the characteristically poor repeatability of the “threshold value” impact sensitivity ratings yielded by these methods. It is pointed out that this trait is primarily due to the poor statistics of the test procedures used. It is further shown that impact sensitivity alone, even when measured by the most accurate and reliable technique, is not an adequate description of the potential fire or explosion hazard of a material; reaction intensity must also be considered. With this background, typical results from two new test techniques are presented and discussed. In one of these, impact sensitivity is measured in terms of the drop height at which a material has a 50% probability of reaction. In the other, reaction intensity is measured in terms of the maximum peak pressure of the air shock wave generated by the reaction. Presented at the 23rd A...

P. M. Ku

Papers

Gear Failure Modes—Importance of Lubrication and Mechanics

Properties of inorganic energy-conversion and heat-transfer fluids for space applications

Mechanisms of Wear in Misaligned Splines

Boundary Lubrication Behavior of Organic Films at Low Temperatures

New Test Techniques for Evaluating the Compatibility of Materials with Liquid Oxygen under Impact