Program Accomplishments Lubrication

NBS has pioneered the development of instruments and methods to establish state-of-the-art technology for the analysis of lubricating films in boundary lubrication. An understanding of how lubricants work has begun to emerge and should lead to the development of new lubricant systems. The key advancement is in the unique way in which various analytical tools have been combined to give analytical chemical data. These include development of methods utilizing 4-ball wear tests in a combination with GPC-GFAA (Gel Permeation Chromotography-Graphite Furnace Atomic Absorption) to track fluid-ceramic interactions, the use of TGA (Thermal Gravimetric Analysis) and DSC (Differential Scanning Calorimetry) in combination with |¿-FTIR (micro-Fourier Transform Infrared) to yield organic film structural data and the use of SEM-EDAX (Scanning Electron Microscope-Elemental Diffraction Analysis X-ray) for particle and surface analysis.

The most significant accomplishment in the ability to analyze the chemical reactions in the contact zone has been the progress toward the development of a wear facility with micro-Raman, real-time, in-situ, tribochemi-cal film-analysis capabilities. The system under development is based on time-resolved micro-Raman spectroscopy and uses an Nd-YAG laser to provide periodic pulses of monochromatic light which are focused onto tribocontacts of a specially designed wear tester. The scattered light is collected by an optics system and recorded by a gated intensified-diode-array detector. The detector system is governed by a device-specific controller and data storage, with retrieval and analysis performed on-line.

A lubrication model was developed at Northwestern University for the power-loss analysis of gears. This model includes sliding-traction and rolling-traction analyses for the prediction of power loss and gear efficiency. The model has been developed specifically for spur gears which are the most commonly used gear-tooth geometry.

The analytical predictions, which have been verified by experimental measurements of traction coefficient against slide-to-roll ratio, show that at small shear rates or low slide-to-roll ratios the dependency is linear; increasing sliding gives rise to progressive non-linearity in the traction coefficient which, at large pressure, reaches a maximum value of 0.05-0.1. Further increase in slide-to-roll ratio leads to a fall in the traction curve.

As for the power loss in spur gears, the analytical prediction indicates that at low speeds and high loads the sliding power loss accounts for most of the power > losses, while at high speeds and low loads the rollingpower toss becomes significant and can contribute substantially to the total power loss. Moreover, at

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