Chemical-Mechanical Interaction in Gears,
ARMY RESEARCH OFFICE RESEARCH TRIANGLE PARK NC
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A theory of chemo-mechanical interaction is developed to explain several disparate phenomena in the field of tribology on a quantitative basis. The important new quantity in this theory is the variation of the Gibbs chemical potential with stress, a quantity formulated and calculated explicitly using statistical thermodynamics and many-body theory, called the chemo-stress coefficient. The theory gives the basis for quantitative explanation of stress corrosion, fretting corrosion, the Rehbinder effect, and enhanced chemical activity on solid surfaces. In particular it suggests methods of arresting corrosion by controlling the charge distribution of electrolytes near the surface of the solid. A mechanism for pitting corrosion observed on lubricated load bearing surfaces of mechanical components such as gears is proposed. This theory emphasizes the importance of specific ions in the lubricant which migrate to the tips of cracks and diffuse through near-surface layers of the metal thereby causing volumetric changes leading to blistering or pitting.