Adhesion Between Metals and its Effect on Fixed and Sliding Contacts

Abstract

Recent studies of adhesion between metals measured as a function of pressure, temperature and time have resulted in a quantitative understanding of the process. Creep causes the spaces between the point contacts to be filled in and molecular seizure occurs. Recent work by O. L. Anderson has shown that seizure can occur between two sets of metals if a twist is superposed on a compression. By this technique, the area of contact is increased over that resulting from compression alone, and a large enough area of contact results so that the adhesive stresses overbalance the elastic stresses which tend to disrupt the adhesive bond. Hence seizure occurs. By studying the coefficient of adhesion as a function of the applied stress, Amonton's law of friction has been verified from the adhesion side, thus confirming the Bowden–Tabor theory of stick-slip friction. Adhesion between metals due to compression, occurring over a finite time, is essential for such connections as the solderless wrapped connection and is important for contacts left under pressure in the same position for a length of time as in printed circuit type connections. Adhesion between metals caused by both compression and shear is the cause for mechanical seizure, plowing and wear experienced in sliding contacts. Direct force measurements have shown the nature of the slip-stick process.