境界摩擦における接線力と微小変位との関係

抄録

This paper describes how the boundary lubrication actually affects the relative tangential micro-displacement between two bodies in contact, the displacement being caused by a tangential force weaker than the force of maximum friction. The micro-displacement is measured with a differential transformer and the tangential force with an electromagnet, its current determining the magnitude of the force. The curve of tangential force vs. tangential displacement and that of tangential force vs. contact resistance are recorded on an electromagnetic oscillograph.
The tangential displacement caused by a tangential force weaker than to give rise to sliding becomes larger for a wide range of the force when the contact is lubricated. This confirms the obvious effect of lubricants on the process of plastic deformation before the sliding sets in.
The coefficient of maximum friction and the tangential displacement just before the beginning of sliding are measured under boundary-lubricated condition at the temperature ranging from 25°C to about 180°C. As the temperature rises, the displacement becomes smaller and the observed values of the coefficient become random.
With unlubricated steel specimens, irregular stick-slip occurs even during the micro-displace-ments prior to the sliding. The magnitude of this stick-slip is 0.2μ_??_1μ which is considered to be of the order of the area of individual real contacts dotted over the apparent area of contact.
When the tangential force is increased, the contact resistance decreases and remains very nearly so even the former is decreased again. The increase of real contact area following the increase of tangential force seems therefore to be due chiefly to plastic deformation in normal direction at the real contacts.