Friction and Wear with Surface Melting at High Sliding Speed and High Contact Pressure (1st Report,An Experimental Approach to the Condition of the transition to a Melting Lubrication)

Abstract

Based on the recent demands for higher sliding velocity of components, the excessive wear of the slider due to it has been discussed. However, since R. S. Montgomery reported his experimental work on the wear at high sliding speeds, no one has reported theoretical analysis of the slider wear. In this study, the frictional resistance was examined with static intrusion and dynamic acceleration tests. In the static intrusion test, the static frictional resistance increases linearly as the slider travel increase until the slider come to fully contact the cylinder. Meanwhile, the dynamic acceleration test revealed that the dynamic frictional resistance is about 30-40% of the static one with the slider travel up to approximately 50 mm, and that it then falls to the level of about 10% as the slider travel further increases. Such the sudden change corresponds to the estimated values of the friction coefficient : the friction coefficient estimated from the dynamic acceleration test results is about 0.1 in the earlier stage and falls to about 0.03 in the later stage, while the static intrusion test results only show a constant coefficient value of about 0.3. This drastic reduction of the friction coefficient in the dynamic test is considered to be attributable to the surface liquefaction of the slider material, where a melting lubrication may occur. The transitional condition to such a melting lubrication can be quantitatively expressed and evaluated by means of the melting lubridcation index, BLI.