Future preventive maintenance system (PMS) wear tests for diesel engines may include analysis of lubricating oil to detect a foreign metal that has been purposely embedded at a specified depth below a sliding surface.
Our experiment used cobalt (Co) embedded in a piston ring and barium (Ba) embedded in white bearing metal. A pin-on-disk wear test of each material showed that cobalt may be applicable to oil analysis for preventive mainte-nance. More consideration is needed, however, for such use of barium.