Paper II (iv) Lubricant Screening for Debris Effects to Improve Fatigue and Wear Life

This paper discusses the mechanisms of surface damage induced by lubricant borne debris in rolling element contacts. Particular emphasis is placed on how debris particles cause damage and how the extent of this damage is related to debris size and material properties. The study is broadly divided into two parts: first, an investigation into the mechanisms of particle entry and behaviour in rolling contacts; and second, an analysis of the extent of rolling element surface damage caused by these particles. The results of optical ehd experiments show how various types of debris particle deform or fragment in the contact entry region. High speed video and short duration flash photography have been used to track the movement of debris particles as they approach and pass through an elastohydrodynamic contact, or are swept around the sides. Simple analyses are presented for predicting the maximum particle size and number which may be entrained into the contact. To investigate lubricant contaminant damage potential, a rig, designed to accumulate debris dent geometries, has been constructed. The results of experimentation, using this rig with lubricants contaminated with ductile and brittle particles, have been compared to theories for the prediction of surface damage. © 1992.