Erosion of Bearing Alloys in Oil Film

Abstract

In the plain bearing under fluctuating loads, the shaft repeatedly closes to and separates from the bearing surface intermediated by a thin oil film, and occasionally bearing metals show erosion pits or spalling. In the previous paper, erosion tests were carried out by vibrating the disc at the free end of the magnetostrictive oscillator close to the steel plate or the plane surface of bearing alloy lining on steel plate in water or in various lubricating oils. The damages are due to fatigue by the collapse pressure of cavitation bubbles under a thick oil film and due to fatigue by the surface shearing of squeezed film under a thin oil film. At small film thickness, fatigue cracks are found near the periphery of eroded area and these lead to a catastrophic failure of the bearing by flaking off the lining metal. In the present paper, further erosion tests are carried out in the lubricating oil on copperlead bearing alloy as well as tin-base white metal. Copper-lead alloy is damaged more severely than tin-base white metal, because the failure of the former grows in networks of lead. The strength in the thin oil film becomes higher as the lining thickness is smaller, because the surface strains are more restrained by the backing steel. Meanwhile, the effect of lining thickness is hardly found at the thick oil film. Erosion damages in spindle oil with oleic acid are more intensive under the thin oil film than under the thick oil film, because the failure is due to the surface shearing in the former case and to the subsurface damage in the latter case.