A mechanical part, which supports the moving part, is termed a mechanical bearing and can be classified into rolling (ball or roller) bearings and sliding bearings. This article discusses the failures of sliding bearings. It first describes the geometry of sliding bearings, next provides an overview of bearing materials, and then presents the various lubrication mechanisms: hydrostatic, hydrodynamic, boundary lubrication, elastohydrodynamic, and squeeze-film lubrication. The article describes the effect of debris and contaminant particles in bearings. The steps involved in failure analysis of sliding bearings are also covered. Finally, the article discusses wear-damage mechanisms from the standpoint of bearing design.

An aluminum bronze bushing that serves as a guide in a crimping machine began to fail after 50,000 cycles or approximately two weeks of operation. Until then, typical run times had been on the order of months. Although the bushings are replaceable and relatively inexpensive, the cost of downtime adds up quickly while operators troubleshoot and swap out worn components. Initially, the quality of the bushings came into question, but after a detailed analysis of the entire crimping mechanism, several other issues emerged that were not previously considered. As a result, the investigation provides information on not only better materials, but also design changes intended to reduce wear and increase service life.

A heat transport pump in a heavy water reactor failed (exhibiting excessive vibration) during a restart following a brief interruption in coolant flow due to a faulty valve. The pump had developed a large crack across the entire length of a bearing journal. An investigation to establish the root cause of the failure included chemical and metallurgical analysis, scanning electron fractography, mechanical property testing, finite element analysis of the shrink fitted journal, and a design review of the assembly fits. The journal failure was attributed to corrosion fatigue. Corrective actions to make the journals less susceptible to future failures were implemented and the process by which they were developed is described.

Examination of a connecting-rod shell bearing from a six-cylinder gasoline engine was done after it was returned to the factory. Copper-lead alloy SAE 485 bonded to a low-carbon steel backing was used to make the bearing and the oil used in the engine was the recommended one. Measurable material loss was visible over most of the bearing halves particularly in a wide region at the centerline. A brittle waxlike substance identified to be a mixture of copper and lead sulfides covered the visible shallow pits and the darkened region. Change of oil with greater frequency to prevent the buildup of sulfur compounds or bearing halves that have corrosion-resistant overlay materials were recommended as best solutions.

An investigation of wear and failure of babbitt bushes was completed in this study. The results showed that wear at dry sliding of babbitt obtained by plasma spraying was less than that of babbitt in the as-cast state and after a deformation heat treatment. The failure of babbitt bushes was caused by a simultaneous and interrelated exhibition of fatigue and wear processes that depend considerably on cohesion strength between the bush and the bearing base and accumulation of defects on the contact surface between the bush and the shaft.