The Life of Bearings, Explained
October 10, 2022When functioning under typical conditions, the inner and outer rings of the bearing and the rolling elements are continually loaded and unloaded as the bearing rotates. This leads to fatigue in the material, which finally leads to bearing failure. The term “basic rating life” refers to the total number of revolutions that must be reached or exceeded by 90 per cent of a suitably large group of bearings that appear to be identified before the first sign of material fatigue occurs. This statistic is based on bearings that have been tested.
Load Bearing
That manufacturer normally publishes load ratings for each bearing that a manufacturer of ball bearings produces. Ratings can be calculated using a variety of different ways, which can vary from maker to manufacturer. The shape of the bearing, the number of balls, their size, the diameter of the bearing pitch, and the materials used for the ring and the balls all contribute to the dynamic load rating. When calculating the bearing’s fatigue life, this load rating is considered in conjunction with the actual radial load applied.
Load Rating
The static load rating refers to the limiting loads that can be placed on bearings that are not spinning. The maximum contact stress between the balls and either of the two raceways determines which of the two raceways has the highest static load rating. Any variation in the size of the pitch circle’s diameter can affect the dynamic load rating. Similarly, any ball’s diameter or quantity variation can affect either load rating. If you change all of these factors simultaneously, your dynamic capacity may shift one way, while your static capacity will shift in the opposite direction.
High-Temperature Conditions
Bearings made to order can withstand temperatures of more than 350 degrees Celsius. The bearing material and the lubrication need to be considered when designing a custom bearing that will operate in such conditions. Chrome steel grade 52100 can tolerate temperatures as high as 125 degrees Celsius, making it an ideal material for the ball and roller bearings. For temperatures higher than 350 degrees Celsius, heat-stabilised materials are required. In addition, the design ought to integrate high-temperature grease or oil capable of functioning up to 285 degrees Celsius.
Corrosive Conditions
Bearings are susceptible to damage from both water and chemicals, which can drastically reduce their useful life. Although stainless steel is frequently used in the production of rings and components, one option to consider is nitrogen-enhanced martensitic stainless steel. This type of stainless steel has a corrosion resistance that is five times higher than standard stainless steel. Similarly, the ceramic material can be used for rolling elements, which perform well in corrosive conditions.
Vacuum Conditions
The retainers and the lubricants are affected when subjected to vacuum conditions, such as those found in space. Outgassing is the process by which gases or vapour that have been trapped in these components might escape and then condense on optical elements including lenses, solar cells, and navigation sensors. At higher temperatures, the rate of outgassing rises, necessitating the use of solid lubricants such as gold, silver, molybdenum disulphide, and polytetrafluoroethylene. In addition, austenitic stainless steel AISI 304 is the material of choice for the retainer because it lowers the amount of torque that is transmitted between the rolling elements and the retainer.
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