Typical Rolling Bearing Fatigue Even under very good operating conditions, ie with elastohydrodynamic lubricating oil film, best cleanliness and optimum temperature, load-related fatigue failures of bearing parts can occur. If the equivalent load is greater than the fatigue limit load Cu, fatigue failure will be formed after long-term operation in this state. The fatigue limit load Cu value is shown in the bearing dimension table in the catalogue. Such typical fatigue failures caused by subsurface cracks rarely occur. Fatigue failure of FAG rolling bearings due to poor lubrication or cleanliness of the rolling contact surfaces often occurs. When the damage spreads further, the cause of the failure is difficult to pinpoint. Phenomenon: subsurface cracks in raceways and rolling elements, material flaking (relatively deep pits), undamaged portions of raceways indicate good lubrication at the beginning of failure (see Figure 23). However, as the damage progresses, the dented rotating parts (see Figure 31) will show more and more dimples, see Figures 41 to 43. 28 Evaluation of running characteristics and damage on the removed bearing rolling contact pattern 41 : Typical fatigue judged by pitting corrosion on the inner ring raceway of deep groove ball bearings. Fatigue spreads further and material spalls across the raceway. 42: Further fatigue damage on deep groove ball bearings Fatigue caused by cyclic movement of external particles When there are rough impurities in the bearing, the fatigue life will be greatly reduced, see Figure 44. In practical applications, the degree of hazard of failure caused by foreign particles is related to the hardness, size, number and bearing size of the foreign particles. In terms of fatigue, ball bearings are more sensitive to impurities than roller bearings, and bearings with small rolling elements are more sensitive than bearings with large rolling elements. The pits formed by foreign particles can have a significant impact on the rolling material. Especially the rotational motion under stress has a great influence on the initial crack, the SEM images are in Section 4. Phenomenon: material flaking; pits formed by foreign particles develop in a V-shape in the rolling direction (V-shaped pits), Figure 45. Reason: craters caused by flaking raceway material and hard particles (foundry sand, abrasive particles) are especially dangerous. Remedy: Thoroughly clean parts such as bearing housings, if necessary, coating. When installing, cleaning and careful improvement of seals are required. Use of dust-proof bearing structure. Cleanliness of lubricants is important. Evaluation of running characteristics and damage of bearings under rolling contact mode 44: Reduction of life due to different contamination : Destruction after about 1000 hours of operation c: Destruction after about 1200 hours of operation.