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The Basic Form Of Roller Bearing Failure

  The failure of roller bearings can generally be divided into two types: stoppage failure and precision loss. Stoppage failure is the termination of rotation of the bearing due to the loss of working ability, such as stuck, broken, and so on. Loss of accuracy means that the bearing loses the accuracy required by the original design due to dimensional changes. Although it can continue to rotate, it is an abnormal operation, such as wear and corrosion. The influencing factors of bearing failure are very complex, and due to the differences in the working conditions and structures of various types of bearings, the failure forms and morphological characteristics are also different. According to its damage mechanism, it can be roughly divided into several basic modes: contact fatigue failure, friction and wear failure, fracture failure, deformation failure, corrosion failure, and clearance change failure.

  1. Contact fatigue (fatigue wear) failure

  Contact fatigue failure is one of the very common failure modes of all kinds of bearings, which is caused by the repeated action of cyclic contact stress on the surface of roller bearings. Contact fatigue spalling on the surface of bearing parts is a process of fatigue crack initiation and propagation to cracks. The initial contact fatigue crack first occurs from the contact surface with large orthogonal shear stress and then expands to the surface to form pitting spalling or small cracks. Flake spalling, the former is called pitting or pitting spalling, and the latter is called shallow spalling. If the initial crack occurs in the junction area between the hardened layer and the core, resulting in the early spalling of the hardened layer, it is called the spalling of the hardened layer.

  2. Failure of adhesion and abrasive wear

  It is one of the very common failure modes of various bearing surfaces. The relative sliding friction between bearing parts leads to the continuous loss of metal on the surface, which is called sliding friction. Continuous wear will change the size and shape of the parts, increase the bearing clearance, and deteriorate the working surface appearance, thereby losing the rotation accuracy and making the roller bearings unable to work properly. The forms of sliding wear can be divided into abrasive wear, adhesive wear, corrosive wear, fretting wear, etc. Among them, abrasive wear and adhesive wear are common.

  The phenomenon of friction surface wear caused by foreign hard particles or metal grinding between the friction surfaces of stainless steel needle roller bearings belongs to abrasive wear, which often causes chisel-type or furrow-type scratches on the bearing surface. Foreign hard particles often come from dust in the air or impurities in the lubricant. Adhesion wear is mainly due to the uneven force on the friction surface due to the profile peak of the friction surface, and the local friction heat increases the temperature of the friction surface, causing the lubricant film to rupture. In severe cases, the metal on the surface layer will partially melt, and the contact points will produce a cycle of adhesion, peeling, and re-adhesion, and in severe cases, the friction surface will be welded and stuck.