Correct installation of bearings can prevent premature failure

1. Contact fatigue failure

Contact fatigue failure refers to failure occurring on the bearing working surface due to the action of alternating stresses. Contact fatigue spalling occurs on the bearing working surface and is often accompanied by fatigue cracks. It first develops at points of higher alternating shear stress beneath the contact surface, then propagates to the surface, forming various spalling patterns, such as punctate spalling (pitting) or small-scale spalling. As the spalling surface gradually expands, it often penetrates deeper layers, resulting in deep-layer spalling. Deep spalling is the source of fatigue failure in contact fatigue.

2. Bearing Wear Failure

Wear failure refers to the failure caused by continuous wear of the metal on the working surfaces due to sliding friction between surfaces. A rolling bearing is a bearing assembly comprising two or more of the aforementioned bearing structures. Examples include needle roller and thrust cylindrical roller combined bearings, needle roller and thrust ball combined bearings, and needle roller and angular contact ball combined bearings. Continuous wear will cause the bearing assembly to deteriorate gradually, leading to a loss of dimensional accuracy and other related issues. Wear may affect dimensional changes, an increase in clearance, and alterations to the working surface profile; it may also affect the lubricant or cause contamination to a certain extent, resulting in a complete loss of lubrication function. Consequently, the bearing loses its rotational precision and may even fail to operate normally. Wear failure is one of the most common failure modes for various types of bearings; based on the form of wear, it is typically classified into the more common types of abrasive wear and adhesive wear.

Abrasive wear refers to wear caused by the intrusion of external hard particles, hard foreign matter, or metal swarf between the bearing working surfaces, which move across the contact surfaces. This often results in plough-like scratches on the bearing working surfaces. Hard particles or foreign matter may originate from within the host machine or be carried into the bearing by the lubricant from other adjacent components within the host system. Adhesive wear refers to wear caused by uneven force distribution on the contact surfaces due to microscopic asperities or foreign particles on the friction surfaces. When lubrication conditions deteriorate severely, localised friction generates heat, which can easily lead to partial deformation of the friction surfaces and micro-welding. In severe cases, the surface metal may partially melt; as the surfaces move, the force exerts a tearing action, tearing the micro-welded points away from the base material and increasing plastic deformation. This cycle of adhesion and tearing

-adhesion cycle constitutes adhesive wear. Specifically, mild adhesive wear is termed scuffing, whilst severe adhesive wear is termed seizure.

3. Bearing Fracture Failure

The primary causes of bearing fracture failure are defects and overload. When an external load exceeds the material’s strength limit, resulting in component fracture, this is termed overload fracture. The primary causes of overloading are sudden failures in the host machine or improper installation. Defects in the bearing, such as micro-cracks, shrinkage cavities, gas bubbles, large foreign particles, overheated structures and localised burning, can also lead to cracking at the defect site under impact loads or severe vibration; this is known as defect-induced cracking. It should be noted that during the bearing manufacturing process, the presence of the aforementioned defects can be accurately analysed using instruments during incoming inspection of raw materials, quality control of casting and heat treatment, and machining process control; however, control measures must continue to be strengthened. However, generally speaking, the majority of bearing failure cases are due to overloading. Causes of excessive bearing temperature include: lubricant quality failing to meet requirements or deterioration; excessive lubricant viscosity; excessive tightness of the assembly (insufficient clearance); over-tightening of the bearing; bearing rings rotating on the shaft or within the housing; excessive load; or fracture of the bearing cage or rolling elements.

1) The roundness of the shaft and housing bore, as well as the perpendicularity of the shoulder, must meet the corresponding precision requirements of the bearing. With the rapid development of China’s bearing industry, the variety of bearings has expanded, product quality and technical standards have improved, and the scale of the industry has grown. A specialised production system has now been established, featuring a comprehensive range of product categories and a reasonably structured production layout.

2) It is essential to correctly design both the interference fit of the rotating ring and the appropriate clearance of the stationary ring. The interference fit of the rotating ring should be kept as small as possible within the permissible range. Only by effectively accounting for the effects of thermal expansion at operating temperatures and centrifugal forces at higher speeds can creep or slippage at the contact surfaces of a tight fit be prevented. For the stationary ring, depending on the magnitude of the operating load and the bearing dimensions, a clearance fit or interference fit with the smallest possible clearance should be selected; a fit that is too loose or too tight is detrimental to maintaining the original correct geometry.

3) If bearings are operating at high speeds and under high operating temperatures, particular care must be taken to ensure that the rotating ring is not fitted too loosely, to prevent eccentric vibration, and that the stationary ring is not fitted with a gap, to prevent deformation of the ring under load and the resulting vibration.

Rolling bearings are permitted to produce slight operational noise during operation. However, if the noise is excessive or if there are abnormal noises or knocking sounds, this indicates a bearing fault. Imported bearings: China’s bearing industry has developed rapidly, with the variety of bearings increasing from few to many, and product quality and technical standards rising from low to high,