Bearing Knowledge

The influence of bearing performance and structure on installation factors

The primary objective of analysing the service life of rolling bearings is to identify the main factors causing bearing failure based on extensive background material, analytical data and failure modes, so as to propose targeted improvement measures, extend the service life of the bearings and prevent sudden premature failure.

The method of installing rolling bearings depends on the bearing fit, conditions and structure. Generally, as the shaft is usually rotating, the inner ring requires an interference fit. Bearings for cylindrical bores are usually pressed in using a press or fitted using a hot-fitting method. In the case of tapered bores, they are either mounted directly onto a tapered shaft or fitted using a sleeve.

Wear failure refers to failure caused by the continuous wear of the working surface metal resulting from relative sliding friction between surfaces. Continuous wear leads to the gradual deterioration of rolling bearing components, ultimately resulting in the loss of dimensional accuracy and other related issues. Wear may affect dimensional changes, increase clearance and alter the surface topography of working surfaces. It may also affect the lubricant or cause contamination to such an extent that lubrication function is completely lost, thereby causing the bearing to lose rotational precision or even become unable to operate normally. Wear failure is common types: abrasive wear and adhesive wear.

one of the common failure modes for various types of bearings; according to the form of wear, it is typically classified into the most

1. Thrust Angular Contact Ball Bearings Thrust angular contact ball bearings generally have a contact angle of 60°. Commonly used thrust angular contact ball bearings are typically double-direction thrust angular contact ball bearings, primarily used in the spindles of precision machine tools. They are generally used in conjunction with double-row cylindrical roller bearings to withstand axial loads in both directions. They offer advantages such as high precision, good rigidity, low temperature rise, high rotational speed, and ease of installation and removal.

Second: Deep Groove Ball Bearings Structurally, each ring of a deep groove ball bearing features a continuous groove-type raceway with a cross-section approximately one-third the circumference of the ball's equator. Deep groove ball bearings are primarily used to bear radial loads, though they can also withstand a certain degree of axial load. When the radial clearance of the rolling bearing is increased, it exhibits the characteristics of an angular contact ball bearing and can withstand alternating axial loads in both directions. Compared to other types of bearings of the same dimensions, this type of bearing has a low coefficient of friction, high limiting speed and high precision, making it the preferred choice for users when selecting bearings. Deep groove ball bearings are simple in structure and convenient to use; they are the most widely produced and have the broadest range of applications.

Third: Thrust Tapered Roller Bearings As the rolling elements in thrust tapered roller bearings are tapered rollers, the rolling generatrices and the raceway generatrices of the washers intersect at a single point on the bearing's axis. Consequently, the rolling surfaces can achieve pure rolling, resulting unidirectional axial loads. The type designation for thrust tapered roller bearings is 90000.

in a higher limiting speed than that of thrust cylindrical roller bearings. Features: Thrust tapered roller bearings can withstand Structure and Performance Characteristics of Double-Row Tapered Roller Bearings Double-row tapered roller bearings come in a wide variety of designs, with the 35000 series being the most common. This type features a double-raceway outer ring and two inner rings, with a spacer between the inner rings; the clearance can be adjusted by altering the thickness of the spacer. This type of bearing can withstand bidirectional axial loads whilst bearing radial loads, and can limit the axial displacement of the shaft and housing within the bearing' s axial clearance range. Structural characteristics of tapered roller bearings. The type designation for tapered roller bearings is 30000; tapered roller bearings are separable bearings. Tapered roller bearings are primarily used to support combined radial and axial loads, with the radial load being predominant. Compared to angular contact ball bearings, they have a higher load-carrying capacity but a lower limiting speed. Tapered roller bearings can withstand axial loads in one direction and can limit axial displacement of the shaft or housing in that direction.

During operation, rolling bearings may experience changes in their original clearance due to external or internal factors, leading to reduced precision or even ' seizing'—a condition known as clearance variation failure. External factors such as excessive interference fit, improper installation, thermal expansion caused by temperature rise, and momentary overloads, as well as internal factors such as residual austenite and residual stresses in an unstable state, are the primary causes of clearance variation failure.

The anti-rust oil applied to bearings possesses excellent lubricating properties; for general-purpose bearings or those filled with grease, it is not necessary to clean them before use. However, for instrument bearings or those intended for high-speed rotation, the anti-rust oil must be removed using a clean washing oil. In such cases, the bearings are susceptible to rust and must not be left unused for extended periods.

Clean the bearings and housings, ensuring there are no scratches or burrs left from machining. The interior of the housing must be completely free of abrasives (such as SiC or AlzOs), moulding sand, swarf and other debris.

The manufacture of rolling bearings generally involves multiple processing stages, including casting, heat treatment, turning, grinding and assembly. The rationality, sophistication and stability of each manufacturing process also affect the bearing's servicelife. Among these, the heat treatment and grinding processes, which influence the quality of the finished bearing, often have a more direct relationship with bearing failure. Recent research into the altered layers on bearing working surfaces has shown that there is a close relationship between the grinding process and the surface quality of the bearing.