This kind of problem is always encountered in the use o […]
This kind of problem is always encountered in the use of bearings. The inspection is qualified before the bearing leaves the factory, but after the actual installation, the bearing will stagnate or the early rotation failure during use will fail.
Its main manifestations are: 1. The rotation is with a stagnation feeling; 2. The working surface is severely peeled; 3. The cage is severely worn or even twisted or broken;
After analysis of the failure results at the later stage, it is concluded that this result belongs to the quality of the bearing itself, which causes not many failures, and most of them are caused by improper installation and use. Therefore, high temperature resistant bearings make some common bearing failure modes and mechanisms. A superficial review can serve as a reference.
First, the failure mechanism of the bearing:
Contact fatigue failure
Refers to the failure of the bearing working surface due to the effect of alternating stress.
Contact fatigue spalling occurs on the bearing working surface, which is often accompanied by fatigue cracks. It first occurs from the large alternating shear stress below the contact surface, and then extends to the surface to form different spalling shapes, such as pitting or pitting. Exfoliation into small pieces is called shallow exfoliation. Due to the gradual expansion of the exfoliation surface, which tends to expand deeper, forms a deep exfoliation.
Deep spalling is the fatigue source of contact fatigue failure.
2. Wear failure
Refers to the failure caused by the continuous wear of the working surface metal caused by the relative sliding friction between the surfaces.
Continued wear will cause gradual damage to bearing parts, and eventually lead to loss of bearing dimensional accuracy and other related problems.
The wear may affect the shape change, the increase of the fit clearance and the change of the working surface morphology, which may affect the lubricant or make it contaminated to a certain extent and cause the complete loss of the lubricating function, thus causing the bearing to lose its rotational accuracy and even fail to operate normally.
Wear failure is one of the common failure modes of various types of bearings.
1) Wear of abrasive particles
Abrasive wear refers to the wear caused by the intrusion of foreign hard particles or hard foreign objects or abrasive debris on the surface of the bearing between the working surfaces of the bearing and the relative movement of the contact surface. Often, a furrow-like abrasion is caused on the working surface of the bearing. Hard particles or foreign objects may come from the host or from other adjacent parts of the host system and are fed into the bearing by the lubricant.
2), adhesive wear
It refers to the uneven uneven force on the friction surface due to the micro-protrusions or foreign objects on the friction surface. When the lubrication conditions are severely deteriorated, the local friction generates heat due to local friction, which can easily cause the local deformation of the friction surface and the friction micro-welding phenomenon. The metal may locally melt, and the force on the contact surface will tear the local friction welding point from the substrate and increase plastic deformation. This cycle of adhesion-tearing-adhesion constitutes adhesive wear. In general, slight adhesive wear is called abrasion, and severe adhesive wear is called bite.
3. Fracture failure
Defects such as micro-cracks, shrinkage holes, air bubbles, large foreign objects, overheated tissues, and local burns of bearing parts can also cause fractures at the defects during impact overload or severe vibration, which is called defect fracture.
When the applied load exceeds the strength limit of the material and causes the part to fracture, it is called overload fracture.
The main reason for overload is sudden host failure or improper installation.
The main reason is the two major factors of defects and overload.
Although in the manufacturing process of the bearing, the original inspection of raw materials, forging and heat treatment quality control, and process control can be used to correctly analyze the existence of the above-mentioned defects through instruments, the control must be strengthened in the future. But in general, the most common bearing fracture failures are overload failures.