Several common damage states of outer bearing

Several common damage states of outer bearing
1. Mechanical damage
In severe cases, metal peeling occurs on the contact surface and a large area of messy scratch appears; Under normal conditions, the mechanical damage of outer spherical bearing means that the alloy surface of bearing bush shows different degrees of groove marks. Contact surface damage and ablation exist at the same time. The main reason for bearing mechanical damage is that the outer spherical bearing surface is difficult to form oil film or the oil film is seriously damaged.
2. Bearing cavitation
The surface layer has plastic deformation and cold work hardening, and the sliding outer spherical bearing is under the repeated action of cylinder pressure (impact load). Part of the deformation ability is lost, and the grain gradually forms and expands from time to time. Then, with the scattering of wear debris, the loaded surface layer forms a cavity. When the common bearing bush is pitted, it first presents pits, and then the pits gradually expand and cause the cracking of the alloy layer interface. The cracks expand along the parallel direction of the interface until they peel off. The main reason for the cavitation of sliding bearing is that the sudden change of the cross section of structural elements such as oil groove and oil hole causes the intense disorder of oil flow. The vacuum area with disordered oil flow forms bubbles, and then cavitation occurs due to the collapse of bubbles due to the increase of pressure. Cavitation usually occurs in the high load area of the outer spherical bearing, such as the lower bearing bush of the main outer spherical bearing of the crankshaft.
3. Fatigue pitting
Due to the overload of the starter, the fatigue and pitting of the outer spherical bearing refers to. The bearing is overheated and the clearance of the outer spherical bearing is too large, resulting in fatigue damage, fatigue pitting or fatigue scattered in the middle of the bearing. This damage is mostly caused by overload, excessive clearance of F bearing, or unclean smooth oil and foreign matters mixed in it. Therefore, attention should be paid to avoid overload operation of outer spherical bearing, and do not run at too low or too high speed; When idling, adjust the starter to a stable state; Ensure the normal clearance of outer spherical bearing to avoid too high or too low speed of the starter; Check and adjust the working condition of the cooling system to ensure that the working temperature of the starter is suitable.
4. Alloy corrosion of outer spherical bearing
The chemical impurities (acid oxides, etc.) in the smooth oil oxidize the bearing alloy to form acidic substances. The common corrosion area of the bearing alloy with seat is the impure smooth oil. The alloy part of the bearing is scattered, forming irregular small cracks or pits. The main causes of alloy corrosion of outer spherical bearing are improper selection of smooth oil, poor corrosion resistance of outer spherical bearing materials, or rough operation of starter and high temperature transition.
5. Outer spherical bearing melting
The component is at high temperature, and there is a small convex metal surface in direct contact between the journal and the bearing friction pair. Under the condition of lack of smoothness and poor cooling, the outer spherical bearing alloy is blackened or partially burned. This problem is often caused by too tight fit between journal and bearing; The lack of smooth oil pressure is also easy to burn out the outer spherical bearing.