En el cubo del automóvil, la transmisión, el diferencial se utilizan en una variedad de rodamientos, como rodamientos de bolas, rodamientos de agujas, rodamientos de rodillos cónicos, rodamientos lineales, rodamientos lisos, la cantidad de cada automóvil hasta docenas, en los últimos años, el El rápido desarrollo de la tecnología automotriz y los requisitos de presión de protección ambiental, el bajo consumo de combustible de los automóviles y los automóviles de larga tendencia de garantía de calidad, los rodamientos de automóviles también enfrentan el problema de una vida útil prolongada y liviana sin precedentes.
Teniendo vida, según la teoría de Lundbber y Palmgren, puede calcular la vida teórica. Pero, de hecho, en el uso de automóviles, transmisión, aceite diferencial mezclado con cuerpos extraños, selección del método de instalación y alta temperatura generada por el funcionamiento a alta velocidad, por lo que la vida útil real del rodamiento es más corta que el valor de cálculo teórico, por lo que el estudio del modo de falla del rodamiento, el análisis de la formación de factores y la prevención es particularmente importante.
Modo de falla y análisis de causa del rodamiento:
1. Modo de falla del rodamiento
1.1 Pelado
El rendimiento principal: cuando el rodamiento está bajo carga giratoria, la pista de rodadura del anillo interior y el anillo exterior o la superficie del cuerpo rodante muestran un fenómeno de descamación de escamas de pescado debido a la fatiga por rodadura.
Causa: Debido al efecto de la tensión alterna en la superficie de trabajo y la falla, que ocurre principalmente en la superficie de trabajo del cojinete, a menudo acompañada de grietas, primero desde la superficie de contacto por debajo de la tensión de corte alterna máxima, y luego se extiende a la superficie para formar diferentes Formas de desprendimiento, como picaduras o desprendimiento de picaduras, desprendimiento en una pequeña escama llamada desprendimiento superficial. Debido a la expansión gradual de la superficie de desconchado y, a menudo, a la expansión profunda, la formación de desconchado profundo.
1.2 fluencia
Cuando hay una holgura entre las superficies de contacto de los cojinetes, se produce un deslizamiento relativo entre las superficies de contacto, y las superficies de contacto en las que se produce la fluencia muestran una superficie especular brillante u oscura, a veces acompañada de un desgaste atascado.
La fricción de deslizamiento relativa entre las superficies de trabajo de los cojinetes conduce a la falla del metal en la superficie de trabajo que se desgasta constantemente. El desgaste continuo causará daños graduales a las piezas de los rodamientos y, eventualmente, conducirá a la pérdida de la precisión dimensional del rodamiento y otros problemas relacionados. El desgaste afecta el aumento de la holgura de ajuste y el cambio de la topografía de la superficie de trabajo, lo que puede causar que el lubricante o su contaminación alcancen un cierto grado y la función de lubricación se pierda por completo, y luego el rodamiento perderá la precisión de rotación o incluso no podrá funcionar. normalmente. La falla por desgaste es uno de los modos de falla comunes de todo tipo de rodamientos, que se pueden dividir en el desgaste abrasivo más común y el desgaste adhesivo según la forma de desgaste.
1.3 tensión
The surface damage caused by minor burns on the working face of the bearing and the surface of the rolling body is manifested as linear scratches on the surface of the slide surface and raceway body in the circumferential direction.
The wear caused by the grinding of external hard particles or hard foreign bodies or metal surfaces and the relative movement of the contact surface is often caused by furrow scratches on the bearing working surface.
1.4 Stick
The transfer of material from one working surface to another is accompanied by frictional heating and sometimes by surface tempering or re-quenching. This process creates local stress concentrations in the contact area and may lead to cracking or spalling.
Due to the uneven stress on the working face caused by the micro-convex or foreign matter on the working face, when the lubrication is seriously deteriorated, the local friction heat is generated, which is easy to cause the local deformation of the working face and friction microwelding phenomenon. In serious cases, the metal on the working face may be locally melted, and the contact surface forces will tear the local friction welding points from the matrix and increase the plastic deformation. This cycle of sticking, tearing, sticking, slight sticking wear is called abrasions, and severe sticking wear is called occlusion.
1.5 Fracture
The fracture failure of bearing ring is rare and is usually caused by sudden overload. The main reasons for bearing fracture failure are defects and overload factors, such as raw material defects of bearings (bubbles, shrinkage holes), forging defects (overburning), heat treatment defects (overheating), processing defects (local burns or surface micro-cracks), main engine defects (poor installation, poor lubrication), etc. When the external load exceeds the strength limit of the material and the parts fracture is called overload fracture, once the overload impact load or violent vibration may make the ring fracture. But generally speaking, the most common bearing fracture failure is overload fracture.
1.6 Electric Corrosion
Refers to the bearing in the process of operation, the current through the bearing body, in the bearing inner and outer ring working face and rolling body working face due to spark discharge caused by melting of the working face, and rough discoloration corrosion.
When the current flows in the contact part of the circulating rotating bearing raceway wheel and the rolling body, sparks occur through the thin lubricating oil film, causing local melting and concave-convex phenomenon on the surface.
1.7 Hydrogen embrittlement
Refers to the bearing in the process of operation, between the bearing inside and outside raceway and rolling body to generate positive and negative electric fields, so that water molecules ionize, penetrate to the raceway surface, raceway working surface hydrogen evolution cracks, and then spallation.
The rolling body and the inner and outer rings will generate static electricity during operation. The bearing assumes the role of the iron wire in the overall structure of the vehicle, which causes the rolling body to be positively charged, and the inner and outer rings to be negatively charged, generating electric fields, and the rolling body to produce microscopic chemical reactions with the raceway of the inner and outer rings. The water in the grease or the external environment is electrolyzed with positively charged hydrogen ions. Under the action of electric field, hydrogen ions adsorb the surface layer of the inner and outer raceway under the action of negative charge of the inner and outer raceway. With the increase of hydrogen ion concentration, hydrogen ions penetrate the surface layer of the raceway and enter the sub-surface layer. In this way, the stable structure between atoms in the surface layer is destroyed, resulting in tiny cracks. Especially in the bearing area of delicate raceway, due to the influence of shear stress and high temperature, it is most easy to produce hydrogen embrittlement and make the bearing area of raceway spalling.
2. Prevention of bearing failure
Bearing failure is often caused by a variety of factors, all influencing factors in the design and manufacturing process may cause bearing failure, so it is not easy to judge. In general, from the use of factors and internal factors two aspects of consideration and analysis.
2.1 Internal factors mainly refer to the three factors that determine bearing quality, such as structural design, manufacturing process and material quality
First of all, the structure should be advanced at the same time of reasonable design, so as to achieve a longer bearing life.
Design factors are the key factors affecting the life of bearings, strictly according to the bearing load, speed, and other conditions to design a reasonable structure form, reasonable precision and clearance selection requirements. Design to put forward a clear installation, use, maintenance of technical requirements for later maintenance.
The manufacturing process of the second bearing should go through forging, heat treatment, turning, grinding and assembly and other processing procedures. In addition, the technical level, rationality, advancement and stability of the process of each process will also affect the bearing life. Among them, heat treatment and grinding process, which affect the quality of finished bearings, are often more directly related to the failure of bearings. The microscopic analysis of the metamorphic layer of the bearing working surface shows that the grinding process is closely related to the quality of the bearing surface.
The third bearing material is also the main factor affecting the early failure of bearings. With the continuous development of new bearing materials, the selection range of bearing materials is becoming wider and wider. It is very important to select suitable materials according to the design requirements and the environmental requirements of use.
2.2 Usage factors mainly refer to whether installation, adjustment, use and maintenance meet technical requirements
Installation conditions are one of the primary factors in the use of the bearing, often due to inappropriate installation of bearings, resulting in changes in the stress state between the parts of the whole set of bearings, so that the bearing in the abnormal state of operation and early failure. According to the technical requirements of bearing installation, use, maintenance and maintenance, check the load, speed, working temperature, vibration, noise and lubrication conditions of bearings in operation, and find out the cause immediately if any abnormality is found. In addition, it is also important to choose the right grease.
3.Conclusion
This paper discusses the common failure mode and failure mechanism of automobile bearings. Although bearings are precise and reliable mechanism foundation, improper use, lubrication, disassembly and assembly can also cause failure. In general, if bearings can be used correctly, they can be used until fatigue life. The early failure of bearings is mainly caused by the manufacturing accuracy, installation quality, service conditions, lubrication effect, external foreign body intrusion and other factors of the matching parts of the shaft and bearing seat. Therefore, the correct and reasonable use of bearings is a systematic engineering. In the process of bearing structure design, manufacturing and installation, appropriate measures can be taken for the early failure of the link, which can effectively improve the service life of bearings and assembly parts, reduce the user's use cost and improve user satisfaction.
2023-01-09