Bearing is one of the most important components of rotating machinery, but it is also one of the most easily damaged components. According to the statistics at the present stage, about 1/3 of the rotating machinery failures are caused by bearing faults. Therefore, it is of great significance to effectively judge the running state of the bearing [1]. Bearing failure is a multi-state process that gradually evolves from normal to failure. The state existing in this process can not be observed directly, and the measurement signal needs to be analyzed with the help of external equipment [2]. In order to make a reasonable analysis of the bearing operation, the extraction of characteristic parameters is very important.

There are many classification methods for rolling bearings. If they are classified according to the load direction or nominal contact angle they can bear, they can be divided into two types, i.e. radial bearings and thrust bearings

According to GB/T 272-1993, the rolling bearing code uses letters and numbers to indicate the structure, size, tolerance class, technical performance and other characteristics of the rolling bearing. Here is a description of the bearing code for general purposes.

The inner and outer ring raceways and rolling elements of the bearing carry out relative rolling motion under the action of high contact stress, and the general contact stress is between 1000 and 4000 MPa. At the same time, there is inevitably a small amount of sliding friction and rolling friction between the rolling elements and the raceway. In addition, there are also frictions between the rolling elements, cages, and ring ribs

The internal geometric structure factors of the rolling bearing will seriously affect the overall bearing capacity, friction and wear, accuracy, rigidity and other properties of the bearing. Small differences in the internal design will make the bearing performance significantly different. For example, a small change in the radius of curvature of a ball bearing raceway will greatly change the bearing load capacity and friction characteristics, and a small modification of the shape of the roller generatrix will greatly improve the bearing capacity of the roller bearing.

The size of the contact load directly affects the stress, deformation and fatigue life. In particular, the load of the most loaded rolling element in the bearing has the most significant impact on the bearing capacity and fatigue life. In addition, the rolling element load also affects the friction and lubrication of the bearing, and the size of the loaded area also affects the slipping of the high-speed operating bearing. Therefore, calculating bearing load distribution is an indispensable content in bearing performance analysis.

There are three types of preservation methods for bearing: anti-rust oil, Vapor Phase lnhibitor, and water-soluble anti-rust agent. At present, anti-rust oil is widely used. Commonly used anti-rust oils are 204-1, FY-5 and 201, etc. .

The installation of the bearing should be carried out in a dry and dust-free room, and should be far away from metal processing or other equipment that will generate debris and dust. When the bearing must be installed in an unprotected environment (it is often encountered when installing larger bearings), appropriate measures must be taken to protect the bearings and related components from contamination by dust or moisture, etc., until the installation is completed.

During regular inspections or replacement of parts, the bearings need to be dismounted. For this case, the shaft and the bearing housing can be used continuously, aw well as the bearings. Therefore, when designing the structure of the machine, it should be considered that the bearings, shafts, bearing housings and other parts will not be damaged during the process of dismounting the bearings. At the same time, appropriate disassembly tools should be prepared. When dismounting the ring with an interference fit, the pulling force can only be applied to the ring, but cannot be applied to the rolling elements.

Before bearing installation, precautions are as follows:1 Choose the bearings in undamaged package for installation.2 Under normal circumstances, there is no need to clean the anti-rust agent on the new bearing, just wipe the outer surface and the bore surface of the bearing. However, if the lubricant used is not compatible with the anti-rust agent, the bearing needs to be carefully washed and dried before installation.

The failures of rolling bearings mainly occur in the rolling elements, outer ring, and inner ring. The general failure modes are shown in Figure 1. Different modes of failures of rolling bearings have different impact intervals and strengths, which result in different frequency and amplitude of vibration signals. This frequency characteristic can be calculated based on the mutual movement frequency of the components.

Rolling bearings are widely used rotating general-purpose parts. The quality of their operating conditions is directly related to the performance and safety of the equipment, and the failure of rolling bearings is an important reason for the failure of machinery and equipment. Effective fault diagnosis of rolling bearings can not only prevent the decrease of mechanical operating accuracy, reduce or eliminate accidents, but also maximize the operating potential of bearings, ensure the maximum continuous operation time of large-scale mechanical equipment systems, and save related maintenance expenses.

In the visual test on the fall-block of rib and the fracture, the broken blocks originate from the inner side of the oil ditch, and the fracture morphology is an impact fracture. The appearance morphology is shown in Figure 1 to 3.

Through visual test, it was found that the bearing inner ring was axially cracked, and through fracture test, it was found that the fracture originated at the small rib chamfer. After magnification and test with a stereo microscope, it was found that the bearing has bump damage at the small ribs and chamfers. The appearance and conclusions are shown in Figures 1 to 5.

The traces of the bearing outer ring are normal, the rolling surface of the roller is normal, and the cage with thickness of 1.0mm is partially broken at the corner of the vertical beam barrier. The test results are shown in Figure 1 to Figure 6. The enlarged test fracture morphology has fatigue growth characteristics as shown in Figure 7, and the organic processing and tear characteristics of the crack morphology are shown in Figure 8 and Figure 9.

The test result is that #1 inner ring and #1 outer ring of the bearing are cracked, #1 outer ring of is scratched on one side of the rib, and the rib of #1 inner ring and #1 outer ring are scratched. The fracture originates from the scratch of the rib and the end of the roller. Scratches, fatigue peeling of raceway of #2 inner ring, scratches on rib surface, scratches on raceway surface, as shown in Figure 1 to Figure 12.

Rolling bearings are widely used in rotor systems, and their dynamic characteristics are one of the key factors determining the dynamic properties of rotor systems. In this paper, a single-disc, two-support rotor-bearing system test rig was first built, and experimental studies were conducted on the unbalanced vibration characteristics of the rotor system during the bearing thermal equilibrium process and under different lubricating oil temperatures. Secondly, an identification method for bearing stiffness and clearance based on rotor vibration response was proposed, obtaining the stiffness and clearance of the bearing during the thermal equilibrium process and under different lubricating oil temperatures. Finally, a dynamic model of the rotor-bearing system was established using the Lagrange method, with the identified results of bearing stiffness and clearance as input conditions. The effects of rotational speed, unbalance, and lubricating oil temperature on the vibration response of the rotor system, as well as the vibration characteristics of the system during the bearing thermal equilibrium process, were analyzed. The research results provide technical support for the identification of bearing performance parameters under thermal effects and the analysis of vibration characteristics of rotor systems.

This paper introduces a kind of large cylindrical roller bearing vibration testing machine, Including its structure, working principle and the design of main structure parts. This testing machine as a cylindrical roller bearing factory testing instrument, it is simple operation, measuring value accurately. This tester is used to effectively reduce the labor intensity of operators, improve the working efficiency.