1 Structural materials of sliding bearings

1.1 Surface coating of heavy-duty plain bearings

Common surface treatment processes to improve the service life of bearings include electroplating, magnetron sputtering, bonding self-lubricating liners, inlaying solid self-lubricating materials, etc., but electroplating pollutes the environment, magnetron sputtering film production efficiency is low and target utilization efficiency is low , The liner composed of aramid fiber is not resistant to high temperature, and the mosaic structure reduces the structural strength of the bearing. Bearing surface treatment urgently needs a new material that meets the requirements of green and mass production.

1.2 Rolling mill heavy-duty bearings

According to the information collected from enterprises such as Baosteel, Anshan Iron and Steel, Wuhan Iron and Steel, and Benxi Iron and Steel, rolling mill bearings have problems such as short service life and large-area fatigue spalling; on the operating side, the failure rate of the bearing is significantly higher than that on the driving side; 90% of the bearings are from Fatigue spalling occurs at the first and second row of rollers and their corresponding outer roller paths on the side of the roller body. Through the comprehensive principle of the micro-scale equivalent roll system of the rolling mill and the analysis of the change of the degree of freedom of the mechanism under no-load and heavy load, Professor Shu Xuedao clarified the abnormal eccentric loading mechanism of the rolling mill bearings, thrust bearings and rolling mill axial adjustment threads , it provides a scientific method for the development and design of the rolling mill micro-scale controllable static bar system, and at the same time provides a new idea and a new way for effectively solving major equipment accidents such as rolling mill bearings.

1.3 Electron Radiation Technology

With the development of modern technology, functional materials with complex properties are becoming more and more important. In view of the fact that the traditional material preparation process cannot combine materials with different properties, electron radiation technology fills the gap in this field. Researchers can effectively utilize aluminum foil materials and vapor phase coating techniques to prepare multifunctional materials. In addition, traditional fusion techniques are difficult to obtain compounds that connect across metals, which makes it difficult to fabricate structures composed of steel and titanium in pipe connections. Ustinov prepared a titanium-steel bimetal compound by diffusion welding, which can meet the requirements of installation and connection, and has the advantages of high strength and plasticity.

2 Bearing finite element model

2.1 Load setting

According to the research needs, set the force load and displacement load conditions for the model. The longer yellow arrow whose starting point is the coordinate origin represents the direction of gravity load, and the shorter yellow arrow whose starting point is the reference point (RP) represents the direction of concentrated force. According to the established bearing Pro/E model in Adams, the dynamic Scientific simulation to extract the load data of the bearing. The radial load on the bearing is 1.8×104N, and the rotation speed of the bearing is 90r/min.

2.2 Setting Boundary Conditions

When setting the boundary conditions, it is necessary to limit the axial displacement of the inner surface of the inner ring, and the boundary conditions are applied to the inner surface of the inner ring of the bearing. The outer ring of the bearing is fixed on the bearing seat, so a fixed constraint is imposed on the outer surface of the outer ring. Since the lubricating oil represented by the Euler body is restricted by the various parts of the bearing, it is difficult to flow out of the space between the outer wall of the inner ring and the inner wall of the outer ring, so the flow velocity of the Euler body on its two annular sides is limited to 0.

2.3 Sliding bearing test equipment

Aiming at the designed mandrel sliding bearing, the preliminary operating performance is tested, and the corresponding sliding bearing testing machine is built. According to the task of the subject project, the developed testing machine mainly verifies the film-forming ability of the sliding bearing, that is, the initial operating ability and start-up performance. Ability to stop. The mandrel of the sliding bearing to be tested is fixed on the test bearing seat, the inner hole of the pulley simulates the inner hole of the planetary wheel, the outer edge of the mandrel matches the inner hole of the pulley, and the cooperation between the mandrel and the inner hole of the planetary wheel is simulated. The pulley is connected to the speed-regulating motor through four SPB narrow V-belts, driven by the motor, simulating the speed of the planetary wheel when it starts and stops. The load is applied on the outer surface of the pulley through the hydraulic loading system to simulate the equivalent load received by the planetary wheel when it starts and stops. The load applied by the hydraulic cylinder is transmitted through the flange plate and the guide rod at the upper end of the test bearing seat, and the load is distributed to the two rolling bearings through the fisheye rod end joint bearing. The linear bearing and the limit block are used to fix the movement direction of the guide rod to the vertical direction. Ensure that the load applied by the hydraulic cylinder acts on the center of the sliding bearing, and the radial load of the tested sliding bearing is applied by contacting the outer circle of the rolling bearing with the pulley. The inner hole of the mandrel and the supporting shaft are designed to be tight fit. When assembling, it can be inserted from the end cover on the right side of the bearing housing as a whole. When disassembling, it is only necessary to remove the end cover and pull out the supporting shaft and mandrel bearing directly, which can be quickly disassembled. Measurement and control system: There are four sensors for real-time monitoring of changes, namely pressure, temperature, speed, and displacement sensors. Photoelectric speed sensors are used to monitor changes in speed in real time; thermocouple temperature sensors are arranged at the oil outlet to measure oil temperature rise. In addition, there are flowmeters and temperature gauges on the oil supply station. Since the initial conditions of the oil supply are constant, the initial temperature and flow information of the oil supply can be directly read.

3 Influence of load and rotational speed changes on lubrication performance

3.1 Effects of load and speed changes on oil film pressure

 In the bearing lubrication system, the change of load and speed will affect the oil film pressure. As the speed increases, the oil film force increases continuously. The rotation speed of curve a is 90r/min, and the rotation speed of curve b and c are 110r/min and 130r/min respectively. The maximum oil film pressure in curve a is 1GPa, and the secondary peak of pressure reaches 0.96GPa; the maximum oil film pressure in curve b is 1.09GPa, and the secondary peak of pressure reaches 1.089GPa; the maximum oil film pressure in curve c is 1.14GPa, and the secondary peak of pressure reaches 1.158 GPa. The shape of the pressure distribution curve has changed significantly. The secondary peak of the pressure is obvious under the condition of low speed. With the increase of the speed, the secondary peak of the pressure almost disappears, and the maximum value of the pressure also continuously moves to the inlet area. .

3.2 Effects of load and rotational speed changes on oil film thickness

When the bearing speed increases, the oil film thickness also increases, and the position of the minimum oil film thickness moves from both sides to the outlet area on the center surface. When the speed increases from 90r/min to 130r/min, the minimum oil film thickness increases from 0.2mm to 0.65mm. As the load gradually increases, the thickness of the oil film decreases and gradually becomes thinner. When the load increased from 1.8×104N to 2.4×104N, the minimum oil film thickness decreased from 0.2mm to 0.01mm.

 Conclusion

Sliding bearings have very important applications in many fields. Sliding bearings can be found in both aerospace and daily life. Structural parameters of sliding bearings directly affect the performance of sliding bearings, so the structural parameters must be considered in the design of sliding bearings. To this end, a sliding bearing test bench is designed, and the start-stop test under simulated working conditions is carried out. Through this test machine, the start-stop wear of the copper alloy and diamond-like coating surface material specimens is investigated. After completing the same number of start-stop tests under similar working conditions, the surface wear was observed. The bearing specimens with copper alloy surface material had more wear marks than the diamond-like coating surface bearing specimens. In the unstable state of starting and stopping, the diamond-like coating specimen performed better, but it was also found that the abrasive wear of the diamond-like coating would cause coating wear, and it was necessary to filter and clean the lubricating oil.