Abstract: With the rapid development of economy and science and technology, along with the development of machinery industry, especially high-speed train and aerospace industry, bearing technology research and development to meet the service requirements of high speed, heavy load and other extreme environment is very important to improve the safety, reliability and life of aeroengine. This meeting provides a lot of research results and technologies with important reference value for the research and application development of high temperature bearing materials, as well as material selection, design, life evaluation and structural integrity evaluation.

Key words: plain bearing; Structure type; Structural parameters; Bearing performance

Quotation

With the rapid development of civil aviation engine technology, low fuel consumption, low pollution emission and high safety have become the targets of large bypass ratio turbofan engine. For traditional dual axial direct drive high bypass ratio turbofan engine, increasing fan diameter, reducing fan pressure ratio and exhaust velocity are usually adopted to improve propulsion efficiency. Bearing is an important basic component of aero engine. Complex and harsh environment such as high temperature, high pressure, fatigue and wear seriously affect the service life of bearing. Improving the service life of aero engine bearing has always been a hot issue in scientific research.

1. Structural materials of sliding bearing

1.1 Surface coating of heavy-duty plain bearings

Common surface treatment processes to improve the service life of bearings include electroplating, magnetron sputtering, adhesive self-lubricating liner, inlaid solid self-lubricating material, etc., but electroplating pollution environment, magnetron sputtering film production efficiency is low and target material utilization efficiency is low, the liner composed of arylon fiber is not high temperature resistant, inlaid structure reduces the strength of bearing structure. Bearing surface treatment is in urgent need of a new material to meet the requirements of green and mass production.

1.2 Heavy duty bearing for rolling mill

The information collected from Baosteel, Angang, Wuhan Iron and Steel, Bensteel and other enterprises found that the rolling mill bearing has problems such as short service life and easy to appear large area fatigue spalling. On the operating side, the failure rate of the bearing is obviously higher than that on the driving side. 90% of the bearing fatigue flaking occurs from the first and second row of rollers and their corresponding outer roller paths on the roll body side. By analyzing the comprehensive principle of the micro-scale equivalent roll system of rolling mill and the change of degree of freedom of the mechanism under no-load and heavy load, Professor Shu Xuedao clarified the abnormal eccentric loading mechanism of rolling mill bearing, thrust bearing and rolling mill axial adjustment thread, which provided a scientific method for the development and design of the micro-scale controllable static rod system of rolling mill, and also provided an effective solution for the important equipment such as rolling mill bearing The accident provides new ideas and new ways.

1.3 Electronic radiation technology

With the development of modern technology, functional materials with complex properties are becoming increasingly important. In view of the traditional material preparation technology can not combine materials with different properties, electron radiation technology fills the gap in this field. The researchers were able to effectively use aluminum foil and vapor phase coating technology to produce multifunctional materials. In addition, conventional fusion techniques have difficulty obtaining compounds that are linked across metals, making it difficult to make structures made of steel and titanium, such as those used in pipe connections. Ustinov prepared titanium steel bimetallic compounds by diffusion welding method, 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, load conditions of force and displacement load conditions are set for the model. The long yellow arrow whose starting point is the origin of coordinates represents the direction of gravity load, and the short yellow arrow whose starting point is the reference point (RP) represents the direction of concentrated force. The dynamic simulation of the established bearing Pro/E model in Adams is carried out to extract the bearing load data. The radial load on the bearing is 1.8×104N, and the rotating speed of the bearing is 90r/min.

2.2 Setting boundary conditions

When setting boundary conditions, it is necessary to limit the axial displacement of the inner surface of the bearing inner ring, and the boundary conditions are imposed on the inner surface of the bearing inner ring. The bearing outer ring is fixed on the bearing seat, so a fixed constraint is applied to the outer surface of the outer ring. Because the lubricating oil represented by the Euler body is limited by each part 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 rate of the Euler body on its two annular sides is limited to 0.

2.3 Plain bearing test equipment

Based on the designed mandrel plain bearing, the preliminary operation performance was tested and the corresponding plain bearing testing machine was built. According to the task of the project, the developed testing machine was mainly used to verify the film forming ability of plain bearing, namely the preliminary operation ability and start-stop operation ability. The test bearing mandrel is fixed on the test bearing seat. The inner hole of the belt wheel simulates the inner hole of the planet wheel. The outer edge of the mandrel is matched with the inner hole of the belt wheel to simulate the match between the mandrel and the inner hole of the planet wheel. The belt pulley is connected with the speed-regulating motor through four SPB narrow V belts, which is driven by the motor to simulate the rotation speed of the planetary wheel when it starts and stops. A hydraulic loading system is applied to the outer surface of the belt pulley 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 and 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 guide rod movement direction in the vertical direction, so as to ensure the load action applied by the hydraulic cylinder and the center of the sliding bearing. The radial load of the tested plain bearing is applied by contacting the outer circle of the rolling bearing with the pulley. The inner hole of the mandrel is designed to fit closely with the supporting shaft. When assembling, it can be inserted from the right end cover of the bearing seat as a whole. When disassembling, just remove the end cover and pull out the supporting shaft and mandrel bearing directly, which can be quickly disassembled. Measurement and control system: real-time monitoring changes of the sensor four, respectively are pressure, temperature, speed, displacement sensor, the use of photoelectric speed sensor real-time monitoring speed changes; A thermocouple temperature sensor is arranged at the oil outlet to measure the oil temperature rise. In addition, there are flowmeters and thermometers in the oil supply station. Since the initial condition of oil supply is constant, the initial temperature and flow information of oil supply can be read directly.

3. Influence of load and speed change on lubrication performance

3.1 Influence of load and speed change on oil film pressure

In the bearing lubrication system, the load and speed change will affect the oil film pressure. With the increase of rotational speed, the oil film force increases continuously. The rotation speed of curve a is 90r/min, and that of curve b and c is 110r/min and 130r/min respectively. In curve a, the maximum oil film pressure is 1GPa and the secondary peak pressure is 0.96GPa. In curve b, the maximum oil film pressure is 1.09GPa and the secondary peak pressure is 1.089GPa. In curve c, the maximum oil film pressure is 1.14GPa and the secondary peak pressure is 1.158GPa. The shape of pressure distribution curve changes obviously, and the secondary pressure peak is obvious under the condition of low rotational speed. With the increase of rotational speed, the secondary pressure peak almost disappears, and the maximum pressure constantly moves to the entrance area.

3.2 Influence of load and speed change 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 rotation speed increases from 90r/min to 130r/min, the minimum oil film thickness increases from 0.2mm to 0.65mm. With the increase of load, the thickness of oil film decreases and becomes thinner. When the load increases from 1.8×104N to 2.4×104N, the minimum oil film thickness decreases from 0.2mm to 0.01mm.

Conclusion

Sliding bearings have very important applications in many fields, whether in the field of aerospace, or in daily life can be found in the shadow of sliding bearings. The structural parameters of sliding bearing directly affect the performance of sliding bearing, so the structural parameters must be considered in the design of sliding bearing. For this purpose, a sliding bearing test bench was designed and start-stop tests were carried out under simulated conditions. The start-stop wear conditions of copper alloy and diamond-like coating surface material specimens were investigated through the experimental machine. After the completion of the same number of start-stop tests under similar conditions, the surface wear of the bearing specimen with copper alloy surface material is observed to have more wear marks than that with diamond-like coating surface. In the unstable state of start-stop, diamond-like coating specimens perform better. However, it is also found that the abrasive wear of diamond-like coating will lead to the wear of coating, so it is necessary to do a good job of lubricating oil filtration and cleaning.

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