With the rapid development of economy and science and technology, with the development of machinery industry, especially high-speed train and aerospace industry. The research and development of bearing technology that meets the service requirements in extreme environments such as high speed and heavy load is crucial to improving the safety, reliability and lifespan of aeroengines. The convening of this conference provided many 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 assessment and structural integrity assessment.
Keywords: sliding bearing; structural type; structural parameters; bearing performance
With the rapid development of civil aviation engine technology, low fuel consumption, low pollution emissions and high safety have become the goals pursued by large bypass ratio turbofan engines. For traditional dual-shaft direct-drive high-bypass-ratio turbofan engines, propulsion efficiency is usually improved by increasing the fan diameter and reducing the fan pressure ratio and exhaust speed. Bearings are important basic components of aeroengines, and complex and harsh environments such as high temperature, high pressure, fatigue, and wear seriously affect the service life of bearings. Improving the service life of aeroengine bearings has always been a hot issue in scientific research.
Sliding bearing structural materials
Heavy-duty sliding bearing surface coating
Common surface treatment processes that improve the service life of bearings include electroplating, magnetron sputtering, bonded self-lubricating liners, inlaid solid self-lubricating materials, etc. However, electroplating pollutes the environment, and magnetron sputtering film production efficiency is low and the target material utilization efficiency is low. , the padding composed of aramid fiber is not resistant to high temperatures, and the inlaid structure reduces the strength of the bearing structure. Bearing surface treatment urgently requires a new material that meets green and mass production requirements.
Rolling mill heavy-duty bearings
Information collected from Baosteel, Anshan Iron and Steel, Wuhan Iron and Steel, Benxi Iron and Steel and other enterprises found that rolling mill bearings have problems such as short service life and prone to large-area fatigue spalling; on the operating side, the failure rate of bearings is significantly higher than that on the driving side; 90% of bearings are Fatigue spalling occurs on the first and second rows of rollers on the roller body side and their corresponding outer roller paths. By analyzing the comprehensive principles of the micro-scale equivalent roll system of the rolling mill and the changes in 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. , provides a scientific method for the development and design of micro-scale controllable static rod systems in rolling mills, and also provides new ideas and new ways to effectively solve major equipment accidents such as rolling mill bearings.
Electronic radiation technology
With the development of modern technology, functional materials with complex properties are becoming increasingly important. Since traditional material preparation processes 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 technology to prepare multifunctional materials. In addition, it is difficult to obtain compounds for cross-metal connections using traditional fusion techniques, which makes it difficult to create structures composed of steel and titanium, such as those used in pipe connections. Ustinov used the diffusion welding method to prepare a titanium-steel bimetallic compound, which can meet the requirements of installation connections and has the advantages of high strength and plasticity.
Bearing finite element model
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 the gravity load. The shorter yellow arrow whose starting point is the reference point (ＲP) represents the direction of concentrated force. According to the dynamic simulation of the established bearing Pro/E model in Adams, the load data of the bearing is extracted. The radial load on the bearing is 1.8×104N, and the bearing rotation speed is 90r/min.
Set boundary conditions
When setting boundary conditions, it is necessary to limit the axial displacement of the inner surface of the inner ring, and the boundary conditions are all imposed on the inner surface of the bearing inner ring. The outer ring of the bearing is fixed on the bearing seat, so fixed constraints are imposed on the outer surface of the outer ring. Since the lubricating oil represented by the Euler body is restricted by various parts of the bearing and is difficult to flow out of the space between the outer wall of the inner ring and the inner wall of the outer ring, the flow rate of the Euler body on its two annular sides is limited to 0.
Sliding bearing testing equipment
For the designed mandrel sliding bearing, its preliminary operating performance was tested, and a corresponding sliding bearing testing machine was built. According to the tasks of the project, the developed testing machine mainly verified the film-forming ability of the sliding bearing, that is, the preliminary operating ability and start-up. Stop operation capability. The mandrel of the sliding bearing under test is fixed on the test bearing seat. The inner hole of the pulley simulates the inner hole of the planet wheel. The outer edge of the mandrel matches the inner hole of the pulley to simulate the cooperation of the mandrel and the inner hole of the planet wheel. The pulley is connected to the speed-regulating motor through four SPB narrow V-belts, and is driven by the motor to simulate the speed of the planetary wheel when it starts and stops. A hydraulic loading system is used to apply a load on the outer surface of the pulley to simulate the equivalent load on the planetary wheel when it starts and stops. The load exerted by the hydraulic cylinder is transmitted through the flange and guide rod at the upper end of the test bearing seat. The load is distributed to the two rolling bearings through the fisheye rod end spherical bearing. The linear bearing and limit block are used to fix the movement direction of the guide rod in the vertical direction. Ensure that the load exerted by the hydraulic cylinder acts on the center of the sliding bearing, and the radial load of the sliding bearing under test is applied by the contact between the outer circle of the rolling bearing and the pulley. The inner hole of the mandrel and the support shaft are designed to fit tightly. When assembling, the bearing can be integrally inserted from the end cover on the right side of the bearing seat. When disassembling, just remove the end cover and pull out the support shaft and mandrel bearing directly, which can be quickly disassembled. Measurement and control system: four sensors that monitor changes in real time, namely pressure, temperature, rotational speed, and displacement sensors. Photoelectric rotational speed sensors are used to monitor rotational speed changes in real time; a thermocouple temperature sensor is arranged at the oil outlet to measure the oil temperature rise. In addition, there are flow meters and temperature meters on the oil supply station. Since the initial oil supply conditions are constant, the initial temperature and flow information of the oil supply can be directly read.
Effect of load and speed changes on lubrication performance
Effect of changes in load and speed on oil film pressure
In the bearing lubrication system, changes in load and speed will affect the oil film pressure. As the rotational speed continues to increase, the oil film force continues to increase. The rotation speed of curve a is 90r/min, and the rotation speed of curves b and c are 110r/min and 130r/min respectively. The maximum oil film pressure in curve a is 1GPa, and the secondary peak pressure reaches 0.96GPa. The maximum oil film pressure in curve b is 1.09GPa, and the secondary peak pressure reaches 1.089GPa. The maximum oil film pressure in curve c is 1.14GPa, and the secondary peak pressure reaches 1.158GPa. The shape of the pressure distribution curve has changed significantly. The secondary pressure peak is obvious under low rotational speed. As the rotational speed increases, the secondary pressure peak almost disappears, and the maximum value of the pressure continues to move toward the inlet area.
Effect of load and 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 plane. When the rotational 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 oil film thickness decreases and gradually becomes thinner. When the load increases from 1.8×104N to 2.4×104N, the minimum oil film thickness drops from 0.2mm to 0.01mm.
Conclusion
Sliding bearings have very important applications in many fields. Sliding bearings can be found in aerospace and daily life. The structural parameters of sliding bearings directly affect the performance of sliding bearings, so their structural parameters must be considered when designing sliding bearings. For this purpose, a sliding bearing test bench was designed to conduct start-stop tests under simulated working conditions. Through this experimental machine, the start-stop wear of copper alloy and diamond-like coating surface material specimens was investigated. After completing the same number of start-stop tests under similar working conditions, the surface wear was observed. It was found that the bearing specimens with copper alloy surface material had more wear marks than the bearing specimens with diamond-like coating surface. 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 will cause coating wear, and the lubricating oil needs to be filtered and cleaned.
