Technology Knowledge

Abstract : Taking the high speed ceramic bearing electric spindle used in laboratory for example, its characteristic, lubricating, the cooling system as well as electric spindle moving control are introduced. They lay a solid foundation for the application of the ceramic bearing electric spindle in the lathe. Key words: ceramic bearing; electric spindle; characteristic; moving control   0 Introduction The high-speed electric spindle is directly driven by an internal AC variable frequency servo motor, which can maintain good dynamic balance at high speeds The stator of the high-speed electric spindle is laminated with high-quality silicon steel sheets with high permeability, and the stator cavity is equipped with punched wire slots The function of the rotor is to convert the electromagnetic field energy of the stator into mechanical energy. It consists of three parts: the rotor core, squirrel cage, and shaft Electric spindle has the advantages of compact structure, light weight, small inertia, and good dynamic characteristics, and can improve the dynamic balance of the machine tool to avoid vibration and noise.   1 Ceramic bearing electric spindle 1.1 Characteristics of ceramic bearing electric spindle Ceramic bearing electric spindle is a high-speed electric spindle assembled with ceramic ball bearings as the spindle support. It can combine the advantages of high speed, high stiffness, high power, and long service life The structure of the ceramic bearing electric spindle system is shown in Figure 1.   Figure 1 Structure of Electric Spindle System The laboratory electric spindle uses a hybrid ceramic ball bearing as the spindle support, which is made of silicon nitride material (Si3 N4) to make ceramic balls as rolling balls. The inner and outer rings of the bearing are still GCr15 steel rings Although the steel ball has only been transformed into a silicon nitride ball, on the other hand, the geometric dimensions of the channel have also been improved to optimize bearing performance This type of bearing not only reduces centrifugal force, but also reduces the friction between the ball and the track, resulting in lower temperature rise and better high-speed performance The most important characteristics of hybrid ceramic bearings compared to all steel bearings of the same model are as follows.   The operating speed increases because the low density of silicon nitride balls means a decrease in centrifugal force. The rigidity increases because the elastic modulus of silicon nitride is 50% higher than that of bearing steel. Reduced heat generation. Silicon nitride balls have the characteristics of low friction coefficient and good sports performance. The thermal stability is better because the thermal expansion coefficient of silicon nitride is 1/3 of that of steel. Design flexibility is greater because the performance of silicon nitride material allows bearing designers to…

Abstract: Using ceramics as a rolling bearing material can expand the range of use of bearings, enabling them to reach the highest operating speed. Ceramic bearings can be applied in special fields without lubrication or medium lubrication, as well as in working environments such as corrosion resistance and heat resistance. However, corresponding manufacturing processes and new standards for component assembly must be adopted in order to fully utilize the advantages of ceramics. Keywords: ceramic bearings; Hybrid bearings; Performance; application   Characteristics of ceramic bearings In conventional bearings, lubricants are required to completely isolate the moving surfaces from each other to avoid severe wear. If the bearing operates under insufficient lubrication conditions, the requirements for the material are extremely high. Firstly, high hardness and low adhesion wear are required. In addition, the material cyclic load requires the material to have a uniform organizational structure. The high hardness and wear resistance of ceramics enable their excellent application in rolling bearings.   Ceramic bearings can be divided into two basic types. Hybrid ceramic bearings only have rolling elements made of silicon nitride, and rings made of steel or special metal materials (stainless steel, high-speed tool steel, or nickel based metal). And all ceramic bearings are generally made of ceramics except for the cage, and almost only silicon nitride is used. Recently, zirconia (ZrO2) with high mechanical strength and localized stabilization treatment has also been used in specific applications.   The cage is mainly made of high-temperature plastic, especially PEEK, which has outstanding stability and can also be used in corrosive media. Bearings made of these materials can be used at high temperatures of 250 ℃. The use of PEEK or PI with molybdenum disulfide solid lubricant provides additional good friction performance under non lubricated operating conditions. The use of heat-resistant steel and nickel based alloys can reach temperatures of 500 ℃ and above. When the temperature is higher, bearings without cages are used.   Hybrid ceramic bearings have greatly improved their performance due to the optimization of material pairs. The use of silicon nitride rolling elements in hybrid ceramic bearings can greatly increase the rotational speed, as the centrifugal force of the silicon nitride ball on the outer ring raceway is reduced by about 60%, thereby improving rolling motion. As the speed increases, the rotational friction of high-speed hybrid spindle bearings is significantly lower than that of steel bearings, so hybrid spindle bearings can reduce bearing friction and heat generation. Due to its advantageous material pair, hybrid ceramic bearings can be lubricated with lean oil or long-life grease, greatly improving their lifespan. In addition, hybrid ceramic bearings also have insulation effects, which can become an important standard for use in motors.   All ceramic bearings…

Abstract: The paper proposes one kind of new support material ,ceramics material ,applied in the finishing process of bearing rings. And the respects such as the material behavior ,friction - wear mechanism ,the manufacture technology of the ceramics support material ,and so on ,are studied. The results show that the ceramics support material has an advantage over the tradi2 tional support materials for improving the processing accuracy and the surface quality of the bearing rings ,and can eliminate the defection of support trace brought by the support material. Key words : Ceramics support ;Bearing rings;Finishing process;Applied research   Introduction Rolling bearings, as standard components, are widely used in industries such as aerospace, automotive, metallurgy, and household appliances, and have a huge domestic and international market. In order to expand domestic demand and earn foreign exchange through exports, domestic bearing manufacturing enterprises are striving to improve the internal accuracy of bearings while also paying attention to the appearance quality of bearing products. However, often due to the appearance quality of bearing products not meeting customer requirements (the host country is unable to effectively eliminate support marks), they cannot compete with world-renowned enterprises in the international market, causing huge economic losses to the country every year.   Centerless fixtures are widely used in grinding and ultra precision machining of bearing rings. Its characteristics are: high repeated positioning accuracy, no clamping deformation, convenient adjustment, easy loading and unloading of workpieces, radial runout of the spindle does not affect processing accuracy, and is easy to achieve automation. However, unintentional fixtures can easily leave support marks or cause surface scratches on the positioning surface during use. In order to eliminate support marks and surface scratches, the domestic bearing industry generally increases the polishing process, which will inevitably increase the cost of bearing processing. At the same time, improper control of the polishing process can also easily cause damage to the accuracy of ring processing. Therefore, it is necessary to find a new support material to replace the commonly used centerless fixture support material.   Ceramic materials have characteristics such as high strength, high temperature resistance, wear resistance, corrosion resistance, good thermal stability, self-lubrication, and highly accurate product dimensions, which make them unparalleled in other traditional bearing ring grinding and ultra precision machining support materials. This article will study the application technology of ceramic support materials in ring ultra precision machining from both theoretical and experimental perspectives.   Material characteristics and wear mechanism 2.1 Defects in Traditional Support Materials At present, nylon and bakelite supports are commonly used in the ultra precision machining of ferrules, which are subjected to pressure and clamping force from oilstones. When the collar rotates rapidly, on the one hand, due to the high…

Abstract: Explore the detection techniques for surface characteristics of ceramic bearing parts, including optical methods, ultrasonic methods, acoustic emission, staining methods, and ray methods. Provide a detailed introduction to the advantages and disadvantages of these detection methods and the corresponding items that can detect the surface characteristics of ceramic bearing parts. Keywords: ceramic bearings; Parts; Surface characteristics; detection   Engineering ceramic materials such as silicon nitride used in rolling bearings have advantages such as wear resistance, high temperature resistance, corrosion resistance, non magnetism, low density, low thermal expansion coefficient, and insulation. They are suitable for working in special environments such as high temperature, high speed, corrosion resistance, non magnetism, oil free lubrication, and light weight, and have attracted more and more attention from people. Due to the limitations of ceramic manufacturing technology and material characteristics, there are often various defects such as cracks, pores, inclusions, and additive segregation on the surface or inside of ceramic bearing parts (mainly referring to rolling elements and rings), as well as changes in the physical and mechanical properties of the surface layer. This not only reduces friction and wear performance, leading to a significant decrease in strength, but also seriously affects the service performance and fatigue life of bearings. Therefore, during the processing and operation tests of bearing related parts, it is necessary to strictly inspect their surface characteristics, which means that in addition to checking the size, shape accuracy, and surface roughness of the parts, the surface defect characteristics should also be detected. In order to promote the research of non-destructive testing methods for the surface characteristics of ceramic bearing parts, based on recent experiments and research on the rolling contact fatigue, wear, lubrication, and processing and surface coating of related parts of ceramic bearing performance both domestically and internationally, this article explores the corresponding main detection technologies.   Detection of surface roughness, spherical error, and hardness 1.1 Surface roughness and waviness Like ordinary bearings, the measurement methods for surface roughness of ceramic bearing parts can be divided into two categories: contact type and non-contact type based on whether they are in contact with the measured surface. The most commonly used contact roughness tester currently is a stylus profilometer (such as the Talysurf -6 model).   Non contact detection techniques are used for measuring steel balls, such as interference microscopy and laser speckle method. They do not come into contact with the measured surface during the measurement process, so they do not affect the morphology of the measured surface. It is generally believed that evaluating surface roughness solely based on Ra is not enough, and Ry must also be added, as the latter has a significant impact on the surface of ceramic balls (such…

Abstract: Premature bearing failures of wind turbine generators are occurring frequently. The reasons are mani2 fold, but based on application studies and bearing investigations two main root causes have been identified: electrical current passage, electrical erosion respectively, due to frequency converter supply of doubly - fed induction generators and lubrication and wear related problem s. Strives to give an overview on typical root causes for premature bearing failures in wind turbine generator applications and introduces extra - large (XL) hybrid deep groove ball bearings as a new  solution to significantly reduce generator bearing failures and to increase the overall reliability and operating availability of wind turbines. Key words: w ind turbine genera tors; bearings; solution   Introduction The application of power electronics technology in variable speed control is increasing, replacing many traditional speed control methods, such as mechanical gearbox drive, hydraulic drive, etc. The application of frequency converters enables the motor to freely adjust speed from zero to rated speed and keep it running at the appropriate operating point, thereby improving the efficiency and dynamic response ability of the motor while reducing energy consumption. The same technology is also applied to wind turbines. In the past 5 to 6 years, the "doubly fed generator" in large-scale wind turbine equipment has become a typical application and is becoming increasingly popular, allowing wind turbines to operate over a relatively wide speed range. The rotor winding in a doubly fed generator is powered by a frequency converter, and the motor can optimize the generation energy and maintain a stable line frequency while adjusting the active and reactive power while changing the rotor speed. However, due to the introduction of frequency converter systems, bearing failures caused by overcurrent frequently occur and become the main cause of early generator failures. At the same time, it was confirmed that another major cause of bearing failure was lubrication and corresponding wear.   This article elaborates on the fundamental reasons for early bearing failure in wind turbine applications, and introduces the technology of ultra large hybrid ceramic ball bearings. This  proposed technology can significantly reduce bearing failure in generators and increase the overall reliability and operational stability of the equipment.   Failure of bearings in wind turbines Among various mechanical equipment components, bearings are the most important part. The failure of bearings in motors can also be caused by many other reasons, such as exceeding expected loads, improper lubrication, improper handling during transportation and shutdown, electrical corrosion, damage caused by installation and disassembly, internal pollution of bearings, seal failure, and improper tolerance fit between shafts and bearing chambers. Each factor can cause different damages, and at the same time, they leave their own unique marks in the bearings.…

Abstract: High speed machine tools have become one of the main trends in contemporary development, and one of the key components of high-speed machine tools is the high-speed electric spindle. The bearings supporting the electric spindle are subjected to external loads and rotations on the contact points of the ring and rolling element due to the rotation of the spindle, resulting in repeated contact pressure and deformation. The main form of failure of steel bearings is fatigue peeling, with a short anti fatigue life. Ceramic bearings (Si3N4) have advantages such as low density, medium elastic modulus, small thermal expansion coefficient, high hardness, high temperature resistance, corrosion resistance, and no magnetism, which can significantly improve the contact fatigue life of bearings and are more suitable for high-speed applications. This article explores the application of ceramic bearings in high-speed machine tools. Keywords: high-speed machine tools, steel bearings, ceramic bearings   Preface High speed machining technology (HSM) is a very important advanced manufacturing technology in contemporary times, which has been increasingly widely applied in mechanical processing industries such as aerospace, automotive manufacturing, and mold industry, and has achieved significant technological and economic benefits. With the development of high-speed machining technology, high-speed and high-precision machine tools have also become one of the main development trends, and one of the key components of high-speed machine tools is the high-speed electric spindle, The bearing supporting the electric spindle is subjected to external load and rotation at the contact point between the ring and the rolling element due to the rotation of the spindle, resulting in repeated contact pressure and deformation. Traditional steel bearings are not suitable for high-speed machine tools due to their own materials and high density, which result in significant centrifugal force during operation and short fatigue life. Ceramic bearings (Si3N4) have the advantages of low density, medium elastic modulus, small coefficient of thermal expansion, high hardness, high temperature resistance, corrosion resistance, and no magnetism, which can significantly improve the contact fatigue life of bearings. Especially, high-speed ceramic bearings can be applied at high speeds of 12000~75000 r/min, suitable for high-speed machine tool spindles and other high-precision equipment.   1.Performance characteristics of high-speed machine tools 1.1 Overview of high-speed machine tools High speed machine tools are generally CNC and precision machine tools, which shorten the cutting and non cutting time during processing. For complex shapes, difficult to machine materials, and high hardness materials, the machining process is reduced to maximize the accuracy and quality of products, improve labor productivity, and achieve economy. High speed machine tools should have the following conditions.   The spindle of mechatronics integration, namely the electric spindle. A modern spindle is an organic combination of an electric motor and a spindle, using…

There are various types of ceramic materials, and only silicon nitride (Si3N4) can be competent as a ceramic material for rolling bearings in terms of rolling fatigue life and reliability. Silicon nitride has excellent properties such as lightweight, insulation, insulation, non magnetic, high temperature resistance, corrosion resistance, wear resistance, low centrifugal force during high-speed rotation, and low operating temperature rise. Ceramic bearings that utilize these properties have been applied to machine tool equipment such as aerospace, military, petroleum, and high-speed electric spindles, corrosion resistance, and are gradually developing new application fields to fully utilize the performance of ceramic materials.   1.Performance of ceramic bearings 1.1 Physical and mechanical properties of silicon nitride materials Table 1 shows the comparison of physical properties between silicon nitride and bearing steel. Silicon nitride has a high elastic modulus, so its contact stress is higher than that of steel bearings under the same load.   Table 1 Comparison of Physical Properties between Silicon Nitride and Bearing Steel 1.2 Rated static load The rated static load of all ceramic bearings should be studied for the allowable load when silicon nitride cracks occur. The calculation method for the rated static load is the same as that of steel bearings. Regarding hybrid ceramic bearings, research should be conducted on the permanent deformation of the ring, with a rated static load of approximately 85% of that of steel bearings. Some literature suggests using Hertz induced cracking load to evaluate the rated static load of ceramic bearings. When bearing steel balls or silicon nitride balls are loaded onto silicon nitride plates, the cracking load is 10 times the rated static load obtained by traditional calculation methods for steel bearings.   1.3 Rolling fatigue life Based on the rated dynamic load, operating load, and rotational speed of ceramics, the lifespan of bearings can be calculated using a life calculation formula. Figure 1 shows the comparison test results of the lifespan of ceramic bearings and steel bearings. The test conditions are: axial load 5 800 N, rotational speed 8 000 r Π Min, temperature 70 ± 2 ℃, lubricant is aviation turbine oil 500.   Figure 1 Rolling Fatigue Life Test Results The experimental results show that the working life of ceramic bearings is longer than the expected life and that of steel bearings of the same type. The rated dynamic load of steel bearings can be used for ceramic bearings of the same size.   1.4 Crushing load The crushing load of silicon nitride balls is 30% of the crushing load of steel balls of the same specification 5% to 47% is caused by the increase in contact surface caused by plastic deformation of the steel ball. The contact stress level…

Abstract: This article summarizes the research and development status of ceramic rolling bearings both domestically and internationally, focusing on the preparation and processing technologies of ceramic balls and ceramic rings, and pointing out the future research directions of ceramic bearings. Keywords: ceramic bearings, rolling bearings, ceramic materials, machining centers   1 The necessity and urgency of developing new ceramic bearings With the development of the mechanical industry towards high-precision, high-efficiency, and highly automated directions, the working speeds of various machines continue to increase. For example, the spindle speed of CNC machining centers has increased from 5000 rpm in the 1980s to 25,000~30,000 rpm now. The dn value (product of bearing diameter and speed) of high speeds has reached 3 million, and the experimental value has reached 3.5~4 million. Machinery that operates in certain high-tech fields and special environments, such as the aerospace industry, nuclear energy industry, chemical industry, petroleum industry, food industry, etc., needs to work in special environments such as high temperature, high speed, corrosion resistance, vacuum, non-magnetic, oil-free lubrication, and light weight. Nowadays, steel bearings cannot meet these requirements. The main problem with high-speed bearings is the decrease in bearing life, increase in temperature rise, decrease in stiffness and accuracy caused by high-speed, and the large centrifugal force caused by rolling balls. This centrifugal force causes the pressure between the ball and the outer ring raceway to even exceed the effect of external loads, thereby reducing the bearing life. At the same time, too high rotating speed will exert a large gyroscopic torque on the ball, which will make the ball and the ring slip, increase the Friction torque, increase the heating and generate additional pressure on the cage, resulting in large temperature rise and cage damage. Therefore, the needs of high-speed machinery and special working environments such as high temperature and corrosion resistance cannot be met solely by improving the structure and lubrication conditions of current steel bearings. It is necessary to make fundamental breakthroughs and innovations in ceramic materials, research and development of new materials for bearings, in order to meet the requirements of high-tech and industrial production development.   As a modern high-tech new material, engineering ceramics have developed rapidly and their technology is becoming increasingly mature. It has wear resistance, high temperature resistance, corrosion resistance, low magnetic density (only about 40% of bearing steel), low thermal expansion coefficient (25% of bearing steel), and high elasticity coefficient (1.5 times that of bearing steel), ceramic bearings made of ceramic materials are very suitable for working in special environments such as high speed, high temperature, and corrosion resistance. Because of its low density, using ceramic balls as rollers can greatly reduce centrifugal force and gyroscopic torque at high speed,…

Abstract: The paper proposes one kind of new support material, ceramics material, applied in the finishing process of bearing rings. And the respects such as the material behavior, friction - wear mechanism, the manufacture technology of the ceramics support material, and so on, are studied. The results show that the ceramics support material has an advantage over the traditional support materials for improving the processing accuracy and the surface quality of the bearing rings, and can eliminate the defection of support trace brought by the support material.   Key words: ceramics support; bearing rings; finishing process; applied research Introduction As a standard part, rolling bearings are widely used in aerospace, automobile, metallurgy, household appliances and other industries, and have a huge domestic and foreign market. In order to expand domestic demand and earn foreign exchange through export, domestic bearing manufacturing enterprises have begun to pay attention to the appearance quality of bearing products while trying to improve the internal accuracy of bearings. However, because the appearance quality of bearing products cannot meet the requirements of customers (the host country cannot effectively eliminate the bearing seal), they are unable to compete with world-renowned enterprises in the international market, causing huge economic losses to the country every year.   Centerless fixtures are widely used in the grinding and Superfinishing of bearing rings. Its characteristics are: high repeated positioning accuracy, no clamping deformation, convenient adjustment, easy loading and unloading of workpieces, radial runout of the spindle does not affect the machining accuracy, and it is convenient to realize automation. However, centerless fixtures are easy to leave support marks on the positioning surface or cause surface scratches during use. In order to eliminate support marks and surface scratches, the domestic bearing industry generally increases the light grinding process, which is bound to increase the bearing processing cost accordingly. At the same time, improper control of the light grinding process is also easy to cause damage to the processing accuracy of the ferrule. Therefore, it is necessary to find a new support material to replace the currently widely used centerless fixture support material. The characteristics of ceramic materials, such as high strength, high temperature resistance, wear resistance, corrosion resistance, good thermal stability, self-lubrication and highly accurate product size, make them have incomparable material characteristics compared with other traditional bearing ring grinding and superfinishing support materials. This paper will study the application technology of ceramic support materials in the Superfinishing of rings from the aspects of theory and experiment.   Material characteristics and wear mechanism 2.1 Defects of traditional supporting materials At present, nylon and bakelite support are widely used in the Superfinishing of ferrule, and the ferrule is under the pressure and clamping force of…

1 Existing problems A company's existing external groove grinding machine uses hard alloy material for fixed support, as shown in Figure 1. Due to the high friction coefficient and poor self-lubrication of hard alloy, surface scratches or support marks are generated when the outer diameter of the outer ring rubs against the alloy, which has a certain impact on the surface accuracy and appearance of the outer diameter. Due to some users' requirements for unsupported outer diameter printing, the outer diameter Z final return process is adopted to eliminate it. After the ultra precision machining of the channel is completed, return to the outer diameter process before assembly for outer diameter grinding. This process not only has a large workload and low efficiency, but also can easily cause mixing, posing certain risks to product quality, and also bringing difficulties to organizational production.   Figure 1: Support before improvement   Due to the difficulty in adjusting the eccentricity of the fixed support, and the variation of the eccentricity with the wear of the support, it affects the size of the part groove, and the shape error of the workpiece surface before grinding will be reflected on the surface of the workpiece after grinding. In addition, the use of this support does not significantly improve the roundness of the parts.   2 Improvement measures As a supporting material, it must have high hardness, strength, and wear resistance, as well as a certain degree of self-lubrication. It cannot be bonded or embedded with metal, and metal materials cannot meet the above conditions. The use of ceramic materials is a good way to solve the above problems. For this reason, oxide ceramics with both high hardness and certain impact resistance were selected. However, due to the extremely hard nature of ceramic materials, general grinding wheels cannot grind them, and they are not conductive and cannot be processed by wire cutting. So when manufacturing supports, it is necessary to minimize the shrinkage during the mold production stage based on the characteristics of ceramic pressing and sintering molding. To reduce the number of pressing molds, when designing various specifications of supports, it is necessary to ensure the performance of each type of bearing processed by the support, while also striving to meet universality.   The improved support adopts floating support. The floating support is made of copper or stainless steel material with a ceramic rod embedded in the matrix. The floating support and support frame are in a clearance fit and can rotate around the pin shaft with a floating amount of 0.2-0.4mm. The use of ceramic materials has the advantages of low friction coefficient, less adhesion to metal, and good wear resistance, which can remove…

Abstract: This article first briefly introduces the process of traditional ceramic materials transitioning to modern new ceramic materials. New ceramic materials overcome the internal defects of traditional ceramics, greatly improving their performance and expanding their application fields. Then it discusses the classification of new ceramic materials into structural ceramics and functional ceramics, as well as their high-temperature resistance, biocompatibility, electromagnetic properties, light weight, and other characteristics, as well as their respective application fields. The focus is on the application of new ceramic materials in aerospace, military, bioengineering, electronic industry, etc. Finally, it briefly explains the recent status and development trends of new ceramic materials. Keywords: New type of ceramics; Materials; Application; develop   Introduction: In today's highly developed Industrial society, every achievement of industrialization is inextricably linked to material science, material manufacturing and actual use, which makes some new scientific ideas, ideas and production processes come true. Without materials science and the materials industry, many scientific creations and inventions in the world are difficult to achieve or achieve. Ceramic materials are the most important type of inorganic non-metallic materials that people have paid attention to after metal materials and non-metallic polymer materials, because they combine the common advantages of both metal and polymer materials. In addition, their brittle and cracking properties have been greatly improved through continuous modification processes. Therefore, there has been a significant improvement in its application fields and various products.   1. Evolution from Traditional Ceramic Materials to New Ceramic Materials The term 'Ceramics' comes from the ancient Greek word' Keramos', meaning the God of Earth. Traditional ceramic materials have a wide range of meanings, mainly referring to nitrides, carbides, glass, and silicates of aluminum and silicon. Although traditional ceramics have certain chemical corrosion resistance characteristics, high resistivity, high melting point, high-temperature resistance, high hardness, wear resistance, high chemical stability, and non corrosion. But it also has drawbacks such as poor plastic deformation ability, susceptibility to brittle failure, and difficulty in processing and forming, which greatly limit its application in industry, especially in the mechanical industry. And its application in electrical appliances is mainly limited to a few aspects such as high-voltage ceramic bottles and insulation components.   For this reason, people have carried out research on modification of traditional ceramic materials and artificial synthesis and development of related materials. Modern synthesis technology has been able to transform traditional ceramics or artificially synthesize ceramic materials with few defects, including Si3N4, A12O3, etc. Compared with traditional ceramic materials, the performance of synthesized ceramic materials is greatly improved. Compared with other materials, these materials have good chemical, thermal, mechanical, and tribological properties at the same strength. It is lightweight, can withstand high temperatures, has high hardness, and sometimes exceeds the compressive…

Abstract: Silicon nitride ceramic bearings have many excellent physical properties such as high strength, high hardness, low density, and high temperature resistance, and are widely used in the aerospace field, especially in aviation engines. With the rapid development of the aviation industry, there are stricter requirements for the performance of silicon nitride ceramic bearings. Silicon nitride ceramic bearings need to operate faster and smoother under high temperature and heavy load conditions. Based on the comparative analysis method, the development status, defects, and future trends of silicon nitride ceramic bearings and steel bearings were compared and analyzed. Previous studies have shown that the high temperature resistance, corrosion resistance and working life of silicon nitride ceramic bearings are far better than those of steel bearings, but their mechanical properties such as fracture toughness and tensile strength still have much room for improvement.   0 Introduction Silicon nitride ceramics have excellent comprehensive properties such as high strength, high hardness, low density, high temperature resistance, and ultra high speed, and are widely used in the fields of aerospace and equipment manufacturing. Bearings are an important component in mechanical equipment and are widely used. Its main function is to support the mechanical rotating body, reduce its friction coefficient during movement, and ensure its rotational accuracy. Its function is similar to that of human joints, so it is known as a "mechanical joint". A series of problems such as severe wear and tear, overheating, seizure, and lubricant deterioration of bearings will directly lead to malignant failure of equipment and systems. In aviation engines, the working environment of bearings is very harsh, and being in a high-temperature environment poses a great challenge to the performance of bearings, which can easily lead to bearing failure. The fundamental method to solve this problem is to use materials with better comprehensive performance and further optimize the performance of bearings.   Ceramic bearings have applications in various fields. Zhu Aihua and others compared the performance of steel bearings and silicon nitride ceramic bearings, and found that the main advantage of using silicon nitride ceramic bearings for locomotive traction motor bearings is that they can effectively prevent "electrical corrosion" damage caused by current passing through the bearings; The grease life of ceramic bearings is 3-4 times longer than that of ordinary steel bearings. Zhang Baolin and others studied the new progress of hybrid silicon nitride ceramic bearings. Wen Huaixing et al. studied the research status and development trend of lubrication technology for silicon nitride ceramic bearings. Xun Changtian et al. studied the corrosion behavior of silicon nitride in acid solutions such as H2SO4, HNO3, HCl, HF, and high-temperature SO2 and HCl gases, and summarized its corrosion mechanism. The above results all indicate…

In recent years, variable voltage and variable frequency control AC traction motors have been installed on newly manufactured electric vehicles. These AC traction motors have the characteristics of light weight, compact structure, and high-speed operation. However, in order to adapt to the characteristics of high-speed rotation of bearings and temperature rise of various components of traction motors, it is necessary to solve the "electrical corrosion" hazard of existing steel bearings to improve the heat resistance and durability of bearings and lubricating grease.   Note: Electrical erosion refers to the damage caused by local melting caused by electric current passing through the very thin oil film in the rolling contact area of the bearing during rotation. Figure 1. Axial current corrosion phenomenon via network   1.Basic requirements for insulated bearings for traction motors At present, the solution to electrical corrosion is to set up a bypass circuit to allow current to flow to the outside of the bearing, or to insulate the surrounding area of the bearing to cut off the current. The specific methods are: Install a grounding device on the main shaft or casing of the traction motor to prevent current from passing through the inside of the bearing.   Use insulated bearing racks or insulated bearings.   From the perspective of price and reliability, insulated bearings are the main method.   There are roughly three types of insulated bearings used for traction motors, namely: resin coated bearings; Hybrid ceramic bearings; Ceramic sprayed bearings.   ① Resin coated bearings The most commonly used type of bearing is PPS (polyphenylene sulfide) insulated bearing, whose outer surface is coated with PPS insulation resin to prevent bearing corrosion. The advantage is excellent electrical insulation performance and low price. The disadvantage is that this type of bearing is not suitable for machinery with rapidly increasing bearing temperature or occasions with strict requirements for interference changes, so it is often used in motors with relatively loose conditions.   ② Hybrid ceramic bearings The only rolling element parts in bearings are made of ceramic materials, also known as hybrid ceramic ball bearings. They use engineering ceramics as bearing materials and have good mechanical and thermal properties, such as sufficient strength, stiffness, hardness, fracture resistance, impact resistance, high temperature resistance, oxidation resistance, and a series of better properties than metal materials. Ceramic materials suitable for bearings mainly include silicon nitride (Si3N4), zirconia (ZrO2) Aluminum oxide (Al2O3). Among these three ceramic materials, silicon nitride has superior comprehensive performance and has become the preferred material for ceramic bearings. Its characteristic is that the failure mode, like that of bearing steel, occurs in the form of pre existing peeling. However, zirconia and alumina both exhibit a form of fragmentation failure.…

Hybrid ceramic bearings provide solutions for addressing current and future technological challenges. The hybrid ceramic bearing adopts steel inner and outer rings and ceramic rolling elements, which can reduce weight, reduce friction, eliminate electrical corrosion, and improve reliability and speed performance. Nowadays, the world is changing rapidly, and global trends are changing our way of travel, business, and lifestyle. With the advancement of urbanization, more and more people are migrating to cities. Digitalization and automation are accelerating our pace of life and work, and the entire society must address the challenges of various environmental issues. At the same time, we also see the rapid progress of electrification (especially electric vehicles) and the continuous development of globalization.   These global trends are driving changes in the field of bearings. Many emerging technologies require bearings to have special performance, such as being suitable for variable frequency drives, reducing maintenance requirements, helping to improve power density, and reducing friction.   Hybrid ceramic bearings provide promising solutions for addressing all of these existing and future technological challenges. The combination of steel inner and outer rings and ceramic rolling elements endows hybrid ceramic bearings with unique performance, making them suitable for various modern applications. SKF hybrid ceramic bearings use silicon nitride rollers. There are two types of Deep Groove Ball Bearing and cylindrical roller bearings to choose from, and they can be customized according to customer needs.   The use of ceramic materials in bearings is not new. From the 1960s to the 1980s, ceramic materials were favored by the international aerospace industry due to their light weight and good heat resistance, and the industry was the first to adopt ceramic bearings. However, it was not until the 1980s that ceramic materials (silicon nitride) were commercially produced. Since the 1990s, modern hybrid ceramic bearings have been applied in numerous applications, including machine tools, wind turbines, railway and electric vehicle traction motors, aerospace industry, and fluid machinery such as compressors, pumps, and vacuum pumps.   The silicon nitride rolling element used in SKF hybrid ceramic bearings has superior characteristics compared to standard steel rolling elements. The compressive strength of silicon nitride is much higher than that of bearing steel, and its elastic modulus is about one-third higher than that of bearing steel, which helps to reduce friction in rolling contact.   Importantly, the hardness of silicon nitride is more than twice that of bearing steel, making it an ideal choice for harsh working conditions such as poor lubrication. Compared to bearing steel, silicon nitride is non-conductive and has a much lower density. In addition, the coefficient of thermal expansion of silicon nitride is very low, which can accurately adjust the bearing clearance, but it needs to…

Abstract: This article introduces the characteristics of ceramic (ball) materials, the application characteristics of ceramic ball bearings, and various inspection and detection methods for ceramic balls. Sensitivity tests were conducted on the penetrant for ceramic ball fluorescence penetration testing using TP series test blocks, and the fluorescence penetration testing process was optimized. The experimental results indicate that the optimized fluorescence penetration testing process can effectively detect surface micro cracks of ceramic balls. Keywords: ceramic balls for bearings; Fluorescent penetrant testing; reliability   Traditional steel bearings, relying on improvements in structure and lubrication conditions, are no longer able to meet the requirements for use in high-speed and high-temperature environments. The hybrid ceramic ball bearing composed of steel inner and outer rings and ceramic balls (hereinafter referred to as "ceramic ball bearing") has become the best choice for engine rotor support [1], and its appearance is shown in Figure 1.     Ceramic balls used in bearings have characteristics such as high temperature resistance, wear resistance, corrosion resistance, electromagnetic insulation, and oil-free self-lubrication, which are incomparable to metal steel balls. Ceramic materials not only possess all the important characteristics of bearing materials, but also can withstand harsh working environments that metal and polymer materials cannot withstand.   Ceramic ball bearings have been widely used in aerospace engines, high-precision and high-speed machine tools, petrochemical machinery, metallurgical machinery, and other fields, and the quality control of ceramic balls is particularly important. The author conducted sensitivity tests on the penetrant for ceramic ball fluorescence detection, optimized the fluorescence penetration detection process, and achieved good experimental results.   1.Characteristics of Ceramic Materials and Application Characteristics of Ceramic Ball Bearings (1) The weight of high-speed ceramic materials is only 40% of the weight of steel, which can achieve lightweight and high-speed bearings. When aerospace engine ceramic ball bearings rotate at high speed, they can reduce the rolling load caused by centrifugal force. The rotational speed of ceramic ball bearings can reach 1.3-1.5 times that of steel bearings. (2) The elastic modulus of highly rigid ceramics is 1.5 times that of metals, and after being subjected to force, the elastic deformation is small. The stiffness can be increased by 15% to 20%, thereby reducing machine tool vibration. It has good application value in high-precision systems. (3) The hardness of long-lived ceramics is more than twice that of metals, which can reduce wear and has good wear resistance. The tensile strength and bending strength of ceramics are equivalent to those of metals; The compressive strength is extremely high, about 5-7 times that of metal materials; Especially under high temperature conditions, it can still maintain high strength and hardness. The lifespan of ceramic ball bearings with good pressure resistance is…

Abstract: This article introduces the advantages of dynamic and static hybrid bearings, the steps and effects of using them for the transformation of connecting rod bearing shells. Keywords: hybrid bearing of dynamic and static pressure; Connecting rod bearing bush boring machine; reform   The KX-045 type connecting rod bearing bush boring machine used for precision machining of engine connecting rod bearing shells is a key equipment in the 6456 factory. The main component of this equipment, the boring head, is selected as a "C" level precision single row centripetal thrust ball bearing with the old number 46215, consisting of 4 groups in total. Due to the requirements of design accuracy, the boring head has very strict requirements for the selection and assembly of bearings. Even if the selection completely meets the requirements, the service life of the bearings is only 400 hours. Moreover, this type of bearing is expensive, and replacing a set of 4 bearings requires over 2000 yuan. The machine tool has 4 boring heads, and replacing 16 bearings simultaneously costs nearly 10000 yuan. Frequent replacement of boring head bearings has affected the normal operation of the entire factory production line.   After investigation and combined with our factory's situation, if WMB liquid dynamic static hybrid bearings are used to modify the connecting rod bearing bush boring machine, only two of the four key heads can meet the usage requirements (the other two boring heads are used to process the auxiliary connecting rod bushing, and due to the small processing aperture and machine load, the rolling bearings can fully meet the requirements). The cost of renovating two boring heads is only about 40000 yuan, and the bearing technology is mature, reliable, and has a long service life.   Dynamic and static pressure bearings absorb the advantages of dynamic and static pressure sliding bearings and eliminate the disadvantages of both types of bearings. It adopts a surface shallow cavity oil wedge structure and utilizes the throttling principle of static pressure bearings to generate sufficient static pressure bearing capacity in the pressure oil chamber, allowing the main shaft to float when not rotating, thereby overcoming the dry friction caused by the start and stop of liquid dynamic pressure bearings, and improving the service life and accuracy retention of the main shaft and bearings. Moreover, due to natural surface throttling, Without the problem of clogging the throttle in the static pressure bearing, it is reliable to use. After the main shaft is started, the dynamic and static bearing capacity formed by the shallow cavity step effect greatly improves the bearing capacity of the main shaft, while the multi cavity opposed structure greatly increases the stiffness of the main shaft; The homogenization effect of…