As the basic formula in fluid mechanics, the numerical solution of the Reynolds equation has always been one of the important research directions in the field of fluid lubrication.Based on the basic form of Reynolds equation, the process of solving the Reynolds equation by finite differential method, finite element method and finite volume method were introduced separately, and the characteristics and problems of each method were discussed.The application of multigrid method combined with the above methods in solving Reynolds equation was introduced, it was pointed out that the multi-grid method has made a great breakthrough in the efficiency of solving Reynolds equation, but it has not significantly improved the accuracy of solution.The application of isogeometric analysis(IGA) method in solving Reynolds equation was introduced, it was pointed out that the IGA method has high efficiency and accuracy in solving Reynolds equation, but there are still some problems such as the in-interpolation of the spline function and the generality of the IGA in the solution of the Reynolds equation.The research direction of IGA in solving Reynolds equation was put forward, such as introducing a suitable spline representation for a specific Reynolds equation, introducing a new boundary condition loading mode through modifying the discrete mode of IGA theory and Reynolds equation, etc.As there is still no stable and applicable method on the problem of complex solving domain and boundary treatment when solving Reynolds equation, it was suggested to combine IGA method and multigrid method to solve Reynolds equation, so as to further improve the efficiency and accuracy of solution.

The development of rubber and plastic sealing industry and the application in various industries of China in recent years were stated.The structure design, sealing material, inspection and testing technology and manufacturing process of rubber and plastic seal were reviewed in this paper.The existing gap and insufficiency between domestic rubber and plastic sealing industry and the advanced sealing technology in developed countries were analyzed.The development direction and future trend of rubber and plastic sealing technology and industry in China were proposed.

The application of micro-texture is a favourable technology of surface modification to improve the tribological performances of cylinder liner-piston ring rubbing pairs. The functional mechanism on improving lubrication and friction performances of cylinder liner-piston ring by micro-textures was analyzed.The research states and progress of multiple tex-ture,combination texture and bionic texture were summarized.The future emphases of further studies on surface textures were prospected.

Numerical method was used for simulating the flow fields and studying the sealing performance and dynamic characteristics of straight-through,stepped and staggered labyrinth seals.The effects of rotor speed and pressure on leakage and dynamic characteristics were investigated.The results indicate that staggered labyrinth seal has the best sealing per-formance among three kinds of seals,while the straight-through type has the worst sealing performance.Straight-through lab-yrinth seal has better dynamic characteristics at high speed,while the staggered type has better dynamic characteristics at low speed,but its dynamic performance falls sharply with the increasing of rotor speed.At low rotor speed or high pressure difference,staggered labyrinth seal has better sealing performance and dynamic characteristics,while the stepped type has the worst sealing performance and dynamic characteristics.At high speed,straight-through labyrinth seal has better dynamic characteristics,while the staggered type has the worst dynamic characteristics.

Polyurea grease is a kind of high temperature grease with all-round properties, such as excellent oxidation stability, thermal stability, pumping property, mechanical stability, colloid stability and water resistance.The research progress of polyurea grease at home and abroad in recent years was reviewed and summarized.The effects of base oil, thickener and additives on the properties of polyurea grease such as drop point, penetration, oil separation, extreme pressure and wear resistance, were discussed.Combined with the development trend of polyurea grease, the research and development suggestions were proposed as follows.The base oil will still be dominated by mineral oil, but the consumption and proportion of polyolefin, ester oil etc.will rise.The base oil obtained from the regeneration of waste lubricating oil can also be used for the preparation of lubricating grease, and the research and development of degradable base oil should be one of the important directions in the future.The study of structure-activity relationship should be strengthened, so as to achieve the accurate design of thickener molecules that can match well with base oil and additives, thereby achieving the regulation of the comprehensive performance of polyurea.The research and development of new additives should be strengthened according to the personalized characteristics of polyurea grease.The research and development of compound polyurea metal base grease should be strengthened to give polyurea grease more excellent performance.

It is essential to study the predicting,detecting,preventing,evaluating,diagnosis capabilities and other tech-niques,in order to reduce the failure rate and potential hazard for the sealing systems.To develop advanced sealing materi-als and products to meet the requirement of harsh conditions,which is critical for the full lifecycle safety of key industries, major projects and equipment.Facing with the new challenges on the quality technology,safety,and low-emission industry, the integrity and reliability theory of rubber & plastic seals was studied.Taking an example on sealing integrity of the oil & gas industry,including the exploitation,transportation,and processing equipment,the intelligent and green method of de-sign control techniques was analyzed.The research direction of sealing integrity and reliability is prospected.

The theoretical research, design and calculation of dry gas seal is generally based on the assumption of laminar flow.However, as the sealing operating conditions gradually become highly parameterized and the process medium becomes multiphase, the fluid will be in a turbulent flow state under high parameter and extremely complex working conditions, and the traditional laminar flow theory will no longer be applicable.Therefore, the turbulent effect of lubricating gas should be considered in the theoretical design and research of dry gas seals.Three widely used turbulent lubrication models, namely Constantinescu model, Ng-Pan-Elrod model and Hirs model, were summarized, the theoretical basis and applicability of each model was described.The turbulent lubrication equation and its turbulent coefficient expression under different models were explained, and the research progress at home and abroad considering the influence of turbulence effects on the stability and dynamic performance of dry gas seals was reviewed.

In order to explore the reason that polyurea grease is easy to harden at high temperature for a long time,the influence of the structure and composition of organic amines as raw material of the thickener of polyurea grease on the high temperature hardening phenomenon of polyurea grease was analyzed.By means of cone penetration test,thermogravimetric analysis and infrared spectroscopy analysis,the mechanism of high temperature hardening of the prepared biuret,tetraurea and hexaurea grease was investigated.The results show that the thermal stability of polyurea based thickener is obviously higher than that of ordinary biuret grease and the hardening degree of hexaurea grease is the smallest among different urea thickeners at high temperature.Polyaromatic amines can obviously improve the high temperature hardening of polyurea grease.Among the different organic monoamines,the hexaurea greases prepared by mixing alkylamine and aromatic amine have better high temperature resistance and among the different organic diamines,and the grease with diaminodiphenylmethane has the best high temperature resistance.With the increase of working temperature,the N-H and C＝O functional groups of polyurea will be destroyed.The change of urea group structure is the reason for the hardening of polyurea grease at high temperature.

The recent progress of the application of microcapsule in composites was reviewed.The common preparation methods and the application of self-lubricating microcapsules in tribology were summarized.The mechanism of self-lubrica-ting microcapsules in polymer matrix was discussed.And synergistic friction-reducing and anti-wear effect of the self-lubri-cating microcapsule in the composites was pointed out.

In order to study the low temperature characteristics of reciprocating spring energized seal ring,two-dimensional axial symmetric model was developed by equivalent spring.ANSYS was used to analyze the stress and friction force of the PTFE jacket of spring energized seal ring during assembly and medium pressure at room temperature,from normal temperature to low temperature and during low temperature pressure process.The results show that the jacket inside and outside lip sealing face is the main pressure bearing area at normal temperature and low temperature,and the stress,contact pres sure,contact width and the friction force of the PTFE jacket inside and outside lip sealing face are increased with the in creasing of medium pressure.The contact at low temperature is larger than that at normal temperature,but the contact width is smaller than that at normal temperature,and the friction force is 2 to 3 times of that at normal temperature.The simulation results show that the spring energized seal ring has good sealing performance at room temperature and low temperature. The correctness of the simulation analysis results is verified by the sealing performance test under normal temperature and low temperature of helium gas and low temperature liquid nitrogen,and the good working performance of the spring energized seal ring is also verified.

The study of the groove etched process for the hydrodynamic mechanical seals was reviewed,and the advanta-ges and disadvantages of various machining techniques in the process of groove were also reviewed,including photochemi-cal machining (PCM),electrical discharge machining (EDM),electrochemical machining (ECM),ultrasonic machining (USM),laser beam machining(LBM),and so on.It was pointed out that the techniques of PCM,EDM and LBM are feasi-ble and successful,among them,laser beam processing(LBM) is the most widely used,but its processing mechanism has not been in-depth studied.ECM technology and USM technology also has the feasibility of processing groove.Due to the ad-vantages of a variety of processing technology,composite processing technology has greater advantages in the groove etched process,and is a future direction of development.The groove etched process technology will be in the direction of precision, complexity and efficiency along with the continuous development of precision machining technology.

Aimed at the shortcomings of traditional piston seal of hydraulic cylinder, such as contact seal and gap seal, a combination of contact seal and gap seal in the prior art was proposed to form a new type of tandem combination seal for a hydraulic cylinder.A numerical analysis model of the structure was established, and the flow field pressure distribution, seal deformation and internal leakage characteristics, as well as the influence of structural parameters on the sealing performance were obtained via numerical simulation.The results show that under the same inlet and outlet pressure, compared with the contact seal, the pressure loss in the internal structure of combination seal greater, and the pressure and impact on the seal ring are smaller, which is conducive to reducing the deformation of the seal.The gap seal at the end of the combination seal structure blocks the oil, weakens the oil impact and pressure on the middle seal ring, and thus the seal ring deformation is smaller.The multi-stage sealing structure of combination seal can better shield leakage and improve sealing performance.The leakage in the combination seal is affected by the gap seal length, seal gap and oil pressure, and increasing the gap seal length and reducing the seal gap and oil pressure can reduce the leakage.The internal leakage physical experiments further shows that the proposed combination seal can effectively reduce internal leakage and hence improve sealing performance, and can still restrain or reduce the internal leakage to a great extent and improve the sealing effect and reliability in case of damage failure of the sealing ring.

A fluid-solid coupling based numerical method for the calculation of leakage of rubber O-ring static seal was proposed .The parallel plate leakage model was improved to make it suitable for the calculation of leakage rate and fluid pressure with variable channel cross section.The finite element simulation was used for solid mechanics analysis to solve the static contact pressure.The Greenwood-Willamson model was used for contact mechanics analysis to solve the average height of the leakage channel.Based on the numerical method, the influence of fluid pressure, ambient temperature and surface topography parameters on the sealing performance of rubber O-ring was studied.The results show that the volume leakage rate gradually increases as the fluid pressure, ambient temperature or the standard deviation of surface height distribution increases.This numerical method uses the leakage rate as a parameter to characterize the sealing performance comprehensively considers the impact of rubber materials, fluid, working conditions and other factors on the sealing performance of O-ring, which is more helpful for the life prediction and failure analysis of rubber O-ring.

The fatigue life of brush seal wire was analyzed based on Miner's linear cumulative damage theory, the S-N curve of brush wire materials was corrected by using the average stress Goodman correction theory, and the fatigue life analysis model of brush seal wire was established by using finite element statics analysis and fatigue life analysis methods.On the basis of verifying the accuracy of numerical model, the structural parameters of brush seal wire fatigue life analysis model were optimized by analyzing the influence of different structural parameters of brush seal wire on the fatigue life of brush wire.The results show that the main failure area of brush seal wire is the root area of brush wire, followed by the middle area of brush wire.Under different structure parameters of the diameter, installation angle and length of brush wire, the fatigue life of the brush wire decreases with the increase of the maximum stress amplitude within the yield stress of the brush wire material.When the brush wire diameter of brush seal is 0.08 mm to 0.12 mm, the inclination angle of brush wire is 45° to 55°, and the length of brush wire is 8 mm to 12 mm, the optimal structural parameters of brush wire fatigue life analysis model of brush seal are obtained.The research can provide theoretical guidance for the design of brush seal.

For the design,manufacturing and performance of groove bearings,the state of the art of such bearings was re-viewed with respect to their bionic design,lubrication theory,friction,wear and manufacturing technology. The types of groove bearings have spool bearing,thrust bearing,conical bearing,spherical bearing and those with variable geometry.The lubricants frequently used are air,oil,water and grease,and the computation methods of lubrication have finite differential method,finite element method and boundary element method.The friction performance of such bearings has Stribeck curve and friction moment,and their wear performance has wear mechanisms,wear rate and anti-wear life. The manufacturing methods have digital controlled milling,form turning,twist squeezing,cover mold corrosion and laser beam cutting etc.The existing problems of groove bearings were proposed,in order to provide a base for improvement of their performance and wide application of groove bearings.

In order to obtain the preparation process of nano molybdenum disulfide with high yield and good reprodu-cibility,a controllable hydrothermal preparation method of nano molybdenum disulfide was proposed.With sodium molyb-date and thioacetamide as precursors,respectively with polyethylene glycol (PEG-20 000),hexadecyl trimethyl ammonium chloride (CTAC),anhydrous ethanol as surfactant,sphere and flower molybdenum disulfide nanoparticles were prepared by hydrothermal method.By X-ray diffraction (XRD),scanning electron microscope (SEM),the characteristics of the product were characterized.And the extreme pressure property test of 2% nano molybdenum disulfide in N46 lubricating oil was carried out by four-ball friction and wear tester.The results show that in the acidic conditions,when adding surfactant PEG-20 000 and CTAC,the sphere structure of molybdenum disulfide nanoparticles with uniform particle size of about 100 nm can be obtained;when adding surfactant anhydrous ethanol,the flower structure of molybdenum disulfide nanoparticles, with particle size of 190 nm in sulfuric acid environment and 70 nm in hydrochloric acid environment,can be obtained.In sulfate environment,the yield of molybdenum disulfide is the highest when polyethylene glycol is used as surfactant,which can be up to 78.82%.Prepared nano-spherical molybdenum disulfide as lubricating oil additives significantly improves the extreme pressure properties of lubricating oil.As compared with comercial molybdenum disulfide,the maximum nonseizure load can be increased about 42% at most.

In order to solve the problem of seal failure caused by friction and wear of dry friction mechanical seal under high speed operating condition,the friction and wear properties of several typical friction pairs under dry friction were analyzed by experiments.Antimony-dipped graphite M106D and resin-immersed graphite M106K were selected to pair with the hard ring of 38CrMoAlA and the 38CrMoAlA sprayed Cr₂O₃,Al₂O₃ respectively.Plint friction and wear tester was used to monitor the friction coefficient under the condition of high speed dry grinding.The effects of axial load and linear velocity on the friction coefficient were analyzed,and the morphology of the end face before and after the test was observed by white light interferometer.The results show that under dry friction,the sprayed 38CrMoAlA hard ring surface has less graphite transfer adhesion than the 38CrMoAlA hard ring,which is more wear-resistant and has lower wear degree,and the wear degree of antimony graphite is less than that of resin graphite.The main wear form of six friction pairs is abrasive wear,and the friction coefficient of 38CrMoAlA sprayed Al₂O₃/antimony-impregnated graphite friction pair is the smallest.Due to the self-lubricity of graphite,it is beneficial to reduce the friction coefficient of the end face by proper increase of rotating speed and axial load.

Based on statistical model,the calculation model of hybrid lubrication and wear of textured bearing was established.By generating virtual rough surface of bearing bush,the average flow Reynolds equation,K-E elastic-plastic contact model,Boussinesq integral and Archard wear equation were used to solve oil film pressure,rough peak contact pressure, elastic deformation of bearing bush and shaft,and abrasion on tile surface respectively. The finite difference method and Newton downhill method were used to solve the model of hybrid lubrication and wear,and the oil film pressure,rough peak contact pressure,elastic deformation of bearing bush and shaft,and abrasion on tile surface at different eccentricities were obtained.The calculation results were compared with those of other mixed lubrication models,and the validity of the model was verified.Taking circular pit texture as an example,the effects of lubrication state transformation and texture on wear process under various working conditions were studied.The results show that texture can form secondary lubrication,which is beneficial to fluid lubrication.With the increase of eccentricity,the load-carrying capacity and rough peak contact load are increased rapidly,and the inflection point of friction coefficient appears.In the mixed lubrication state,the surface texture will reduce the load-carrying capacity and increase the wear in the early stage of wear process,while with the further wear of sliding bearings,the surface texture can play a role in reducing wear.

Based on the DMT contact model, the friction force and friction coefficient of nano-friction on diamond surfaces were calculated.An atomic force microscope was used to study the tribological characteristics of the diamond specimens by mechanical polishing and focused ion beam (FIB) etching in the atmospheric environment, with diamond probes and flaky diamond specimens as friction pairs.The experimental results were compared with the calculated results of the DMT contact model.The results show that the friction coefficient decreases with the increase of the load, which is consistent with the previous research on diamond micro-friction.The calculated results of the DMT contact model are in good agreement with the experimental results of mechanically polished surfaces, but slightly higher than the experimental results of FIB etched surfaces, verifying the applicability of the DMT model in the study of diamond nanofriction.Through the surface roughness and carbon atom chemical state analysis, it is found that the hindering effect of rough surfaces on probe sliding and the friction reduction effect of amorphous carbon produced during FIB etching are the reasons for the differences in the DMT model applied to the above two machined surfaces.

Aeroengine engine spindle cylindrical roller bearings often fails due to poor working conditions.The failure analysis of the cylindrical roller bearing after service was carried out by using optical microscope, scanning electron microscope, energy spectrometer, Raman spectroscopy, X-ray photoelectron spectroscopy.The results show that according to the failure mechanism and the micro-morphology, the failure modes of cylindrical roller bearings can be divided into eight different failure modes, including lacerations and abrasions, slippage, crater pi, fatigue spalling, vibration pattern, thermal discoloration, inner ring burn, cage silver plating wear.The bearings with the failure modes of slippage, inner ring burn and cage silver plating wear were analyzed.The results show that the O element is found on the bearing surface with slippage failure, indicating that oxidative wear occurs during the process of slip and bruise.The oxides of Fe, FeO and Fe₂O₃ are found on the surface of burned bearing, indicating that the bearing has a higher temperature during burns, the lubricating oil film is damaged, and the roller and inner ring are in contact with each other to cause severe wear.The silver layer on the surface of the cage falls off, and some of the wear area exposes the copper surface, indicating that friction and wear of the cage occurs during service.

Inflow control valve is the core of intelligent well technology.In the complex environment of high temperature and high pressure of oilfield well,the sealing effect of the inflow control valve directly influence the normal operation of valve.According to the working condition of intelligent well,its metal seal structure and flow control valve structure were designed.The finite element model of metal seal structure was established by using the software of ANSYS,and the effect on the sealing performance of sealing structure by the sensitivity parameters was analyzed,including the maximum interference value,the taper of sealing ring contact area,the geometry size of sealing ring inner groove and the downhole pressure.The results show that with the increasing of maximum interference value of the metal seal,the maximum contact stress is re-duced and maximum equivalent stress is increased.Along with the increasing of contact taper,the length of contact surface is increased,while contact pressure and maximum equivalent stress show the downward trend. The inner groove taper of sealing ring has less influence on metal contact,but great influence on equivalent stress of seal ring,and with the increasing of inner groove taper,the equivalent stress is increased greatly. Considering the influence of stress comprehensively,the suitable maximum interference value should be chosen,the contact taper of seal ring should be not too large,and the taper of the inner groove surface should be reduced as much as possible.

Silver lubrication coatings of 8 μm in thickness were prepared on the surface of 718 alloy by magnetron sput-tering.The phases and surface morphology of the coatings were observed by XRD,and the friction and wear properties were investigated experimentally under low temperatures and vacuum conditions.The worn surfaces of silver coatings were meas-ured with SEM-EDS to study the mechanisms of friction and transfer film lubrication in different experiment conditions.It is found that the surface of silver coating has fine grain and high density,there is a good binding properties between the coat-ing and the substrate,and the size of silver coating is about 200 nm.The silver coatings show promising lubrication roles in experiment conditions,the furrow marks are appeared at polishing scratches and the wear mechanism is abrasive and adhe-sive wear at 25℃.The cracks and holes are observed on the local area of polishing scratches coating at 0℃.The silver coatings present the optimal friction and wear properties at -50℃,a minimum friction coefficient and wear loss are deter-mined,and the wear mechanism is slight abrasive wear.The furrow marks are appeared again,and the wear mechanism is peeling and brittle fracture at -100℃.

High temperature will reduce the saturation magnetization strength of the magnetic fluid and cause demagnetization of the permanent magnet, which affects the reliability and stability of the magnetic fluid seal device.In order to explore the heat transfer characteristics of the magnetic fluid seal device, the magnetic fluid seal of large shaft diameter centrifugal compressor was used as the research object, the influence of magnetic fluid friction heat and bearing friction heat on the heat transfer characteristics of magnetic fluid sealing devices was considered simultaneously, and the method of combining finite element numerical calculation with theoretical analysis of magnetic fluid and bearing frictional power consumption was used to study the temperature distribution law of the seal device.The effect of tooth width, seal gap and rotational speed on the maximum steady-state temperature of permanent magnet and magnetic fluid was analyzed, and the required coolant mass flow rate for relevant working conditions was determined.The results show that due to the large shaft diameter and high surface linear velocity of the centrifugal compressor, the viscous frictional heat of the magnetic fluid and the frictional heat of the bearing have a significant effect on the heat transfer characteristics of the seal device.The maximum temperature of the seal device exceeds the ultimate operating temperature of the magnetic fluid and the permanent magnet under the non-cooling condition, and cooling treatment needs to be carried out through convection heat transfer.The maximum steady-state temperature of the permanent magnet and magnetic fluid increases with the increase of tooth width, and decreases with the increase of seal gap.The maximum steady-state temperature of the permanent magnet and magnetic fluid increases with increase of rotational speed, and the higher the speed, the greater the temperature difference between the same speed gradient.

To improve the high temperature friction and wear properties and the stability of friction coefficient of friction materials at high temperature, the formulation of various fiber reinforced phenolic resin based friction materials was optimized by orthogonal test.Through range analysis, the influence of various fibers and content on the performance of friction materials and the wear mechanism of friction materials were discussed.It is shown that hybrid fiber reinforced resin-based friction materials have excellent wear resistance.The ceramic fiber has high hardness and can be evenly distributed in the resin matrix after being dispersed and mixed, which has the greatest impact on the hardness, internal shear strength and friction coefficient of the phenolic resin friction material.The carbon fiber has the characteristics of high temperature resistance, wear resistance and self-lubrication, and its content change has the greatest impact on the wear rate of phenolic resin friction materials.At high temperatures, the carbon fiber has a more significant impact on the wear rate.It is gradually worn during the friction process and distributed to the whole friction surface, which can significantly reduce the material wear rate.The difference in fiber content causes the change of wear mechanism, and the main wear forms of the friction material are abrasive wear, thermal wear, fatigue wear and adhesive wear.

In order to analyze the cause of poor oil-collecting efficiency of intershaft bearings of a certain type of aeroengine,a three-dimensional transient simulation model of oil-gas two-phase flow of bearing oil-collecting structure was established by multi-phase flow numerical calculation method based on VOF model and slip grid technology.The flow field and oil distribution of the oil-collecting structure were calculated,the mechanism of oil movement and the mechanism of oil-collecting loss in the oil-collecting structure were revealed,and the influence of oil flow on oil-collecting efficiency was given.The results show that the counter-flow and vortex ring in the oil-collecting structure are formed in the oil-collecting structure.The main reason for oil collection loss is that the oil droplets formed after the oil column impinges on the cage wall are carried into the slit between the oil dam and the collector by the vortex,and then thrown out to the bearing cavity, resulting in a decrease in oil-collecting efficiency.The oil-collecting efficiency of the oil-collecting structure is independent of the oil flow rate,and depends only on its own structure.The oil-collecting efficiency of the oil-collecting structure studied in this paper is 62%,so the oil-collecting structure must be improved to improve its oil collecting efficiency.

In order to study the current carrying friction and wear properties of impregnated-metal carbon stripmetal impregnated carbon slide with different copper content, the friction and wear properties of three kinds of metal impregnated carbon slide with different copper content (mass fractionof copper is 1.17%, 27.8% and 50.45% respectively) and copper silver alloy contact wire under current carrying conditions were studied on a ring block tester, and the changes of wear surface morphology under different current were compared.The results show that the copper content in the contact strips has a certain effect on the friction and wear performance of the contact strips.The overall abrasion loss of the material with copper mass fraction of 1.17% is relatively small under the condition of 200 A low current, but under the condition of 400 A high current, the high temperature of about 500 ℃ generated by arc heat and Joule heat will lead to the vaporization and block falling of the strip material, which will seriously aggravate the material wear loss.The material with copper mass fraction of 50.45% has the largest abrasion loss under the condition of low current, but the overall operating temperature of the material is lower, that is, the material has better heat dissipation performance.The material with copper mass fraction of 27.8% has the best comprehensive wear performance under the condition of low current and high current.The materials with high copper content show relatively obvious adhesive wear, the higher the copper content of the material, the more obvious the adhesive wear phenomenon.

According to the spin motion characteristics of angular contact ball bearings,and considering the elastohydrodynamic lubrication(EHL) effect,the EHL model of angular contact ball bearings considering spin motion was built.The multi-grid method was used to solve the elastic deformation,and the finite difference method was used to solve the Reynolds equation iteratively to obtain a more accurate numerical solution.The effects of spin motion on bearing oil film pressure,thickness and oil film stiffness were analyzed under different Hertz contact pressure and surface roughness of raceway.The results show that when considering spin motion,with the increase of Hertz contact pressure and spin angular velocity,the oil film thickness is decreased and the oil film pressure is increased,and the oil film pressure area is slender and close to the contact center.With the increases of the surface roughness amplitude of raceway,the film pressure and film thickness fluctuate,and when considering spin motion,the oil film thickness is decreased obviously and the local pressure peak of the oil film is larger.The film stiffness is decreased with the increase of entrainment velocity and lubricating viscosity,and the value of oil film stiffness is increased when considering spin motion.As the spin angle velocity increases,the film stiffness is increased gradually.

In view of the problems of oil pollution and low reliability existing in the oil-lubricated ball bearing of a certain inland airborne pod ECS turbine, airborne aerodynamic foil bearings(AFB) was developed based on pod turbine actual using conditions, and the verification experiments on performance, function vibration, storing-starting storing and starting tests in low and high temperature were conducted.The results show that the cooling capability, rotor floating pressure and speed of turbine with AFB satisfy the operation requirements.The results of function vibration tests, storing and starting tests at -55 ℃ and 70 ℃ are better than performance requirements.The plate foil coatings are in good integrity after overspeed test and over a hundred times start-stop tests, and the start-stop times will be more than 10 000.

To study the influence of residual stress and strain hardening produced by manufacture process on compres-sion and resilience performance of corrugated metal gaskets,a finite element analysis method of compression and resilience process for corrugated metal gaskets was established,which considered the effect of residual stress caused by manufacture process and is based on the experiments.By comparing the analysis results with the experimental results,it is shown that the finite element calculation results are in good agreement with the experimental results,the error of the maximum com-pressive load is 9.08%,the error of compression rate is 9.08% and the error of resilience is 13.90%. The deformation mechanism was analyzed by dividing the deformation process of the corrugated metal gasket into three stages according to the finite element calculation results,and the compression and resilience process of the corrugated metal gasket under the axial load was studied.The result shows that elastic deformation,plastic yielding and elastic recovery stages of corrugated metal gasket occur under the axial load.

Flexible drill pipe has become an important tool for old well reconstruction and production increase and efficiency improvement.In order to ensure the reliability of the spherical seal of flexible drill pipe, numerical simulation and experimental research were carried out on a designed O-ring spherical seal structure.Based on ANSYS finite element analysis software, the effects of sealing clearance, fluid pressure, rotation angle and whether there is a retaining ring on the sealing characteristic parameters such as von Mises stress, contact stress and effective sealing width of O-ring were investigated.The results show that there is a coupling relationship between fluid pressure and sealing clearance, and the higher the fluid pressure, the smaller the sealing clearance is required.Reciprocating rotation will lead to an increase in the maximum von Mises stress and maximum contact stress, and the impact will increase as the seal gap increases.The installation of the retaining ring can effectively prevent the O-ring from squeezing into the gap when the sealing gap and fluid pressure are high.The reliability of the O-ring spherical sealing structure is verified through indoor tests, which provides a theoretical basis and technical support for field applications.

In order to test the performance of thin-wall bearing for harmonic drive reducer,a performance testing rig for thin-wall bearing was designed,which is composed of mechanical part,electrical part,auxiliary part and data-acquisition part.The preliminary test of the testing rig was also carried out.The testing rig can simulate the complex working condition of thin-wall bearing,such as high speed,dynamic load and long-time running.The testing rig can also online detect the pa-rameters of thin-wall bearing,such as rotating speed,load,temperature,vibration and axis center track,which provides reli-able experimental conditions and data for the manufacturing and performance evaluation for thin-wall bearing.

The wear resistance of plastic ring plays an important role in composite seal.In order to select suitable anti-friction materials, this paper studied the micro-friction and wear of QT500 with five kinds of high molecular weight polyethylene (UHMWPE), PTFE+40% copper powder, PTFE+7% carbon fiber, PTFE+7% carbon fiber +5% MoS₂, polyether ether ketone (PEEK).Two materials, PTFE+7% carbon fiber and UHMWPE, were screened out for comparative experiments under different fretting stroke and lubrication conditions.The results show that the average friction coefficient of UHMWPE material increases with the increase of fretting stroke under both dry friction and oil lubrication conditions, and the friction coefficient of PTFE+7% carbon fiber material has little fluctuation with the number of cycles when it reaches a stable state.According to the test results, PTFE+7% carbon fiber is recommended when the fretting stroke is less than or equal to 0.2 mm, and UHMWPE is recommended when the fretting stroke is greater than 0.2 mm.

The effect of ultrasonic viscosity reduction technology on the viscosity and temperature of lubricating oil was studied.The relationship between the viscosity and temperature of lubricating oil under the action of ultrasound and water bath was studied,and the mechanism of ultrasonic viscosity reduction was analyzed.The results show that,under the same temperature point,the effect of ultrasonic viscosity reduction is better than that of water bath viscosity reduction,and the viscosity reduction of ultrasonic viscosity reduction is greater than that of water bath heating.The viscosity reduction rate of lubricating oil is increased first and then tended to be stable with the increasing of ultrasonic action time. The viscosity reduction rate of lubricating oil 10W-50 is 74.1% under the ultrasonic action of 42 kHz and 70 W for about 30 min.The ultrasonic viscosity reduction mechanism of lubricating oil includes ultrasonic cavitation and mechanical effect besides the thermal effect of ultrasound.At the same temperature,the thermal effect of ultrasound on viscosity reduction of high-viscosi-ty oil samples is better than that of low-viscosity oil samples.The mechanical effect of ultrasound could play the role of stir-ring and homogenization,which can promote the homogenization of lubricating oil temperature.

Based on the related literature, the rough surface simulation method was proposed.The micro-rough surface contact finite element model was established in ANSYS by software tools.The model was used to analyze the effect of load on elastoplastic deformation and contact area.The results show that with the increase of positive pressure, the elastic contact deformation occurs for more and more micro-convex peaks on the rough surface, and the number of contact spots (or contact spot group) is gradually increased, and the elastic deformation of the center of the spots quickly reaches the maximum.When the micro-convex peak is deformed, the surrounding area of the spot is also squeezed.At the initial contact, the micro-convex peak with a large profile height is first elastically deformed.As the pressure increases, the stress of the metal material reaches the yield limit.The concentrated area of elastic deformation and plastic deformation of the rough surface is increasing, and the real contact area is increasing.The increase of the number of contact areas and the increase of the contact area can lead to an increase in the actual contact area on the contact surface.As the pressure increases, the increase in the true contact area is not due to an increase in the number of contact regions, but an increase in the area of the microscopic contact regions.

Taking the gas radial hybrid bearing as research object,considering the turbulent lubrication,the improved compressible Reynolds equation with turbulence factor was solved by the finite difference method.The pressure distribution of the turbulently lubricated gas hybrid journal bearings was calculated.The basic parameters of bearing capacity,static stiffness,cross stiffness,principal stiffness,cross damping and principal damping were obtained to characterize the static and dynamic characteristics of gas hybrid journal bearings.The influences of structural parameters such as eccentricity, groove depth,groove number and length-to-diameter ratio,and the conditions of journal speed and air supply pressure on the dynamic and static performance of the bearing were analyzed.The results show that the static characteristics of continuous slot-restriction turbulent lubrication static gas hybrid journal bearings are better than those of discontinuous slot-restrictions.The bearing capacity is increased with the increase of eccentricity and length-to-diameter ratio,and decreased with the increase of groove length and groove depth,while the groove number has little effect on the bearing capacity.The static stiffness of bearing is first increased and then decreased with the increase of eccentricity,and it is increased with the in crease of length-to-diameter ratio,groove depth and groove number,and decreased with the increase of groove length.The large eccentricity and the higher rotational speed can improve bearing capacity and static stiffness of the bearing.With the increase of eccentricity,the cross stiffness is increased gradually,the main stiffness is increased first and then decreased, while the cross damping and main damping are increased.

The oil specifications in China's automotive market are mainly based on API specifications and D1 specification in China, so the evaluation of the compatibility between automotive engine seals and oil products should use ASTM D7216-22.Therefore, the evaluation method of the compatibility of lubricating oil and rubber by using ASTM D7216-22 was proposed, and the effects of common base oil, ashless dispersant and anti-oxidation and anti-corrosion agent in engine oil on rubber compatibility were evaluated.The results show that Class I and Class III base oils have an impact on the shrinkage of nitrile rubber (NBR) and polyacrylate rubber (ACM), and on the expansion of fluororubber (FKM), silicone rubber (VMQ) and polyethylene acrylate rubber (MAC), but both meet the requirements of D1-2019 specification in China for rubber compatibility.The oil-rubber compatibility of CK4 15W-40 blended with polyisobutylene succinimide ashless dispersant RHY161(macromolecule conventional type) and RHY162(macromolecule soot type) meets the requirements of D1 specification.The dibutyl dithiocarbamate with purity of 99.86% has good compatibility with five kinds of rubber sheets studied.The oil products blended with Class I base oil (MVI500), Class III base oil (VHVI6), dispersant RHY162, dibutyl dithiocarbamate (antioxidant) and other additives show good rubber compatibility.

A new oil-air mixer for oil-air lubrication system was designed, and its working principle, structure design, flow pattern of the oil-air mixer and oil supply at the end of the oil and air pipe were studied.The fluid domain model including the spiral tube was established, and the whole fluid domain was divided into initial region of lubricating oil, oil-air mixing region, spiral tube region and end straight tube region.A transient model was established by using Fluent software to analyze the formation mechanism of oil-air two-phase flow in the case of a single oil injection, and a new theoretical model of oil-air mixing was proposed.The results show that the integral type oil-air mixer has a compact structure and can realize accurate and quantitative oil and air supply.The high-speed compressed air can divide the lubricating oil into two parts.One part of the lubricating oil is attached to the pipe wall and flows forward at a lower speed, and the other part flows forward at the center of the pipe with the air at a higher speed, so that the lubricating oil can be evenly distributed on the pipe wall of the whole pipe in a short time.

In order to investigate the effect of rotational speed on rolling contact fatigue and wear properties of wheel steel under water lubrication,the spalling life,friction coefficient and wear rate of wheel steel samples at different rotational speeds were measured by rolling-sliding test.Based on the observation of wear morphology and crack growth morphology,the influence factors of spalling life,friction and wear at different rotational speeds were compared and analyzed.The results show that the oxidation degree of wheel material as well as the friction coefficient are gradually increased with the increase of rotational speed.When the rotational speed is increased from 250 r/min to 500 r/min,the friction coefficient is increased slightly,and the wear rate is decreased due to the increase of strain rate.When the rotational speed is increased from 500 r/min to 1 000 r/min,the wear rate is increased because of the sharp increase of friction coefficient.With the increase of rotational speed,the thickness of plastic flow layer,crack propagation angle,crack branching depth and maximum crack propagation depth show a decreasing trend.The increase of friction coefficient caused by the increase of rotational speed not only shortens the crack initiation life,but also reduces crack branching depth,which leads to the decrease of rolling contact fatigue life with the increase of rotational speeds.

The overall design scheme of the large journal bearing test-bed was presented,and the designed test-bed in-cluded five systems,mechanical structure,drive system,lubrication system,control system and acquisition system.Finite el-ement simulation was used to analyze the rationality of the design of the test-bed.The technologies of digital modeling,sim-ulation software,electrical control,sensors and signal processing were used to ensure the stability and reliability of the de-veloped test-bed.Through analyzing the corresponding test data,including rotational speed,temperature,pressure,displace-ment and vibration acceleration,the effectiveness of the test-bed was verified,indicating that the developed test-bed can meet the normal and stable operation requirements of large dynamic pressure sliding bearing.

The application of genetic algorithm (GA) optimized support vector machine (SVM) in aircraft engine wear fault diagnosis was researched.The implementation process of the algorithm of GA optimized SVM was discussed,the key parameters were analyzed,and the penalty factor and kernel function parameters in SVM was optimized by improved GA. GA optimized SVM was used to analyze the abrasive particles in the aero-engine oil,and the diagnostic accuracy of GA optimized SVM,BP neural network and RBF neural network were compared from the aspects of diagnostic precision,com-putational time and anti-noise ability.The results show that GA optimized SVM can effectively diagnose the wear fault of aero-engine.The diagnostic accuracy of the GA optimized SVM is obviously higher than that of RBF and BP neural network,and its diagnostic accuracy is still higher than that of RBF and BP under noisy conditions.However,its training time is longer due to its structure and training method.