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Governing Body: China Association for Science

Organizer: Chinese Mechanical Engineering Society Guangzhou Mechanical Engineering Research Institute Co.,Ltd

Chief Editor: HE Shizhong

Address: No2,Xinrui Road,Huangpu,Guangzhou

Postcode: 510700

Telephone: 02032385313

Email: rhymf@gmeri.com



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    Volume 48,2023 Issue 8
    • Point Contact Mixed Lubrication Analysis for Modified Gear Based on the Static Model
      ZHOU Changjiang; LV Yunyan; ZHENG Ming; HOU Shengwen

      Abstract:Point contact mixed lubrication model for crowed modified gear was established based on the average Reynolds equation and Zhao-Maietta-Chang(ZMC)elastic-plastic contact model.Lubrication characteristic parameters were calculated by progressive mesh densification method.The correctness of proposed model was verified by comparing with the simulation results of steady-state point contact mixed lubrication model.The lubrication characteristics of engaging-in,pitch and engaging-out point were investigated.Effects of gear geometrical parameters,operating parameters on crowed modified tooth surface lubrication characteristics were analyzed.The results show that film pressure,contact pressure and total pressure are the largest at engaging-in point,and the minimum at engaging-out point.Nominal film thickness is the largest at engaging-out point and the smallest at engaging-in point.With the increase of modulus,pressure angle and rotating speed,the film pressure,asperity contact pressure and total pressure decrease,and the oil film thickness increases.As the power and crowned modification increase,the oil film pressure,asperity contact pressure and total pressure increase,and the oil film thickness decreases.Therefore,the rough tooth surface lubrication state can be improved by increasing modulus,pressure angle and speed,and reducing power and crowned modification.

    • Study on Thermo-elasto-hydrodynamic Lubrication Characteristics of Mechanical Seal for Ultra High-speed Turbopump
      MENG Xiangkai; QU Xingyuan; ZHAO Wenjing; LIANG Yangyang; PENG Xudong

      Abstract:Aimed at the ultra high-speed turbopump mechanical seal,in view of the unclear problems on thermo-elasto-hydrodynamic lubrication characteristics and deformation behavior of sealing interface due to the multi-field coupling effect under the ultra high-speed operating conditions,a mathematical model was proposed on the seal rings(rotor and stator) and lubrication liquid film.The end face lubrication characteristics and deformation behavior were investigated at the different seal pressures and rotational speeds.The sealing performance laws with the operating conditions were analyzed.Numerical results show that the convergent film gap along the leakage direction is generated in the sealing interface at the ultra high-speed conditions due to the thermoelastic deformation of the seal rotator.With the increase of seal pressures,the coning angle of the convergent film gap decreases,the maximum film thickness and leakage rate increase,the temperature rise on the end face significantly decreases.With the increase in the rotational speed,the coning angle of the convergent film gap is enlarged,the temperature rises and leakage rate increases,while the frictional torque decreases.The proposed fluid-solid thermal and mechanical coupling model can be applied for the optimization design of ultra high-speed mechanical seal for turbopump.

    • Coupling Analysis of Deformation and Lubrication of Connecting Rod Small End Bearing under Low Speed and Heavy Load Conditions
      YAN Shanheng; JI Bingwei; LI Jianfeng; SU Yu; LIU Ruichao; MENG Xianghui

      Abstract:Connecting rod small end bearing is the key friction pair in internal combustion engines.It is prone to deformation and seizure failure under low speed and heavy load conditions,which is an important reason affecting the reliability of heavy-duty truck engines.To reveal the performance of connecting rod small end bearings under low speed and heavy load conditions,the tribological dynamic model of piston-connecting rod-crankshaft was established to analyze the connecting rod small end bearing of a 6-cylinder diesel engine.The torque of the connecting rod small end bearing and the piston pin hole bearing on the piston pin was considered in the model.Then the transient elastic deformation of the small end bearing was coupled into the model,and the influence of bearing deformation on the tribological performance prediction results was analyzed.The results show that under the low speed and heavy load conditions,ignoring the bearing deformation may make the predicted rotation direction of the piston pin opposite.During the suction stroke,the small end bearing is severely deformed and resulting in lubrication deterioration between the bearing and the piston pin.

    • Tribological Properties of WC-10Co-MoS2@Ni Self-lubricating Cemented Carbide and Titanium Alloy
      HE Nairu; ZHI Binbin; JIA Junhong; YANG Jie; CHEN Wei

      Abstract:In order to investigate the tribological performance of WC-10Co-MoS2@Ni self-lubricating cemented carbide and TC4 titanium alloy,cemented carbide specimens with different contents of MoS2@Ni were prepared by hot press sintering,the microstructure and mechanical properties of self-lubricating cemented carbide were analyzed by the scanning electron microscopy,3D profilometer and Vickers hardness tester,etc.The tribological properties of cemented carbide and titanium alloy under dry friction,cutting fluid and cryogenic conditions were studied by reciprocating friction tester.The results show that with the increase of MoS2@Ni content in the cemented carbide,the surface pores decrease and the mechanical properties slowly decline.The friction coefficient decreases with the increase of MoS2@Ni content under dry friction,cutting fluid and cryogenic conditions.Due to the adhesion of titanium alloy,the lubrication effect of MoS2 is hindered during dry friction,and the main wear forms are adhesion and oxidation.In the cutting fluid environment,the abrasive wear and adhesive wear are dominant.In cryogenic environments,oxidation and adhesion are reduced,and the main wear form is abrasive wear,accompanied by delamination.

    • Analysis of Transient Characteristics of Gas Bearing-Rotor System under Fluid-structure Interaction and Supply Pressure Reduction
      ZHENG Shaolin; MA Wenqi; SUN Peigeng; DING Yi

      Abstract:To research the influence of supply pressure fluctuation on the transient characteristics of gas bearing-rotor system,it is taken that the numerical simulation of fluid-structure interaction combine with experiment validation to study the rule of the rotor lower end offset and axis trajectory under no-load and loading conditions with different rotational speeds and the supply pressure reduction.The results show that supply pressure reduction on a slope causes the phenomenon that the distance that rotor lower end deviates from the ideal trajectory varies in a wavy manner,and the axis track repeatability of power frequency becomes worse.Before and after the supply pressure reduction,the offset difference increases with the increment of loading force or speed and during loading,it is significantly higher than that of the no-load state.

    • Influence of Lubricating Oil Viscosity on Temperature Field Distribution of Full Ceramic Ball Bearing Cavity
      SUN Jian; YANG Jiaxing; YAO Jinmei; WANG Zhishuang; TIAN Junxing; XIA Zhongxian; LI Songhua; WU Yuhou

      Abstract:In order to reveal the distribution and change of internal temperature field of full ceramic ball bearing under the condition of oil lubrication,improve the operation performance and service life of full ceramic ball bearing,taking 7007C silicon nitriding full ceramic angular contact ball bearing as an example,the internal temperature field and lubricating oil distribution of full ceramic ball bearing under different working conditions and viscosity conditions were simulated and analyzed by using simulation software.The dynamic characteristics tests of the full ceramic ball bearing were carried out on the bearing life testing machine under the same conditions to study the temperature rise characteristics of the full ceramic ball bearing under the condition of oil lubrication.The results show that with the increase of the speed of the bearing,the temperature of the cavity increases and the volume fraction of lubricating oil decreases.By changing the lubricating oil with different viscosities,it is found that the optimal viscosity value makes the temperature of the full ceramic ball bearing chamber reach the minimum value,and the bearing has the best service performance.The research results provide a technical reference for the selection of optimal lubricating oil for full ceramic ball bearings in practical production.

    • Numerical Study on Fatigue Life of Brush Seal Based on Miner’s Linear Cumulative Damage Theory
      LIU Wei; SUN Dan; ZHAO Huan; MU Wei; MA Ting; WEN Shuaifang

      Abstract: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.

    • Analysis of the Lubrication Performance of Low-Speed Sliding Bearing Considering the Effect of Viscosity-Temperature and Cavitation
      SHENG Minghui; HUANG Qianwen; ZHAO Zeyu

      Abstract:In the case of heavy load and low speed,the viscosity of lubricating oil drops due to temperature rise and the cavitation induced by low local pressure seriously affect the lubrication performance such as film pressure and load-carrying capacity.To explore the lubrication performance of low-speed sliding bearing considering the effect of viscosity-temperature and cavitation,a UDF program for the viscosity-temperature equation was formed,the finite element model was established in Fluent and the cavitation effect of Mixture multiphase flow was considered.The lubrication performance of the bearing under different operating conditions was systematically calculated.The effects of eccentricity,shaft speed and viscosity-temperature effect were analyzed and compared.The results show that the maximal pressure,temperature,load-carrying capacity and volume fraction of cavities in the cavity region considering viscous-temperature effect are less than those with constant viscosity.And the increase in shaft speed and eccentricity leads to an enlargement in maximal volume fraction of cavity region.

    • Numerical Simulation of the Steady Characteristics for Aerostatic Dry Gas Seal with Slit Restrictor
      REN Junjie; XU Hengjie; SONG Pengyun

      Abstract:To optimize the opening ability of gas film of dry gas seal,the aerostatic dry gas seal with slit restrictor was designed by combining the slit restrictor with aerostatic dry gas seal.The influence of the structural parameters and arrangement of slit restrictors on dry gas sealing performance was investigated by Fluent software.The results show that the slit throttling aerostatic dry gas seal has a higher opening force than the classic orifice aerostatic dry gas seal on the premise of same throttling area.The influence of slit circumference-radial length ratio on the opening force is independent of equalizing groove circumference-radial length ratio,there is an optimal circumference ratio that maximizes the opening force of the gas film.Under the premise of a certain radial width,the more abundant the plane space of the equalizing groove,the wider the range of the gas film high-pressure zone within the sealing gap,and the better the pressure distribution effect.The opening force grows as the radial and circumferential column number of slit increases.Compared to circumferential continuous slit arrangement,the discontinuous slit arrangement results in higher opening force.

    • Experimental Study on Effect of Repeating Impact on Grease Film Formation
      LV Zhendong; XIE Weidong; HAN Yiming; ZHANG Mingyu; WANG Jing

      Abstract:Impact phenomenon exists widely in mechanical components such as rolling element bearings and industrial chains,which can cause impact wear in the worst case.To investigate the effect of impact load on film formation under grease lubrication conditions,impact tests were carried out to study the grease film thickness evolution under lithium grease lubrication on a point contact optical interferometric test rig.During the experiment,the initial distance between the steel ball and the glass disk is set to zero and the load repeatedly varies in the form of a triangle wave.The results indicate that during the first impact period,there exists big lump of thickener fibers in the contact area,which results in an entrapment of the grease film.With the increase of the impact periods,the big lump thickener disappears,the film thickness is gradually reduced and lubrication state turns to be thin film lubrication.At last,surface damage occurs in the surfaces of both the steel ball and the glass disk.In each impact period,either central or minimum film thickness mainly exhibits a constant value.The central film thickness decreases with the increase of the impact periods.The minimum film thickness varies only slightly in the first 100 periods and gradually decreases to zero.

    • Study of Heat Transfer Characteristics of Magnetic Fluid Seal in Large Shaft Diameter Centrifugal Compressor
      WU Chaojun; ZHU Weibing; YAN Zhaoqiang; ZHANG Lin; ZHOU Shaoyu; WANG Heshun

      Abstract: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.

    • Research on Topological Grinding of Array Traveling Wave Surface with Structured Grinding Wheel
      WANG Wei; LI Xingshan; LYU Yushan; SUN Yi; LI Xinyu

      Abstract:The traveling wave surface is an important surface in the structured surface,which has excellent reduction friction performance.In order to grind the traveling wave dimple surface with array pattern,a method of planar topological mapping for grinding structured surfaces was proposed.Based on the theory of point set topology,the topological feature of the traveling wave unit and arrangement was analyzed,and the feature parameters were extracted.Combined with the generating mechanism of dimple surface during grinding,the topological space mapping relationship between the grinding wheel and the workpiece during grinding was established,and the structured abrasive cluster grinding wheel was designed.MATLAB software was used to simulate and analyze the grinding process of the traveling wave surface,the influence law of the relevant parameters was obtained,and the grinding of the structured surface was realized by grinding experiments.The results show that the structured grinding wheel designed based on the topology theory can realize the grinding of the dimple surface with an array traveling wave structure,and the topological properties of the traveling wave dimple surface remain unchanged after grinding.The topological feature parameters change correspondingly with the change of grinding parameters.

    • Study of Damage Processes in PTFE-filled Copper Mesh Composites
      PENG Shuaihao; LIU Jian; LI Jialun; DU Sanming; ZHANG Yongzhen

      Abstract:In order to investigate the frictional wear performance and fine damage mechanism of polytetrafluoroethylene (PTFE)-filled copper mesh composites,full-life wear tests were conducted using a reciprocating friction and wear tester,and the material friction surface and wear chips were characterized by scanning electron microscopy,optical microscopy and three-dimensional morphometry.The results show that the full-life (202 h) wear process of PTFE-filled copper mesh composites is mainly divided into three stages:wear-in,stable wear and severe wear.In the first 20 h wear stage,the friction coefficient gradually increases,and a large amount of PTFE is extruded under high load,resulting in a large wear rate,while a transfer film is generated,and the failure is mainly in the form of spalling under mechanical shear.In the 20 h to 190 h stable wear stage,the friction coefficient first decreases and then increases and has a large fluctation,and the wear rate tends to be stable.The wear mechanism is mainly abrasive wear,and the abrasive chips change from lamellar to powder.The roughness of the friction surface gradually decreases and the wear is not uniform.Through microscopic characterization,it is found that the copper mesh weave junction and the convex peak are seriously worn.Through force analysis,it is found that the copper mesh weave junction and the convex peak have stress concentration phenomenon,which corresponds to the area of serious wear in the test,the test and numerical simulation correlate.In the 190 h to 202 h severe wear stage,the friction coefficient and wear amount further increase,and the wear resistance and lubrication performance of the material decrease sharply,and finally the material is worn through and failed.

    • Research on Optimization of Layout Parameters for High Speed Spur Gear Lubrication Nozzle
      FAN Jingyuan; HU Yumei; LUO Wenjun; YANG Duan

      Abstract:In order to explore the optimal location of lubrication nozzle for spur gear with high linear speed,the computational fluid dynamics transient simulation method was used to conduct a single-phase flow gas field simulation analysis of the gear meshing at different linear speeds.The pressure distribution and airflow motion law around the meshing area and tooth profile of the gear pair was revealed.According to the law of airflow motion,a method for determining location of lubrication nozzle was proposed,and the effectiveness of the method was verified by the simulation analysis of two-phase flow transient oil jet lubrication.The results show that with the increase of gear linear speed,the pressure difference in the gear meshing area has a linear increase trend,the air barrier effect is more obvious,the radiation range is wider.The weakest trace formed by the “meeting” of the two swirling airflow gradually slopes towards the pinion.The optimal location of lubrication nozzle can be determined by whether the airflow velocity streamline of the nozzle to be selected can enter the gear meshing area.The lubricating nozzle is preferably arranged in the area of the gear meshing side and the end face angle is 0°.When the jet direction of the nozzle is consistent with the flow line of the optimal injection point,the gear lubrication effect is well.

    • Effect of Surface Roughness on Leakage Rate of Metal Flat Pad
      FU Lei; LEI Xuelin; ZHANG Lanzhu

      Abstract:To investigate the effect of surface morphology of metal gaskets on leakage rate,the local scanning of Cu,Al and 316L metal gaskets with different surface roughness was carried out by 3D morphometer,and the real microscopic contact model of flange gaskets was constructed.The statics and computational fluid dynamics analysis was carried out to investigate the influence of surface roughness and contact pressure on the leakage rate under different medium pressure by setting different boundary conditions in the fluid domain.The simulation results show that the metal gaskets of three materials exhibit a trend of greater surface roughness leading to greater leakage rate.Among them,the leakage rate of Al gasket is the most sensitive to surface roughness,while the leakage rate of 316L gasket is the least affected by surface roughness.When the surface roughness is constant,the greater the applied contact pressure,the lower the leakage rate.However,when the contact pressure reaches a certain value,the effect of increasing the contact pressure on reducing the leakage rate will become smaller and smaller.

    • Analysis of the Wear Effect of End-face Friction Pair on Movable Scroll Plate of Scroll Compressor under Multiple Speeds
      CHEN Xuehui; ZHANG Yuxi; DING Xiaolong; WANG Yu; HUANG Lei; LIU Wei

      Abstract:In view of the problem of gas leakage caused by excessive surface wear on the end-face of the movable scroll plate during the working process of the scroll compressor,taking a certain type of scroll compressor as the research object,the force analysis model of the end-face friction pair of the movable scroll plate was established,and the change of the load on the end-face of the movable scroll plate during the operation was analyzed.The dynamic contact stress change cloud diagram of the end-face friction pair of the movable scroll plate at different rotational speeds under typical working conditions was obtained by finite element numerical simulation.The wear coefficient of QT400,a commonly used material for the movable scroll plate,was measured on the end-face wear testing machine.The wear depth value of QT400 at different speeds was calculated by modifying the Archard wear model and combining finite element wear simulation,and an experimental plan was designed to analyze the wear mechanism of QT400 according to the material PV value principle.The results show that the faster the orbiting scroll rotates,the greater the wear depth value in the area with larger contact stress value.The wear mechanism of QT400 is mainly fatigue wear,which is continuously transformed into adhesive wear with the increase of load,accompanied by a small amount of abrasive wear.This research provides a good reference for the improvement of the scroll compressor orbiting scroll structure.

    • Performance Analysis and Parameter Optimization of Splitter Packer Cup
      YI Xianzhong; XING Hongxian; ZHANG Hua; WAN Jifang; WANG Lijun; HE Yuxian; GE Xianchi; FAN Xiaomei

      Abstract:The splitter packer is the most important tool in the sand scraping and flushing technology,which directly affects the efficiency of sand flushing and well washing.In view of the problem that the cups of the splitter packer is prone to tearing and wear,the study on the mechanical characteristics of the cups was carried out.Using a combination of finite element method and experiments,the effects of the outer and bottom diameters of the push cylinder,the horizontal distance and inner and outer diameters of the cup on the sealing performance of the splitter packer were studied,and the structural parameters of the cup assembly were optimized.The results show that the main factors affecting the cup seal are the outer diameter,inner diameter,horizontal distance of the cup,bottom diameter and outer diameter of the push cylinder in order.The optimal structural parameters are 192 mm outer diameter of the push cylinder,188 mm bottom diameter,185 mm inner diameter of the cup,216 mm outer diameter and 46 mm horizontal distance.The test results show that the optimized cup meets the using requirements of 244.5 mm casing,and the static seal pressure of 20 MPa and dynamic seal pressure of 10 MPa.The overall performance is improved and the accuracy of finite element simulation analysis is verified.The results of the study can provide reference for the overall performance improvement and application of the splitter packer.

    • Research on Nano-tribology of Diamond Surface Based on DMT Model
      YANG Xin; YANG Ning

      Abstract: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.

    • Comparative Study on Friction and Wear of Cylinder Liner with Different Piston Ring Coatings under the Condition of Lack of Lubricating Oil
      MA Fei; GUO Wuming; WANG Chuang; ZENG Xiaoxiao; GUO Lingyan; ZHOU Feng; WANG Yongxin

      Abstract:In order to study the tribological properties of different piston ring coatings and cylinder liner at different temperatures under the condition of lack of lubricating oil,five commercial piston ring coatings were selected,and the cross-sectional morphologies of different coatings were observed by scanning electron microscope.Using a reciprocating friction and wear tester, the friction and wear tests were carried out under the condition of lack of lubricating oil at normal temperature,200℃ and 350℃,respectively.The results show that the CrN-based coating and the CKS coating are mainly adhesive wear,which has a large wear on the cylinder liner,and the tribological properties are stable at different temperatures.The DLC-containing coatings are mainly abrasive wear,which have small friction coefficient at room temperature,but have significant differences at high temperatures.The comprehensive performance of CDC+DLC coating is the best.

    • Friction and Wear Behavior of Graphene Oxide and Nano-SiO2 Reinforced PTFE Composites
      PENG Yichao; GONG Jun; GAO Gui; WANG Honggang; LU Guoku

      Abstract:In order to study the effect of the interaction between nano-fillers with layered and spherical structures on the friction and wear behavior of polytetrafluoroethylene composites,nano-silica(nano-SiO2) and graphene oxide(GO) filled polytetrafluoroethylene(PTFE)composites were prepared by freeze-drying-ultrasonic blending-cold pressing-hot sintering method.The tribological properties of the nano-SiO2 and GO compound-modified PTFE composites were tested under dry friction conditions using the LSM-2R reciprocating friction and wear tester,and the transfer film morphology,elements distribution and three-dimensional morphology on the wear track were characterized by MicroXAM-800 non-contact three-dimensional surface profiler,scanning electron microscope(SEM) and energy spectrometer(EDS).The friction reduction mechanism of nano-SiO2 and GO was also revealed from the microscopic level.The results show that the friction and wear properties of PTFE composites can be improved by filling nano-SiO2 and GO separately,and GO is significantly better than nano-SiO2 in improving the wear resistance of PTFE at a low additive amount.There is a synergistic effect between GO and nano-SiO2 when composite filling,which further improves the tribological properties of the composite material compared to a single filling.Compared to pure PTFE,the wear rate of 3%nano-SiO2/0.5%GO/PTFE composite material is reduced by 60.36%.The mechanism analysis shows that the synergistic effect and the formation of uniform continuous transfer film are the main reasons for the excellent performance of nano-SiO2 and GO reinforced PTFE composites.

    • Study on the Sustainable Design of Rotary Shaft Lip Seal
      ZHANG Fuying; WU Jihao; LIU Yuangang; YANG Pengwei

      Abstract:The sustainable standard of rotary shaft lip seal was investigated and determined.According to the specific structure and production process of rotary shaft lip seal,by using a combination of quantitative and qualitative methods,the environmental,social and economic sustainable indexes such as energy consumption,carbon emission,per unit production time,cost at each stage of rotary shaft lip seal life cycle were calculated and analyzed based on a life-cycle assessment(LCA) method.The sustainable improvement strategy of rotary shaft lip seal was determined,which are that environmental sustainability focuses on reducing energy consumption during the use stage,social sustainability focuses on innovation in production processes,and economic sustainability focuses on extending lifespan design.The sustainable design of rotary shaft lip seal was implemented from two aspects of prolonging service life and optimizing the friction state during the operation.The influences such as macro section shape and size,the roughness and surface texture of microscopic appearance,seal lip material on the sustainable performance of rotary shaft lip seal were analyzed.The results show that thin lip and surface micro texture as well as wear-resistant materials play positive roles in reducing energy consumption and carbon emissions of rotary shaft lip seal.The research results are of great significance for improving the sustainability of rotary shaft lip seal.

    • Hysteresis Loops Modeling of Bolted Joint Considering Impact Force
      GONG Mingguang; LIU Wenguang; YANG Yang; ZHANG Gongping; LI Ji

      Abstract:Due to the impact load,the bolted joint structure shows obvious nonlinear hysteresis phenomenon,which will affect the overall connectivity of the structure.Traditional dynamic research only considers the micro/macro slippage of the joint,and rarely studies the pinning force caused by the collision between the bolt rod and the hole wall.Based on the BRAKE’s RIPP model,a new“pinning contact force” model considering energy loss was proposed,so as to realize the modeling of the overall hysteresis loops of the three stages of tangential force.The influence of preload and friction coefficient on hysteresis loop was analyzed based on this model.The proposed model is in good agreement with existing research results,verifying the validity of the overall hysteresis model.The result shows that the increase in friction and preload will expand the area enclosed by the hysteresis loop,leading to a gradual increase in energy loss caused by tangential slip within a single cycle.Compared to the friction coefficient,the preload has a more significant impact on the hysteresis characteristics of the micro slip stage.The proposed model can reflect the influence of “pinning” contact process on hysteresis characteristics,help to better reveal the response characteristics and nonlinear behavior of bolted joints under impact load,and provide help for the subsequent dynamic modeling of bolted joints.

    • Influence Mechanism of Flow Field on Micro-Vibration of Aerostatic Bearing
      LI Yifei

      Abstract:In order to investigate the influence factor of the aerostatic bearing micro-vibration,the numerical simulation was conducted for the aerostatic bearing clearance flow field,and the relationship between the Reynolds number and the micro-vibration was discussed.Firstly,the transonic flow field structure of the aerostatic bearing clearance was studied under several sets of air supply pressure.Then the influence of Reynolds number on the vortex flow-induced excitation was discussed,and the structure-fluid coupling method was further used to investigate the influence of Reynolds number on the micro-vibration.Finally,the approximate model was established to study the influences of the air pocket volume,orifice diameter,and air film thickness on the maximum Reynolds number in the flow field,i.e.the influence of bearing parameters on vortex flow-induced excitation.The results indicate that the maximum Reynolds number of the flow field can be used to represent the strength of the vortex-induced excitation.However,the micro-vibration also depends on the dynamic performances of the air film-floating facility system.With smaller air pocket volume,the vortex excitation is weakened,and it means that the stability of the aerostatic bearing is improved.The flow mechanism analysis can provide a reference for the aerostatic bearing design to reduce the micro-vibration.

    • Influence Analysis of Aircraft Pipeline Sealing Performance under Vibration Environment
      CUN Wenyuan; WANG Boya; QIAN Jin; ZHANG Jieyi; LI Lisen; CHEN Guo

      Abstract:To solve the problem of sealing performance in aircraft pipeline under actual working conditions,a multi-body contact finite element model of aircraft pipeline connection was established based on the structural characteristics of the expanded hydraulic pipeline connector and considering the multiple contact relationships of the connector contact pairs.Three main sealing criteria were proposed to ensure the basic sealing performance of the expanded pipeline connector,including the sealing closed loop,effective sealing area,and effective sealing pressure ratio.Using finite element simulation software ANSYS/Workbench,the variation process of pipeline sealing performance under vibration working conditions and the influence of vibration load location and amplitude on pipeline sealing performance were analyzed.The results show that the outer nut of the pipeline connector will gradually become loose under vibration conditions,leading to the degradation of pipeline sealing performance.As the vibration period increases,the loosening angle of the outer nut increases.When the amplitude of vibration load is the same,the closer the vibration load location is to the threaded connection pair,the faster the sealing performance of the pipeline connection decreases.When the vibration load location is the same,the larger the amplitude of vibration load,the faster the degradation rate of the pipeline sealing performance.To reduce the impact of vibration on pipeline sealing performance,the pipeline connector should be kept away from vibration excitation sources as far as possible,and the amplitude of vibration load should be reduced.In practical engineering applications,the deterioration process of pipeline connection sealing performance is generally mitigated by blowing fuses.

    • Research Progress of Turbulence Effect on Dry Gas Sealing Performance
      DING Xuexing; JIANG Haitao; XU Jie; YAN Ruqi; DING Junhua

      Abstract: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.

    • Development of Polyurea Grease(I)——Composition,Structure and Properties
      LI Xiaohui; HU Yuanhai; YANG Lulu; GAO Fan; WANG Wenzhen; YANG Yi; YAO Wenzhao

      Abstract: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.

    • Design and Performance Analysis of Hydrostatic Bearings for Turbopump
      DU Jialei; HU Xiaorui; LIANG Guozhu; WANG Yixuan

      Abstract:The design and application of hydrostatic bearings in liquid rocket engine turbopumps was concerned.The design method of hydrostatic bearings for a turbopump rotor,which is originally designed supported by rolling bearings,was proposed.The design schemes of hydrostatic bearings with maximized stiffness were obtained using the particle swarm optimization algorithm.The performance of the hydrostatic bearings and the rotor dynamic characteristics of the rotor-bearing system were analyzed.The results show that the load capacity and stiffness of the optimized hydrostatic bearings can meet the requirements of the turbopump rotor.However,the total mass flow rate of the bearings is up to 21% of the pump flow rate,which will significantly lower the overall efficiency of the turbopump.The stability of the rotor-bearing system can not meet the requirements only by replacing the rolling bearings with hydrostatic bearings without other improvements.In the design of hydrostatic bearing rotor system,the bearing should be placed at the position where the rotor has larger displacement,so as to give full play to its damping effect.

    • Lubricating Oil Monitoring Data Analysis and Threshold Values Determination of Main Bearing of Shield Machine
      CHEN Wenyuan

      Abstract:Lubricating oil monitoring is one of the important methods of condition monitoring and fault diagnosis of shield machine main bearings.However,the current diagnostic threshold values are mostly empirical data,and there is a lack of systematic analysis of a large amount of lubricating oil monitoring data.In order to establish a reasonable threshold for oil monitoring and fault diagnosis of shield machine main bearing,the oil monitoring scheme for main bearing of shield machine was designed,the sampling method,sampling period and sampling period under special circumstances for oil monitoring of shield machine main bearing were proposed,and a large amount of oil monitoring data were obtained.The benchmark value,warning value and critical value of the monitoring items were calculated by statistical method,which were consistent with the current monitoring threshold values established through empirical data,and the rationality of the current monitoring threshold values were proved theoretically.The regression analysis was performed on the lubricating oil monitoring data by linear regression method to explore the relationship between lubricating oil monitoring data and excavation mileage,so the lubricating oil monitoring threshold values of the main bearings in each stage of the life cycle were more reasonably determined,which complemented the threshold values calculated by the statistical methods.Through correlation analysis,the internal relationship of the data changes in the lubricating oil monitoring was identified,and it was pointed out that the water content in the lubricating oil was the primary control factor in the condition monitoring of shield machine main bearings.

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