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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

CN:CN44-1260/TH

ISSN:ISSN0254-0150

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    Volume 49,2024 Issue 2
    • Study on Thermal Elastohydrodynamic Lubrication of Planetary Gears in Circulating Water Pump of Nuclear Power Plant
      DONG Qingbing; WANG Hanming; FENG Chengcheng; WEI Jing; HE Dong; YANG Haishi

      Abstract:The good lubrication performance of the nuclear power gearbox is an important guarantee for the reliable operation of the nuclear power circulating pump,and the fully considering the influence of tooth surface morphology and tooth profile modification on internal and external meshing gear pairs is a prerequisite for accurately evaluating lubrication characteristics.The thermal elastohydrodynamic lubrication model of the helical gears of the planetary transmission system in the nuclear power circulating pump was established under typical working conditions.The meshing state of the helical gear pair was geometrically equivalent to the contact problem of a conical roller,and by considering the contact deformation and tooth profile bias of the helical gears,the oil film thickness,lubrication pressure,friction stress,and flash temperature at different positions in the contact area of internal and external meshing gear pairs were calculated.Considering the tooth surface running-in effect,the moving average filtering method was used to smooth the initial morphology without running-in,and the influence of the tooth surface topography on the lubrication behavior was analyzed.The tooth profile was modified to improve the lubrication characteristics.The results show that surface roughness and tooth profile modification have significant influences on lubrication performance,and the rough morphology of the tooth surface can cause a decrease in oil film thickness,so as to affect the lubrication characteristics and reduce the load-bearing capacity of the oil film.By modifying the tooth profile,the geometric transition at the gear meshing boundary can be improved,the stress concentration and surface temperature in this area can be reduced,and the lubrication state at the end of the meshing line can be significantly improved.

    • Study on Tribological Properties of NiTiFe Alloy Coating by High Frequency Induction Cladding
      DONG Jianwei; GUO Yanbao; WANG Deguo; ZHANG Zheng

      Abstract:In order to enhance the wear resistance of metal surface,NiTiFe alloy coating was prepared on the surface of HT300 substrate by high frequency induction cladding technology.Scanning electron microscope (SEM),energy dispersive spectrometer (EDS),microhardness tester and X-ray diffractometer (XRD) were used to characterize and analyze the microstructure,element composition,hardness,phase composition and bonding with substrate of NiTiFe alloy coating.The friction and wear tester was used to test the tribological properties of the coating and analyze its friction and wear mechanism.The results show that the coating has compact structure,no cracks and gaps,good molding quality,and the average thickness reaches 0.7 mm,which realizes metallurgical bonding with HT300 substrate.The coating mainly consists of three phases,including Fe2Ti,Fe6.94Ti0.36 and Ni3Fe.The addition of Fe element causes lattice distortion and increases hardness of the coating,with an average hardness of 997.36HV,which is about 5 times the average hardness value of the HT300 substrate.Through the friction and wear test,it is found that the friction coefficient between NiTiFe alloy coating and the counter-friction pair is low in the early stage of the test,and it is maintained at about 0.2.The failure of the counter-friction pair leads to the change in the contact form between the friction pairs,resulting in a step in the friction coefficient.With the increase of load,the width of wear marks on the coating is also increasing,and the exposed area of the counter-friction pair is also increasing.After the friction and wear test,the friction surface of NiTiFe alloy coating is smooth and flat,and only slight abrasive wear occurs,the wear volume is much smaller than that of the counter-friction pair.It shows excellent friction and wear resistance.

    • Research on Dynamic and Static Characteristics of Air Floating Foil Bearing of High Speed Fan Based on Fluid Domain Simulation
      ZHANG Chen; XU Liang; SUN Dan; LI Yuwei; GAO Fei; JING Jianping

      Abstract:The characteristics of air bearing have a significant impact on the stability of high-speed fan rotors,and the calculation of static and dynamic characteristics of air bearing is the basis for accurately obtaining the unstable speed of the rotor system.A physical model of air bearing and corresponding fluid domain model was established,by setting the parameters of air bearing under working conditions,the distribution of fluid domain of air bearing under working conditions was simulated.By adjusting the axis position,the axis position under standard working conditions was found,and the static characteristic calculation of air bearing was achieved.On the basis of the results of static characteristics calculation,the journal was subjected to disturbances of the same frequency,and the fluid domain distribution was simulated to obtain the force distribution of the journal under the given disturbance.The stiffness and damping coefficients corresponding to the air bearing were solved based on the changes in force,and the calculation of the dynamic characteristics of the air bearing was achieved.The results indicate that as the rotational speed continues to increase,the stable axis position will gradually approach the center of the air floating foil bearing.With the increase of speed within a certain operating speed range,the direct stiffness coefficient of the bearing decreases,while the direct damping coefficient increases after reaching a low value within the operating speed range.This provides a theoretical basis for conducting research on rotor subsystem dynamics by analyzing the variation between the characteristic coefficient of the air bearing and the speed.

    • Effect of Surface Roughness on Reciprocating Sealing Performance of Rubber O-ring
      LIANG He; WANG Tengfei; WANG Wenzhong; GUO Yulong

      Abstract:A three-dimensional deterministic numerical simulation model of mixed lubrication was established.The model adopted the unified Reynolds equation based on the system method and coupled the solid mechanics analysis,fluid mechanics analysis and contact mechanics analysis.Non Gaussian rough surfaces were generated,based on the mixed lubrication model,the effects of surface roughness amplitude,autocorrelation length ratio and texture direction on the sealing properties of O-ring reciprocating seal,such as friction,leakage rate,average film thickness and contact area ratio,were investigated by using the non-Gaussian rough surface.The results show that with the increase of surface roughness,the friction coefficient,average film thickness and leakage rate increase.When the Ra increases to a certain value and the contact area of the lubrication area is greater than 40%,the average film thickness and leakage rate begin to decrease.For a rough surface with transverse texture,there is an appropriate γ,which makes the comprehensive performance and lubrication state of the seal optimal.When θ =π/10,the friction coefficient reaches the minimum value.

    • Stress Corrosion Simulation of Q345 Steel Based on Multiphysics Simulation Coupling
      PEI Wenle; PEI Bingbing; WANG Jianmei; SHUAI Meirong; XIE Zhuangzhuang

      Abstract:Offshore wind turbine support structures and the related transformer platform are particularly corrosive-prone,and corrosion flaws can result in stress concentration,which adversely affects the wind turbine equipment’s service life.Using Q345 steel as the research object,a finite element model for the growth prediction of surface corrosion defects in Q345 steel was established using COMSOL coupling Multi-physics simulation software,and the stress corrosion behavior of Q345 steel in different states in the marine environment was simulated.The Tafel relation of Q345 steel was determined using an electrochemical corrosion test,the impact of stress on electrochemical corrosion at corrosion defects was predicted using multi-physics coupling,and corrosion defect increase prediction was performed in conjunction with Faraday’s law.The results indicate that as the tensile strain and defect depth increase,the stress at the defect is increased,and the failure at the defect is accelerated.When stress causes plastic deformation at the defect site,local corrosion activity is significantly enhanced.The mechanical and electrochemical effects at the defect site alter the stress distribution at the defect center,enhancing the corrosion rate at the defect center.

    • Study on the Performance of High-Speed Rotating Lip Seal Based on Fluid-Solid-Heat Multi-field Coupling
      ZHAO Huanan; LV Xiaoren; LV Baohua; XIANG Chong; GUO Fei

      Abstract:A numerical simulation model for quantitatively analyzing the sealing performance of a rubber material high-speed rotating lip seal was established by combining its structure and actual application conditions,using methods such as equation discretization calculation.Based on the established model,the coupling relationship between multiple physical processes such as interface fluid mechanics,macroscopic solid mechanics,surface roughness peak microscopic contact mechanics,and lip friction heat generation under the actual service state of the seal was analyzed,and the accuracy of the numerical simulation model was verified and improved through experiments.Based on the numerical simulation model,the change law of the key parameters of the sealing performance,such as the contact pressure distribution,the temperature of the lip,the friction moment and the leakage rate,with the rotating speed were studied.The results show that,when the friction heat generation is considered under the condition of high rotating speed,the radial force of oil seal decreases,the contact width increases and the friction torque decreases,which indicates that the friction heat has a great influence on the sealing performance of oil seal.

    • Current Carrying Tribological Properties of Cu-10Sn Alloy Prepared by Selective Laser Melting
      FANG Changyang; JI Dehui; XIONG Guangyao; XIAO Yelong; ZHAO Huoping; SHEN Mingxue

      Abstract:To improve the mechanical and current carrying tribological properties of Cu-10Sn alloy,the Cu-10Sn alloy was prepared by selective laser melting (SLM).The microstructure and hardness of Cu-10Sn alloy were analyzed,and the effects of different loads and currents on the current carrying tribological behavior of Cu-10Sn alloy were studied.The mechanism of tribo-electric performance was analyzed by scanning electron microscope.The results show that compared with the load of 10 N,the average friction coefficient of the friction pair increases,the contact resistance and arc energy decrease and the wear are deepened at 30 N.The surface of Cu-10Sn alloy rubbed with GCr15 ball is oxidized,and the copper element of which is transferred and adhered to the ball forming adhesive wear.Compared with pure mechanical friction behavior,the wear marks are deepened,the amount of adhesive and oxide increases obviously on the surface of Cu-10Sn alloy,and the friction coefficient and wear volume change significantly with current.The arc ablation occurs on the surface of the wear marks under low load and small current.When the current is 10 A,the lubrication of the oxide film formed on the wear surface slows down the wear of the material.The wear mechanisms are mainly fatigue wear and adhesion wear without current,and the electrochemical oxidation and adhesive wear are significantly enhanced with current.This research can provide reference for the preparation of Cu-Sn alloy by SLM technology and its application in contact lines and other electrically conductive contact materials.

    • Effect of Surface Morphologies of Contact Wires on Friction and Wear Properties of Metal-impregnated Carbon Strips
      HE Quanxin; ZENG Ziyi; CHEN Guangxiong; REN Wenjuan; ZHAO Pengpeng; DONG Bingjie

      Abstract:During the pantograph-contact wire current-carrying friction and wear process,the contact wire will produce different cross-sectional shapes,and the change of contact wire morphology may affect the contact relationship between the pantograph and the wire,and thus affect the current-carrying friction and wear performance between the pantograph and the wire.In order to study the effect of surface morphologies of contact wires on the current-carrying friction and wear properties of metal-impregnated carbon strips,the tests on the contact wire with conventional,pitted and slanted morphologies sliding against contact strips were carried out using a block-on-ring-high-speed current-carrying friction and wear test machine.The friction coefficient,arc energy,wear amount and surface morphology of the metal-impregnated carbon strips sliding against the contact wires with different morphologies were compared.The results show that under the passage of direct current,the friction pair composed of the conventional morphology contact wire and the metal-impregnated carbon strips has the smallest friction coefficient and the lowest wear of strip.The friction pair composed of the slanted morphology contact wire and the metal-impregnated carbon strips has the highest friction coefficient and the maximum wear of strip.〖HJ1.8mm〗The wear morphology of the metal-impregnated carbon strips was observed by a SEM microscope.It is found that the worn scar of the contact strips rubbing against the contact wire with conventional morphology is mainly characterized by oxidation wear,and more oxides are produced.The worn scar of the contact strips rubbing against the contact wire with pitted morphology is mainly characterized by ablation and abrasive wear,and small cracks,ablation pits,and more wear debris and peeling layers are produced.The worn scar of the contact strips rubbing against the contact wire with slanted morphology is mainly characterized by wire arc ablation,and large cracks,furrows,and more white globules are produced in the ablation area.Research shows that when the morphology of the contact wire changes,it can lead to increased wear of the strip and exacerbate the arcing discharge between the contacts,thereby deteriorating the contact state.Therefore,when the wear and deformation of the contact wire becomes severe,it should be replaced in time.

    • Oil-Air Lubrication Analysis of Radial Sliding Bearing Considering Journal Inclination and Cavitation Motion
      TIAN Tianci; FANG Liqing; SHI Sushuang; ZHANG Hao; SHI Zhanqun

      Abstract:The journal tilting phenomenon caused by heavy load and manufacturing errors will change the eccentricity and oil film thickness at different sections of the bearing.When the sliding bearing is running at high speed,the oil film gap will inevitably be mixed with tiny bubbles.Therefore,it is necessary to explore the influence of oil-gas two-phase flow on the lubrication characteristics of radial sliding bearing when the journal tilts.Combining the modified Rayleigh-Plesset equation considering the motion of bubbles with the Reynolds equation,the corresponding algorithm was written to solve the coupled equation,and the influences of gas holdup,bubble parameters and journal inclination on the static characteristics of the sliding bearing were analyzed.The results show that the static characteristics of maximum oil film pressure,bearing capacity,end discharge and friction force decrease with the increase of gas holdup at different rotating speeds.The influence of bubble parameters on lubrication performance is related to eccentricity.Increasing the surface expansion viscosity of bubble has the same effect on bearing lubrication as decreasing the initial bubble radius.Journal inclination will change the oil film pressure distribution and values,and make the cavitation area tilt.With the increase of inclination of journal,the static characteristic parameters of sliding bearing gradually increase,and it is more significant when the eccentricity and the inclination are large.Appropriate changes in bubble parameters and oil gas holdup will weaken the influence caused by the journal tilt to some extent.

    • Numerical Simulation and Experimental Research on Micro Negative Pressure Flow Field of Gecko-inspired Adhesive Arrays
      QIU Haifei; ZHANG Jiayou; LI Chengchuang; WU Zhenyang; WANG Chaohui; XU Hao

      Abstract:Aiming at the unique climbing and multi terrain adaptability of gecko,the biological adhesion array of the animal was simulated by means of negative pressure control.On the basis of vacuum pressure analysis and adsorption force calculation,the two equation turbulence model in standard k-ε form was applied to the numerical simulation of negative pressure inside the suction cup.A non-structural fluid calculation domain with single-phase and steady-state was constructed by ICEM CFD and FLUENT software,and pressure-velocity coupling solving and analysis of the flow field was carried out through SIMPLE algorithm.It is found that there is obvious turbulent in the flow field,the dynamic pressure (0.154 MPa) and flow velocity (503 m/s) in outlet pipeline are much larger than those in inner field,and the central velocity in the outlet area is about 4.8 times of that in the inlet area,which is helpful to the air flow vacuumization and formation of the negative pressure.The results of finite element static analysis show that there is local stress concentration (>180 MPa) at bottom edge of the wall on suction cup,and the thickness of this area should be increase appropriately.The feasibility of adsorption mechanism with negative pressure and its realization method is verified by performance test of bionic prototype,and the experimental results of adsorption and mobile meet the expectation of flow field simulation.The study provides valuable support for bionic research and practical application of gecko adhesion array.

    • Study on Corrosion Inhibition and Synergistic Effects of BTA and TT-LYK on Copper CMP
      MENG Ni; ZHANG Xianglong; LI Xianghui; XIE Shunfan; QIU Yuxuan; NIE Shenao; HE Yangang

      Abstract:In copper chemical mechanical polishing,the typical corrosion inhibitor benzotriazole (BTA) has a strong chemical protection effect on the copper surface,resulting in a low copper removal rate.In order to achieve better corrosion inhibition effect and copper surface quality,the corrosion inhibition effects of BTA corrosion inhibitor and novel inhibitor of ethanol,2,2′-[[(methyl-1H-benzotriazol-1-yl) methyl] imino] bis-(TT-LYK) in near-neutral solutions were compared.The mixed inhibition of these two inhibitors was also investigated.The results show that both of the corrosion inhibitors can effectively inhibit copper surface corrosion in near-neutral solutions.The combination of two corrosion inhibitors has a synergistic effect,and adding them to the polishing solution can achieve better copper surface quality and lower roughness.This may be due to their similar types of passivation films formed,which enables another inhibitor can supplement the passivation film generated by one inhibitor,resulting a denser and better protective dual-layer passive film on the metal surface.

    • Influence of Environment Humidity on Wear and Temperature Rise of Metal-impregnated Carbon Strip
      ZENG Ziyi; HE Quanxin; CHEN Guangxiong; ZHAO Pengpeng; DONG Bingjie

      Abstract:In order to explore the influence of ambient humidity on the arc discharge energy,the temperature rise and strips wear of the metal-impregnated carbon strip during the sliding process of a catenary-pantograph system,the ring-block high-speed current-carrying friction and wear test bench was used to study the arc energy,the temperature rise of the strip and strip wear with the sliding speed,current and normal force in different humidity conditions.It is found that the arc energy and strip temperature rise increase sharply with the increase of sliding velocity and current under different ambient humidity.Arc heat is the main heat source leading to temperature rise of strip.Increasing the normal force has significant effects on restraining arc discharge and decreasing the temperature rise of the strips,but the effect on the wear of the strips is completely opposite under different humidity conditions.In the high humidity environment,the water film attached to the contact pair improves the contact condition and heat dissipation,and the arc energy and temperature rise of the strips are less than those in the low humidity environment.In the low humidity environment,the strip surface is subjected to more serious mechanical friction,and its surface condition is worse than that in high humidity environment.The wear of the metal-impregnated carbon strip can be reduced by appropriately increasing the normal force in summer when the average humidity is high,and appropriately decreasing the train speed in winter when the average humidity is low.

    • Influence of Temperature on Sealing Performance of Combined Texture Oil Seals
      ZHANG Zhixiang; ZHANG Fuying; XIA Jingwei; MA Jun; LIU Yuangang

      Abstract:Coupled with fluid dynamics,deformation analysis,contact mechanics,energy conservation equation and viscosity-temperature and viscosity-pressure equations,a numerical model of mixed lubrication in the sealing area of the oil seals with combined surface texture was established,and the influence of temperature on the sealing performance of the oil seals was studied.The numerical equation was solved by finite difference method to obtain the temperature distribution of the lip of oil seals with combined surface texture and its maximum temperature at different speeds,and the effect of temperature rise on the pump suction rate,oil film thickness,friction torque and other sealing properties of the oil seals was compared and analyzed.The results show that the maximum temperature of oil seal is located at the tip of the lip,and the maximum temperature of the non-textured oil seal is slightly higher than that of the textured oil seal.The maximum temperature of the oil seal increases with the increase of speed.The presence of texture will cause an increase in oil seal pumping suction rate and average oil film thickness.With the increase of temperature,the pump suction rate,friction torque and oil film thickness of the oil seal will gradually decrease,and the sealing performance of the oil seal will decrease significantly.When the temperature rises to a certain extent,the oil seal pump suction rate will become negative.

    • Effect of Plate Structure on Leakage Flow Characteristics of Brush Seals
      LI Chuan; LIU Meihong; SONG Xiaolei; TANG Junfeng; XU Jiahui

      Abstract:In order to study the influence of the front and back plate structures on the pressure and flow field of the brush seal,the nonlinear Darcian porous medium model was used to establish the brush seal solution models of six different front and back plate structures.The rationality of the model was verified by comparing with the relevant experimental data.The pressure and flow field of the brush seals of six different front and back plate structures were numerically analyzed by ANSYS software.The results show that pressure ratio and plate structure play a key role in the sealing performance of brush seals.The leakage of brush seals increases with the increase of pressure ratio.The long front plate structure can reduce the leakage,and there is no difference in leakage between the basic and annular cavity back plate structures,while the through cavity back plate structure can significantly increase the leakage.The long front plate structure can reduce the pressure in the brush tow,and the back plate structure plays a decisive role in the pressure distribution of the brush seal.The through cavity back plate can eliminate some radial pressure gradient and improve the life of the brush seal.

    • Tribological Properties of Micro-texture Babbitt Alloy Surface with Light Curing h-BN
      NI Kan; ZHOU Yuankai; ZUO Xue

      Abstract:In order to improve the tribological properties of Babbitt alloy under oil lubrication condition,a composite lubrication structure composed of hexagonal boron nitride(h-BN) solid lubricant and surface micro-texture was prepared by filling h-BN solid lubricant into the micro-textured dimples on the surface of Babbitt alloy by light curing method.The tribological properties of the composite lubrication structure and the mechanism of antifriction and lubrication under the condition of oil lubrication were studied.The results show that the tribological properties of the composite lubrication structure are much higher than that of the untextured and pure textured surfaces.When the dimple diameter is small and the micro-texture is between 10% to 20%,the friction coefficient of the composite lubrication structure is low.When the dimple diameter is large,the friction coefficient of the composite lubrication structure decreases gradually with the increase of dimple density.When the dimple density is less than 20%,the friction coefficient of the composite lubrication structure with smaller dimple diameter is low.As the dimple density reaches 30%,the friction coefficient of the composite lubrication structure decreases with the increase of dimple diameter.The composite lubrication structure can greatly improve the tribological properties of Babbitt alloy surface because the release of h-BN solid lubricant forms a solid lubricant film on the surface of Babbitt alloy,which avoids the direct contact between the Babbitt alloy surface at the thinner part of the lubricating oil film and the surface of 45 steel,and the micro-textured dimples after the release of h-BN play the role of collecting abrasive particles and storing lubricating oil.

    • Optimization Design of Structural Parameters of New Shaft end Seal for Train Gearbox
      LIN Jiaxu; SHA Zhihua; LI Baoliang

      Abstract:In order to further improve the sealing effect of the sealing structure at the bearing end cover of the train gearbox,and effectively prevent the fluid exchange between the inside and outside of the reducer,based on the previously designed sealing structure,the sealing structure parameters,such as the inner diameter of the impellers on both sides,the inclination of both sides of the blade,the inclination of the bottom of the blade,the fillet of the side of the blade and the number of blades in the middle of the impeller,were optimized and analyzed.Combining the hydrodynamic analysis results and the previous experimental data of the sealing structure,the influence of various parameters on sealing effect was explored.The results show that the inner diameter of the impeller blades on both sides and the inclination angle of the blade side have great influence on the sealing effect,while other parameters have little influence on the sealing effect.Compared to the original sealing structure,the average pressure difference on the key plane between the impeller in the middle and the impeller on the opposite sides of the shaft end seal structure after optimization is increased from 22.97 Pa to 357.94 Pa.And it is found from the velocity streamline diagram that an obvious isolation zone is formed in the middle of the seal structure,which can effectively prevent the fluid leakage inside and outside the gearbox and improve the sealing performance of the shaft end.

    • Force Analysis and Expansion Test Verification of Solid Expansion Cone of Expandable Tubular
      GUO Huijuan; WANG Xin; ZHAO Yuncai

      Abstract:Expandable tubular technology is mainly applied in the field of oil and gas field development.Expansion cone is one of the main tools of expandable tubular technology,which is subjected to great interface stress during operation.Therefore,the rapid wear of expansion cone surface is one of the main problems restricting the development of expandable tubular technology.To investigate the surface friction and stress distribution of the expansion cone during the expansion process,the calculation models for the contact stress and friction of the expansion cone were derived based on elastic-plastic theory.The finite element method was used to simulate the expansion process of the expansion tube,and to study the changes in surface stress,contact friction stress,and expansion thrust of the expansion cone.The rationality of the finite element simulation results was verified through expansion tests.The results show that the main factors affecting the contact stress and friction of the expansion cone are the yield strength of the expansion tube and the cone angle of the expansion cone.The maximum equivalent stress of the expansion cone is concentrated at the fillet of its large radius,and the maximum friction stress is concentrated at the position of the small and large diameters of expansion cone.The expansion zone of the expansion cone only partially contacts with the inner wall of the expansion tube.The position of the small diameter of expansion cone is subjected to tensile stress,while the position of the large diameter of expansion cone is subjected to compressive stress.The maximum contact compressive stress is concentrated at the position of the large diameter of expansion cone.

    • Analysis of Pre-tightening Stress Error of the Test Gasket of Multi Specimen Gasket Accelerated Life Test Device
      YAO Bingyang; SHAO Chunlei; ZHANG Yunhao; KONG Jing; HU Kang

      Abstract:Gaskets are the core components of bolted flange connection systems.Predicting the life of gaskets can improve the reliability of the bolted flanged connection,while reducing the experimental error of gasket life evaluation devices can improve the accuracy of gasket life prediction.Taking flexible graphite spiral wound gaskets as example,the influence of flange and gasket thickness deviation,loading coaxiality deviation and gasket installation deviation on the stress distribution of the gasket of the multi specimen gasket accelerated life test device were studied.The load ratio under different temperatures and pre-tightening stress was obtained,and the maximum allowable deviation of the test device was determined.The influence of temperature and pre-tightening stress on the pre-tightening stress error of the test gasket was revealed,and the method of controlling the pre-tightening stress error was put forward.The results show that the pre-tightening stress error decreases with the increase of temperature,the pre-tightening stress error caused by the thickness deviation of the flange and gasket decreases with the increase of pre-tightening stress,and the coaxiality deviation of test device loading and the pre-tightening stress error of the gasket caused by the gasket installation deviation increases with the increase of preloading stress.Taking the pre-tightening stress error of the test gasket of 1% as the index,it is obtained that the thickness deviation of the flange and gasket should be controlled between -0.02 mm to 0.005 mm,the coaxiality deviation loaded by the test device should not be greater than 0.33 mm,and the installation deviation of the test gasket should not be greater than 1.24 mm.For other types of gaskets,the range of thickness deviation between flange and gasket,coaxiality deviation loaded by test device and installation deviation of test gasket can also be determined by the method established in this paper.

    • Adaptability of Bayes Analysis for Reliability of Mechanical Seals of Nuclear Main Pumps
      GAO Deng; SUN Jianjun; ZHANG Yuyan

      Abstract:The reliability of mechanical seal has an important influence on the safe and stable operation of nuclear main pump.To achieve the reliability evaluation of the mechanical seal of the nuclear main pump under the condition of zero-failure data,the operating data of the mechanical seal of the Daya Bay nuclear main pump were analyzed,its reliability distribution was determined.A reliability analysis model combining Bayes theory was established,and the zero-failure data was simulated from the determined reliability distribution by using Monte Carlo method.The influence of the value of packets c on the accuracy of E-Bayes estimation and multi-layer Bayes estimation was investigated when the prior distribution was Beta distribution in the case of zero-failure data.The results show that when packets c<8,multi-layer Bayes estimation is preferred,when c>8,E-Bayes estimation is preferred,and when c=8,the average relative errors of both methods reach a lower level and the multilayer Bayes estimation is lower.The research results have guiding significance for the reliability analysis of mechanical seal of nuclear main pump based on Bayes theory in the case of zero-failure data.

    • Analysis of Influencing Factors of Y-ring of Throttle Valve under Ultra-high Pressure,High and Low Temperature Conditions
      FENG Chunyu; QIAN Qi; XU Mingjun; YANG Zhongwu; XIE Qi

      Abstract:In order to study the influencing factors under the high and low temperature working conditions of the Y-rings under ultra-high pressure in natural gas equipment, PTFE and its four modified materials were selected as sealing materials, and the effect of the lip interference, lip angle and back lip angle on the static sealing performance of the Y-rings was analyzed.The results show that the maximum von Mises stress of the Y-ring decreases with the increase of lip interference, first increases and then decreases with the increase of lip angle and lip back angle.The maximum contact stress of the inner lip increases with the increase of lip interference and lip angle, and first increases and then decreases with the increase of lip back angle.Five parameters,including the width of the Y-ring,substrate height,lip tip height, lip front angle, and lip back angle,were selected,the sensitivity analysis of each parameter was conducted by ISIGHT software.It is found that the width of the sealing ring and the substrate height have the greatest impact on the maximum Mises stress and inner lip contact stress of the Y-ring.The optimal size of the Y-ring was obtained by multi-island genetic algorithm.and the theoretical design result was verified through experiments.

    • Evaluation Method for Noise Performance of Precision Bearing Grease Based on BeQuiet+ Tester
      JIANG Cheng; SU Huaigang; WANG Chao; YU Hongyuan; LOU Wenjing

      Abstract:With the continuous progress of bearing manufacturing technology,grease gradually becomes an important factor affecting the noise performance of precision bearings.For different stages of bearings running,the noise value of grease in the start-up stage of bearings,the noise level,vibration value and damping value in the middle and high frequency bands during the running stage of bearings were evaluated by using BeQuiet+ tester.The evaluation results of BeQuiet+ tester were compared with those of S0910-Ⅲ bearing vibration tester.It is found that for greases with large difference in noise performance,the test results of the two instruments have the same trend,while for the greases with small difference in noise performance,the test method of BeQuiet+ tester has better differentiation.An evaluation method for the noise performance of precision bearing grease using the BeQuiet+ tester was established,and the evaluation method was validated using six greases with different impurity particles and microscopic morphology.This evaluation method focuses on the noise performance during the whole operation stage of the bearing and the stability of the noise during operation,which can better distinguish the noise performance of the precision bearing grease.

    • Influence of Initial Oil Film Thickness on Static and Dynamic Performances of Dovetail Hydrostatic Guide
      HAN Yanwei; LI Hui; ZHAO Yubo

      Abstract:The performance of dovetail hydrostatic guideway is closely related to the selected initial oil film thickness.The relationship between the initial oil film thickness and the static and dynamic performances of the closed hydrostatic guide regulated by PM flow controller was analyzed and derived.The results show that increasing the initial oil film thickness of both bottom large surface and dovetail surface can effectively improve the bearing capacity of the guide,but the increase is not significant.Reducing the initial oil film thickness of both bottom large surface and dovetail surface can improve the static stiffness and dynamic stiffness of the dovetail guide.The change in initial oil film thickness on the bottom large surface of the guide has a greater impact on static stiffness,while the change in initial oil film thickness on the dovetail surface has a greater impact on dynamic stiffness.In actual working conditions,an appropriate initial oil film thickness should be selected based on the designed guide operating conditions.

    • Optimization of Sealing Performance of Spiral Groove Rotating Sealing Device for Cabin Partition
      QU Jiahui; WU Xingwei; GAO Zhen; HOU Tianzhu; CHEN Wuchao; LI Songshan

      Abstract:In order to study the sealing performance of a spiral groove rotary sealing device used for cabin partition,and to obtain the optimal value range of the spiral groove structure,theoretical analysis was conducted on the influence of various parameters of the spiral groove on the leakage rate.The significant influencing factors of the leakage were selected,the Box-Behnken optimization method was used to design the leakage test of the sealing device,and the leakage results of the multi type prototypes were obtained.The mathematical model between leakage and influencing factors was established,the second-order interaction response surface of different factors on leakage was obtained,and the interaction law between different factors was analyzed.The results show that the leakage of the spiral groove sealing device increases first and then decreases with the increase of the number of grooves,spiral angle,and groove depth ratio,and gradually increases with the increase of the circumferential groove platform ratio and the radial groove platform ratio.The calculation results of the mathematical model have a strong correlation with the experimental data,indicating that the model can be used to accurately predict the leakage of the spiral groove rotating sealing device for cabin partition.Therefore,combining response surface experimental design method,genetic algorithm,and theoretical method to study the sealing performance of spiral grooves can quickly and accurately obtain the optimal range of spiral groove parameters.

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