Volume 49,2024 Issue 4

• Prediction of Minimum Oil Film Thickness of Tilting Pad Thrust Bearing During Idling
  HUANG Bin; YUAN Faxu; PU Kexin; FEI Dongdong; DU Pengcheng
  Abstract:In order to establish a prediction method for the minimum oil film thickness of tilting pad thrust bearing during idling,based on the actual working conditions of the thrust bearing of the nuclear main pump and the self compiled program of Reynolds equation,the calculation and numerical simulation analysis of the lubrication performance parameters of the main and auxiliary bearing pads under hot and cold conditions were carried out,and the theoretical formula for the minimum oil film thickness of tilting pad thrust bearing was proposed.The calculated minimum film thickness was compared with the theoretical value.The results show that with the decrease of the rotating speed,the minimum film thicknesses of the main bearing pad monotonically decreases,while the minimum film thickness of the auxiliary bearing first increases and then decreases.The calculated minimum film thickness of the main and auxiliary bearing pads can correspond well with the fitted values,verifying the reliability of the theoretical fitting formula.The theoretical fitting formula can predict the minimum oil film thickness under various working conditions through the calculation results of minimum oil film thickness at rated speed,which provides an important reference for the safety of the idling of the main pump.

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• Influence of Nozzle Position on the Oil-air Lubrication Tow-phase Flow Inside the Bearing Cavity
  WANG Baomin; FANG Wenbo; ZHU Shengqiao; LIU Hongqin; WU Zaixin
  Abstract:Based on the theory of gas-liquid two phase flow,a numerical calculation model of angular contact ball bearing was established by using the multi-reference frame method.The oil volume fraction,the oil-air flow characteristics on the cage surface,inner ring and outer ring were compared and analyzed under different nozzle positions and rotating speeds.The results show that at low bearing speed,the oil volume fraction inside the bearing cavity when the nozzle is at the front end is higher than that when the nozzle is at the rear end,and the variation with the circumferential angle is more obvious.When the nozzle is at the front end,the accumulation of lubricating oil will occur on the lower side of the cage,resulting the lubrication oil cannot be discharged from the outlet in time.When the nozzle is at the rear end,the distribution of lubrication oil on the cage surface is uniform.The oil volume fraction on the left side of the inner ring is higher when the nozzle is at the front end,and the distribution of oil on the outer ring changes greatly.The oil volume fraction on the right and middle side of the inner ring,as well as on the middle side of the outer ring,is higher when the nozzle is at the rear end.Under the different rotating speed,the effect of nozzle position on the distribution of lubrication oil is different.At low rotating speed,the oil volume fraction is higher when the nozzle is at the front end.At high rotating speed,the nozzle position has little effect on the distribution of lubrication oil inside the bearing cavity,the lubrication oil is uniformly distributed inside the bearing cavity,and its accumulation on the lower side of the cage is not obvious.

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• Static Performance Analysis of Aerostatic Bearing with Radial Wedge Groove Structure
  YIN Xianxiong; YU Puliang; LI Shize; LU Jiong; XU Hui; HU Hui
  Abstract:To improve the static performance of the aerostatic bearing,a new type of aerostatic bearing with radial wedge groove structure was presented.The wedge groove is radial,with fan-shaped circumferential section,rectangular radial section and trapezoidal axial section.The CFD models of aerostatic bearing with the radial wedge groove were established.The influence of the radial wedge groove structural parameters on the loading capacity and stiffness of aerostatic bearing was investigated.The results show that the radial wedge groove can improve the loading capacity and stiffness of aerostatic bearing,and optimize the pressure distribution of gas film compared with the traditional pressure groove.The loading capacity of the aerostatic bearing increases gradually with the increase of radial angle,inlet height and wedge angle,and the loading capacity of the aerostatic bearing increases first and then decreases with the increase of the groove radius.The stiffness of aerostatic bearing increases gradually with the increase of wedge groove radius,radial angle,inlet height of wedge groove and wedge angle.Experimental results of load capacity agree with the simulation results greatly,which verifies the feasibility and accuracy of the model.

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• Numerical Simulation and Analysis of Multi-lip Reciprocating Slip Ring Combined Seal
  WANG Yueming; LIU Lili; LV Xiaoren; XIANG Chong; HUANG Le; GUO Fei
  Abstract:A numerical model for multi-lip reciprocating slip ring combined seal was established,which includes solid mechanics analysis,fluid mechanics analysis,contact mechanics analysis and fluid-structure coupling analysis.Taking PS seal with three sealing lips as an example,the oil film thickness distribution,oil film pressure distribution,rough peak contact pressure distribution,internal and external stroke flow rate and friction force of sealing interface were obtained based on numerical model.This numerical calculation method solves the problem that boundary conditions are difficult to determine in multi-lip seal,and the boundary conditions of each sealing lip in steady state can be obtained through iterative calculation.The sealing mechanism of multi-lip PS seal was clarified,and the influence of different reciprocating speed on sealing performance was analyzed.The results show that the boundary conditions of each lip vary greatly in the internal and external stroke of multi-lip PS seal.In the external stroke,there is a certain pressure at the gap between the two lips,while in the internal stroke,the gap pressure is 0.The contact pressure of the sealing surface of the outer stroke is less than that of the inner stroke.The increase of reciprocating speed will increase the net leakage of multi-lip PS seal and decrease the friction force.

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• Molecular Dynamics Simulation of the Tribological Properties of Nylon 6 Synergistically Reinforced by Carbon Nanotubes and Graphene
  LI Yipeng; WANG Yan; BAI Tao
  Abstract:In order to study the micro mechanism of synergistic enhancement of the tribological and mechanical properties of nylon 6(PA6) composites by carbon nanotube (CNT) and graphene nanosheets (GNS),the tensile process and tribological behavior of PA6 and its composites were simulated by molecular dynamics,and the effects of CNT and GNS on the mechanical and tribological properties of PA6 composites were analyzed.Tribological models consisting of Fe atoms and pure PA6 and PA6/CNT,PA6/GNS,PA6/GNS/CNT composites were established,and the models were geometrically optimized,annealed and dynamically balanced.Friction simulation was carried out by applying 0.2 GPa stress and 0.01 nm/ps velocity to Fe atoms.The results show that the friction coefficient of PA6/GNS/CNT composite is 0.252,which is the lowest among all materials.Compared to the other three materials,PA6/GNS/CNT composite material has the best shear resistance,and both the elastic modulus and shear modulus are improved.By comparing and analyzing the radial distribution function,friction interface temperature and total potential energy of the four materials,the synergistic reinforcement mechanism of CNT and GNS on the tribological and mechanical properties of PA6 composites was revealed.It is pointed out that the addition of CNT/GNS reduces the interaction between PA6 and Fe atomic friction pairs through van der Waals and electrostatic forces,and one-dimensional CNT and two-dimensional GNS form a 3D hybrid stacking system through π-π stacking hybridization,synergistically enhancing the tribological performance of PA6.

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• Study on Contact Characteristics Between Rubber Asperity and Metal Surface Considering Creep Characteristics
  CHU Hongyan; YU Qiang; ZHANG Zheng; ZHANG Ze
  Abstract:Metal-rubber contact widely exists in sealing structure,and the interaction between asperities on the sealing contact surface directly affects the contact characteristics of the entire sealing interface,thereby affecting its sealing performance.Based on a single asperity of rough seal interface,the contact characteristics between the rubber asperity and the metal surface was studied by combining theoretical analysis and simulation research,considering the creep characteristics of rubber.Based on the results of compression creep experiment of rubber material,a calculation model of rubber creep was established.The finite element model between the hemispherical asperity and the metal plate was established,the simulation was conducted by considering the creep properties,and the contact characteristics were analyzed and compared with the calculated values of Hertz contact theory.The results show that with the increase of creep time at the creep stage,the contact radius,normal deformation and maximum equivalent creep strain all increase,and the maximum contact pressure decreases,which may lead to the decline of sealing performance.With the increase of loads,the contact radius,normal deformation,maximum contact pressure and maximum equivalent creep strain all increase,but the increasing trend gradually decreases.The equivalent modulus between the rubber asperity and metal surface decreases with the increase of creep time,and increases with the increase of loads.

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• Analysis on Preload Characteristics of Ultra-high Pressure Fracturing Manifold Union
  HUA Jian; MA Zhongjie; YUAN Zhiqiang; HUANG Tiancheng; HU Jiahao; WANG Linhu
  Abstract:In order to solve the problem of structural damage or seal leakage caused by improper installation preload of ultra-high pressure fracturing manifold union,the 175 MPa ultra-high pressure union developed by a company was taken as the research object,and the contact model was established by ABAQUS.The stress analysis,strength evaluation and sealing performance judgment of the union were carried out by using the finite element method.The analysis results show that the preload has almost no effect on the stress of the female union,but has a significant effect on the stress of the male union,the airfoil nut and the three-petal retaining ring,and all of them show a positive correlation.When the preload exceeds 250 kN under the rated working conditions,the stress at the fillet of the shoulder of the male union exceeds the allowable stress of the material,and the structural static strength does not meet the requirements and may cause structural damage.When the preload is less than 150 kN,it is not enough to resist the internal pressure,and the male and female ball cone sealing structures are separated.Within the preload range of 150 kN to 250 kN that can ensure the tightness of the ball cone and the structural safety,the surface contact stress of the HNBR sealing ring is always greater than the real-time fluid working pressure,and the sealing ring has good sealing performance.The recommended installation preload range is 150 kN to 250 kN,within which the sealing ring structure can meet the requirements of static strength and sealing performance.

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• Research on Wall Pressure Fluctuation Effects in Turbulent Lubrication Journal Bearings
  ZENG Fang; ZHANG Hao; LI Xin; ZHEN Dong; XIAO Sen
  Abstract:Wall pressure fluctuation is one of the major excitation sources of random vibration in turbulent lubrication journal bearings.Establishing the correlation between turbulent excitation characteristics and the dynamic response of journal bearings is significant for condition monitoring and fault diagnosis of high speeds,low viscosity lubrication journal bearings.In order to study the wall pressure fluctuation effects in turbulent lubrication journal bearings,the influence of adverse pressure gradients in the fluid film was considered,Rozenberg model and Generalized Corcos model were used to characterize the auto-power and cross-power spectrum density of wall pressure fluctuation,the turbulent wall pressure fluctuation model was solved by the modal summation method in wavenumber domain to study the excitation characteristics of wall pressure fluctuation and the dynamic response of journal bearings under different operating conditions.The results show that turbulent wall pressure fluctuation in low wavenumber region is the main factor in the high frequency random vibration of journal bearings.As the viscosity of the lubricating oil decreases,the modal response amplitude of the bearing in the high-frequency range increases,and a wider frequency band and higher amplitude are generated near the resonance peak.As the shaft neck speed and radial load increase,the turbulent pressure gradient increases,and the modal response amplitude of the bearing in the high-frequency range also increases.

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• Study on Lubricating Properties of Soybean Protein Thickeners for Dysphagia
  ZHANG Cheng; QIAN Shanhua; SONG Xiaofei; JIANG Yujing; HUANG Jianfeng
  Abstract:In order to explore the feasibility of soybean protein as a food thickener for patients with dysphagia,based on the rheological and tribological evaluation methods,the rheological behaviors of soybean protein solutions with different mass fraction were tested on the MCR301 rheometer,and the lubricating properties of soybean protein at different sliding rates under soft friction conditions were studied on the MFT-5000 wear tester.The results were compared with those of common starch and xanthan gum thickeners.The results show that the soybean protein solution shows the properties of weak gel,the viscosity of the solution increases with the increase of the soybean protein mass fraction,and the solutions still maintain a high viscosity after artificial saliva dilution.The soybean protein solution shows good lubricating properties under soft oral friction,and the friction coefficients decrease with the increase of the soybean protein mass fraction.Compared with starch and xanthan gum thickeners,the solution of soybean protein has a lower friction coefficient,and the research results provide a reference for the development of functional food for dysphagia.

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• Study on the High Frequency Reciprocating Piston Offset Character under Clearance Seal
  YANG Mingzhuo; JIAO Kexin; CHI Chunyun; LIN Mingqiang; LI Ruijie; MOU Jian; HONG Guotong
  Abstract:It is a common phenomenon that the balance position of the piston is offset in the thermal machinery composed of high-frequency reciprocating piston with clearance seal.For linear compressor and free-piston Stirling generator,the piston offset phenomenon will lead to the fracture of the plate spring,the decrease of output efficiency and the impact between piston and cylinder.In order to study the internal mechanism of the piston offset character under clearance seal and its affecting factors,the flow and leakage model of the clearance was established,and the accuracy of the model was verified through numerical simulation.Based on the sealing structure of the hundred watt free-piston Stirling generator,a thermodynamic and dynamic model was established,and the character of the piston offset caused by the clearance size and the external force was analyzed through the model.The results show that the reason of the piston offset phenomenon is that the net leakage of clearance is greater than zero in one cycle.The piston offset increases with the increase of the clearance size and external force under certain conditions.

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• Effect of Surface Texture of SLM Forming on Dry Friction and Wear Properties of TC4 Titanium Alloy
  FENG Qingyuan; TIAN Bin; HUANG Zhigang; WANG Ziyan; RAN Zhiyong
  Abstract:TC4 titanium alloy samples with pitted texture on the surface were carried on by a 3D metal printer with selective laser melting(SLM) technology,based on the one-step method.Optical camera,ultra-depth of field microscope and scanning electron microscope were employed to investigate the forming quality of pit textures.Laser confocal displacement tester and micro-Vickers hardness tester were used to analyze the surface roughness and surface hardness.The effects of texture density on the tribological properties of TC4 titanium alloy samples under different loads were studied by the tribological wear tester under dry friction conditions.The surface morpholoies before and after the friction test were analyzed by scanning electron microscopy.The results show that the one-step method of SLM forming is feasible to form pit texture on TC4 titanium alloy surface.With the increasing of texture density ,the surface roughness of TC4 titanium alloy sample increases and the surface hardness decreases.Under dry friction conditions,increasing the texture density of TC4 titanium alloy sample is beneficial for the collection of wear chips so as to reduce three body wear of the sample,increasing the load is beneficial for improving the contact state of the friction pair.Under 5 N load,the average friction coefficient and wear trace width of the sample with 40% texture density are the smallest,and compared with the TC4 substrate sample,the average friction coefficient and wear trace width are reduced by 12% and 16% respectively.For sample with 40% texture density,the increasing of loads will cause more wear loss and lower friction coefficient,along with more furrows and fragments on the worn surface.Under dry friction conditions,the surface texture prepared by 3D printing one-step method can significantly improve the abrasive wear and adhesive wear of TC4 titanium alloy sample.

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• Sealing Structure Design of High Pressure Vessel Based on PTFE Rectangular Sealing Ring
  LU Zhaijun; SUN Yonglong; ZHONG Mu
  Abstract:PTFE rectangular seal ring has the advantages of good chemical resistance and high section stability,which can effectively solve the sealing problem of corrosive media.However,in actual use,the size design of PTFE rectangular ring and its matching groove lacks reference.In view of the above problems,according to the shape and stress characteristics of the end sealing structure of high pressure vessels,a two-dimensional axisymmetric model of PTFE rectangular seal ring was established in Ansys Workbench,and a bilinear isotropic hardening model was used to characterize the mechanical properties of PTFE.The sealing structure of PTFE rectangular seal ring for high pressure vessels end face was analyzed and designed,and the influence of compression ratio,geometric parameters of PTFE rectangular seal ring and groove structure parameters on the physical quantities related to the sealing performance of pressure vessel end face was discussed.The results show that the compression ratio,height and width of the rectangular ring,and the gap between the rectangular ring and the groove sidewall have a greater impact on the sealing performance,while the inner diameter has a smaller impact on the sealing performance.Therefore,when designing,priority should be given to the parameters such as groove depth,cross-sectional size of the rectangular ring,and assembly position between the rectangular ring and the groove.The dimensions of PTFE rectangular seal ring and matching groove were determined,and the sealing performance of the designed sealing structure was verified using finite element simulation at room temperature and 30 MPa high pressure,confirming the rationality of the design.

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• Effect of Deposition Temperature on the Tribological Properties of CrN Coatings under Dry Friction and Soybean Oil Lubrication Conditions
  LI Yang; SUN Huilai; YANG Shuyan; CAO Lei; WAN Yong
  Abstract:To investigate the effect of deposition temperature on the tribological properties of CrN coatings,find a green lubricant suitable for the coatings,the CrN coatings were prepared by magnetron sputtering technique at different deposition temperatures.Their microstructure,mechanical properties,as well as friction and wear properties were evaluated by using X-ray diffraction,scanning electron microscope,atomic force microscope,scratch tester,nano-indentation and tribotester respectively.The results show that the CrN coatings deposited at 250 ℃ have the densest crystalline structure and the best mechanical properties.Tribological experiments show that the CrN coatings deposited at 250 ℃ exhibit the optimum tribological properties under both dry friction and soybean oil lubrication conditions.XPS analysis shows that the soybean oil undergoes a tribochemical reaction due to the presence of friction and forms a chemisorbed film on the coating surface.This film effectively reduces the friction and wear of the coatings.CrN coatings deposited at 250 ℃ have the optimum mechanical and tribological properties,and soybean oil is an excellent lubricant for CrN coatings.

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• Influence of Radial Clearance on Thermal Characteristics of Two-phase Flow in Angular Contact Ball Bearing
  WANG Zhan; YIN Zhichao; WANG Zinan; LIU Zhenpeng
  Abstract:Radial clearance directly affects the distribution of two-phase flow and the thermal characteristics of angular contact ball bearings.In order to explore the thermal characteristics of oil-gas lubrication two-phase flow in angular contact ball bearings under different radial clearance,a numerical analysis model was established based on two-phase flow theory and bearing heat transfer mechanism to simulate the flow characteristics of oil-gas two-phase flow in bearing cavities,and to analyze the effects of radial clearance and bearing operating conditions on the flow field distribution and temperature rise in bearing cavities.The simulation results was verified by the bearing temperature rise test results.The results show that the oil phase is mainly distributed in the bearing outer ring under the influence of centrifugal force,and the increase of radial clearance reduces the volume fraction of oil phase.Bearing temperature rise decreases with the increase of radial clearance,and increasing radial clearance can reduce bearing heat generation to a certain extent.The research results provide a reference for exploring the oil-gas lubrication thermal characteristics of angular contact ball bearings and improving the structural parameters of the bearing cavity.

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• Thermodynamic Behavior and Tribological Performance of Textured Brake System in a Heavy Vehicle
  LI Jiachen; LI Junning
  Abstract:The transient high temperature and water intrusion can easily lead to the degradation of thermodynamic behavior and braking performance of the brake system of heavy vehicles.To investigate the influence of surface texture on the thermodynamic behavior and tribological characteristics of brake systems,the thermodynamic analysis of the brake system was carried out based on the finite element method,and considering the extreme case of liquid lubrication in brake systems as a large amount of water intrusion,an improved lubrication analysis model of the textured brake system was established.The results show that the horizontal groove texture of the brake lining can make the temperature and stress distribution of the brake disc more uniform,thereby avoiding the occurrence of vehicle brake failure caused by local high temperature in the contact area.With the increase of the groove inclination angle,the load capacity increases and the friction coefficient decreases.For the different combination textures types,the cylindrical and ellipsoidal combined textures have the highest surface bearing capacity and the lowest friction coefficient,while the taper and ellipsoidal combined textures have the lowest surface bearing capacity and the highest friction coefficient.It is helpful to improve the working performance of the brake system in a heavy vehicle by constructing groove texture and combination texture on the brake lining surface.

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• Sealing Performance Analysis of Rectangular Special-shaped Piston in Cement Ring Crusher
  WU Mengdi; WANG Guorong; ZHONG Lin; ZHANG Linfeng; WANG Dangfei; FENG Qing; ZENG Qintao; ZHANG Wenchao
  Abstract:Aimed at the problem of inadequate load-bearing capacity of the traditional cylindrical hydraulic piston,a rectangular piston was proposed and its sealing performance under different working conditions was investigated.Based on Abaqus software,the finite element model of the special-shaped piston was established to study the influence of medium pressure,sealing gap,piston motion state and friction coefficient on the sealing performance,and the stress distribution and overturning of the special-shaped sealing ring at different positions were analyzed.The results show that the higher the medium pressure,the higher the maximum Mises stress and the maximum contact stress of the seal ring; the smaller the seal gap,the higher the maximum Mises stress and the maximum contact stress.Compared to the static seal,the maximum Mises stress and maximum contact stress both increase significantly during the internal stroke and increase with the friction coefficient.However,the difference between the maximum Mises stress and the maximum contact stress in the external stroke is relatively small compared to the static seal.The maximum stress values under all working conditions occur in the circular arc section of the sealing ring.During the movement of the piston,the sealing ring did not flip,but there is a displacement in its position.The results prove the feasibility of the special-shaped piston and its good sealing performance,and provide a basis for the design and optimization of the piston structure.

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• Effect of Groove-texture on Disc Braking Squeal
  ZHU Qi; TANG Mingzu; TANG Li; DENG Yangyang
  Abstract:To study the effect of groove-texture on disc brake squeal of disc brake systems,based on the frictional self-excited vibration theory,the finite element models of disc brake system with ordinary pad and grooved pad were established respectively.The friction self-excited vibration characteristics of the disc brake systems were studied by using complex eigenvalue analysis method.The parametric analysis of groove width and depth was carried out by using the finite element model,and the variation law of their effects on brake squeal was obtained.The results show that the friction self-excited vibration between the brake pad and the brake disc is the main cause of brake squeal.The grooved pad has a significant effect on restraining the possibility of brake squeal.Parametric analysis shows when the groove depth is in the range of 5 mm to 20 mm,the stability of disc braking system shows a gradual decrease with the increase of groove depth,indicating that the smaller the groove depth,the less the possibility of friction self-excited vibration.When the groove width is in the range of 5 mm to 20 mm,the stability of the brake system decreases first and then increases.When the groove width is 10 mm,the system is most likely to brake squeal.

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• Structural Parameter Analysis of U-spring Based on Finite Element Analysis and Response Surface Method
  LIU Dengyu; ZHAO Jun; LI Shuangxi; YAN Xinxin; CHENG Tianfu
  Abstract:Compression performance of spring energized seal is the key to evaluating the reliability of electro-hydraulic actuator.While as the elastic component of the spring energized seal,the compression stiffness and maximum elastic compression of U-spring are the main factors determining the energized performance.An elastic-plastic finite element model of U-spring was established based on the standard measured material parameters.The compression stiffness,maximum elastic compression and maximum linear compression of U-spring were obtained.The influence of typical structural parameters of U-spring on compression performance was analyzed,and a multi-factor mathematical model was constructed based on the response surface method.The accuracy of the calculation model was verified through multiple spring compression tests.The results show that spring thickness,total section length,slotting width,period width and bending radius are the main influencing factors of compression stiffness,and their effects decrease sequentially.Spring thickness,total section length,and root arc radius are the main influencing factors of maximum elastic compression,and their effects decrease sequentially.The repeated compression test shows that the plastic deformation caused by spring yield will accumulate with the number of compression cycles,leading to a decrease in the width of the spring opening and a decrease in the dynamic sealing performance of the sealing ring.When the energy storage sealing ring is used for dynamic sealing,its compression should not exceed the maximum elastic compression.

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• Performance Analysis of Packer Rubber Tube under Closed Annulus Pressure Variation in Deep Water Test
  SUN Qiaolei; XIA Le; LIU Yuwei; FENG Ding; HOU Lingxia; DENG Long
  Abstract:In order to investigate the deformation and strength of double packers in deep water test under closed annulus pressure variation,a mechanical analysis model of double packer rubber tube structure was established.According to the packers closed annulus pressure variation during the working process,the sealing performance of the rubber tube was analyzed,and the strain,equivalent stress and contact stress of each rubber tube were obtained.The contact characteristics of the packer rubber tube and casing at different circular chamfer parameters of the tube were analyzed,the influence of the tube chamfer parameters on the sealing performance of the packer was studied,and the optimized structural parameters of the packer were obtained.The results show that the strain,equivalent stress,and contact stress of each rubber cylinder all increase with the increase of the closed annulus pressure,and the increase of the lower rubber cylinder is the most significant.With the increase of circular chamfer,there is no significant change in the deformation of each rubber tube,but the equivalent stress decreases.As the circular chamfer increases,the contact stress of the upper rubber tube and the middle rubber tube increases,while the contact stress of the lower rubber tube increases first and then decreases.The conclusion shows that the increase of chamfer is beneficial to the sealing performance of the packer,and the structure is optimal when chamfer radius is 0.75 mm.

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• Influence of Floating Ring Elastic Deformation on the Lubrication Characteristics for Floating Ring Hydrodynamic/Hydrostatic Bearing
  YANG Shuai; HOU Junxing; XI Shuanghui; AN Xiaodong
  Abstract:The floating ring will generate elastic deformation under the effect of the lubricated film pressure for high-speed journal floating ring bearing,which affects the bearing lubrication performance.For a floating ring hydrodynamic/hydrostatic bearing with deep/shallow pockets,the finite element method and finite difference method were employed to solve Reynolds equation coupled with energy equation and temperature-viscosity equation,and the deformation matrix method was applied to solve the elastic deformation equation.The floating ring deformation distribution was obtained,and the influences of deformation on the ring speed ratio,load carrying capacity and oil flow leakage were analyzed based on floating ring equilibrium.The results indicate that the elastic deformation distribution is consistent with film pressure field,and the elastic deformation increases with the increase of shaft speed and eccentricity.While considering floating elastic deformation and the floating ring reaches equilibrium,the inner film eccentricity ratio increases,the ring speed ratio drops,and both load carrying capacity and friction moment increase.Due to the different influence of the elastic deformation on inner and outer clearances and flow resistances,inner film flow leakage grows,whereas the outer film flow leakage drops.

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• Experiment and Simulation Research on Friction Noise Based on Pin-on-Disc Test Machine
  ZHAO Pengpeng; CHEN Guangxiong; DONG Bingjie; FENG Xiaohang; ZENG Ziyi; HE Quanxin
  Abstract:In order to study the generation mechanism and influencing factors of friction noise,a friction noise experiment was carried out on the pin and disc samples made of the materials which are the same as that used to make the crankshaft-flange of a rotary compressor using a pin-on-disc test machine.The finite element model of the pin-on-disc test machine was established by ABAQUS finite element software,and the main frequency of the friction noise of this friction system was predicted by the complex eigenvalue method and compared with the experiment results.The influence of relevant parameters on the stability of system and friction noise was discussed.The results show that the coupling of the normal and lateral vibrations of the pin and disc is an important factor causing self-excited vibration and friction noise.When the friction coefficient at the friction interface of the system exceeds the critical friction coefficient of the system,the system unstable vibration appears,and the larger the friction coefficient,the larger the occurrence propensity of the system unstable vibration and the friction noise are.The normal load has little effect on the unstable vibration of the system.Selecting a friction pair material with appropriate elastic modulus can suppress the generation of friction noise.

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• Research on the Wear Rule of Universal Cross Shaft of Screw Drill Based on Archard Model
  ZHANG Ruiyao; FANG Zhixue; ZHANG Jingwang; REN Bijing; XIAO Ping; ZHU Zhongxi
  Abstract:The cross cardan shaft plays an important role in the transmission of torque and speed of screw drilling tools.However,the movement wear of the cross cardan shaft greatly reduces the transmission efficiency.In order to explore the motion law of the engagement surface of the cross universal joint shaft and the wear law of the anti-wear alloy block,the joint simulation physical model of the multi-body motion of the cross universal joint shaft and the calculation of the wear volume of the alloy block was established.According to Hertz contact theory and Archard wear theory,the contact boundary conditions of the simulation model were set,and the wear conditions were defined.The law of motion between mating surfaces and the law of contact force variation of conjugate motion pairs were studied.The movement path and contact force peak value of the meshing surface obtained from multi-body motion simulation were used as the boundary conditions for wear analysis of the anti-wear alloy block,and the influence of different structural forms on the wear volume of the anti-wear alloy block was studied.The results show that when the meshing is stable,the meshing surface will produce reciprocating sliding friction along the composite direction of tangential and axial direction,and the contact force presents a periodic fluctuation law.The different structure shapes and key structural parameters of the contact surface have significant effects on the wear amount of the alloy block,the use of concave double slope structure can effectively improve the wear resistance of alloy blocks.This research can provide a reference for the structural optimization design of the cross cardan shaft and the improvement of its wear resistance.

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• Research on Spalling of Prefabricated Defective Ball Bearings
  YANG Jinglai; TONG Wenwei; LIU Yujia; SUN Jigang; LIU Dongxu; TIAN Rugang
  Abstract:To study the spalling law of aviation engine ball bearings,four sets of ball bearings were used to simulate the actual pits or spalling pits by forming different numbers and distribution of pits on the surfaces of the outer races.The spalling tests of prefabricated defective main bearing were carried out on a bearing tester,and atomic emission spectroscopy,laser net fines analysis and ferrography were used to analyze wear particles in the lubricating oil.The results show that the wear particles generated during bearing peeling are mainly fatigue particles,supplemented by severe sliding particles and cutting particles,and oxidation phenomenon is also found.The spherical particles are mainly below 5 μm,a few distributes from 6 μm to 10 μm,barely above 10 μm.There is an increase (sometimes a sharp increase) in the total particles or the number of large-sized particles during the bearing peeling process.The spalling mechanism of aviation engine ball bearings is as follow:fatigue cracks first appear at the edges of prefabricated pits,and then diffuse to the surface or sub-surface of the outer ring raceway to form a peeling zone,which is caused by the poor dynamic lubrication behind the pits.The peeling area continues to expand along the circumference towards both sides,gradually covering the prefabricated pits,forming a large peeling zone and ultimately leading to bearing failure.

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• Optimization Design and Analysis of Rubber Ring for Thermal Pipelines Based on ANSYS
  ZHOU Xia; HUANG Jian
  Abstract:Focuses on the fracturing phenomenon that occurs after the aging of the sealing structure at the interface of cast iron pipes,the structure of the sealing ring was optimized.Four new rubber sealing ring structures were proposed by reducing the compression rate of the soft rubber part of the original hard rubber and soft rubber combination sealing ring and improving the shape of the soft rubber part.Finite element simulation analysis was conducted on the rubber sealing ring using ANSYS,and static simulation analysis was conducted on the rubber sealing ring under the conditions of considering partial load and minimum compression.The results show that the new structure,which transforms the soft rubber part from circular to lemon shaped and reduces compression rate,has the best sealing performance.However,under eccentric loading,the stress concentration at the soft hard rubber connection is severe,and due to structural reasons,there is a stress “inflection point” at the head.The new structure is optimized,and the optimized structure can effectively improve the stress concentration phenomenon under eccentric loading and compression without reducing the sealing force.

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• Analysis of Magnetic Field in a Non-contact Mechanical Seal Hydrodynamical Lubricated by Magnetic Fluid
  ZHANG Penggao; WEI Long; FENG Xiu; FENG Fei
  Abstract:To study the magnetic field characteristics in a non-contact mechanical seal lubricated by the magnetic fluid,the magnetic field intensity and the magnetic induction intensity in the sealing system were numerically simulated by Ansoft Maxwell.The effects of the magnetic fluid film thickness and the current intensity on the magnetic field intensity and the magnetic induction intensity were analyzed,and the relationship between the magnetic induction intensity and the current intensity in the magnetic fluid film was fitted by the last square method.The results indicate that the magnetic induction lines appear as complete “O” loops in the whole sealing system,and the magnetic induction intensity in the magnetic fluid film is the largest.The magnetic induction lines pass through the magnetic film vertically and evenly.When the current intensity is constant,both the magnetic induction intensity and the magnetic intensity are constant along the film thickness direction,both of which increase with the increase of current intensity.

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