Volume 49,2024 Issue 3

• Research on Multi Focus Fusion Algorithm of Ferrographic Wear Particle Image
  WANG Han; ZUO Hongfu; LIU Zhenzhen; FEI Hang; SU Yue
  Abstract:Ferrography is a commonly used wear monitoring technology.Limited by the depth of field under the high- magnification objective lens,a ferrography image of large wear particles often has only the features of clear local focus.In order to solve the problem of automatic and clear collection and high- magnification image fusion of ferrography large wear particle images under high magnification objective lens,an automatic scanning microscope system was designed and constructed,which can automatically scan and collect the multifocal ferrography images.A multifocal fusion algorithm of ferrography images based on phase consistency was presented to fuse the automatically scanned multifocal images,and clearer wear particle images were obtained.The experimental results show that the automatic scanning microscope system can quickly complete the automatic acquisition process of multifocus ferrography images,and the image fusion algorithm presented has higher image evaluation quality than the traditional wavelet image fusion algorithm,and can obtain clearer image edge information.

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• Effects of Groove Parameters on Sealing Performances of Liquid-film Seal with Inclined-straight Grooves
  LI Zhentao; PANG Minmin; WEI Huijuan; ZHOU Yangli; LI Xiaoying; HAO Muming
  Abstract:To further explore the effect mechanism of the inclined-straight groove on the sealing performances,the hydrodynamic lubrication model of the liquid-film seal with inclined-straight groove was established based on the boundary of mass conservation and the liquid film density ratio defined.The finite difference method was adopted to discretize the equation,and the theoretical and experimental values of cavitation zone in the liquid film were compared and analyzed to verify the accuracy of the calculated model and program.The influences of structure parameters of inclined-straight groove on the sealing performances were investigated，including groove number,groove depth,radial and circumferential groove width ratios.Results show that within the critical range under different slant angles,increasing the groove number or groove depth is helpful to improve the liquid-film load-carrying capacity,increase the leakage and effectively reduce the liquid-film cavitation zone,especially under the condition of larger slant angles.In a certain range,although increasing the radial and circumferential groove width ratios can enhance the liquid-film load-carrying capacity,promote the cavitation occurrence,and increase leakage,the influence laws are not the same.With the liquid-film load-carrying capacity as the improvement goal,the optimal groove parameters are as follows:groove number 42,groove depth 25 μm,radial and circumferential groove width ratio 0.7 and 0.6,respectively.

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• Static Characteristics Analysis of Radially Misaligned Textured Gas Foil Journal Bearing
  HE Zhenpeng; ZOU Yuchen; WANG Zhi; ZHAO Fuxing; YU Hao; LI Baichun; LIU Quan; XIN Jia
  Abstract:To further investigate the effect of surface morphology on gas foil bearings,the effect of surface roughness and surface texture on the static characteristics of radial gas foil bearings under misalignment was investigated by numerical analysis.The Reynolds control equation of the gas foil bearing was solved by Successive Over Relaxation (SOR) and finite difference method.The static characteristics of the bearings were analyzed under different parameters,including the texture shape,texture depth,texture number,texture ratio and surface roughness.The results show that the effects of different shapes of textures on the performance of gas foil bearings are different,and the elliptical texture is more effective in improving the static characteristics of the bearings.There exists a set of relatively optimal values of the texture depth,texture number and texture ratio,which can improve the bearing load capacity and reduce the frictional moment at the same time.Compared with the non-textured radial gas foil bearings,the radial gas foil bearing with specific texture can increase the load carrying capacity by 36.32% and reduced the frictional torque by 1.66%.

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• Study on Gearbox Labyrinth Seal Leakage Based on Transient Finite Element
  CHEN Ziang; FAN Jingyuan; SHEN Longjiang; HU Yumei; YANG Guangcheng
  Abstract:A finite element model of gearbox and labyrinth seal structure was established based on ANSA software and the multiphase flow transient simulation analysis was carried out by FLUENT software to solve the lubricating oil leakage problem of a high-speed train gearbox labyrinth seal.The influences of the relative meshing depth,throttle tooth thickness,radial clearance,diameter and number of oil return hole,distance between tooth and step,tooth width and seal clearance on the oil leakage of labyrinth seal structure were studied.The results show that when the relative meshing depth is greater than 0.5,the oil leakage is negatively correlated with the relative meshing depth.The oil leakage is negatively correlated with the throttle tooth thickness,the diameter and number of oil return hole.The oil leakage is positively correlated with radial clearance,tooth width,distance between tooth and step and seal clearance.According to the study results,the labyrinth seal structure was improved,and the oil leakage of the improved labyrinth seal structure was reduced to 3.6% of the original leakage.

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• Static Characteristics of Dynamic and Hydrostatic Pressure Gas Bearings with Herringbone Grooves and Axial Micro-channels
  LI Shusen; MA Tianxiao; MU Yanpu
  Abstract:The dynamic and hydrostatic gas bearing with herringbone groove and axial micro through groove was designed,and the static characteristics were simulated and analyzed by FLUENT.The effects on the bearing stiffness and bearing capacity were studied by changing the parameters such as axial micro through groove depth,eccentricity,film thickness and air supply pressure.The results show that when other conditions remain unchanged,the greater the eccentricity,the smaller the bearing stiffness and the greater the bearing capacity.Herringbone grooves can enhance the bearing capacity and stiffness of gas bearing,the faster the spindle speed,the stronger the dynamic pressure effect,and the greater the bearing stiffness and bearing capacity.As the axial micro groove depth increases,the bearing stiffness first increases and then remains stable,and the bearing capacity first increases and then decreases.Therefore,when the axial micro groove depth is too large,the bearing stiffness changes little,but the bearing capacity will decrease.

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• Effect of Structure and Morphology of Aramid Yarn on the Tribological Properties of Aramid/PTFE Fabric Composites
  CAI Ming; ZHANG Zhaozhu; JIANG Wei; LI Peilong
  Abstract:In order to study the effect of yarn structure and morphology on the tribological properties of fabric composites,three kinds of aramid yarns with different structure and morphology were prepared from para-aramid fiber,namely filament parallel yarn,filament twisted yarn and short fiber twisted yarn.Three kinds of aramid/PTFE fabric composites were prepared by the same process.The tribological properties of the composites were evaluated by multi-specimen test machine.The structure and morphology,mechanical properties and tribological properties of aramid/PTFE hybrid fabrics and corresponding composites were analyzed.The experimental results show that the structure and morphology of aramid yarn can affect the tribological properties of aramid/PTFE fabric composites.This is because the structure and morphology of aramid yarn directly change the yarn strength,the yarn pull-out strength,and the interfacial bonding force with the resin.The abrasion resistance of the hybrid fabrics varies with wear conditions.When the load is relatively low,the wear rate of aramid short fiber twisted yarn/PTFE fabric composite is lower,while when the load is higher,the abrasion resistance of aramid filament twisted yarn/PTFE fabric composite is better.

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• Multi Physical Field Coupling Characteristics of High Speed Graphite Seals
  ZHOU Huaning; LI Guoqing; WANG Chenfeng
  Abstract:Graphite seals operating at high circumferential velocity are often accompanied by high heat frictional wear,in order to meet the sealing requirements of high circumferential velocity and low-pressure differential conditions,multiple physical coupling model was established based on the four segments graphite seal.The accuracy of the calculation model was verified by comparing the calculated results with the experimental results.Based on the multi physical field coupling analysis,the coupling characteristics of flow field,temperature field and structural field of high velocity graphite seals under high circumferential velocity and low-pressure differential conditions were studied.The results show that the pressure of the sealing gas at the circumferential groove and the lap of the sealing ring is unbalanced,the velocity distribution is uneven and the flow field is disordered near the outlet.The leakage amount decreases with the increase of seal circumferential velocity and increases with the increase of seal pressure difference.The temperature,deformation and stress of the seal ring increase with the increase of the seal circumferential velocity.The temperature field has the greatest influence on the structure of the seal ring.The sealing gas can alleviate the deformation of the seal ring,but the gas force will increase the stress value of the seal ring.The friction heat has a significant effect on the sealing structure,the lap joint of ring section and anti-rotation pin are the weakest links of seal ring.

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• Structure Design and Static Characteristics Analysis of a New Variable Controllable Three Oil Wedge Bearing
  FAN Fengcheng; GUO Hong; SHI Minghui; CHEN Shujie
  Abstract:The traditional three-oil wedge bearing has a fixed structure shape and a single operating condition,in order to adapt to the changing working conditions,a variable and controllable three-oil wedge bearing was proposed.The piezoelectric stack is introduced into the bearing structure,and the piezoelectric stack generates a driving force under the action of DC drive voltage,so that the inner surface of the bearing changes from a round to a three-oil wedge shape,and the bearing deformation can be controlled by changing the voltage.The structure and working principle of the bearing were introduced,CREO software was used to establish the geometric model of the oil film under different driving voltages and the model was imported into the pretreatment software icem for structured meshing.The static characteristics of the bearing under different voltages,eccentricities and speeds were calculated and analyzed based on the two-phase flow model in fluent software.The results show that changing the driving voltage can change the oil film clearance of the three-oil wedge bearing,and then adjust the oil film pressure distribution and static characteristics.At the same speed and eccentricity,with the increase of the driving voltage,the deformation of the variable three oil wedge bearing increases,the bearing capacity and friction force gradually decrease,and the flow rate gradually increases.

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• Analysis of Creep Relaxation Characteristics of Latex Gasket at Different Temperatures
  GUO Ziyu; LI Yuxian; LIU Meihong; ZHANG Jingquan; ZHANG Jie
  Abstract:Creep relaxation occurs when the gaskets of bolted flange joints are used for a long time.Creep relaxation of the gasket can cause fluid leakage inside the joint.To prevent leakage of sealing fluid from flange joints,it is important to establish a method to predict gasket creep and stress relaxation.A three-parameter Kelvin fluid model was used to establish an analytical model for predicting the residual stress of gaskets at high temperature creep with time,and the creep relaxation experiments of the latex composite gasket at different temperatures and different stress loads were carried out.The results indicate that under the same stress load,the higher the temperature of the latex composite gasket,the more obvious the residual stress decreases,the greater the stress load,the more stress is lost,and the residual stress decreases gradually over time.The high temperature creep relaxation behavior of the gasket can lead to the decrease of the mass and thickness of the gasket.But as the gasket stress load continues to increase,the decreased trend of mass and thickness of the gasket at the stress load will be slowed down.However,with the increase of temperature,the mass and thickness of the gasket continue to decrease,and the downward trend will not slow down.The predicted value of the three-parameter Kelvin fluid model is very close to the experimental data,and the maximum error is 4104%.The model can accurately describe the mechanical behavior of the gasket and the stress load loss caused by the creep relaxation.

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• Research on the Journal Center Motion Trajectory of Spherical Hybrid Sliding Bearings
  QIN Wei; SHEN Jingfeng; ZHU Rui; CHENG Pan; XUE Hao; XUE Weiqiang
  Abstract:In order to study the influence of external load on the stability of the rotor bearing system,the dynamic model of the rotor system of spherical hybrid sliding bearings with orifice throttling was established.The bearing lubricating mathematical model was solved,and the nonlinear oil film force was obtained.The external load on the rotor was analyzed,the Euler algorithm was used to predict the displacement,velocity and acceleration of the shaft center at the next time,and the influence of rotor system mass,unbalanced load and step load on the rotor motion trajectories was analyzed.The results show that the increase of the rotor system mass leads to the increase of the oil film force and the shaft center vibration amplitude,thereby reducing the rotary accuracy of the rotor.Compared to not considering unbalanced loads,the vibration shape is elliptical and the vibration amplitude increases after the unbalanced load is considered.Reducing the unbalance value will reduce the vibration amplitude and increase the rotary accuracy.As the step load increases,the equilibrium convergence time also increases.

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• Tribological Properties of High Entropy Carbide (AlTiVCrNb) C Coating Prepared By Magnetron Sputtering
  ZHANG Yinghao; HOU Xuebin; CAI Haichao; XUE Yujun; PEI Lulu; TIAN Changling
  Abstract:In order to improve the tribological properties of high-entropy alloy coatings,(AlTiVCrNb)C coatings were prepared by co-sputtering of graphite and high-entropy alloy,and the tribological properties of(AlTiVCrNb)C coatings were studied.Scanning electron microscopy (SEM) and X-ray diffraction (XRD) were used to analyze the composition,surface morphology and phase of the film.The hardness,elastic modulus and tribological properties of the coatings were tested by nanoindentation and ball-on-disk friction and wear tester.The wear of the coating was characterized by white light interference three-dimensional topography instrument.The experimental results show that with the increase of carbon content of the coating,the high entropy component changes from BCC/FCC dual phase to single FCC structure,and the microstructure of the coating also changes.Due to the formation of carbides and solid solution strengthening,the coating exhibits good tribological properties.When the carbon atom fraction of the coating is 20.83%,the friction and mechanical properties of the coating are optimal,and the friction coefficient is the lowest of 0.35,the hardness and elastic modulus of the coating are the highest,which are 17.84 GPa and 182.72 GPa,respectively.It can be concluded that the high-entropy carbide (AlTiVCrNb) C coating with good tribological properties can be obtained by co-sputtering graphite and AlTiVCrNb high-entropy alloy in magnetron sputtering process.

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• Research on Antifriction Performance of Copper Doped Carbon Quantum Dots in a Wide Temperature Range
  CHEN Shihao; WANG Junhai; LI Xinran; ZHANG Lixiu; LI Ting
  Abstract:To improve the friction performance of mechanical system in a wide temperature range,taking copper gluconate and diethylenetriamine as raw material,copper doped carbon quantum dots (Cu-CQDs) was synthesized with one-step hydrothermal method.Cu-CQDs was dispersed into PAO base oil,and the tribological properties of the oil sample containing Cu-CQDs were studied in atmospheric environment and at different temperatures(25 ℃,100 ℃,200 ℃,300 ℃).The results were compared with those of the oil sample containing zinc dialkyl dithiophosphate (ZDDP).The results indicate that Cu-CQDs and ZDDP can increase antifriction and wear resistant properties of PAO base oil,but the performance of Cu-CQDs is superior to that of ZDDP.Especially at 300 ℃,the oil sample containing Cu-CQDs has the most obvious antifriction and wear resistant advantages,its average friction coefficient decreases by 51% compared to PAO base oil and by 11% compared to oil sample containing ZDDP.The high temperature friction mechanism of Cu-CQDs was analyzed.It is found that Cu-CQDs undergoes complex frictional chemical reaction on the surface of the friction pair during high-temperature friction,generating a series of metal oxides,carbides,and other frictional chemical products.These substances form a protective layer on the surface of the friction pair,which has the effect of relieving the contact and friction of friction pair.

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• Effect of Environmentally Friendly Corrosion Inhibitor Chito-oligosaccharide on CMP of 304 Stainless Steel
  ZHANG Xin; CHEN Guomei; NI Zifeng; JI Mingjie; ZHENG Shikun; BIAN Da; QIAN Shanhua
  Abstract:In order to study the effect of environmentally friendly additive chito-oligosaccharide(COS) on the chemical mechanical polishing process of 304 stainless steel,and to explore its interaction and adsorption mechanism with metal surface during the polishing process,the influence of COS organic molecules on chemical mechanical polishing of 304 stainless steel was studied using methods such as chemical mechanical polishing experiments,contact angle measurements,scanning electron microscopy (SEM) and energy dispersive spectrometer(EDS) analysis.The global reaction parameters of COS molecules were studied by quantum chemical calculation,the reaction active sites were analyzed and calculated,the adsorption of organic molecules on metal surface was simulated by molecular dynamics,and the radial distribution of active atoms was analyzed.The results show that the incorporation of COS in the chemical mechanical polishing (CMP) process leads to the formation of a hydrophobic film on the surface of 304 stainless steel via adsorption mechanisms.This film effectively hinders the etching action of oxidizing agents on the stainless steel surface,thereby enhancing the resulting surface quality after the polishing treatment.The best surface quality with surface roughness of 1.65 nm is obtained when the mass concentration of COS is 400 mg/L.Quantum chemistry studies show that the active reaction sites of COS are mainly O atoms,which can form multicentric adsorption on metal surfaces.Molecular dynamics simulations show that COS organic molecules can be adsorbed on metal surfaces in parallel,and O atoms in organic molecules can form coordination bonds with iron atoms,which dominates adsorption.

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• Simulation Study of Thermal and Oxygen Aging and Friction Properties of Molybdenum Disulfide/Nitrile Butadiene Rubber
  LIU Zhongqiang; CHEN Jichi; WANG Shijie; GUAN Xueming; LIU Xiaofei
  Abstract:In order to investigate the effect of molybdenum disulfide (2H-MoS2) on the thermo-oxidative aging and tribological properties of the composites of antioxidant 4020 and nitrile butadiene rubber (NBR),molecular dynamics (MD) simulations were used to establish the models of 4020/NBR and MoS2/4020/NBR composites,respectively.The effects of 2H-MoS2 on the thermo-oxidative aging properties,mechanical properties,and tribological properties of the composites at different temperatures were analyzed.The results show that the compatibility,stability and thermo-oxidative aging properties of the composites are effectively improved after adding MoS2,and the mechanical properties are also significantly improved.Even at a high temperature of 398 K,the composite can show excellent thermo-oxidative aging properties and mechanical properties.Compared with 4020/NBR composite,the friction coefficients of MoS2/4020/NBR composite at 298 K and 398 K are reduced by about 30% and 25%,respectively,and the wear rates are reduced by 5% and 7%,respectively,which indicates that MoS2 can effectively improve the tribological properties of NBR composites.

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• Numerical Simulation of Erosion of High-pressure Elbow Considering Load Action
  YANG Siqi; FAN Jianchun; LI Dening; LIU Mingtao; HAN Lihong; WANG Jianjun; YANG Shangyu; LI Jiao
  Abstract:In the process of hydraulic fracturing,under the coupling effect of complex solid-liquid two-phase flow and severe loads,the weak parts of high-pressure manifold such as elbows,tees and joints suffer from severe erosion wear for a long time,which would easily lead to the fracture and damage of the pipe fittings and pose a serious threat to the personnel and equipment on site.The erosion wear experiments involving applied stress were carried out.According to the test results,a new erosion model considering the effect of stress state was developed based on E/CRC erosion model,and the agreement between the new model and the erosion test data can reach more than 95%.The three-dimensional numerical simulation of the erosion performance of the high-pressure pipe fitting was carried out using the computational fluid dynamics-discrete phase model (CFD-DPM),and the severity and spatial distribution of erosion wear under different fracturing conditions were investigated.The results show that the main erosion zone is located on the elbow extrados near the elbow exit,and the maximum erosion rate of the elbow is also located there.Under the action of the secondary flow vortex on the inside of the elbow,driven by the secondary flow vortices inside the elbow section,some particles move and accumulate in the inner wall of the downstream straight pipe near the elbow exit.Accordingly,the secondary erosion region is made apparent in this area.With the increase of the particle Stokes number coefficient,the area of the main erosion zone increases and the area of the secondary erosion zone decreases.In addition,after embedding the new erosion model,it can be observed that the erosion wear rate at the elbow of the high-pressure elbow increases significantly as the operating pressure increases.

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• Simulation Research and Verification of Assembly Process of VL Composite Seal For Shaft
  WANG Yueming; LV Xiaoren; XIANG Chong; HUANG Le; GUO Fei
  Abstract:The rubber seal is composed of a rubber ring and a plastic seal ring.The deformation of the plastic ring during installation has an important effect on the sealing performance.VL type combined seal for shaft was taken as an example,based on three-dimensional finite element simulation model and visual seal assembly platform,the assembly process of different processes was studied.The sealing ring assembly process was restored in the finite element simulation,the visual sealing assembly platform was built,and the sealing assembly test was carried out to verify the accuracy of the finite element simulation assembly process.The key parameters such as contact pressure and contact width of sealing interface were extracted to evaluate sealing performance.The relationship between sealing performance and assembly process was established,the sealing installation and correction process was optimized to solve the randomization and experience of assembly process.The test results indicate that the contact width of the sealing surface is smaller than that of the heating installation at room temperature.In terms of the shaft,under identical medium pressure conditions,a narrower contact width corresponds to higher contact pressure on the sealing surface and superior sealing performance.Therefore,it can be concluded that assembling at room temperature yields improved sealing performance.

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• Research on the Sealing Performance of Y-shaped Combined Sealing
  ZHANG Fuying; YANG Pengwei; WU Jihao; HAN Zhao
  Abstract:The finite element model of YO-shaped combined seal was established by ABAQUS software.The static contact pressure and Mises stress distribution in the seal area were compared between Y-shaped composite seal and Y-shaped seal,two Y-shaped composite seals made of polyurethane and nitrile rubber(NBR) materials.The influences of O-ring diameter on the performance of Y-shaped combined seal made of the two materials were analyzed.The results show that the contact pressure and Mises stress of Y-shaped combined seal in the sealing area are greater than those of Y-shaped ring with the same specification and material during the instroke and outstroke of the piston rod,and the increase of contact pressure of the Y-shaped combined seal is more obvious and the stress distribution is more uniform during the outstroke of the rod,which verifies the characteristics of the double sealing and the improvement of root tear resistance of Y-shaped combined seal.When the O-ring diameter is the same,the maximum contact pressure difference between the outstroke and instroke of the polyurethane combined seal is much higher than that of the NBR combined seal,while the Mises stress distribution of the NBR combined seal is more uniform.With the increase of the O-ring diameter,the maximum contact pressure of the polyurethane combined seal increases first and then decreases,while the maximum contact pressure of the NBR combined seal gradually decreases.But the Mises stress of both show a gradually increasing trend,and the increase in NBR combined seal is more significant.The research results provide a reference for the selection of seals under different working conditions.

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• Effect of Cutting Fluid on the Surface Quality of β-Ga2O3 Wafer of Diamond Wire Saw Slicing
  WANG Xiaolong; GAO Pengcheng; TAN Baimei; DU Haoyu; WANG Fangyuan
  Abstract:In order to develop a cutting fluid more suitable for β-Ga2O3 wafer slicing,the effects of different cutting fluids on the surface quality of β-Ga2O3 wafer in the process of diamond wire saw slicing were explored.The wettability of different cutting fluids on β-Ga2O3 wafer surface was studied by measuring the contact angle and surface tension.The surface of the wafer was tested and characterized using roughness measuring instrument,non-contact thickness gauge,and scanning electron microscopy (SEM),and the effects of deionized water,the water-based cutting fluid and emulsified cutting fluid with AEO-9 on the surface roughness,surface topography,total thickness variation and sub-surface damage layer depth of β-Ga2O3 (010) wafer sliced under different wire speed and feed rate were investigated.The results show that both the emulsified cutting fluid and the water-based cutting fluid can effectively reduce the contact angle and surface tension on the β-Ga2O3 surface compared to deionized water,which indicates that the lubricating capacity of both cutting fluids is improved.The effect of emulsified cutting fluid fluctuates greatly with the change of process parameters,and the wafer surface quality can be obviously optimized only under the conditions of low cutting heat and large cutting force.However,the higher wafer surface quality can be stably obtained with the water-based cutting fluid.Therefore,the water-based cutting fluid is more suitable for β-Ga2O3 single crystal slicing.

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• Extrusion Failure Analysis and Structural Optimization of Sealing Ring of Pulley under Pressure
  WU Zebing; JIANG Mengjie; YANG Chenjuan; HU Shiyao; ZHANG Wenxi
  Abstract:In response to the problem of leakage caused by the extrusion failure of the sealing ring when the pulley under pressure is subjected to ultra high pressure in the working environment,combining the sealing structure and sealing principle of the sealing pulley,the finite element analysis model of the sealing structure was established,and the cause of the sealing failure was analyzed.It is found that the main reason for the failure of the sealing ring is that the gap between the inner and outer shells is too large,because the outer shell and inner shell of the pulley under pressure are clearance fit due to considerations of machining accuracy and cost,the excessive clearance between the inner and outer shells is produced when subjected to medium pressure and cable weight under actual working conditions,and there is also a certain gap between the rectangular retaining ring set on the pressure bearing surface of the sealing ring groove and the inner wall of the shell for ease of assembly.The O-ring cannot compensate for the larger gap between the inner and outer shells,and it will be squeezed into the gap under the pressure of the medium,and a stress concentration is also produced.An optimization scheme was proposed to replace the rectangular retaining ring with a triangular retaining ring.Through finite element analysis,it is found that the triangular retaining ring can effectively compensate for the gap between the inner and outer shells,preventing the sealing ring from being squeezed out and damaged.

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• Design of Oil-air Lubrication Parameter Optimization Test System and Platform for High-speed Spindles
  ZHANG Wenliang; AILIXIATI Yilihamu; XIE Xiaopeng; GAO Guogang
  Abstract:Oil-air lubrication is the most effective cooling and lubrication method for high speed spindle.However,to achieve the best lubrication effect,accurate oil air lubrication parameters must be set for different types of bearings and different working conditions.This requires reliable experimental equipment to conduct a large amount of experimental analysis.An experimental platform was built to simulate the operating conditions of the spindle,the oil-air lubrication system and an oil-air mixing and distributor that combines the functions of oil-air mixer and oil-air distributor were designed.The experimental results show that the optimal speed range of the experimental platform is from 0 to 30 000 r/min,which meets the speed requirements for high-speed machine tool spindle testing.The oil feeding error of the oil-air mixing and distributor meets the industry standard of ±10%,and its service life reaches 120 000 times.Therefore,the established experimental platform and oil-air lubrication system have high reliability in conducting experimental research on oil-air lubrication parameters of high speed spindle.

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• Experimental Study on Takeoff Speed and Bearing Capacity of Radial Spiral Groove Air Bearing
  HAN Yuanzhen; YIN Yufeng; WANG Jiayu
  Abstract:Take-off speed is an important performance index of air bearing.Taking spiral groove air bearings as the research object,perturbation method was used to solve the differential equation of pressure distribution of spiral groove gas lubricated bearings under isothermal compressible conditions,and the pressure distribution and bearing capacity of air bearings were obtained.Aiming at the maximum bearing capacity,the structural parameters of the spiral groove air bearing were calculated,and the designed air bearing was tested to explore its take-off velocity under different loads.The test results show that,under no-load condition,when the rotating speed is about 1 200 r/min,the rotor of the air bearing is out of contact with the bearing sleeve and the take-off speed is reached.The take-off speed and take-off torque both increase gradually with the increase of load,and the bearing capacity also increases with the increase of rotating speed.It is proved that the designed spiral groove air bearing has good performance,which provides the theoretical and practical basis for the subsequent design optimization and practical application of spiral groove bearing.

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• Lubrication Effect of Polyethylene Glycol/Polyvinyl Alcohol Composite Lubrication Film on Micro-arc Oxidation Ceramic Layer of Aluminum Alloy Surface
  FENG Zhi; JIA Endong; LIU Tao; LU Hailin
  Abstract:Micro-arc oxidation (MAO) technology can obviously improve the mechanical properties and surface properties of aluminum alloy.However,the ceramic layer obtained by MAO shows high roughness,which leads to great wear of aluminum alloy during friction.To improve the wear resistance of aluminum alloys,a composite film with excellent lubrication performance was prepared on the ceramic layer surface of aluminum alloy after MAO using hot pressed polyvinyl alcohol (PVA) and polyethylene glycol (PEG) polymers.The lubrication performance of the composite film was characterized under different frequencies,loads and lubrication conditions.X-ray diffraction (XRD) and Fourier transform infrared (FTIR) were used to analyze the formation mode and lubrication mechanism of the composite film.The results show that the composite film has good lubrication performance,and its friction coefficient is only 1/4 of that without the film.The composite film maintains good lubrication characteristics under dry friction,oil lubrication,and high-speed working conditions,but it will undergo local dissolution in water environment,resulting in poor lubrication performance.The network structure of the composite film and the self-lubricating characteristics of the polymer play an excellent lubricating role together.

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• Orthogonal Test and Multi Index Weighted Optimization of Resin Based Friction Materials for CR 200J
  SUN Hui; WANG Xiufei; CHEN Shaohua; YIN Cailiu; MENG Jieli
  Abstract:To explore the high wear-resistant resin based friction materials used for CR 200J,nine resin based friction material formulations with different content of friction reducing components (flake graphite,petroleum coke) and friction increasing components (NFJ high-temperature binder,cashew shell oil friction powder) were designed using orthogonal experimental method. The sample was prepared by thermoforming method,and the average friction coefficient of the samples was tested at braking pressure of 0.8 MPa and rotational speeds of 3 300 r/min,4 200 r/min,and 5 400 r/min.The volume wear rate,thermal degradation performance,and dual mass wear of the samples were calculated.Perform range analysis and homogenization treatment on the average friction coefficient,volume wear rate,thermal degradation performance,and dual mass wear of the samples were carried out,and the formula with excellent comprehensive performance was selected using multiple index weights.The results indicate that flake graphite has a stabilizing effect on the average friction coefficient of resin based friction materials and reduces their thermal degradation performance at high rotational speeds,while the petroleum coke has a stabilizing effect on the average friction coefficient of resin based friction materials during low-speed braking.The NFJ high-temperature binder has no significant effect on the various properties of resin based friction materials,while the cashew shell oil friction powder exhibits excellent viscoelasticity at high rotational speeds,which is beneficial for improving the average friction coefficient of the materials,reducing the volume wear rate and dual mass wear of the materials.The optimal formula was obtained by using multiple indicator weights,with a combination of mass fraction of 1% flake graphite,4% petroleum coke,3% NFJ high-temperature binder,and 6% cashew shell oil friction powder.

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• Study on Wear Particle Chain Segmentation Based on Color and Shape Information
  YANG Hai; SHENG Chenxing
  Abstract:In order to segment the wear particle chain in the ferrography image effectively and improve the accuracy of wear particle feature extraction,a wear particle chain segmentation method combining the color and shape features of the ferrography image was proposed by analyzing the characteristics of different regions of the ferrography wear particle chain image.Firstly,the image of abrasive chain was pre segmented based on morphological operation,and the abnormal large abrasive was extracted and the adhesion part of abrasive chain was disconnected.Then,the wear particle chain was segmented by the method of marked watershed and gray clustering.Finally,considering the difference of color information of different abrasive chains,the gray clustering was improved by combining the adaptive threshold method to realize the adaptive segmentation of abrasive chains.The results show that,compared with traditional segmentation methods,the proposed method can effectively avoid over segmentation and under segmentation,which has better segmentation effect,high applicability,and the operation is simple.

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• Influence of Test Bench Constraint on Identification Accuracy of Dynamic Characteristic of Sliding Bearing
  CHEN Runlin; TANG Jie; XU Fan; DU Chen; CUI Yahui; LIU Kai
  Abstract:In the dynamic characteristic test of sliding bearing,the test-bed parameters have an important influence on the test accuracy.An inverted dynamic characteristic test rig was taken as the research object,and a simulation evaluation method for the identification accuracy of the dynamic characteristic coefficient of the sliding bearing was proposed based on the forward and reverse problem of bearing dynamics.The influence of the constraint stiffness and constraint damping of the test bench on the identification accuracy of the dynamic characteristic coefficient of the bearing at different excitation frequencies was analyzed,and the range of excitation frequency and constraint parameters was optimized.The results show that at lower excitation frequencies,when the constraint stiffness and constraint damping of the test bench are small,the identification accuracy of the dynamic characteristic coefficients is not significantly affected by testing errors.As the constraint stiffness and constraint damping increase to a certain value,the identification accuracy of the dynamic characteristic coefficients is rapidly increased by the influence of the test errors.For this studied test bench,when selecting an excitation frequency between 30 Hz and 300 Hz,selecting the test bench constraint stiffness less than 0.3% of the test bearing stiffness,and the test bench constraint damping less than 7% of the test bearing damping,a good testing accuracy of the bearing dynamic characteristic coefficient can be ensured.

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• Coupling Analysis of Heat-fluid-solid in a Spiral Groove Mechanical Seal Lubricated by Magnetic Fluid
  ZHANG Penggao; WEI Long; FENG Xiu; FENG Fei
  Abstract:To study coupling effect of heat-fluid-solid in a spiral groove mechanical seal lubricated by magnetic fluid,the pressure distribution,temperature distribution of magnetic fluid film and deformation of rotating ring were calculated by ANSYS Workbench,and the effects of current intensity,rotating speed,and magnetic particle volume fraction on pressure,temperature of magnetic fluid film and deformation of rotating ring were analyzed.Results indicate that the pressure,temperature of magnetic fluid film and deformation of rotating ring increase with the increase of current intensity,rotating speed,and magnetic particle volume fraction.Near the inner radius,the temperature of magnetic fluid at the inner diameter is higher but the hydrodynamic pressure is lower,and the base fluid of magnetic fluid is prone to vaporization.The pressure deformation is far less than thermal deformation of rotating ring.The pressure and temperature obtained by numerical solution are larger than those obtained by analytical solution and experimental values,mainly because the effects of seal weir and centrifugal force on magnetic fluid film are considered in the numerical solution.

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• Research on the Application Characteristics of Electrochemical Impedance Spectroscopy Oil Condition Sensor
  LIU Minglei; WANG Zhihuan
  Abstract:On-line monitoring of oil conditions in the lubrication system of large machinery and equipment is one of the key technologies for lubrication fault diagnosis,and the difficulty lies in accurately monitoring the critical points of abnormal moisture and lubricating oil aging failure.According to the characteristics of slow and complex oil aging process and the change of lubricating oil impedance value caused by various factors,an oil condition sensor based on electrochemical impedance spectroscopy technology was studied.By continuously on-line monitoring the changes in bulk impedance,interface impedance,and high-frequency impedance of sensors under different lubricating oil states,it is found that the data trend of bulk impedance,interface impedance and high-frequency impedance can be used to judge the oil conditions.It is manifested that the lubricating oil state affects the bulk impedance and interface impedance values of the sensor,while the additive state affects the interface impedance values.The longer the oil is used,the higher the degree of aging and the higher the bulk impedance value.Pollutants and decomposition products affect high-frequency impedance values.The realization principle of the oil condition sensor was introduced,and the feasibility of the oil condition sensor to monitor the critical point of moisture and lubricating oil aging failure was demonstrated through experiments and engineering.The results show that,in a specific application scenario,the electrochemical impedance spectroscopy oil condition sensor can distinguish different oil conditions,and can accurately monitor the abnormal moisture and the critical point of aging failure in the lubrication system,which provides a basis for the safe operation and maintenance strategy of equipment lubrication.

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