The dynamic load distribution within in-service axlebox bearings of high-speed trains is crucial for the fatigue reliability assessment and forward design of axlebox bearings. This paper presents an in situ measuremen...The dynamic load distribution within in-service axlebox bearings of high-speed trains is crucial for the fatigue reliability assessment and forward design of axlebox bearings. This paper presents an in situ measurement of the dynamic load distribution in the four rows of two axlebox bearings on a bogie wheelset of a high-speed train under polygonal wheel–rail excitation. The measurement employed an improved strain-based method to measure the dynamic radial load distribution of roller bearings. The four rows of two axlebox bearings on a wheelset exhibited different ranges of loaded zones and different means of distributed loads. Besides, the mean value and standard deviation of measured roller–raceway contact loads showed non-monotonic variations with the frequency of wheel–rail excitation. The fatigue life of the four bearing rows under polygonal wheel–rail excitation was quantitatively predicted by compiling the measured roller–raceway contact load spectra of the most loaded position and considering the load spectra as input.展开更多
Aviation turbine engine oils require excellent thermal-oxidative stability because of their high-temperature environments.High-temperature bearing deposit testing is a mandatory method for measuring the thermal-oxidat...Aviation turbine engine oils require excellent thermal-oxidative stability because of their high-temperature environments.High-temperature bearing deposit testing is a mandatory method for measuring the thermal-oxidative performance of aviation lubricant oils,and the relevant apparatus was improved in the present study.Two different commercial aviation turbine engine oils were tested,one with standard performance(known as the SL oil)and the other with high thermal stability,and their thermal-oxidative stability characteristics were evaluated.After 100 h of high-temperature bearing testing,the SL oil was analyzed by using various analytical techniques to investigate its thermal-oxidative process in the bearing test,with its thermal-oxidative degradation mechanism also being discussed.The results indicate that the developed high-temperature bearing apparatus easily meets the test requirements of method 3410.1 in standard FED-STD-791D.The viscosity and total acid number(TAN)of the SL oil increased with the bearing test time,and various deposits were produced in the bearing test,with the micro-particles of the carbon deposits being sphere-like,rod-like,and sheet-like in appearance.The antioxidant additives in the oil were consumed very rapidly in the first 30 h of the bearing test,with N-phenyl-1-naphthylamine being consumed faster than dioctyldiphenylamine.Overall,the oil thermal-oxidative process involves very complex physical and chemical mechanisms.展开更多
High-speed trains typically utilize helical gear transmissions,which significantly impact the bearing load capacity and fatigue service performance of the gearbox bearings.This paper focuses on the gearbox bearings,es...High-speed trains typically utilize helical gear transmissions,which significantly impact the bearing load capacity and fatigue service performance of the gearbox bearings.This paper focuses on the gearbox bearings,establishing dynamic models for both helical gear and herringbone gear transmissions in high-speed trains.The modeling particularly emphasizes the precision of the bearings at the gearbox's pinion and gear wheels.Using this model,a comparative analysis is conducted on the bearing loads and contact stresses of the gearbox bearings under uniform-speed operation between the two gear transmissions.The findings reveal that the helical gear transmission generates axial forces leading to severe load imbalance on the bearings at both sides of the large gear,and this imbalance intensifies with the increase in train speed.Consequently,this results in a significant increase in contact stress on the bearings on one side.The adoption of herringbone gear transmission effectively suppresses axial forces,resolving the load imbalance issue and substantially reducing the contact stress on the originally biased side of the bearings.The study demonstrates that employing herringbone gear transmission can significantly enhance the service performance of high-speed train gearbox bearings,thereby extending their service life.展开更多
Multisensor data fusionmethod can improve the accuracy of bearing fault diagnosis,in order to address the problems of single-sensor data types and the insufficient exploration of redundancy and complementarity between...Multisensor data fusionmethod can improve the accuracy of bearing fault diagnosis,in order to address the problems of single-sensor data types and the insufficient exploration of redundancy and complementarity between different modal data in most existing multisensor data fusion methods for bearing fault diagnosis,a bearing fault diagnosis method based on a Multiple-Constraint Modal-Invariant Graph Convolutional Fusion Network(MCMI-GCFN)is proposed in this paper.Firstly,a Convolutional Autoencoder(CAE)and Squeeze-and-Excitation Block(SE block)are used to extract features of raw current and vibration signals.Secondly,the model introduces source domain classifiers and domain discriminators to capture modal invariance between different modal data based on domain adversarial training,making use of the redundancy and complementarity between multimodal data.Then,the spatial aggregation property of Graph Convolutional Neural Networks(GCN)is utilized to capture the dependency relationship between current and vibration modes with similar time step features for accurately fusing contextual semantic information.Finally,the validation is conducted on the public bearing damage current and vibration dataset from Paderborn University.The experimental results showed that the delivered fusion method achieved a bearing fault diagnosis accuracy of 99.6%,which was about 9%–11.4%better than that with nonfusion methods.展开更多
A theoretical study has been performed to investigate the influence of manufacturing errors on the bearing housing of a gas lubricated journal bearing with compliant surface I in particular on the bearing load capacit...A theoretical study has been performed to investigate the influence of manufacturing errors on the bearing housing of a gas lubricated journal bearing with compliant surface I in particular on the bearing load capacity. A gas film thickness distribution is presented, in which errors o f both circumferential and axial bearing housing are considered. The influence of the errors on bearing performance is compared between rigid and compliant surface bearings. It was shown that the compliant surface bearings are less sensitive to the manufacturing errors than the rigid surface bearings. Thelefore, the cost of compliant surface bearing could be reduced by setting a larger manufacturing error tolerance.展开更多
The critical speeds for a vehicle turbocharger with hybrid ceramic ball bearing are researched. The ball bearing-rotor system produces resonance when it working in critical speed and that makes the turbocharger injury...The critical speeds for a vehicle turbocharger with hybrid ceramic ball bearing are researched. The ball bearing-rotor system produces resonance when it working in critical speed and that makes the turbocharger injury working for a long time. The calculation and analysis methods of the critical speed for the vehicle turbocharger are described. The critical speed is computed by two methods including Riccati transfer matrix and DyRoBeS finite element method for a vehicle turbocharger with hybrid ceramic ball bearing. The vibration experiment had been taken to validate the calculating result, Comparison between the results by two calculation methods and the test results show that the first critical speed differences are 6.47 % and 5.66 %, the second critical speed differences are 2.87 % and 2.94 % respectively. And then, the primary factors which influence the critical speed are analyzed, the conclusions will be helpful for the vehicle turbocharger bearing-rotor system design.展开更多
Currently,there are two types of defect detection systems used to monitor the health of freight railcar bearings in service:wayside hot-box detection systems and trackside acoustic detection systems.These systems have...Currently,there are two types of defect detection systems used to monitor the health of freight railcar bearings in service:wayside hot-box detection systems and trackside acoustic detection systems.These systems have proven to be inefficient in accurately determining bearing health,especially in the early stages of defect development.To that end,a prototype onboard bearing condition monitoring system has been developed and validated through extensive laboratory testing and a designated field test in 2015 at the Transportation Technology Center,Inc.in Pueblo,CO.The devised system can accurately and reliably characterize the health of bearings based on developed vibration thresholds and can identify defective taperedroller bearing components with defect areas smaller than 12.9 cm2 while in service.展开更多
Research on practical and verifiable prediction methods for the service life of bearings plays a critical role in improving the reliability and safety of aircraft engines. The concept of grade-life （GL） is introduce...Research on practical and verifiable prediction methods for the service life of bearings plays a critical role in improving the reliability and safety of aircraft engines. The concept of grade-life （GL） is introduced to de- scribe the service life of bearings. A GL prognostic model for aircraft engine bearings is proposed based on sup- port vector machine （SVM） and fuzzy logic inference. Firstly, the mathematical model is discussed to predict the physics-based GL （PGL）. Then, the diagnostic estimation model based on SVM is presented in detail to predict the empirical GL （EPL）. Thirdly, a fuzzy logic inference is adopted to fuse two GL predicted results. Finally, the GL prognostic model is verified by the run-to-failure data acquired from an accelerated life test of an aircraft bearing. The results show that the model provides a more practical and reliable prediction for the service life of bearings.展开更多
Aiming at the stability and others properties of active magnetic bearing （AMB） system influenced by the periodic unbalance stimulation synchronous with rotor rotational speed, a new real-time adaptive feed-forward u...Aiming at the stability and others properties of active magnetic bearing （AMB） system influenced by the periodic unbalance stimulation synchronous with rotor rotational speed, a new real-time adaptive feed-forward unbalance force compensation scheme is proposed based on variable step-size least mean square（LMS） algorithm as the feed-forward compensation controller. The controller can provide some suitable sinusoidal signals to com- pensate the feedback unbalance response signals synchronous with the rotary frequency, then reduce the fluctua- tion of the control currents and weaken the active control of AMB system. The variable step-size proportional to the rotational frequency is deduced by analyzing the principle of normal LMS algorithm and its deficiency in the application of real-time filtering of AMB system. Experimental results show that the new method can implement real-time unbalance force compensation in a wide frequency band, reduce the effect of unbalance stimulant force on the housing of AMB system, and provide convenience to improve rotational speed.展开更多
The finite element method （FEM） is introduced to calculate the oil film pressure and temperature distribution of a journal bearing. The perturbation is performed directly on the finite element equation. Consequently...The finite element method （FEM） is introduced to calculate the oil film pressure and temperature distribution of a journal bearing. The perturbation is performed directly on the finite element equation. Consequently, the Jacobian matrices of the oil film forces are concisely obtained. The equilibrium position of the bearing with a given static load is found by the Newton-Raphson method. As byproducts, dynamic coefficients are obtained simultaneously without any extra computing time. From the numerical results, it is concluded that the effects of film temperature on stiffness coefficients are bigger than those on damping coefficients. With the increase of rotational speed, the load capacity and the stiffness coefficients of the journal bearing are increased when the eccentricity is small, while decreased when the eccentricity is big.展开更多
By analyzing the existing methods for the bridge bearing capacity assessment, an analytic hierarchy pro cess estimation model with a variable weight and fuzzy description is proposed based on the nondestructive infor ...By analyzing the existing methods for the bridge bearing capacity assessment, an analytic hierarchy pro cess estimation model with a variable weight and fuzzy description is proposed based on the nondestructive infor mation. Considering the actual strength, the bearing capacity is first calculated from its design state, and then modified based on the detection information. The modification includes the section reduction and the structure deterioration. The section reduction involves the concrete section and the steel cross-section reduction. The structure deterioration is decided by six factors, i.e. , the concrete surface damage, the actual concrete strength, the steel corrosion electric potential, the chloride ion content, the carbonization depth, and the protective layer depth. The initial weight of each factor is calculated by the expert judgment matrix using an analytic hierarchy process. The consistency approximation and the error transfer theory are used. Then, the variable weight is in- troduced to expand the influences of factors in the worse state. Finally, an actual bridge is taken as an example to verify the proposed method. Results show that the estimated capacity agrees well with that of the load test, thus the method is objective and credible展开更多
Friction and lubrication simulation analysis of internal combustion engine bearings are studied. A series of software implementary precepts for mathematical modeling, to analytic calculating and realizing simulation o...Friction and lubrication simulation analysis of internal combustion engine bearings are studied. A series of software implementary precepts for mathematical modeling, to analytic calculating and realizing simulation outcome are brought forward. As a dynamic simulating technique is introduced into the process of engine bearing design, simulation models of the oil film are built and the emulational analysis of the shaft center track is carried out. A software program package “Engine Bearing Friction and Lubrication Dynamic Simulation System” is developed to realize the real time simulation of the working status of bearing during the design process. Through developing virtualized products, the defects of the product design can be found in time and improve the products at once. Thus the purpose of predicting and controlling the cost, quality and design period of the products can be achieved.展开更多
The coupled dynamic characteristics of the conical electromagnetic bearing are presented and their definitions are given. On the basis of the analyses of the characteristics, the dynamic model of five degrees of freed...The coupled dynamic characteristics of the conical electromagnetic bearing are presented and their definitions are given. On the basis of the analyses of the characteristics, the dynamic model of five degrees of freedom (five-DOF) rotor-conical electromagnetic bearing system is made, and the influence of the coupled characteristics on the system optimal controller is analyzed.展开更多
Water-lubrication bearings are critical components in ship operation.However,studies on their maintenance and failure detection are highly limited.The use of sensors to continually monitor the working operation of bea...Water-lubrication bearings are critical components in ship operation.However,studies on their maintenance and failure detection are highly limited.The use of sensors to continually monitor the working operation of bearings is a potential approach to solve this problem,which is collectively called intelligent bearings.In this literature review,the recent progress of electrical resistance strain gauges,Fiber Bragg grating,triboelectric nanogenerators,piezoelectric nanogenerators,and thermoelectric sensors for in-situ monitoring is summarized.Future research and design concepts on intelligent water-lubrication bearings are also comprehensively discussed.The findings show that the accident risks,lubrication condition,and remaining life of water-lubricated bearings can be evaluated with the surface temperature,coefficient of friction,and wear volume monitoring.The research work on intelligent water-lubricated bearings is committed to promoting the development of green,electrified,and intelligent technologies for ship propulsion systems,which have important theoretical significance and application value.展开更多
In an active magnetic bearing(AMB)system,the catcher bearings(CBs)are indispensable to protect the rotor and stator in case the magnetic bearings fail or overload.A new CB structure composed of two ball bearings is in...In an active magnetic bearing(AMB)system,the catcher bearings(CBs)are indispensable to protect the rotor and stator in case the magnetic bearings fail or overload.A new CB structure composed of two ball bearings is introduced.Detailed simulation models containing contact model between rotor and inner race,double-decker catcher bearing(DDCB)model as well as single-decker catcher bearing(SDCB)model are established using multibody dynamics simulation software MSC.ADAMS.Then,using those established models,the rotor orbits and the contact forces between rotor and inner race are simulated respectively after rotor drop on DDCBs and SDCBs.The simulation result shows that the rotor vibration range using DDCBs is significantly smaller than that using SDCBs;the maximum contact forces drop about 15%—27% compared with the contact forces using SDCBs.Finally,the test bench for the rotor drop experiments is built and the rotor drop experiments for different types of CBs are carried out.Labview data acquisition system is utilized to collect the displacement of rotor and the rotating frequencies of both inner race and intermediate races after rotor drop.The experimental results are comparatively analyzed,and the conclusion that DDCB can help to reduce vibration amplitude and collision force is obtained.The studies can provide certain theoretical and experimental references for the application of DDCBs in AMB system.展开更多
Tilting pad gas journal bearing is one of the most widely used types of aerodynamic bearings due to its inherent excellent stability in high speed applications.A practical method for analyzing and calculating the per-...Tilting pad gas journal bearing is one of the most widely used types of aerodynamic bearings due to its inherent excellent stability in high speed applications.A practical method for analyzing and calculating the per- formances of such bearings is presented as well as its rotordynamics based on the computer aided technique.The method of calculation and the philosophy of programming with a microcomputer for the computer aided analysis are highlighted.展开更多
Identifying the stiffness and damping of active magnetic bearings(AMBs)is necessary since those parameters can affect the stability and performance of the high-speed rotor AMBs system.A new identification method is pr...Identifying the stiffness and damping of active magnetic bearings(AMBs)is necessary since those parameters can affect the stability and performance of the high-speed rotor AMBs system.A new identification method is proposed to identify the stiffness and damping coefficients of a rotor AMB system.This method combines the global optimization capability of the genetic algorithm(GA)and the local search ability of Nelder-Mead simplex method.The supporting parameters are obtained using the hybrid GA based on the experimental unbalance response calculated through the transfer matrix method.To verify the identified results,the experimental stiffness and damping coefficients are employed to simulate the unbalance responses for the rotor AMBs system using the finite element method.The close agreement between the simulation and experimental data indicates that the proposed identified algorithm can effectively identify the AMBs supporting parameters.展开更多
Aimed at aeroengine vibration failure, bearing loads of dual rotor-bearing system caused by unbalance are calculated under stationary and transient conditions. The three-dimensional （3-D） finite element method （FEM...Aimed at aeroengine vibration failure, bearing loads of dual rotor-bearing system caused by unbalance are calculated under stationary and transient conditions. The three-dimensional （3-D） finite element method （FEM） model of dual rotor-bearing system was established. Applying the ro- tor dynamics function of Ansys 12.0, bearing loads were calculated under various unbalance force in stationary condition, and the transient vibration characteristics and the effect of acceleration on bearing loads were discussed. On the basis of simulation results, the influence disciplines of unbal- ance on bearing loads and theoretic reference for reducing bearing loads during start-up were ob- tained.展开更多
Sound multipath propagation is very important for target localization and identification in different acoustical zones of deep water. In order to distinguish the multipath characteristics in deep water, the Northwest ...Sound multipath propagation is very important for target localization and identification in different acoustical zones of deep water. In order to distinguish the multipath characteristics in deep water, the Northwest Pacific Acoustic Experiment was conducted in 2015. A low-frequency horizontal line array towed at the depth of around 150 m on a receiving ship was used to receive the noise radiated by the source ship. During this experiment, a beating-splitting phenomenon in the direct zone was observed through conventional beamforming of the horizontal line array within the frequency band 160 Hz- 360 Hz. In this paper, this phenomenon is explained based on ray theory. In principle, the received signal in the direct zone of deep water arrives from two general paths including a direct one and bottom bounced one, which vary considerably in arrival angles. The split bearings correspond to the contributions of these two paths. The beating-splitting phenomenon is demonstrated by numerical simulations of the bearing-time records and experimental results, and they are well consistent with each other. Then a near-surface source ranging approach based on the arrival angles of direct path and bottom bounced path in the direct zone is presented as an application of bearing splitting and is verified by experimental results. Finally, the applicability of the proposed ranging approach for an underwater source within several hundred meters in depth in the direct zone is also analyzed and demonstrated by simulations.展开更多
To reduce the cost of backfilling coal mining and utilize the underground space of coal mines,a new backfilling mining method with low backfilling rate called constructional backfilling coal mining(CBCM)is proposed.Th...To reduce the cost of backfilling coal mining and utilize the underground space of coal mines,a new backfilling mining method with low backfilling rate called constructional backfilling coal mining(CBCM)is proposed.The "backfilling body-immediate roof" cooperative bearing structure of CBCM is analyzed by establishing the model of the medium thick plate on an elastic foundation.The influence of the backfilling rate on the stability of overlying strata is analyzed by the numerical simulation experiment.The control effect of CBCM is verified by a physic similar simulation test.The economic benefit of CBCM is analyzed.The conclusions are:the deformation characteristics of the immediate roof and critical backfilling spacing in CBCM can be analyzed based on the Hu Haichang’s theory.Exerting the bearing capacity of the immediate roof is beneficial to the stability of the overlying strata.The CBCM has a good control effect on the overburden in Xinyang Mine when the backfilling rate is lower than 25%.The backfilling cost of per ton coal is 37.39 yuan/t when the backfilling rate is 13.7%,with a decrease rate of 56.63%than the full-filling.The research results can provide theoretical support for the application of CBCM in coal mining.展开更多
基金supported by the National Natural Science Foundation of China (Grant No. 12302238)the National Key Research and Development Program of China (Grant Nos. 2021YFB3400701, 2022YFB3402904)。
文摘The dynamic load distribution within in-service axlebox bearings of high-speed trains is crucial for the fatigue reliability assessment and forward design of axlebox bearings. This paper presents an in situ measurement of the dynamic load distribution in the four rows of two axlebox bearings on a bogie wheelset of a high-speed train under polygonal wheel–rail excitation. The measurement employed an improved strain-based method to measure the dynamic radial load distribution of roller bearings. The four rows of two axlebox bearings on a wheelset exhibited different ranges of loaded zones and different means of distributed loads. Besides, the mean value and standard deviation of measured roller–raceway contact loads showed non-monotonic variations with the frequency of wheel–rail excitation. The fatigue life of the four bearing rows under polygonal wheel–rail excitation was quantitatively predicted by compiling the measured roller–raceway contact load spectra of the most loaded position and considering the load spectra as input.
基金supported by the National Key Research and Development Program of China(2022YFB3809005)by SINOPEC(120060-6,121027,and 122042).
文摘Aviation turbine engine oils require excellent thermal-oxidative stability because of their high-temperature environments.High-temperature bearing deposit testing is a mandatory method for measuring the thermal-oxidative performance of aviation lubricant oils,and the relevant apparatus was improved in the present study.Two different commercial aviation turbine engine oils were tested,one with standard performance(known as the SL oil)and the other with high thermal stability,and their thermal-oxidative stability characteristics were evaluated.After 100 h of high-temperature bearing testing,the SL oil was analyzed by using various analytical techniques to investigate its thermal-oxidative process in the bearing test,with its thermal-oxidative degradation mechanism also being discussed.The results indicate that the developed high-temperature bearing apparatus easily meets the test requirements of method 3410.1 in standard FED-STD-791D.The viscosity and total acid number(TAN)of the SL oil increased with the bearing test time,and various deposits were produced in the bearing test,with the micro-particles of the carbon deposits being sphere-like,rod-like,and sheet-like in appearance.The antioxidant additives in the oil were consumed very rapidly in the first 30 h of the bearing test,with N-phenyl-1-naphthylamine being consumed faster than dioctyldiphenylamine.Overall,the oil thermal-oxidative process involves very complex physical and chemical mechanisms.
基金financial support provided by the National Key Research and Development Project of China(Grant No.2022YFB3402901)the National Natural Science Foundation of China(Grant No.52305070,52302467)。
文摘High-speed trains typically utilize helical gear transmissions,which significantly impact the bearing load capacity and fatigue service performance of the gearbox bearings.This paper focuses on the gearbox bearings,establishing dynamic models for both helical gear and herringbone gear transmissions in high-speed trains.The modeling particularly emphasizes the precision of the bearings at the gearbox's pinion and gear wheels.Using this model,a comparative analysis is conducted on the bearing loads and contact stresses of the gearbox bearings under uniform-speed operation between the two gear transmissions.The findings reveal that the helical gear transmission generates axial forces leading to severe load imbalance on the bearings at both sides of the large gear,and this imbalance intensifies with the increase in train speed.Consequently,this results in a significant increase in contact stress on the bearings on one side.The adoption of herringbone gear transmission effectively suppresses axial forces,resolving the load imbalance issue and substantially reducing the contact stress on the originally biased side of the bearings.The study demonstrates that employing herringbone gear transmission can significantly enhance the service performance of high-speed train gearbox bearings,thereby extending their service life.
基金supported by the National Key R&D Program of China(2021YFF0501101)the Youth Project of Hunan Provincial Department of Education(22B0586)the Education Reform Project of Hunan Provincial Department of Education(2022JGYB186).
文摘Multisensor data fusionmethod can improve the accuracy of bearing fault diagnosis,in order to address the problems of single-sensor data types and the insufficient exploration of redundancy and complementarity between different modal data in most existing multisensor data fusion methods for bearing fault diagnosis,a bearing fault diagnosis method based on a Multiple-Constraint Modal-Invariant Graph Convolutional Fusion Network(MCMI-GCFN)is proposed in this paper.Firstly,a Convolutional Autoencoder(CAE)and Squeeze-and-Excitation Block(SE block)are used to extract features of raw current and vibration signals.Secondly,the model introduces source domain classifiers and domain discriminators to capture modal invariance between different modal data based on domain adversarial training,making use of the redundancy and complementarity between multimodal data.Then,the spatial aggregation property of Graph Convolutional Neural Networks(GCN)is utilized to capture the dependency relationship between current and vibration modes with similar time step features for accurately fusing contextual semantic information.Finally,the validation is conducted on the public bearing damage current and vibration dataset from Paderborn University.The experimental results showed that the delivered fusion method achieved a bearing fault diagnosis accuracy of 99.6%,which was about 9%–11.4%better than that with nonfusion methods.
文摘A theoretical study has been performed to investigate the influence of manufacturing errors on the bearing housing of a gas lubricated journal bearing with compliant surface I in particular on the bearing load capacity. A gas film thickness distribution is presented, in which errors o f both circumferential and axial bearing housing are considered. The influence of the errors on bearing performance is compared between rigid and compliant surface bearings. It was shown that the compliant surface bearings are less sensitive to the manufacturing errors than the rigid surface bearings. Thelefore, the cost of compliant surface bearing could be reduced by setting a larger manufacturing error tolerance.
文摘The critical speeds for a vehicle turbocharger with hybrid ceramic ball bearing are researched. The ball bearing-rotor system produces resonance when it working in critical speed and that makes the turbocharger injury working for a long time. The calculation and analysis methods of the critical speed for the vehicle turbocharger are described. The critical speed is computed by two methods including Riccati transfer matrix and DyRoBeS finite element method for a vehicle turbocharger with hybrid ceramic ball bearing. The vibration experiment had been taken to validate the calculating result, Comparison between the results by two calculation methods and the test results show that the first critical speed differences are 6.47 % and 5.66 %, the second critical speed differences are 2.87 % and 2.94 % respectively. And then, the primary factors which influence the critical speed are analyzed, the conclusions will be helpful for the vehicle turbocharger bearing-rotor system design.
基金This study was made possible by funding provided by The University Transportation Center for Railway Safety(UTCRS),through a USDOT Grant No.DTRT 13-G-UTC59.
文摘Currently,there are two types of defect detection systems used to monitor the health of freight railcar bearings in service:wayside hot-box detection systems and trackside acoustic detection systems.These systems have proven to be inefficient in accurately determining bearing health,especially in the early stages of defect development.To that end,a prototype onboard bearing condition monitoring system has been developed and validated through extensive laboratory testing and a designated field test in 2015 at the Transportation Technology Center,Inc.in Pueblo,CO.The devised system can accurately and reliably characterize the health of bearings based on developed vibration thresholds and can identify defective taperedroller bearing components with defect areas smaller than 12.9 cm2 while in service.
基金Supported by the China Postdoctoral Science Foundation(20100481500)~~
文摘Research on practical and verifiable prediction methods for the service life of bearings plays a critical role in improving the reliability and safety of aircraft engines. The concept of grade-life （GL） is introduced to de- scribe the service life of bearings. A GL prognostic model for aircraft engine bearings is proposed based on sup- port vector machine （SVM） and fuzzy logic inference. Firstly, the mathematical model is discussed to predict the physics-based GL （PGL）. Then, the diagnostic estimation model based on SVM is presented in detail to predict the empirical GL （EPL）. Thirdly, a fuzzy logic inference is adopted to fuse two GL predicted results. Finally, the GL prognostic model is verified by the run-to-failure data acquired from an accelerated life test of an aircraft bearing. The results show that the model provides a more practical and reliable prediction for the service life of bearings.
基金Supported by the National Natural Science Foundation of China(50437010)the National High Technology Research and Development Program of China("863"Program)(2006AA05Z205)the Project of Six Talented Peak of Jiangsu Province(07-D-013)~~
文摘Aiming at the stability and others properties of active magnetic bearing （AMB） system influenced by the periodic unbalance stimulation synchronous with rotor rotational speed, a new real-time adaptive feed-forward unbalance force compensation scheme is proposed based on variable step-size least mean square（LMS） algorithm as the feed-forward compensation controller. The controller can provide some suitable sinusoidal signals to com- pensate the feedback unbalance response signals synchronous with the rotary frequency, then reduce the fluctua- tion of the control currents and weaken the active control of AMB system. The variable step-size proportional to the rotational frequency is deduced by analyzing the principle of normal LMS algorithm and its deficiency in the application of real-time filtering of AMB system. Experimental results show that the new method can implement real-time unbalance force compensation in a wide frequency band, reduce the effect of unbalance stimulant force on the housing of AMB system, and provide convenience to improve rotational speed.
基金Supported by the National″111″Project(B07050)the China Postdoctoral Science Foundation(20100471634)~~
文摘The finite element method （FEM） is introduced to calculate the oil film pressure and temperature distribution of a journal bearing. The perturbation is performed directly on the finite element equation. Consequently, the Jacobian matrices of the oil film forces are concisely obtained. The equilibrium position of the bearing with a given static load is found by the Newton-Raphson method. As byproducts, dynamic coefficients are obtained simultaneously without any extra computing time. From the numerical results, it is concluded that the effects of film temperature on stiffness coefficients are bigger than those on damping coefficients. With the increase of rotational speed, the load capacity and the stiffness coefficients of the journal bearing are increased when the eccentricity is small, while decreased when the eccentricity is big.
基金Supported by the Jiangshu Province Communication Scientific Research Project(06Y21)Zhejiang Province Road Scientific Research Project(2007-013-11L)~~
文摘By analyzing the existing methods for the bridge bearing capacity assessment, an analytic hierarchy pro cess estimation model with a variable weight and fuzzy description is proposed based on the nondestructive infor mation. Considering the actual strength, the bearing capacity is first calculated from its design state, and then modified based on the detection information. The modification includes the section reduction and the structure deterioration. The section reduction involves the concrete section and the steel cross-section reduction. The structure deterioration is decided by six factors, i.e. , the concrete surface damage, the actual concrete strength, the steel corrosion electric potential, the chloride ion content, the carbonization depth, and the protective layer depth. The initial weight of each factor is calculated by the expert judgment matrix using an analytic hierarchy process. The consistency approximation and the error transfer theory are used. Then, the variable weight is in- troduced to expand the influences of factors in the worse state. Finally, an actual bridge is taken as an example to verify the proposed method. Results show that the estimated capacity agrees well with that of the load test, thus the method is objective and credible
文摘Friction and lubrication simulation analysis of internal combustion engine bearings are studied. A series of software implementary precepts for mathematical modeling, to analytic calculating and realizing simulation outcome are brought forward. As a dynamic simulating technique is introduced into the process of engine bearing design, simulation models of the oil film are built and the emulational analysis of the shaft center track is carried out. A software program package “Engine Bearing Friction and Lubrication Dynamic Simulation System” is developed to realize the real time simulation of the working status of bearing during the design process. Through developing virtualized products, the defects of the product design can be found in time and improve the products at once. Thus the purpose of predicting and controlling the cost, quality and design period of the products can be achieved.
文摘The coupled dynamic characteristics of the conical electromagnetic bearing are presented and their definitions are given. On the basis of the analyses of the characteristics, the dynamic model of five degrees of freedom (five-DOF) rotor-conical electromagnetic bearing system is made, and the influence of the coupled characteristics on the system optimal controller is analyzed.
基金Supported by the National Natural Science Foundation of China(Grant No.52171319).
文摘Water-lubrication bearings are critical components in ship operation.However,studies on their maintenance and failure detection are highly limited.The use of sensors to continually monitor the working operation of bearings is a potential approach to solve this problem,which is collectively called intelligent bearings.In this literature review,the recent progress of electrical resistance strain gauges,Fiber Bragg grating,triboelectric nanogenerators,piezoelectric nanogenerators,and thermoelectric sensors for in-situ monitoring is summarized.Future research and design concepts on intelligent water-lubrication bearings are also comprehensively discussed.The findings show that the accident risks,lubrication condition,and remaining life of water-lubricated bearings can be evaluated with the surface temperature,coefficient of friction,and wear volume monitoring.The research work on intelligent water-lubricated bearings is committed to promoting the development of green,electrified,and intelligent technologies for ship propulsion systems,which have important theoretical significance and application value.
基金Supported by the National Natural Science Foundation of China(51205186)the National Science Foundation for Post-doctoral Scientists of China(2012M511264)the Specialized Research Fund for the Doctoral Program of Higher Education of China(20123218120024)
文摘In an active magnetic bearing(AMB)system,the catcher bearings(CBs)are indispensable to protect the rotor and stator in case the magnetic bearings fail or overload.A new CB structure composed of two ball bearings is introduced.Detailed simulation models containing contact model between rotor and inner race,double-decker catcher bearing(DDCB)model as well as single-decker catcher bearing(SDCB)model are established using multibody dynamics simulation software MSC.ADAMS.Then,using those established models,the rotor orbits and the contact forces between rotor and inner race are simulated respectively after rotor drop on DDCBs and SDCBs.The simulation result shows that the rotor vibration range using DDCBs is significantly smaller than that using SDCBs;the maximum contact forces drop about 15%—27% compared with the contact forces using SDCBs.Finally,the test bench for the rotor drop experiments is built and the rotor drop experiments for different types of CBs are carried out.Labview data acquisition system is utilized to collect the displacement of rotor and the rotating frequencies of both inner race and intermediate races after rotor drop.The experimental results are comparatively analyzed,and the conclusion that DDCB can help to reduce vibration amplitude and collision force is obtained.The studies can provide certain theoretical and experimental references for the application of DDCBs in AMB system.
文摘Tilting pad gas journal bearing is one of the most widely used types of aerodynamic bearings due to its inherent excellent stability in high speed applications.A practical method for analyzing and calculating the per- formances of such bearings is presented as well as its rotordynamics based on the computer aided technique.The method of calculation and the philosophy of programming with a microcomputer for the computer aided analysis are highlighted.
基金supported by the National Natural Science Foundation of China(No.51675261)Jiangsu Province Key R & D Programs(No.BE2016180)
文摘Identifying the stiffness and damping of active magnetic bearings(AMBs)is necessary since those parameters can affect the stability and performance of the high-speed rotor AMBs system.A new identification method is proposed to identify the stiffness and damping coefficients of a rotor AMB system.This method combines the global optimization capability of the genetic algorithm(GA)and the local search ability of Nelder-Mead simplex method.The supporting parameters are obtained using the hybrid GA based on the experimental unbalance response calculated through the transfer matrix method.To verify the identified results,the experimental stiffness and damping coefficients are employed to simulate the unbalance responses for the rotor AMBs system using the finite element method.The close agreement between the simulation and experimental data indicates that the proposed identified algorithm can effectively identify the AMBs supporting parameters.
基金Supported by the National Natural Science Foundation of China (50875022)
文摘Aimed at aeroengine vibration failure, bearing loads of dual rotor-bearing system caused by unbalance are calculated under stationary and transient conditions. The three-dimensional （3-D） finite element method （FEM） model of dual rotor-bearing system was established. Applying the ro- tor dynamics function of Ansys 12.0, bearing loads were calculated under various unbalance force in stationary condition, and the transient vibration characteristics and the effect of acceleration on bearing loads were discussed. On the basis of simulation results, the influence disciplines of unbal- ance on bearing loads and theoretic reference for reducing bearing loads during start-up were ob- tained.
基金Project supported by the Program of One Hundred Talented People of the Chinese Academy of SciencesNational Natural Science Foundation of China(Grant Nos.11434012 and 41561144006)
文摘Sound multipath propagation is very important for target localization and identification in different acoustical zones of deep water. In order to distinguish the multipath characteristics in deep water, the Northwest Pacific Acoustic Experiment was conducted in 2015. A low-frequency horizontal line array towed at the depth of around 150 m on a receiving ship was used to receive the noise radiated by the source ship. During this experiment, a beating-splitting phenomenon in the direct zone was observed through conventional beamforming of the horizontal line array within the frequency band 160 Hz- 360 Hz. In this paper, this phenomenon is explained based on ray theory. In principle, the received signal in the direct zone of deep water arrives from two general paths including a direct one and bottom bounced one, which vary considerably in arrival angles. The split bearings correspond to the contributions of these two paths. The beating-splitting phenomenon is demonstrated by numerical simulations of the bearing-time records and experimental results, and they are well consistent with each other. Then a near-surface source ranging approach based on the arrival angles of direct path and bottom bounced path in the direct zone is presented as an application of bearing splitting and is verified by experimental results. Finally, the applicability of the proposed ranging approach for an underwater source within several hundred meters in depth in the direct zone is also analyzed and demonstrated by simulations.
基金supported by the Youth Funds of National Natural Science Foundation of China(No.52004173)the Distinguished Youth Funds of National Natural Science Foundation of China(No.51925402)+2 种基金the Science and Technology Innovation Project of Colleges and Universities in Shanxi Province(No.2020L0066)the China Postdoctoral Science Foundation(No.2022M712922)the Shanxi-Zheda Institute of Advanced Materials and Chemical Engineering(Nos.2021SX-TD001 and 2022SXTD008).
文摘To reduce the cost of backfilling coal mining and utilize the underground space of coal mines,a new backfilling mining method with low backfilling rate called constructional backfilling coal mining(CBCM)is proposed.The "backfilling body-immediate roof" cooperative bearing structure of CBCM is analyzed by establishing the model of the medium thick plate on an elastic foundation.The influence of the backfilling rate on the stability of overlying strata is analyzed by the numerical simulation experiment.The control effect of CBCM is verified by a physic similar simulation test.The economic benefit of CBCM is analyzed.The conclusions are:the deformation characteristics of the immediate roof and critical backfilling spacing in CBCM can be analyzed based on the Hu Haichang’s theory.Exerting the bearing capacity of the immediate roof is beneficial to the stability of the overlying strata.The CBCM has a good control effect on the overburden in Xinyang Mine when the backfilling rate is lower than 25%.The backfilling cost of per ton coal is 37.39 yuan/t when the backfilling rate is 13.7%,with a decrease rate of 56.63%than the full-filling.The research results can provide theoretical support for the application of CBCM in coal mining.
