Heavy-duty freight railway axles are no less important than those of passenger trains,owing to the potentially catastrophic results caused by the derailment of trains carrying hazardous substances.Intrinsic and extrin...Heavy-duty freight railway axles are no less important than those of passenger trains,owing to the potentially catastrophic results caused by the derailment of trains carrying hazardous substances.Intrinsic and extrinsic imperfections challenge classical design theories built based on the safe life concept,and damage tolerance assessment becomes vital for the safety and reliability of long-term serviced railway axles,as pits and scratches are common defects for heavy-duty railway axles.In this work,four-point rotating bending fatigue tests of AAR-CM railway axle steel specimens with semicircular and circumferential groove notches are conducted.The fatigue limit of the semicircular notched specimens was evaluated based on fracture mechanics theory,in which non-conservative results are obtained by the El Haddad model and the S–N curves of circumferential groove notched specimens are correlated by the theory of critical distance(TCD).展开更多
According to the rules of UIC515-3,the service loads of the axles are defined,which include some different loads cases as follows:the static loads;the impact loads resulted from running through the rail joints and une...According to the rules of UIC515-3,the service loads of the axles are defined,which include some different loads cases as follows:the static loads;the impact loads resulted from running through the rail joints and unevenness rails;the loads through curves and from braking.Through the calculating and analysis,the stress distribution of the hollow axles is obtained for 200 km/h high speed motor trains used in China.At the same time,the fatigue crack growth of hollow axles is studied,and the initial surface cracks of 2 mm depth caused by hard objects strike or the other causes are discussed.On the basis of the linear elastic fracture mechanics theory,the stress intensity factor of the crack of the geometry transition outside the wheel seat is also studied.Associated with fatigue crack propagation equation and the corresponding crack propagation threshold,the crack propagation characteristics under different shapes are calculated.Then the running distances are educed with different shapes propagating to the critical length,and the estimation of the residual lives about hollow axles which are the reference values of examine and repair limit of the hollow axle is given.展开更多
This study investigated the fretting wear and fatigue of full-scale railway axles.Fatigue tests were conducted on full-scale railway axles,and the fretting wear and fretting fatigue in the fretted zone of the railway ...This study investigated the fretting wear and fatigue of full-scale railway axles.Fatigue tests were conducted on full-scale railway axles,and the fretting wear and fretting fatigue in the fretted zone of the railway axles were analysed.Three-dimensional finite element models were established based on the experimental results.Then,multi-axial fatigue parameters and a linear elastic fracture mechanics-based approach were used to investigate the fretting fatigue crack initiation and propagation,respectively,in which the role of the fretting wear was taken into account.The experimental and simulated results showed that the fretted zone could be divided into zones I-III according to the surface damage morphologies.Fretting wear alleviated the stress concentration near the wheel seat edge and resulted in a new stress concentration near the worn/unworn boundary in zone II,which greatly promoted the fretting crack initiation at the inner side of the fretted zone.Meanwhile,the stress concentration also increased the equivalent stress intensity factor range DKeq below the mating surface,and thus promoted the propagation of fretting fatigue crack.Based on these findings,the effect of the stress redistribution resulting from fretting wear is suggested to be taken into account when evaluating the fretting fatigue in railway axles.展开更多
Because of the wicked service environment of the high speed train,it is possible that the hollow axle of the train may encounter the foreign object damage and form a sharp notch.Under the fatigue loading a crack can i...Because of the wicked service environment of the high speed train,it is possible that the hollow axle of the train may encounter the foreign object damage and form a sharp notch.Under the fatigue loading a crack can initiate from the notch and propagate to failure.It is noted that the stress intensity factor is the control parameter of the crack propagating,for the purpose of getting the more exact propagation characteristics,the stress intensity factor is studied mainly.The service loads of hollow axles are defined,and the stress distribution of hollow axles is obtained according to the load spectrum.The semi-ellipse crack configuration is defined with three parameters:the aspect ratio,the relative depth and the relative location along the crack front.Quarter point 20-node isoparametric degenerate singular elements are used for the region near the crack tip.The finite element model of crack extension of hollow axle is created,and the crack front is dispersed which can realize orthogonal extension.Based on this the stress intensity factors of crack front were calculated,and the distribution rules of the stress intensity factors of different initial crack shapes are obtained.The conclusions are compared with that of the analytic method and they agree with each other very well,and the calculating results show that there is a close relationship between the stress intensity factor and the initial crack shape.For a round crack the stress intensity factor at the surface point increases faster than the one at the center point with the crock propagation.However,for a narrow crack,the results are in contrast with that of a round one.So,all the cracks with different shapes propagate toward to a similar shape,and they grow at this shape to end.The study may contribute to the crack propagate characteristics research.展开更多
The microstructure,precipitates and properties of 25CrNiMoV(DZ2)steel for high-speed railway axles with different Nb contents were investigated by means of optical microscopy,scanning electron microscopy,electron back...The microstructure,precipitates and properties of 25CrNiMoV(DZ2)steel for high-speed railway axles with different Nb contents were investigated by means of optical microscopy,scanning electron microscopy,electron back-scattering diffraction,transmission electron microscopy and physicochemical phase analysis.The results show that the grain size of the original austenite of the test steels decreases from 20.5 to 14.2 and 10.8μm after adding 0.026 and 0.039 wt.%Nb to a 25CrNiMoV steel,respectively.Moreover,the block width of the tempered martensite in the test steels is refined from 1.91 to 1.72 and 1.60µm,respectively.MC-type precipitates in 25CrNiMoV steel are mainly VC,while(Nb,V)C gradually precipitates when Nb is microalloyed,and the amount of precipitates increases with increasing Nb content.Through strengthening mechanism analysis,it is found that grain refinement strengthening is the primary way to increase the strength.The improvement in the yield strength with increasing Nb content is attributed to a significant increase in precipitation strengthening,grain refinement strengthening and dislocation strengthening.展开更多
Equivalent axle load factor(EALF)is used to characterize the fatigue damage effect of multi-axle loads on asphalt pavement.EALF is calculated as the ratio of the pavement’s fatigue resistance under a single axle load...Equivalent axle load factor(EALF)is used to characterize the fatigue damage effect of multi-axle loads on asphalt pavement.EALF is calculated as the ratio of the pavement’s fatigue resistance under a single axle load to that under a multi-axle load.Existing studies use the same fatigue life function to predict the fatigue life of asphalt mixture under both single-and multi-axle loads,primarily focusing on the differences in pavement strains under these two configurations.However,strain waveforms in asphalt pavement caused by multi-axle loads differ from those under single-axle loads,altering the mixture’s fatigue behavior.To address this issue,this research tests the fatigue responses of asphalt mixtures under actual loading waveforms from single-axle,tandem-axle,and tridem-axle loads.Based on the test results,fatigue life functions are developed for each axle configuration and used to establish an updated EALF model.Since the applied fatigue life functions are based on test results from more realistic strain waveforms,the calculated EALFs provide more reliable predictions of the damaging effect of multi-axle loads on asphalt mixtures.展开更多
Ferroptosis of chondrocytes is a significant contributor to osteoarthritis(OA),for which there is still a lack of safe and effective therapeutic drugs targeting ferroptosis.Here,we screen for anti-ferroptotic drugs in...Ferroptosis of chondrocytes is a significant contributor to osteoarthritis(OA),for which there is still a lack of safe and effective therapeutic drugs targeting ferroptosis.Here,we screen for anti-ferroptotic drugs in Food and Drug Administration(FDA)-approved drug library via a high-throughput manner in chondrocytes.We identified a group of FDA-approved anti-ferroptotic drugs,among which vitamin K showed the most powerful protective effect.Further study demonstrated that vitamin K effectively inhibited ferroptosis and alleviated the extracellular matrix(ECM)degradation in chondrocytes.Intra-articular injection of vitamin K inhibited ferroptosis and alleviated OA phenotype in destabilization of the medial meniscus(DMM)mouse model.Mechanistically,transcriptome sequencing and knockdown experiments revealed that the anti-ferroptotic effects of vitamin K depended on growth arrest-specific 6(Gas6).Furthermore,exogenous expression of Gas6 was found to inhibit ferroptosis through the AXL receptor tyrosine kinase(AXL)/phosphatidylinositol 3-kinase(PI3K)/AKT serine/threonine kinase(AKT)axis.Together,we demonstrate that vitamin K inhibits ferroptosis and alleviates OA progression via enhancing Gas6 expression and its downstream pathway of AXL/PI3K/AKT axis,indicating vitamin K as well as Gas6 to serve as a potential therapeutic target for OA and other ferroptosis-related diseases.展开更多
Invasive inflammation and excessive scar formation are the main reasons for the difficulty in repairing nervous tissue after spinal cord injury.Microglia and astrocytes play key roles in the spinal cord injury micro-e...Invasive inflammation and excessive scar formation are the main reasons for the difficulty in repairing nervous tissue after spinal cord injury.Microglia and astrocytes play key roles in the spinal cord injury micro-environment and share a close interaction.However,the mechanisms involved remain unclear.In this study,we found that after spinal cord injury,resting microglia(M0)were polarized into pro-inflammatory phenotypes(MG1 and MG3),while resting astrocytes were polarized into reactive and scar-forming phenotypes.The expression of growth arrest-specific 6(Gas6)and its receptor Axl were significantly down-regulated in microglia and astrocytes after spinal cord injury.In vitro experiments showed that Gas6 had negative effects on the polarization of reactive astrocytes and pro-inflammatory microglia,and even inhibited the cross-regulation between them.We further demonstrated that Gas6 can inhibit the polarization of reactive astrocytes by suppressing the activation of the Yes-associated protein signaling pathway.This,in turn,inhibited the polarization of pro-inflammatory microglia by suppressing the activation of the nuclear factor-κB/p65 and Janus kinase/signal transducer and activator of transcription signaling pathways.In vivo experiments showed that Gas6 inhibited the polarization of pro-inflammatory microglia and reactive astrocytes in the injured spinal cord,thereby promoting tissue repair and motor function recovery.Overall,Gas6 may play a role in the treatment of spinal cord injury.It can inhibit the inflammatory pathway of microglia and polarization of astrocytes,attenuate the interaction between microglia and astrocytes in the inflammatory microenvironment,and thereby alleviate local inflammation and reduce scar formation in the spinal cord.展开更多
Axle box bearings are critical components of high-speed trains.Localized defects,such as pitting and spalling,on raceways or rollers pose significant threats to the operational safety of railway vehicles.In this work,...Axle box bearings are critical components of high-speed trains.Localized defects,such as pitting and spalling,on raceways or rollers pose significant threats to the operational safety of railway vehicles.In this work,a novel bearing-flexible axle boxvehicle coupling model is established to explore the vibration characteristics of axle box bearings with irregular localized defects.First,based on the contact and kinematic relationship between rollers and raceways,the three-dimensional(3D)bearing force elements are analyzed and formulated.Second,the established model and a flexible axle box are integrated into the vehicle,and the responses of the normal and faulty bearings under the combined excitations of wheel roughness and track irregularities are simulated.Third,the simulation results are verified through a rolling-vibrating test bench for full-scale wheelsets of high-speed trains.The comparisons of the fault-induced repetitive transients in the time-domain and the fault characteristic frequencies in the envelope spectra demonstrate the efficiency of the proposed model.Finally,based on the flexible axle box model,a sensitivity analysis of the accelerometer placements to the bearing faults is carried out,and the optimal one is identified based on both the time-domain and frequency-domain signal-to-noise ratios(SNRs)for engineering applications.展开更多
Purpose–To address the encapsulation challenge of fiber Bragg grating(FBG)sensors in complex railway environments,this paper designs a clip-on composite sensor enabling installation-friendly deployment and long-term ...Purpose–To address the encapsulation challenge of fiber Bragg grating(FBG)sensors in complex railway environments,this paper designs a clip-on composite sensor enabling installation-friendly deployment and long-term axle counting system monitoring.Design/methodology/approach–Wheel–rail mechanical behavior was simulated via finite element analysis(FEA)to determine optimal sensor placement.A clip-on composite sensor was subsequently engineered.Stress transduction efficacy was validated through FEA quantification of stress responses at the axle counter location.Findings–The proposed FBG axle counter integrates temperature compensation and anti-detachment monitoring as well as advantages such as simplified installation with minimal maintenance and sustained operational reliability.It effectively transmits stress,yielding a measured strain of 39μe under static loading conditions without sensitivity-enhancing elements.Originality/value–This study performs FEA of wheel-rail stress distribution and engineers the dual-slot composite sensor,FEAwas conducted to quantify the stress magnitude at the axle sensor position of the dual-slot composite sensor.Additionally,FEA was performed on sensors with different structural configurations,including adjustments to the axle sensor position,number of slots and axle position.The results confirmed that the designed composite sensor exhibits superior stress transfer characteristics.展开更多
Axle box bearings serve as crucial components within the transmission system of high-speed trains.Their failure can directly impact the operational safety of these trains.Accurately determining the dynamic load experi...Axle box bearings serve as crucial components within the transmission system of high-speed trains.Their failure can directly impact the operational safety of these trains.Accurately determining the dynamic load experienced by bearings during the operation of high-speed trains can provide valuable boundary inputs for the study of bearing fatigue life and service performance,thereby holding significant engineering implications.In this study,we propose a high-speed train axle box bearing load estimation method(FMCC-DKF).This method is founded on the Kalman filtering technique of the Maximum Correntropy Criterion(MCC)and employs dummy measurement technology to enhance the stability of estimated loads.We develop a kernel size update algorithm to address the challenges associated with obtaining the key parameter,kernel size of MCC.Comparative analysis of the vertical and lateral loads of the axle box bearing obtained using FMCC-DKF,DKF,and AMCC-DKF,under both measurement noise-free and non-Gaussian noise conditions,is conducted to demonstrate the superiority of the proposed estimation method.The results indicate that the proposed FMCC-DKF method exhibits high estimation accuracy under both measurement noise-free and non-Gaussian noise interference,and maintains its high estimation accuracy despite changes in train speed.The proposed load estimation method demonstrates reliable performance within the low-frequency domain below 70 Hz.展开更多
In this paper,the front axle of a certain model is taken as the research object,and the stress and deformation of the frontaxle under three typical working conditions are analyzed by finite element technology.Based on...In this paper,the front axle of a certain model is taken as the research object,and the stress and deformation of the frontaxle under three typical working conditions are analyzed by finite element technology.Based on the simulation results,the 3D model of the front axle was optimized,and the finite element analysis of the optimized structure of the front axle under three typical working conditions was carried out to verify the correctness of the model.Finally,the fatigue tool module of ANSYS Workbench was used to analyze the fatigue life of the front axle under the optimized emergency conditions,and the feasibility of the model was verified.The analysis data shows that the design of the front axle components still has a lot of potential for lightweighting,and the weight of the front axle can be reduced by 6.73%through optimization,and the performance of the front axle can also meet the needs of use.The research conclusionhas a certain reference value for the lightweight design of automobile front axle.展开更多
基金Supported by National Natural Science Foundation of China(Grant No.12232004)Guangdong Provincial Basic and Applied Basic Research Foundation(Grant No.2022A1515140111)+1 种基金Anhui Provincial Science and Technology Projects(Grant No.JB24075)Sichuan Provincial Science and Technology Program(Grant Nos.2024NSFSC2020,2023YFG0234)。
文摘Heavy-duty freight railway axles are no less important than those of passenger trains,owing to the potentially catastrophic results caused by the derailment of trains carrying hazardous substances.Intrinsic and extrinsic imperfections challenge classical design theories built based on the safe life concept,and damage tolerance assessment becomes vital for the safety and reliability of long-term serviced railway axles,as pits and scratches are common defects for heavy-duty railway axles.In this work,four-point rotating bending fatigue tests of AAR-CM railway axle steel specimens with semicircular and circumferential groove notches are conducted.The fatigue limit of the semicircular notched specimens was evaluated based on fracture mechanics theory,in which non-conservative results are obtained by the El Haddad model and the S–N curves of circumferential groove notched specimens are correlated by the theory of critical distance(TCD).
基金National Basic Research and Development Program of China(973 Program,No.2007CB714705).
文摘According to the rules of UIC515-3,the service loads of the axles are defined,which include some different loads cases as follows:the static loads;the impact loads resulted from running through the rail joints and unevenness rails;the loads through curves and from braking.Through the calculating and analysis,the stress distribution of the hollow axles is obtained for 200 km/h high speed motor trains used in China.At the same time,the fatigue crack growth of hollow axles is studied,and the initial surface cracks of 2 mm depth caused by hard objects strike or the other causes are discussed.On the basis of the linear elastic fracture mechanics theory,the stress intensity factor of the crack of the geometry transition outside the wheel seat is also studied.Associated with fatigue crack propagation equation and the corresponding crack propagation threshold,the crack propagation characteristics under different shapes are calculated.Then the running distances are educed with different shapes propagating to the critical length,and the estimation of the residual lives about hollow axles which are the reference values of examine and repair limit of the hollow axle is given.
基金the Independent Research Project of the State Key Laboratory of Traction Power(No.2018TPL_Z01)the National Natural Science Foundation of China(No.51375406)the Fundamental Research Funds for the Central Universities(No.2682018CX68).
文摘This study investigated the fretting wear and fatigue of full-scale railway axles.Fatigue tests were conducted on full-scale railway axles,and the fretting wear and fretting fatigue in the fretted zone of the railway axles were analysed.Three-dimensional finite element models were established based on the experimental results.Then,multi-axial fatigue parameters and a linear elastic fracture mechanics-based approach were used to investigate the fretting fatigue crack initiation and propagation,respectively,in which the role of the fretting wear was taken into account.The experimental and simulated results showed that the fretted zone could be divided into zones I-III according to the surface damage morphologies.Fretting wear alleviated the stress concentration near the wheel seat edge and resulted in a new stress concentration near the worn/unworn boundary in zone II,which greatly promoted the fretting crack initiation at the inner side of the fretted zone.Meanwhile,the stress concentration also increased the equivalent stress intensity factor range DKeq below the mating surface,and thus promoted the propagation of fretting fatigue crack.Based on these findings,the effect of the stress redistribution resulting from fretting wear is suggested to be taken into account when evaluating the fretting fatigue in railway axles.
基金supported by National Basic Research and Development Program of China(973 Program,Grant No.2007CB714705)
文摘Because of the wicked service environment of the high speed train,it is possible that the hollow axle of the train may encounter the foreign object damage and form a sharp notch.Under the fatigue loading a crack can initiate from the notch and propagate to failure.It is noted that the stress intensity factor is the control parameter of the crack propagating,for the purpose of getting the more exact propagation characteristics,the stress intensity factor is studied mainly.The service loads of hollow axles are defined,and the stress distribution of hollow axles is obtained according to the load spectrum.The semi-ellipse crack configuration is defined with three parameters:the aspect ratio,the relative depth and the relative location along the crack front.Quarter point 20-node isoparametric degenerate singular elements are used for the region near the crack tip.The finite element model of crack extension of hollow axle is created,and the crack front is dispersed which can realize orthogonal extension.Based on this the stress intensity factors of crack front were calculated,and the distribution rules of the stress intensity factors of different initial crack shapes are obtained.The conclusions are compared with that of the analytic method and they agree with each other very well,and the calculating results show that there is a close relationship between the stress intensity factor and the initial crack shape.For a round crack the stress intensity factor at the surface point increases faster than the one at the center point with the crock propagation.However,for a narrow crack,the results are in contrast with that of a round one.So,all the cracks with different shapes propagate toward to a similar shape,and they grow at this shape to end.The study may contribute to the crack propagate characteristics research.
基金supported by National Key R&D Program of China(No.2017YFB0304600).
文摘The microstructure,precipitates and properties of 25CrNiMoV(DZ2)steel for high-speed railway axles with different Nb contents were investigated by means of optical microscopy,scanning electron microscopy,electron back-scattering diffraction,transmission electron microscopy and physicochemical phase analysis.The results show that the grain size of the original austenite of the test steels decreases from 20.5 to 14.2 and 10.8μm after adding 0.026 and 0.039 wt.%Nb to a 25CrNiMoV steel,respectively.Moreover,the block width of the tempered martensite in the test steels is refined from 1.91 to 1.72 and 1.60µm,respectively.MC-type precipitates in 25CrNiMoV steel are mainly VC,while(Nb,V)C gradually precipitates when Nb is microalloyed,and the amount of precipitates increases with increasing Nb content.Through strengthening mechanism analysis,it is found that grain refinement strengthening is the primary way to increase the strength.The improvement in the yield strength with increasing Nb content is attributed to a significant increase in precipitation strengthening,grain refinement strengthening and dislocation strengthening.
基金supported by grants from the National Key R&D Program of China(No.2023YFA1008904)the Guangxi Key Research and Development Project(No.AB22080091)the National Natural Science Foundation of China(No.52108412).
文摘Equivalent axle load factor(EALF)is used to characterize the fatigue damage effect of multi-axle loads on asphalt pavement.EALF is calculated as the ratio of the pavement’s fatigue resistance under a single axle load to that under a multi-axle load.Existing studies use the same fatigue life function to predict the fatigue life of asphalt mixture under both single-and multi-axle loads,primarily focusing on the differences in pavement strains under these two configurations.However,strain waveforms in asphalt pavement caused by multi-axle loads differ from those under single-axle loads,altering the mixture’s fatigue behavior.To address this issue,this research tests the fatigue responses of asphalt mixtures under actual loading waveforms from single-axle,tandem-axle,and tridem-axle loads.Based on the test results,fatigue life functions are developed for each axle configuration and used to establish an updated EALF model.Since the applied fatigue life functions are based on test results from more realistic strain waveforms,the calculated EALFs provide more reliable predictions of the damaging effect of multi-axle loads on asphalt mixtures.
基金supported by grants from the Wenzhou Science and Technology Bureau Foundation,China(Grant No.:ZY2019014)“Pioneer”and“Leading Goose”R&D Program of Zhejiang,China(Grant No.:2022C03144)National Natural Science Foundation of China(Grant Nos.:82172494,and 82372461).
文摘Ferroptosis of chondrocytes is a significant contributor to osteoarthritis(OA),for which there is still a lack of safe and effective therapeutic drugs targeting ferroptosis.Here,we screen for anti-ferroptotic drugs in Food and Drug Administration(FDA)-approved drug library via a high-throughput manner in chondrocytes.We identified a group of FDA-approved anti-ferroptotic drugs,among which vitamin K showed the most powerful protective effect.Further study demonstrated that vitamin K effectively inhibited ferroptosis and alleviated the extracellular matrix(ECM)degradation in chondrocytes.Intra-articular injection of vitamin K inhibited ferroptosis and alleviated OA phenotype in destabilization of the medial meniscus(DMM)mouse model.Mechanistically,transcriptome sequencing and knockdown experiments revealed that the anti-ferroptotic effects of vitamin K depended on growth arrest-specific 6(Gas6).Furthermore,exogenous expression of Gas6 was found to inhibit ferroptosis through the AXL receptor tyrosine kinase(AXL)/phosphatidylinositol 3-kinase(PI3K)/AKT serine/threonine kinase(AKT)axis.Together,we demonstrate that vitamin K inhibits ferroptosis and alleviates OA progression via enhancing Gas6 expression and its downstream pathway of AXL/PI3K/AKT axis,indicating vitamin K as well as Gas6 to serve as a potential therapeutic target for OA and other ferroptosis-related diseases.
基金supported by the National Natural Science Foundation of China, Nos.81971151 (to YW), 82102528 (to XL), 82102583 (to LW)the Natural Science Foundation of Guangdong Province, China, Nos.2020A1515010265 (to YW), 2020A1515110679 (to XL), and 2021A1515010358 (to XL)
文摘Invasive inflammation and excessive scar formation are the main reasons for the difficulty in repairing nervous tissue after spinal cord injury.Microglia and astrocytes play key roles in the spinal cord injury micro-environment and share a close interaction.However,the mechanisms involved remain unclear.In this study,we found that after spinal cord injury,resting microglia(M0)were polarized into pro-inflammatory phenotypes(MG1 and MG3),while resting astrocytes were polarized into reactive and scar-forming phenotypes.The expression of growth arrest-specific 6(Gas6)and its receptor Axl were significantly down-regulated in microglia and astrocytes after spinal cord injury.In vitro experiments showed that Gas6 had negative effects on the polarization of reactive astrocytes and pro-inflammatory microglia,and even inhibited the cross-regulation between them.We further demonstrated that Gas6 can inhibit the polarization of reactive astrocytes by suppressing the activation of the Yes-associated protein signaling pathway.This,in turn,inhibited the polarization of pro-inflammatory microglia by suppressing the activation of the nuclear factor-κB/p65 and Janus kinase/signal transducer and activator of transcription signaling pathways.In vivo experiments showed that Gas6 inhibited the polarization of pro-inflammatory microglia and reactive astrocytes in the injured spinal cord,thereby promoting tissue repair and motor function recovery.Overall,Gas6 may play a role in the treatment of spinal cord injury.It can inhibit the inflammatory pathway of microglia and polarization of astrocytes,attenuate the interaction between microglia and astrocytes in the inflammatory microenvironment,and thereby alleviate local inflammation and reduce scar formation in the spinal cord.
基金supported by the National Natural Science Foundation of China(Nos.12372056,12032017,12393783)the S&T Program of Hebei of China(No.24465001D)。
文摘Axle box bearings are critical components of high-speed trains.Localized defects,such as pitting and spalling,on raceways or rollers pose significant threats to the operational safety of railway vehicles.In this work,a novel bearing-flexible axle boxvehicle coupling model is established to explore the vibration characteristics of axle box bearings with irregular localized defects.First,based on the contact and kinematic relationship between rollers and raceways,the three-dimensional(3D)bearing force elements are analyzed and formulated.Second,the established model and a flexible axle box are integrated into the vehicle,and the responses of the normal and faulty bearings under the combined excitations of wheel roughness and track irregularities are simulated.Third,the simulation results are verified through a rolling-vibrating test bench for full-scale wheelsets of high-speed trains.The comparisons of the fault-induced repetitive transients in the time-domain and the fault characteristic frequencies in the envelope spectra demonstrate the efficiency of the proposed model.Finally,based on the flexible axle box model,a sensitivity analysis of the accelerometer placements to the bearing faults is carried out,and the optimal one is identified based on both the time-domain and frequency-domain signal-to-noise ratios(SNRs)for engineering applications.
文摘Purpose–To address the encapsulation challenge of fiber Bragg grating(FBG)sensors in complex railway environments,this paper designs a clip-on composite sensor enabling installation-friendly deployment and long-term axle counting system monitoring.Design/methodology/approach–Wheel–rail mechanical behavior was simulated via finite element analysis(FEA)to determine optimal sensor placement.A clip-on composite sensor was subsequently engineered.Stress transduction efficacy was validated through FEA quantification of stress responses at the axle counter location.Findings–The proposed FBG axle counter integrates temperature compensation and anti-detachment monitoring as well as advantages such as simplified installation with minimal maintenance and sustained operational reliability.It effectively transmits stress,yielding a measured strain of 39μe under static loading conditions without sensitivity-enhancing elements.Originality/value–This study performs FEA of wheel-rail stress distribution and engineers the dual-slot composite sensor,FEAwas conducted to quantify the stress magnitude at the axle sensor position of the dual-slot composite sensor.Additionally,FEA was performed on sensors with different structural configurations,including adjustments to the axle sensor position,number of slots and axle position.The results confirmed that the designed composite sensor exhibits superior stress transfer characteristics.
基金National Key R&D Program of China(Grant numbers 2022YFB4301201-11,2022YFB4301203-05)National Natural Science Foundation of China(Grant number 52202464).
文摘Axle box bearings serve as crucial components within the transmission system of high-speed trains.Their failure can directly impact the operational safety of these trains.Accurately determining the dynamic load experienced by bearings during the operation of high-speed trains can provide valuable boundary inputs for the study of bearing fatigue life and service performance,thereby holding significant engineering implications.In this study,we propose a high-speed train axle box bearing load estimation method(FMCC-DKF).This method is founded on the Kalman filtering technique of the Maximum Correntropy Criterion(MCC)and employs dummy measurement technology to enhance the stability of estimated loads.We develop a kernel size update algorithm to address the challenges associated with obtaining the key parameter,kernel size of MCC.Comparative analysis of the vertical and lateral loads of the axle box bearing obtained using FMCC-DKF,DKF,and AMCC-DKF,under both measurement noise-free and non-Gaussian noise conditions,is conducted to demonstrate the superiority of the proposed estimation method.The results indicate that the proposed FMCC-DKF method exhibits high estimation accuracy under both measurement noise-free and non-Gaussian noise interference,and maintains its high estimation accuracy despite changes in train speed.The proposed load estimation method demonstrates reliable performance within the low-frequency domain below 70 Hz.
文摘In this paper,the front axle of a certain model is taken as the research object,and the stress and deformation of the frontaxle under three typical working conditions are analyzed by finite element technology.Based on the simulation results,the 3D model of the front axle was optimized,and the finite element analysis of the optimized structure of the front axle under three typical working conditions was carried out to verify the correctness of the model.Finally,the fatigue tool module of ANSYS Workbench was used to analyze the fatigue life of the front axle under the optimized emergency conditions,and the feasibility of the model was verified.The analysis data shows that the design of the front axle components still has a lot of potential for lightweighting,and the weight of the front axle can be reduced by 6.73%through optimization,and the performance of the front axle can also meet the needs of use.The research conclusionhas a certain reference value for the lightweight design of automobile front axle.
