The evolution of artificial intelligence has thrust the Online Judge(OJ)systems into the forefront of research,particularly within programming education,with a focus on enhancing performance and efficiency.Addressing ...The evolution of artificial intelligence has thrust the Online Judge(OJ)systems into the forefront of research,particularly within programming education,with a focus on enhancing performance and efficiency.Addressing the shortcomings of the current OJ systems in coarse defect localization granularity and heavy task scheduling architecture,this paper introduces an innovative Integrated In-telligent Defect Localization and Lightweight Task Scheduling Online Judge(IDL-LTSOJ)system.Firstly,to achieve token-level fine-grained defect localization,a Deep Fine-Grained Defect Localization(Deep-FGDL)deep neural network model is developed.By integrating Bidirectional Long Short-Term Memory(BiLSTM)and Bidirectional Gated Recurrent Unit(BiGRU),this model extracts fine-grained information from the abstract syntax tree(AST)of code,enabling more accurate defect localization.Subsequently,we propose a lightweight task scheduling architecture to tackle issues,such as limited concurrency in task evaluation and high equipment costs.This architecture integrates a Kafka messaging system with an optimized task distribution strategy to enable concurrent execution of evaluation tasks,substantially enhancing system evaluation efficiency.The experimental results demonstrate that the Deep-FGDL model improves the accuracy by 35.9%in the Top-20 rank compared to traditional machine learning benchmark methods for fine-grained defect localization tasks.Moreover,the lightweight task scheduling strategy notably reduces response time by nearly 6000ms when handling 120 task volumes,which represents a significant improvement in evaluation efficiency over centralized evaluation methods.展开更多
In this paper,the nonlinear resonance characteristics of a dual-rotor system are investigated with the consideration of a local defect on the inter-shaft bearing of the system.A simplified model of the dual-rotor syst...In this paper,the nonlinear resonance characteristics of a dual-rotor system are investigated with the consideration of a local defect on the inter-shaft bearing of the system.A simplified model of the dual-rotor system is proposed by considering that there is a local defect on the inner ring of inter-shaft bearing.The local defect is modelled as an inverted isosceles trapezoidal groove,which can make great influence on the inter-shaft bearing force due to the change of radial clearance of the inter-shaft bearing.The motion equations of the dual-rotor system are formulated by using the Lagrange equation.The Runge-Kutta method is employed to solve the motion equation.The amplitude-frequency response curve of the dual-rotor system is obtained,the abnormal resonance characteristics are analyzed.In addition,the influence of defect parameters,rotors and support parameters and inter-shaft bearing parameters on the amplitude-frequency characteristics of the system are discussed.The results show that there are two main resonance peaks and four abnormal resonance peaks on the amplitude-frequency response curve of the dual-rotor with a local defect on the inner ring of the inter-shaft bearing.Through analyzing the vibration response of the abnormal resonance peaks,it is found that the first two abnormal resonances are caused by the combined resonance,which are related to the inner ring fault and the rotational speed of high or low pressure rotors,and the last two resonances are caused by the induced resonance of the inner ring fault.At the same time,when the parameters of defect,rotors and support and inter-shaft bearing change,the resonance of the system also shows the corresponding change law.展开更多
The isothermal local loading forming technology provides a feasible way to form Ti-alloy large-scale rib-web components in aerospace and aviation fields.However,the local loading process forming limit is restricted by...The isothermal local loading forming technology provides a feasible way to form Ti-alloy large-scale rib-web components in aerospace and aviation fields.However,the local loading process forming limit is restricted by forming defects in the transitional region.In this work,the feasibility of controlling forming defects and improving the process forming limit by adjusting die parameters is explored through finite element（FE） simulation.It is found that the common cavum and folding defects in the transitional region are significantly influenced by the fillet radii of left rib and middle rib,respectively.The cavum and folding defects can be effectively controlled by increasing the fillet radii of left rib and middle rib,respectively.The process forming limits considering forming defects in the transitional region are determined by the stepwise searching method under various die parameters.Moreover,the relationship between the process forming limit and die parameters is developed through the response surface methodology（RSM）.The developed RSM models suggest that increasing the fillet radii of left and middle ribs is effective to improve the process forming limit during local loading forming of rib-web components.The results will provide technical basis for the design of die parameters and the reduction amount,which is of great importance to control forming defects and improve the process forming limit in local loading forming of Ti-alloy large-scale rib-web components.展开更多
Gearbox is a key part in machinery,in which gear,shaft and bearing operate together to transmit motion and power.The wide usage and high failure rate of gearbox make it attract much attention on its health monitoring ...Gearbox is a key part in machinery,in which gear,shaft and bearing operate together to transmit motion and power.The wide usage and high failure rate of gearbox make it attract much attention on its health monitoring and fault diagnosis.Dynamic modelling can study the mechanism under different faults and provide theoretical foundation for fault detection.However,current commonly used gear dynamic model usually neglects the influence of bearing and shaft,resulting in incomplete understanding of gearbox fault diagnosis especially under the effect of local defects on gear and shaft.To address this problem,an improved gear-shaft-bearing-housing dynamic model is proposed to reveal the vibration mechanism and responses considering shaft whirling and gear local defects.Firstly,an eighteen degree-of-freedom gearbox dynamic model is proposed,taking into account the interaction among gear,bearing and shaft.Secondly,the dynamic model is iteratively solved.Then,vibration responses are expounded and analysed considering gear spalling and shaft crack.Numerical results show that the gear mesh frequency and its harmonics have higher amplitude through the spectrum.Vibration RMS and the shaft rotating frequency increase with the spalling size and shaft crack angle in general.An experiment is designed to verify the rationality of the proposed gearbox model.Lastly,comprehensive analysis under different spalling size and shaft crack angle are analysed.Results show that when spalling size and crack angle are larger,RMS and the amplitude of shaft rotating frequency will not increase linearly.The dynamic model can accurately simulate the vibration of gear transmission system,which is helpful for gearbox fault diagnosis.展开更多
Based on finite-difference time-domain(FDTD) method,the wave propagation and localization in two-dimensional defect-containing piezoelectric phononic crystals are investigated when the mechanical-electrical coupling i...Based on finite-difference time-domain(FDTD) method,the wave propagation and localization in two-dimensional defect-containing piezoelectric phononic crystals are investigated when the mechanical-electrical coupling is taken into account.The characteristics of localized defect modes are studied,and the effects of the number and direction of defects on the defect modes and transmission coefficients are discussed.Numerical results of defect modes and transmission coefficients are presented for BaTiO3/polymer piezocomposite,and from which we can see that the number and direction of defects have pronounced effects on the defect modes and transmission coefficients.The results also show the existence of elastic wave localization in piezoelectric phononic crystals containing defects.展开更多
A buckling model of Timoshenko micro-beam with local thickness defects is established based on a modified gradient elasticity.By introducing the local thickness defects function of the micro-beam,the variable coeffici...A buckling model of Timoshenko micro-beam with local thickness defects is established based on a modified gradient elasticity.By introducing the local thickness defects function of the micro-beam,the variable coefficient differential equations of the buckling problem are obtained with the variational principle.Combining the eigensolution series of the complete micro-beam with the Galerkin method,we obtain the critical load and buckling modes of the micro-beam with defects.The results show that the depth and location of the defect are the main factors affecting the critical load,and the combined effect of boundary conditions and defects can significantly change the buckling mode of the micro-beam.The effect of defect location on buckling is related to the axial gradient of the rotation angle,and defects should be avoided at the maximum axial gradient of the rotation angle.The model and method are also applicable to the static deformation and vibration of the micro-beam.展开更多
A wire rope defects detection method based on permanent magnet excitation is proposed.A detection system,mainly composed of permanent magnet excitation,distance detection,multi-sensor magnetic flux leakage signal acqu...A wire rope defects detection method based on permanent magnet excitation is proposed.A detection system,mainly composed of permanent magnet excitation,distance detection,multi-sensor magnetic flux leakage signal acquisition and data analysis device,is set up.According to the different characteristics of the multi-sensor magnetic flux leakage signal,the localized fault(LF)and loss of metallic cross-sectional area(LMA)signal is separated,and then the two defects can be detected.The experiments show that the method can effectively detect the two defects when they appear simultaneously on the wire rope.展开更多
In this paper,we study the quantum properties of a bilayer graphene with（asymmetry） line defects.The localized states are found around the line defects.Thus,the line defects on one certain layer of the bilayer graph...In this paper,we study the quantum properties of a bilayer graphene with（asymmetry） line defects.The localized states are found around the line defects.Thus,the line defects on one certain layer of the bilayer graphene can lead to an electric transport channel.By adding a bias potential along the direction of the line defects,we calculate the electric conductivity of bilayer graphene with line defects using the Landauer-Biittiker theory,and show that the channel affects the electric conductivity remarkably by comparing the results with those in a perfect bilayer graphene.This one-dimensional line electric channel has the potential to be applied in nanotechnology engineering.展开更多
Local ageing defects are the main causes of cross-linked polyethylene(XLPE)power cable faults.This research aims at assessing the severity level of typical cable local ageing defects based on the high-voltage frequenc...Local ageing defects are the main causes of cross-linked polyethylene(XLPE)power cable faults.This research aims at assessing the severity level of typical cable local ageing defects based on the high-voltage frequency domain spectroscopy(FDS)non-linearity.Experimentally,typical XLPE cables ageing defect conditions are simulated,with different ageing types,degrees,and local proportions.Then,the high-voltage FDS detection is conducted and the results have been analysed.It has been found that the high-voltage FDS non-linearity is only related to the detection voltage and ageing degree.Especially,it is more sensitive to changes in the ageing severity.Thus,the local ageing defect severity assessment method based on non-linearity has been established.Additionally,the sensitivity has been compared between two diagnostic evaluation methods:the high-voltage FDS and the widely used very-low frequency method(VLF,0.1 Hz).It can be concluded from the comparison result that the proposed assessment method has higher sensitivity than that of the traditional methods.Finally,the effectiveness of the proposed method for evaluating the on-site long cables has been validated.The result demonstrates that the proposed method can assess on-site long cables and has the potential to be formed as quantitative standards.展开更多
Local defected resonance(LDR)is a recently-developed non-destructive testing method,which identifies damage by detecting the vibrational response of the structural surface under the wideband ultrasonic excitation. The...Local defected resonance(LDR)is a recently-developed non-destructive testing method,which identifies damage by detecting the vibrational response of the structural surface under the wideband ultrasonic excitation. The concept of LDR is studied and applied for damage imaging of delamination in composite laminates. Aiming at the problem of poor anti-noise ability and inaccurate damage identification in traditional detection process,an LDR-based multi-frequency method is proposed. Experimental results show that the proposed method can realize the localization and imaging of delamination damage in composite materials.展开更多
The studies on dynamics of a fault bearing system are prevalent in recent years, however, we are studying a completely different frequency range than the one where the bearing faults are best seen. Considering a local...The studies on dynamics of a fault bearing system are prevalent in recent years, however, we are studying a completely different frequency range than the one where the bearing faults are best seen. Considering a local defect on outer raceway,a two-degree-of-freedom analytical model of a rigid-rotor ball bearing system is established. Three pulse force models are introduced to simulate the local defect. The frequency domain method—harmonic balance method with alternating frequency/time domain technique (HB-AFT) is used to calculate the response in a large frequency range. By comparing the performance at different frequencies, the fault systems with different defect models and parameters reveal the super-harmonic resonances,and the reasons for this phenomenon are uncovered as well. Finally, the theoretical calculation is verified qualitatively by the experimental results, through comparing the frequency spectrums of the defective bearing rotor system to the fault-free one.Therefore, the super-harmonic resonances can be regarded as a dynamic feature. Besides, the obvious super-harmonic resonances indicate the magnification of the harmonics of the "characteristic defect frequency" for outer race in the corresponding speed regions, which may be helpful for the diagnosis of a rotor ball bearing system with a local defect.展开更多
The study aimed to explore the cathodic protection of the defect areas of 75 wt.%zinc-rich coatings(ZRCs)under immersion and atmospheric thin liquid film conditions using a wire beam electrode(WBE).Besides,electrochem...The study aimed to explore the cathodic protection of the defect areas of 75 wt.%zinc-rich coatings(ZRCs)under immersion and atmospheric thin liquid film conditions using a wire beam electrode(WBE).Besides,electrochemical impedance spectroscopy,scanning electron microscopy,and surface morphology analysis were used.Under both experimental conditions,high ZRCs content polarised the entire electrode to the protective potential range,thereby reversing the polarity of the defect area steel substrate to cathodic to prevent corrosion.The higher concentration of dissolved oxygen in the surface liquid film and coating activated the zinc powder faster and provided a higher cathodic protection current for the defect area under the atmospheric liquid film condition.Therefore,WBE corrosion potential shifted more negative under the atmospheric liquid film condition,thereby conveying longer-lasting cathodic protection and reducing the corrosion rate of the defect area steel substrate.Compared with the traditional sheet electrode,WBE can provide the current distribution and change information of cathodic protection at the local defects on the ZRCs surface,thereby providing a reliable test and a method for evaluating heterogeneous corrosion and cathodic protection.展开更多
基金supported in part by the Beijing Natural Science Foundation(4212018)the National Key R&D Program of China(2024YFE200500),awarded to Lihua Song.
文摘The evolution of artificial intelligence has thrust the Online Judge(OJ)systems into the forefront of research,particularly within programming education,with a focus on enhancing performance and efficiency.Addressing the shortcomings of the current OJ systems in coarse defect localization granularity and heavy task scheduling architecture,this paper introduces an innovative Integrated In-telligent Defect Localization and Lightweight Task Scheduling Online Judge(IDL-LTSOJ)system.Firstly,to achieve token-level fine-grained defect localization,a Deep Fine-Grained Defect Localization(Deep-FGDL)deep neural network model is developed.By integrating Bidirectional Long Short-Term Memory(BiLSTM)and Bidirectional Gated Recurrent Unit(BiGRU),this model extracts fine-grained information from the abstract syntax tree(AST)of code,enabling more accurate defect localization.Subsequently,we propose a lightweight task scheduling architecture to tackle issues,such as limited concurrency in task evaluation and high equipment costs.This architecture integrates a Kafka messaging system with an optimized task distribution strategy to enable concurrent execution of evaluation tasks,substantially enhancing system evaluation efficiency.The experimental results demonstrate that the Deep-FGDL model improves the accuracy by 35.9%in the Top-20 rank compared to traditional machine learning benchmark methods for fine-grained defect localization tasks.Moreover,the lightweight task scheduling strategy notably reduces response time by nearly 6000ms when handling 120 task volumes,which represents a significant improvement in evaluation efficiency over centralized evaluation methods.
基金supported by the National Natural Science Foundation of China(No.11972129)the National Science and Technology Major Project,China(No.2017-Ⅳ-00080045)。
文摘In this paper,the nonlinear resonance characteristics of a dual-rotor system are investigated with the consideration of a local defect on the inter-shaft bearing of the system.A simplified model of the dual-rotor system is proposed by considering that there is a local defect on the inner ring of inter-shaft bearing.The local defect is modelled as an inverted isosceles trapezoidal groove,which can make great influence on the inter-shaft bearing force due to the change of radial clearance of the inter-shaft bearing.The motion equations of the dual-rotor system are formulated by using the Lagrange equation.The Runge-Kutta method is employed to solve the motion equation.The amplitude-frequency response curve of the dual-rotor system is obtained,the abnormal resonance characteristics are analyzed.In addition,the influence of defect parameters,rotors and support parameters and inter-shaft bearing parameters on the amplitude-frequency characteristics of the system are discussed.The results show that there are two main resonance peaks and four abnormal resonance peaks on the amplitude-frequency response curve of the dual-rotor with a local defect on the inner ring of the inter-shaft bearing.Through analyzing the vibration response of the abnormal resonance peaks,it is found that the first two abnormal resonances are caused by the combined resonance,which are related to the inner ring fault and the rotational speed of high or low pressure rotors,and the last two resonances are caused by the induced resonance of the inner ring fault.At the same time,when the parameters of defect,rotors and support and inter-shaft bearing change,the resonance of the system also shows the corresponding change law.
基金the support of the National Natural Science Foundation of China(Nos.51605388,51675433)111 Project(B08040)+2 种基金the Research Fund of the State Key Laboratory of Solidification Processing(NWPU)in China(Grant No.131-QP-2015)the Fundamental Research Funds for the Central Universitiesthe Open Research Fund of State Key Laboratory of Materials Processing and Die&Mold Technology at Huazhong University of Science and Technology
文摘The isothermal local loading forming technology provides a feasible way to form Ti-alloy large-scale rib-web components in aerospace and aviation fields.However,the local loading process forming limit is restricted by forming defects in the transitional region.In this work,the feasibility of controlling forming defects and improving the process forming limit by adjusting die parameters is explored through finite element（FE） simulation.It is found that the common cavum and folding defects in the transitional region are significantly influenced by the fillet radii of left rib and middle rib,respectively.The cavum and folding defects can be effectively controlled by increasing the fillet radii of left rib and middle rib,respectively.The process forming limits considering forming defects in the transitional region are determined by the stepwise searching method under various die parameters.Moreover,the relationship between the process forming limit and die parameters is developed through the response surface methodology（RSM）.The developed RSM models suggest that increasing the fillet radii of left and middle ribs is effective to improve the process forming limit during local loading forming of rib-web components.The results will provide technical basis for the design of die parameters and the reduction amount,which is of great importance to control forming defects and improve the process forming limit in local loading forming of Ti-alloy large-scale rib-web components.
基金supported by National Key R&D Program of China (No.2022YFB3303600)the Fundamental Research Funds for the Central Universities (No.2022CDJKYJH048).
文摘Gearbox is a key part in machinery,in which gear,shaft and bearing operate together to transmit motion and power.The wide usage and high failure rate of gearbox make it attract much attention on its health monitoring and fault diagnosis.Dynamic modelling can study the mechanism under different faults and provide theoretical foundation for fault detection.However,current commonly used gear dynamic model usually neglects the influence of bearing and shaft,resulting in incomplete understanding of gearbox fault diagnosis especially under the effect of local defects on gear and shaft.To address this problem,an improved gear-shaft-bearing-housing dynamic model is proposed to reveal the vibration mechanism and responses considering shaft whirling and gear local defects.Firstly,an eighteen degree-of-freedom gearbox dynamic model is proposed,taking into account the interaction among gear,bearing and shaft.Secondly,the dynamic model is iteratively solved.Then,vibration responses are expounded and analysed considering gear spalling and shaft crack.Numerical results show that the gear mesh frequency and its harmonics have higher amplitude through the spectrum.Vibration RMS and the shaft rotating frequency increase with the spalling size and shaft crack angle in general.An experiment is designed to verify the rationality of the proposed gearbox model.Lastly,comprehensive analysis under different spalling size and shaft crack angle are analysed.Results show that when spalling size and crack angle are larger,RMS and the amplitude of shaft rotating frequency will not increase linearly.The dynamic model can accurately simulate the vibration of gear transmission system,which is helpful for gearbox fault diagnosis.
基金Sponsored by the National Natural Science Foundation of China(Grant No.10672017 and 10632020)the China Postdoctoral Science Foundation+1 种基金Heilongjiang Province Postdoctoral Science FoundationJapan Society for the Promotion of Science(JSPS)
文摘Based on finite-difference time-domain(FDTD) method,the wave propagation and localization in two-dimensional defect-containing piezoelectric phononic crystals are investigated when the mechanical-electrical coupling is taken into account.The characteristics of localized defect modes are studied,and the effects of the number and direction of defects on the defect modes and transmission coefficients are discussed.Numerical results of defect modes and transmission coefficients are presented for BaTiO3/polymer piezocomposite,and from which we can see that the number and direction of defects have pronounced effects on the defect modes and transmission coefficients.The results also show the existence of elastic wave localization in piezoelectric phononic crystals containing defects.
基金Project supported by the Young Core Instructor and Domestic Visitor Foundation from the Education Commission of Hunan Province(No.21B0315)。
文摘A buckling model of Timoshenko micro-beam with local thickness defects is established based on a modified gradient elasticity.By introducing the local thickness defects function of the micro-beam,the variable coefficient differential equations of the buckling problem are obtained with the variational principle.Combining the eigensolution series of the complete micro-beam with the Galerkin method,we obtain the critical load and buckling modes of the micro-beam with defects.The results show that the depth and location of the defect are the main factors affecting the critical load,and the combined effect of boundary conditions and defects can significantly change the buckling mode of the micro-beam.The effect of defect location on buckling is related to the axial gradient of the rotation angle,and defects should be avoided at the maximum axial gradient of the rotation angle.The model and method are also applicable to the static deformation and vibration of the micro-beam.
文摘A wire rope defects detection method based on permanent magnet excitation is proposed.A detection system,mainly composed of permanent magnet excitation,distance detection,multi-sensor magnetic flux leakage signal acquisition and data analysis device,is set up.According to the different characteristics of the multi-sensor magnetic flux leakage signal,the localized fault(LF)and loss of metallic cross-sectional area(LMA)signal is separated,and then the two defects can be detected.The experiments show that the method can effectively detect the two defects when they appear simultaneously on the wire rope.
基金Project supported by the National Basic Research Program of China(Grant Nos.2011CB921803 and 2012CB921704)the National Natural Science Foundation of China(Grant Nos.11174035,11474025,11504285,and 11404090)+3 种基金the Specialized Research Fund for the Doctoral Program of Higher Education,Chinathe Fundamental Research Funds for the Central Universities,Chinathe Scientific Research Program Fund of the Shaanxi Provincial Education Department,China(Grant No.15JK1363)the Young Talent Fund of University Association for Science and Technology in Shaanxi Province,China
文摘In this paper,we study the quantum properties of a bilayer graphene with（asymmetry） line defects.The localized states are found around the line defects.Thus,the line defects on one certain layer of the bilayer graphene can lead to an electric transport channel.By adding a bias potential along the direction of the line defects,we calculate the electric conductivity of bilayer graphene with line defects using the Landauer-Biittiker theory,and show that the channel affects the electric conductivity remarkably by comparing the results with those in a perfect bilayer graphene.This one-dimensional line electric channel has the potential to be applied in nanotechnology engineering.
基金National Key Research and Development Program of China,Grant/Award Number:2023YFB2406900。
文摘Local ageing defects are the main causes of cross-linked polyethylene(XLPE)power cable faults.This research aims at assessing the severity level of typical cable local ageing defects based on the high-voltage frequency domain spectroscopy(FDS)non-linearity.Experimentally,typical XLPE cables ageing defect conditions are simulated,with different ageing types,degrees,and local proportions.Then,the high-voltage FDS detection is conducted and the results have been analysed.It has been found that the high-voltage FDS non-linearity is only related to the detection voltage and ageing degree.Especially,it is more sensitive to changes in the ageing severity.Thus,the local ageing defect severity assessment method based on non-linearity has been established.Additionally,the sensitivity has been compared between two diagnostic evaluation methods:the high-voltage FDS and the widely used very-low frequency method(VLF,0.1 Hz).It can be concluded from the comparison result that the proposed assessment method has higher sensitivity than that of the traditional methods.Finally,the effectiveness of the proposed method for evaluating the on-site long cables has been validated.The result demonstrates that the proposed method can assess on-site long cables and has the potential to be formed as quantitative standards.
基金supported by the National Natural Science Foundation of China(Nos.51875227,51805261,51775267)the Natural Science Foundation of Jiangsu Province(Nos.BK20181286,BK20180430)the Aviation Science Fund(No.20161552014)
文摘Local defected resonance(LDR)is a recently-developed non-destructive testing method,which identifies damage by detecting the vibrational response of the structural surface under the wideband ultrasonic excitation. The concept of LDR is studied and applied for damage imaging of delamination in composite laminates. Aiming at the problem of poor anti-noise ability and inaccurate damage identification in traditional detection process,an LDR-based multi-frequency method is proposed. Experimental results show that the proposed method can realize the localization and imaging of delamination damage in composite materials.
基金supported by the National Key Basic Research Program of China (Grant No. 2015CB057400)the National Natural Science Foundation of China (Grant No. 11602070)China Postdoctoral Science Foundation(Grant No. 2016M590277).
文摘The studies on dynamics of a fault bearing system are prevalent in recent years, however, we are studying a completely different frequency range than the one where the bearing faults are best seen. Considering a local defect on outer raceway,a two-degree-of-freedom analytical model of a rigid-rotor ball bearing system is established. Three pulse force models are introduced to simulate the local defect. The frequency domain method—harmonic balance method with alternating frequency/time domain technique (HB-AFT) is used to calculate the response in a large frequency range. By comparing the performance at different frequencies, the fault systems with different defect models and parameters reveal the super-harmonic resonances,and the reasons for this phenomenon are uncovered as well. Finally, the theoretical calculation is verified qualitatively by the experimental results, through comparing the frequency spectrums of the defective bearing rotor system to the fault-free one.Therefore, the super-harmonic resonances can be regarded as a dynamic feature. Besides, the obvious super-harmonic resonances indicate the magnification of the harmonics of the "characteristic defect frequency" for outer race in the corresponding speed regions, which may be helpful for the diagnosis of a rotor ball bearing system with a local defect.
基金financially supported by the National Natural Science Foundation of China(Nos.21203034 and 51771057)the GF Research and Cultivation Project of Sun Yat-sen University(No.76110–18843406)the National Science and Technology Resources Investigation Program of China(No.2019FY101400)
文摘The study aimed to explore the cathodic protection of the defect areas of 75 wt.%zinc-rich coatings(ZRCs)under immersion and atmospheric thin liquid film conditions using a wire beam electrode(WBE).Besides,electrochemical impedance spectroscopy,scanning electron microscopy,and surface morphology analysis were used.Under both experimental conditions,high ZRCs content polarised the entire electrode to the protective potential range,thereby reversing the polarity of the defect area steel substrate to cathodic to prevent corrosion.The higher concentration of dissolved oxygen in the surface liquid film and coating activated the zinc powder faster and provided a higher cathodic protection current for the defect area under the atmospheric liquid film condition.Therefore,WBE corrosion potential shifted more negative under the atmospheric liquid film condition,thereby conveying longer-lasting cathodic protection and reducing the corrosion rate of the defect area steel substrate.Compared with the traditional sheet electrode,WBE can provide the current distribution and change information of cathodic protection at the local defects on the ZRCs surface,thereby providing a reliable test and a method for evaluating heterogeneous corrosion and cathodic protection.
