Rotating machinery in the aviation industry is increasingly embracing high speeds and miniaturization,and foil dynamic pressure gas bearing has great application value due to its self-lubrication and self-adaptive def...Rotating machinery in the aviation industry is increasingly embracing high speeds and miniaturization,and foil dynamic pressure gas bearing has great application value due to its self-lubrication and self-adaptive deformation characteristics.This study explores the interaction mechanism between micro-scale variable-sectional shearing flow with hyper-rotation speeds and a three-layer elastic foil assembly through bidirectional aero-elastic coupling in a Multi-layer Thrust Gas Foil Bearing(MTGFB).The bearing capacity of the MTGFB varies non-linearly with the decrease of gas film clearance,while the collaborative deformation of the three-layer elastic foil assembly can deal with different load conditions.As the load capacity increases,the enhanced dynamic pressure effect causes the top foil to evolve from a single arch to multiple arches.The hydrodynamic effects in the gas film evolve to form multiple segmented wedges with different pitch ratios,while the peak pressure of the gas film always occurs near the vaults of the top foil.As the rotational speed frequency approaches the natural frequency,the resonance of the gas film and elastic foil assembly system occurs,and a phase delay occurs between the pressure pulsation and the vibration of foils.The load capacity of the MTGFB also depends on the elastic moduli of the elastic foil assembly.Increasing the elastic modulus decreases the deformation amplitude of the top foil,whereas it increases those of the backboard and middle foil,increasing the load capacity.展开更多
The high-temperature dissolution behavior of primary carbides in samples taken from GCr15 continuous-casting bloom was observed in-situ by confocal laser scanning microscopy.Equations were fitted to the dissolution ki...The high-temperature dissolution behavior of primary carbides in samples taken from GCr15 continuous-casting bloom was observed in-situ by confocal laser scanning microscopy.Equations were fitted to the dissolution kinetics of primary carbides during either heating or soaking.Dissolution of carbides proceeded in three stages(fast→slow→faster)as either temperature or holding time was increased.During the heating process and during the first and third stages of the soaking process,the original size of the carbides determined the steepness of the slope,but during the middle(“slow”)stage of the soaking process,the slope remained zero.The initial size of the carbides varied greatly,but their final dissolution temperature fell within the narrow range of 1210-1235℃,and the holding time remained within 50 min.Fractal analysis was used to study the morphological characteristics of small and medium-sized carbides during the dissolution process.According to changes in the fractal dimension before and after soaking,the carbides tended to evolve towards a more regular morphology.展开更多
Bearing is an indispensable key component in mechanical equipment,and its working state is directly related to the stability and safety of the whole equipment.In recent years,with the rapid development of artificial i...Bearing is an indispensable key component in mechanical equipment,and its working state is directly related to the stability and safety of the whole equipment.In recent years,with the rapid development of artificial intelligence technology,especially the breakthrough of deep learning technology,it provides a new idea for bearing fault diagnosis.Deep learning can automatically learn features from a large amount of data,has a strong nonlinear modeling ability,and can effectively solve the problems existing in traditional methods.Aiming at the key problems in bearing fault diagnosis,this paper studies the fault diagnosis method based on deep learning,which not only provides a new solution for bearing fault diagnosis but also provides a reference for the application of deep learning in other mechanical fault diagnosis fields.展开更多
Rolling contact fatigue performance is among the most important issues for applications of bearing steels.In this work,a recently developed surface modification technique,surface mechanical rolling treatment,was appli...Rolling contact fatigue performance is among the most important issues for applications of bearing steels.In this work,a recently developed surface modification technique,surface mechanical rolling treatment,was applied on a rare-earth addition bearing steel.And rolling contact fatigue behavior of treated samples was compared with that of as-received counterparts at different contacting stresses.The results demonstrated that a 700μm-thick gradient nanostructured surface layer is produced on samples by surface mechanical rolling treatment.The grain size decreases while the microhardness increases gradually with decreasing depth,reaching~23 nm and~10.2 GPa,respectively,at the top surface.Consequently,the rolling contact fatigue property is significantly enhanced.The characteristic life of treated samples is~3.2 times that of untreated counterparts according to Weibull curves at 5.6 GPa.Analyses of fatigue mechanisms demonstrated that the gradient nanostructured surface layer might not only retard material degradation and microcrack formation,but also prolong the steady-state elastic response stage under rolling contact fatigue.展开更多
In this work,fow behavior and dynamic recrystallization(DRX)mechanism of a low carbon martensitic stainless bearing steel,CSS-42L,were investigated using a thermomechanical simulator under the temperature and strain r...In this work,fow behavior and dynamic recrystallization(DRX)mechanism of a low carbon martensitic stainless bearing steel,CSS-42L,were investigated using a thermomechanical simulator under the temperature and strain rate ranges of 900 to 1100℃ and 0.1 to 20 s^(−1),respectively.The Arrhenius-type constitutive equation was established based on the fow stress curves.Moreover,the peak stress decreased with the increase in deformation temperature and the decrease in strain rate.There were two DRX mechanisms during hot deformation of the current studied steel,the main one being discontinuous dynamic recrystallization mechanism,acting through grain boundary bulging and migration,and the auxiliary one being continuous dynamic recrystallization mechanism,working through the rotation of sub-grains.On the basis of microstructural characterizations,power dissipation maps and fow instability maps,the optimized hot deformation parameters for CSS-42L bearing steel were determined as 1050℃/0.1 s^(−1) and 1100℃/1 s^(−1).展开更多
A bearing fault diagnosis method based on the Markov transitionfield(MTF)and SEnet(SE)-IShufflenetV2 model is proposed in this paper due to the problems of complex working conditions,low fault diagnosis accuracy,and poo...A bearing fault diagnosis method based on the Markov transitionfield(MTF)and SEnet(SE)-IShufflenetV2 model is proposed in this paper due to the problems of complex working conditions,low fault diagnosis accuracy,and poor generalization of rolling bearing.Firstly,MTF is used to encode one-dimensional time series vibration sig-nals and convert them into time-dependent and unique two-dimensional feature images.Then,the generated two-dimensional dataset is fed into the SE-IShufflenetV2 model for training to achieve fault feature extraction and classification.This paper selects the bearing fault datasets from Case Western Reserve University and Paderborn University to experimentally verify the effectiveness and superiority of the proposed method.The generalization performance of the proposed method is tested under the variable load condition and different signal-to-noise ratios(SNRs).The experimental results show that the average accuracy of the proposed method under different working conditions is 99.2%without adding noise.The accuracy under different working conditions from 0 to 1 HP is 100%.When the SNR is 0 dB,the average accuracy of the proposed method can still reach 98.7%under varying working conditions.Therefore,the bearing fault diagnosis method proposed in this paper is characterized by high accuracy,strong anti-noise ability,and generalization.Moreover,the proposed method can also overcome the influence of variable working conditions on diagnosis accuracy,providing method support for the accurate diagnosis of bearing faults under strong noise and variable working conditions.展开更多
To investigate the evolution of load-bearing characteristics of pre-stressed beams throughout their service life and to provide a basis for accurately assessing the actual working state of damaged pre-stressed concret...To investigate the evolution of load-bearing characteristics of pre-stressed beams throughout their service life and to provide a basis for accurately assessing the actual working state of damaged pre-stressed concrete T-beams,destructive tests were conducted on full-scale pre-stressed concrete beams.Based on the measurement and ana-lysis of beam deflection,strain,and crack development under various loading levels during the research tests,combined with the verification coefficient indicators specified in the codes,the verification coefficients of bridges at different stages of damage can be examined.The results indicate that the T-beams experience complete,incom-plete linear,and non-linear stages during the destructive test process.In the complete linear elastic stage,both the deflection and bottom strain verification coefficients comply with the specifications,indicating a good structural load-bearing capacity no longer adheres to the code’s requirements.In the non-linear stage,both coefficients exhi-bit a sharp increase,resulting in a further decrease in the structure’s load-bearing capacity.According to the pro-visions of the current code,the beam can be in the incomplete linear stage when both values fall within the code’s specified range.The strain verification coefficient sourced from the compression zone at the bottom of theflange is not recommended for assessing the bridge’s load-bearing capacity.展开更多
Traditional heat treatment methods require a significant amount of time and energy to affect atomic diffusion and enhance the spheroidization process of carbides in bearing steel,while pulsed current can accelerate at...Traditional heat treatment methods require a significant amount of time and energy to affect atomic diffusion and enhance the spheroidization process of carbides in bearing steel,while pulsed current can accelerate atomic diffusion to achieve ultra-fast spheroidization of carbides.However,the understanding of the mechanism by which different pulse current parameters regulate the dissolution behavior of carbides requires a large amount of experimental data to support,which limits the application of pulse current technology in the field of heat treatment.Based on this,quantify the obtained pulse current processing data to create an important dataset that could be applied to machine learning.Through machine learning,the mechanism of mutual influence between carbide regulation and various factors was elucidated,and the optimal spheroidization process parameters were determined.Compared to the 20 h required for traditional heat treatment,the application of pulsed electric current technology achieved ultra-fast spheroidization of GCr15 bearing steel within 90 min.展开更多
Grease is extensively used in rolling bearings due to its inherent sealing properties.However,mechanical degradation typically occurs,resulting in a significantly shorter lifespan for the grease compared to the bearin...Grease is extensively used in rolling bearings due to its inherent sealing properties.However,mechanical degradation typically occurs,resulting in a significantly shorter lifespan for the grease compared to the bearing.Investigating aging mechanisms is essential.This study utilized rolling bearings to obtain mechanically aged greases.The aged samples were then subjected to do rheological test,FTIR test and friction test to examine the effects of aging time,radial load,and rotational speed.An innovative disk-ball-disk device was developed to study the friction characteristics of aged grease in rolling bearings.Additionally,a grease lubrication and friction model were proposed to further evaluate the lubrication performance of aged grease,using measured rheological parameters and the kinematic velocities of the disk-ball-disk device as inputs.The calculated friction coefficients matched well with disk-ball-disk experimental results.FTIR analysis revealed that the non-soap thickener’s structure remained stable,but additives depleted at high speeds.The structure of lithium soap thickener decomposed severely,leading to oil bleeding and a shortened replenishment duration.Over aging time,both greases had lower friction and viscosity due to gradual thickener breakdown,releasing bled oil and extending replenishment.Radial load minimally affected the properties of aged grease.This study may provide valuable insights into the aging mechanisms of grease and the enhancement of rolling bearing lubrication.展开更多
Full ceramic bearings are mission-critical components in oil-free environments,such as food processing,semiconductor manufacturing,and medical applications.Developing effective fault diagnosis methods for these bearin...Full ceramic bearings are mission-critical components in oil-free environments,such as food processing,semiconductor manufacturing,and medical applications.Developing effective fault diagnosis methods for these bearings is essential to ensuring operational reliability and preventing costly failures.Traditional supervised deep learning approaches have demonstrated promise in fault detection,but their dependence on large labeled datasets poses significant challenges in industrial settings where fault-labeled data is scarce.This paper introduces a few-shot learning approach for full ceramic bearing fault diagnosis by leveraging the pre-trained GPT-2 model.Large language models(LLMs)like GPT-2,pre-trained on diverse textual data,exhibit remarkable transfer learning and few-shot learning capabilities,making them ideal for applications with limited labeled data.In this study,acoustic emission(AE)signals from bearings were processed using empirical mode decomposition(EMD),and the extracted AE features were converted into structured text for fine-tuning GPT-2 as a fault classifier.To enhance its performance,we incorporated a modified loss function and softmax activation with cosine similarity,ensuring better generalization in fault identification.Experimental evaluations on a laboratory-collected full ceramic bearing dataset demonstrated that the proposed approach achieved high diagnostic accuracy with as few as five labeled samples,outperforming conventional methods such as k-nearest neighbor(KNN),large memory storage and retrieval(LAMSTAR)neural network,deep neural network(DNN),recurrent neural network(RNN),long short-term memory(LSTM)network,and model-agnostic meta-learning(MAML).The results highlight LLMs’potential to revolutionize fault diagnosis,enabling faster deployment,reduced reliance on extensive labeled datasets,and improved adaptability in industrial monitoring systems.展开更多
Clay deposits typically exhibit significant degrees of heterogeneity and anisotropy in their strength and stiffness properties.Such non-monotonic responses can significantly impact the stability analysis and design of...Clay deposits typically exhibit significant degrees of heterogeneity and anisotropy in their strength and stiffness properties.Such non-monotonic responses can significantly impact the stability analysis and design of overlying shallow foundations.In this study,the undrained bearing capacity of shallow foundations resting on inhomogeneous and anisotropic clay layers subjected to oblique-eccentric combined loading is investigated through a comprehensive series of finite element limit analysis(FELA)based on the well-established lower-bound theorem and second-order cone programming(SOCP).The heterogeneity of normally consolidated(NC)clays is simulated by adopting a well-known general model of undrained shear strength increasing linearly with depth.In contrast,for overconsolidated(OC)clays,the variation of undrained shear strength with depth is considered to follow a bilinear trend.Furthermore,the inherent anisotropy is accounted for by adopting different values of undrained shear strength along different directions within the soil medium,employing an iterative-based algorithm.The results of numerical simulations are utilized to investigate the influences of natural soil heterogeneity and inherent anisotropy on the ultimate bearing capacity,failure envelope,and failure mechanism of shallow foundations subjected to the various combinations of vertical-horizontal(V-H)and vertical-moment(V-M)loads.展开更多
Laminated elastomeric bearings used in seismic isolation rely on the mechanical properties of their constituent elastomers to ensure effective performance.However,despite their resistance to temperature fluctuations a...Laminated elastomeric bearings used in seismic isolation rely on the mechanical properties of their constituent elastomers to ensure effective performance.However,despite their resistance to temperature fluctuations and environmental aggressors,silicone elastomers exhibit relatively low stiffness,limiting their direct applicability in seismic isolation.This study investigates the effect of fumed silica as a reinforcing filler to enhance the mechanical properties of laminated silicone elastomeric bearings.Elastomeric samples were fabricated with varying fumed silica proportions and subjected to Shore A hardness,uniaxial tensile,and lap shear tests to assess the influence of filler content.Additionally,quasi-static tests were conducted on reduced-scale bearing prototypes under combined vertical compression and cyclic horizontal shear to evaluate their seismic isolation performance.The results demonstrate that fumed silica reinforcement significantly increases stiffness,as evidenced by higher Shore A hardness values.However,a trade-off was observed in tensile properties,with reductions in tensile strength and elongation at break.Despite this,the equivalent elastic modulus did not show substantial variation up to large deformations,indicating that stiffness is preserved under most working conditions.Lap shear tests showed that fumed silica improves shear resistance,while quasi-static tests revealed inelastic behavior with small increases in equivalent shear coefficients but no substantial loss in damping ratios.These findings suggest that fumed silica reinforcement enhances silicone elastomers’stiffness and shear resistance while maintaining moderate damping properties,making it a promising approach for improving the mechanical performance of elastomeric bearings in seismic isolation applications.展开更多
Coal pillars are critical supporting structures between underground coal gasification gasifiers.Its bearing capacity and structural stability are severely threatened by high-temperature environments.To elucidate the h...Coal pillars are critical supporting structures between underground coal gasification gasifiers.Its bearing capacity and structural stability are severely threatened by high-temperature environments.To elucidate the high-temperature deterioration mechanism of coal pillars at multiple scales,coal strength features as a function of temperature were investigated via uniaxial compression and acoustic emission equipment.The pyrolysis reaction process and microstructure evolution were characterized via X-ray diffractometer(XRD),scanning electron microscope(SEM),thermogravimetric(TG),Fourier transform infrared spectroscopy(FTIR),and computed tomography(CT)tests.Experimental results reveal a critical temperature threshold of 500℃for severe degradation of the coal bearing capacity.Specifically,both the strength and elastic modulus exhibit accelerated degradation above this temperature,with maximum reductions of 45.53%and 61.34%,respectively.Above 500℃,coal essentially undergoes a pyrolysis reaction under N_(2)and CO_(2)atmospheres.High temperatures decrease the quantity of O_(2)-based functional groups,growing aromaticity and the degree of graphitization.These changes induce dislocation and slip inside the coal crystal nucleus and then lead to deformation of the coal molecular structural units and strain energy generation.This process results in a great increase in porosity.Consequently,the stress deformation of coal increases,transforming the type of failure from brittle to ductile failure.These findings are expected to provide scientific support for UCG rock strata control.展开更多
Background:Early weight bearing can accelerate the recovery of ankle function,but the timing of weight bearing has not been clarifi ed.In this study,the effi cacy and safety of weight-bearing at 1 week and 4 weeks aft...Background:Early weight bearing can accelerate the recovery of ankle function,but the timing of weight bearing has not been clarifi ed.In this study,the effi cacy and safety of weight-bearing at 1 week and 4 weeks after ankle fracture were further investigated.Methods:Forty-six postoperative ankle fracture patients were enrolled and divided into 1-week group(23)and 4-week group(23)according to randomized numerical table method.All patients underwent routine rehabilitation.On this basis,weight-bearing was started at 1 week after surgery in the 1-week group and at 4 weeks after surgery in the 4-week group.Both groups underwent a 6-week trial intervention.Ankle pain and function were assessed by VAS,AOFAS,and OMAS scales at 2,4,and 6 weeks after treatment.Results:There was no statistically signifi cant diff erence in the general data of patients in the 2 groups before surgery(P>0.05).At 2 weeks postoperatively,the VAS of the 1-week group was higher than that of the 4-week group,and the scores of the Pain item in AOFAS and Swelling item in OMAS were lower than that of the 4-week group.At 4 weeks postoperatively,the VAS was higher in the 1-week group than in the 4-week group.At 6 weeks postoperatively,the VAS was lower in the 1-week group than in the 4-week group,and the scores of the Pain,Maximum walking distance,and Sagittal motion items in the AOFAS,and the scores of the Stiff ness and Swelling items in the OMAS were higher than in the 4-week group.Conclusions:A rehabilitation strategy of early weight-bearing implemented 1 week after surgery in patients with ankle fractures can eff ectively reduce the degree of ankle stiff ness and accelerate the recovery of ankle function in patients.展开更多
Spiral pile foundations,as a promising type of foundation,are of significant importance for the development of offshore wind energy,particularly as it moves toward deeper waters.This study conducted a physical experim...Spiral pile foundations,as a promising type of foundation,are of significant importance for the development of offshore wind energy,particularly as it moves toward deeper waters.This study conducted a physical experiment on a three-spiral-pile jacket foundation under deep-buried sandy soil conditions.During the experiment,horizontal displacement was applied to the structure to thoroughly investigate the bearing characteristics of the three-spiral-pile jacket foundation.This study also focused on analyzing the bearing mechanisms of conventional piles compared with spiral piles with different numbers of blades.Three different working conditions were set up and compared,and key data,such as the horizontal bearing capacity,pile shaft axial force,and spiral blade soil pressure,were measured and analyzed.The results show the distinct impacts of the spiral blades on the compressed and tensioned sides of the foundation.Specifically,on the compressed side,the spiral blades effectively enhance the restraint of the soil on the pile foundation,whereas on the tensioned side,an excessive number of spiral blades can negatively affect the structural tensile performance to some extent.This study also emphasizes that the addition of blades to the side of a single pile is the most effective method for increasing the bearing capacity of the foundation.This research aims to provide design insights into improving the bearing capacity of the foundation.展开更多
The pitch bearing is a component in wind turbine units used to adjust the angle of the fan blades to adapt to the wind direction,so as to maximize the utilization of wind energy.Due to the different working mode of th...The pitch bearing is a component in wind turbine units used to adjust the angle of the fan blades to adapt to the wind direction,so as to maximize the utilization of wind energy.Due to the different working mode of the pitch bearing itself compared with ordinary small bearings and the harsh working environment,the pitch bearing is prone to faults such as cracking and deformation.In severe cases,it will lead to overall damage to the pitch bearing,causing the blade to fall from a high altitude and even injuring personnel.Therefore,this paper conducts a patent analysis and technical decomposition of the deformation monitoring device for pitch bearings,analyzes and summarizes the development process of existing deformation monitoring devices for pitch bearings.Combined with the TRIZ evolution theory and based on the S-curve,it is concluded that the current deformation monitoring device for pitch bearings is in the transitional stage between the infant period and the growth period,and discusses the possible subsequent evolution directions.Through reviewing relevant literature,it is found that inner ring cracks first appear near the upper and lower surfaces of the bolt holes in the inner ring of the pitch bearing.To this end,a new type of deformation monitoring device for pitch bearings is designed.The fiber optic displacement sensor is used for qualitative monitoring of initial cracks near the surface of the bolt holes in the inner ring of the pitch bearing.After cracks are detected,the eddy current sensor is used for quantitative monitoring of whether there are extended cracks between the cracked bolt holes and adjacent bolt holes.Finally,the work done in this paper is summarized and prospected.展开更多
As an important part of offshore wind turbine support and fixed units, the multibucket jacket foundation bears large loads and a complex marine environment. In this paper, the horizontal bearing characteristics of the...As an important part of offshore wind turbine support and fixed units, the multibucket jacket foundation bears large loads and a complex marine environment. In this paper, the horizontal bearing characteristics of the four-bucket jacket foundation of offshore wind power in sandy soil are studied. Through model tests and numerical simulations, the influence of bucket foundation sealing properties, load application speed, and loading direction on foundation-bearing capacity are discussed. The results show that the horizontal ultimate bearing capacity of the foundation in the nonsealing condition is decreased by 51.3% compared with the sealing condition;therefore, after the foundation penetration construction is completed, the bucket sealing must be ensured to increase the load-bearing performance of the structure. At a loading speed of 3.25 mm/s, the horizontal ultimate bearing capacity of the foundation is increased by 9.4% over the working condition of 1.85 mm/s. The bearing capacity of the foundation is maximized in the loading direction α =45° and is the smallest when α =0°. That is, the foundation can maximize its loadbearing performance under the condition of single-bucket compression/tension. During the design process, the main load of the structure should be loaded in the 45° direction. The contrast error of the experiment and numerical simulation does not exceed 10%. The research results have important guiding importance for designing and constructing the jacket foundation and can be used as a reference for the stable operation and sustainable development of offshore wind power systems.展开更多
To enhance the gas-damping effect and improve the bearing performance,a restricted layer is applied on the surface of aerostatic porous bearings.Based on the gas lubrication theory,a mathematical model of an aerostati...To enhance the gas-damping effect and improve the bearing performance,a restricted layer is applied on the surface of aerostatic porous bearings.Based on the gas lubrication theory,a mathematical model of an aerostatic porous bearing with a restricted layer is established,and two proportional coefficients,a permeability ratio δ and a thickness ratioγ,are proposed.Critical values of δ and γ are determined through sensitivity analyses of complex restriction-layer parameters.The static characteristics of aerostatic porous bearings with a restricted layer or an unrestricted layer are comparatively analyzed by using Fluent simulation.The results show that when δ≈0.005 and γ≈0.010,the load capacity and static stiffness of the restricted-layer aerostatic porous bearing are high;compared with the unrestricted-layer aerostatic porous bearing,the restricted-layer aerostatic porous bearing has a lower sensitivity to changes in the air supply area.The existence of the restricted layer not only enhances the throttling effect and reduces the mass flow rate,but also effectively improves the static stiffness of the bearing.展开更多
Rolling bearings are important parts of industrial equipment,and their fault diagnosis is crucial to maintaining these equipment’s regular operations.With the goal of improving the fault diagnosis accuracy of rolling...Rolling bearings are important parts of industrial equipment,and their fault diagnosis is crucial to maintaining these equipment’s regular operations.With the goal of improving the fault diagnosis accuracy of rolling bearings under complex working conditions and noise,this study proposes a multiscale information fusion method for fault diagnosis of rolling bearings based on fast Fourier transform(FFT)and variational mode decomposition(VMD),as well as the Senet(SE)-TCNnet(TCN)model.FFT is used to transform the original one-dimensional time domain vibration signal into a frequency domain signal,while VMD is used to decompose the original signal into several inherent mode functions(IMFs)of different scales.The center frequency method also determines the number of mode decompositions.Then,the data obtained by the two methods are fused into data containing the bearing fault information of different scales.Finally,the fused data are sent to the SE-TCN model for training.Experimental tests are conducted to verify the performance of this method.The findings reveal that an average accuracy of 98.39%can be achieved when noise is added and can even reach 100%when the signal-to-noise ratio is 6 dB.When the load changes,the accuracy of the model can reach 97.45%.The proposed method has the characteristics of high accuracy and strong generalization ability in bearing fault diagnosis.Furthermore,it can effectively overcome the effects of noise and variable working conditions in actual industrial environments,thus providing some ideas for future practical applications of bearing fault diagnosis.展开更多
Difficulty in extracting nonlinear sparse impulse features due to variable speed conditions and redundant noise interference leads to challenges in diagnosing variable speed faults.Therefore,an improved spectral amplit...Difficulty in extracting nonlinear sparse impulse features due to variable speed conditions and redundant noise interference leads to challenges in diagnosing variable speed faults.Therefore,an improved spectral amplitude modulation(ISAM)based on sparse feature adaptive convolution(SFAC)is proposed to enhance the fault features under variable speed conditions.First,an optimal bi-damped wavelet construction method is proposed to learn signal impulse features,which selects the optimal bi-damped wavelet parameters with correlation criterion and particle swarm optimization.Second,a convolutional basis pursuit denoising model based on an optimal bi-damped wavelet is proposed for resolving sparse impulses.A model regularization parameter selection method based on weighted fault characteristic amplitude ratio assistance is proposed.Then,an ISAM method based on kurtosis threshold is proposed to further enhance the fault information of sparse signal.Finally,the type of variable speed faults is determined by order spectrum analysis.Various experimental results,such as spectral amplitude modulation and Morlet wavelet matching,verify the effectiveness and advantages of the ISAM-SFAC method.展开更多
基金the financial support from the National Natural Science Foundation of China(No.52206091)the Aeronautical Science Foundation of China(No.201928052008)the Natural Science Foundation of Jiangsu Province,China(No.BK20210303)。
文摘Rotating machinery in the aviation industry is increasingly embracing high speeds and miniaturization,and foil dynamic pressure gas bearing has great application value due to its self-lubrication and self-adaptive deformation characteristics.This study explores the interaction mechanism between micro-scale variable-sectional shearing flow with hyper-rotation speeds and a three-layer elastic foil assembly through bidirectional aero-elastic coupling in a Multi-layer Thrust Gas Foil Bearing(MTGFB).The bearing capacity of the MTGFB varies non-linearly with the decrease of gas film clearance,while the collaborative deformation of the three-layer elastic foil assembly can deal with different load conditions.As the load capacity increases,the enhanced dynamic pressure effect causes the top foil to evolve from a single arch to multiple arches.The hydrodynamic effects in the gas film evolve to form multiple segmented wedges with different pitch ratios,while the peak pressure of the gas film always occurs near the vaults of the top foil.As the rotational speed frequency approaches the natural frequency,the resonance of the gas film and elastic foil assembly system occurs,and a phase delay occurs between the pressure pulsation and the vibration of foils.The load capacity of the MTGFB also depends on the elastic moduli of the elastic foil assembly.Increasing the elastic modulus decreases the deformation amplitude of the top foil,whereas it increases those of the backboard and middle foil,increasing the load capacity.
基金supported by Independent Research Project of State Key Laboratory of Advanced Special Steel,Shanghai Key Laboratory of Advanced Ferrometallurgy,Shanghai University(SKLASS-2023-Z13)the Science and Technology Commission of Shanghai Municipality(No.19DZ2270200)+1 种基金A portion of the work was performed at US National High Magnetic Field Laboratory,which is supported by the National Science Foundation(Cooperative Agreement No.DMR-1157490 and DMR-1644779)the State of Florida.Thanks also to Mary Tyler for editing.
文摘The high-temperature dissolution behavior of primary carbides in samples taken from GCr15 continuous-casting bloom was observed in-situ by confocal laser scanning microscopy.Equations were fitted to the dissolution kinetics of primary carbides during either heating or soaking.Dissolution of carbides proceeded in three stages(fast→slow→faster)as either temperature or holding time was increased.During the heating process and during the first and third stages of the soaking process,the original size of the carbides determined the steepness of the slope,but during the middle(“slow”)stage of the soaking process,the slope remained zero.The initial size of the carbides varied greatly,but their final dissolution temperature fell within the narrow range of 1210-1235℃,and the holding time remained within 50 min.Fractal analysis was used to study the morphological characteristics of small and medium-sized carbides during the dissolution process.According to changes in the fractal dimension before and after soaking,the carbides tended to evolve towards a more regular morphology.
文摘Bearing is an indispensable key component in mechanical equipment,and its working state is directly related to the stability and safety of the whole equipment.In recent years,with the rapid development of artificial intelligence technology,especially the breakthrough of deep learning technology,it provides a new idea for bearing fault diagnosis.Deep learning can automatically learn features from a large amount of data,has a strong nonlinear modeling ability,and can effectively solve the problems existing in traditional methods.Aiming at the key problems in bearing fault diagnosis,this paper studies the fault diagnosis method based on deep learning,which not only provides a new solution for bearing fault diagnosis but also provides a reference for the application of deep learning in other mechanical fault diagnosis fields.
基金The financial supports by the Chinese Academy of Sciences(Nos.XDC04030300 and XDB0510303)CAS-HK Joint Laboratory of Nanomaterials and MechanicsShenyang National Laboratory for Materials Science are acknowledged.
文摘Rolling contact fatigue performance is among the most important issues for applications of bearing steels.In this work,a recently developed surface modification technique,surface mechanical rolling treatment,was applied on a rare-earth addition bearing steel.And rolling contact fatigue behavior of treated samples was compared with that of as-received counterparts at different contacting stresses.The results demonstrated that a 700μm-thick gradient nanostructured surface layer is produced on samples by surface mechanical rolling treatment.The grain size decreases while the microhardness increases gradually with decreasing depth,reaching~23 nm and~10.2 GPa,respectively,at the top surface.Consequently,the rolling contact fatigue property is significantly enhanced.The characteristic life of treated samples is~3.2 times that of untreated counterparts according to Weibull curves at 5.6 GPa.Analyses of fatigue mechanisms demonstrated that the gradient nanostructured surface layer might not only retard material degradation and microcrack formation,but also prolong the steady-state elastic response stage under rolling contact fatigue.
基金fnancially supported by the Scientifc Research Project of the Department of Education in Hunan Prov ince,China(Grant No.23B0533).
文摘In this work,fow behavior and dynamic recrystallization(DRX)mechanism of a low carbon martensitic stainless bearing steel,CSS-42L,were investigated using a thermomechanical simulator under the temperature and strain rate ranges of 900 to 1100℃ and 0.1 to 20 s^(−1),respectively.The Arrhenius-type constitutive equation was established based on the fow stress curves.Moreover,the peak stress decreased with the increase in deformation temperature and the decrease in strain rate.There were two DRX mechanisms during hot deformation of the current studied steel,the main one being discontinuous dynamic recrystallization mechanism,acting through grain boundary bulging and migration,and the auxiliary one being continuous dynamic recrystallization mechanism,working through the rotation of sub-grains.On the basis of microstructural characterizations,power dissipation maps and fow instability maps,the optimized hot deformation parameters for CSS-42L bearing steel were determined as 1050℃/0.1 s^(−1) and 1100℃/1 s^(−1).
基金supported by Hebei Natural Science Foundation under Grant No.E2024402079Key Laboratory of Intelligent Industrial Equipment Technology of Hebei Province(Hebei University of Engineering)under Grant No.202206.
文摘A bearing fault diagnosis method based on the Markov transitionfield(MTF)and SEnet(SE)-IShufflenetV2 model is proposed in this paper due to the problems of complex working conditions,low fault diagnosis accuracy,and poor generalization of rolling bearing.Firstly,MTF is used to encode one-dimensional time series vibration sig-nals and convert them into time-dependent and unique two-dimensional feature images.Then,the generated two-dimensional dataset is fed into the SE-IShufflenetV2 model for training to achieve fault feature extraction and classification.This paper selects the bearing fault datasets from Case Western Reserve University and Paderborn University to experimentally verify the effectiveness and superiority of the proposed method.The generalization performance of the proposed method is tested under the variable load condition and different signal-to-noise ratios(SNRs).The experimental results show that the average accuracy of the proposed method under different working conditions is 99.2%without adding noise.The accuracy under different working conditions from 0 to 1 HP is 100%.When the SNR is 0 dB,the average accuracy of the proposed method can still reach 98.7%under varying working conditions.Therefore,the bearing fault diagnosis method proposed in this paper is characterized by high accuracy,strong anti-noise ability,and generalization.Moreover,the proposed method can also overcome the influence of variable working conditions on diagnosis accuracy,providing method support for the accurate diagnosis of bearing faults under strong noise and variable working conditions.
文摘To investigate the evolution of load-bearing characteristics of pre-stressed beams throughout their service life and to provide a basis for accurately assessing the actual working state of damaged pre-stressed concrete T-beams,destructive tests were conducted on full-scale pre-stressed concrete beams.Based on the measurement and ana-lysis of beam deflection,strain,and crack development under various loading levels during the research tests,combined with the verification coefficient indicators specified in the codes,the verification coefficients of bridges at different stages of damage can be examined.The results indicate that the T-beams experience complete,incom-plete linear,and non-linear stages during the destructive test process.In the complete linear elastic stage,both the deflection and bottom strain verification coefficients comply with the specifications,indicating a good structural load-bearing capacity no longer adheres to the code’s requirements.In the non-linear stage,both coefficients exhi-bit a sharp increase,resulting in a further decrease in the structure’s load-bearing capacity.According to the pro-visions of the current code,the beam can be in the incomplete linear stage when both values fall within the code’s specified range.The strain verification coefficient sourced from the compression zone at the bottom of theflange is not recommended for assessing the bridge’s load-bearing capacity.
基金supported by the National Key R&D Program of China(2020YFA0714900,2023YFB3709903)the National Natural Science Foundation of China(U21B2082,52474410)+6 种基金the Key R&D Program of Shandong Province,China(2023CXGC010406)the Scientific Research Special Project for First-Class Disciplines in Inner Mongolia Autonomous Region(YLXKZX-NKD-001)the International Science and Technology Cooperation Project of Higher Education Institutions in Inner Mongolia Autonomous Region(GHXM-002)the Natural Science Foundation of Inner Mongolia Autonomous Region of China(2024ZD06)the Technology Support Project for the Construction of Major Innovation Platforms in Inner Mongolia Autonomous Region(XM2024XTGXQ16)the Beijing Municipal Natural Science Foundation(2222065)the Fundamental Research Funds for the Central Universities(FRF-TP-22-02C2).
文摘Traditional heat treatment methods require a significant amount of time and energy to affect atomic diffusion and enhance the spheroidization process of carbides in bearing steel,while pulsed current can accelerate atomic diffusion to achieve ultra-fast spheroidization of carbides.However,the understanding of the mechanism by which different pulse current parameters regulate the dissolution behavior of carbides requires a large amount of experimental data to support,which limits the application of pulse current technology in the field of heat treatment.Based on this,quantify the obtained pulse current processing data to create an important dataset that could be applied to machine learning.Through machine learning,the mechanism of mutual influence between carbide regulation and various factors was elucidated,and the optimal spheroidization process parameters were determined.Compared to the 20 h required for traditional heat treatment,the application of pulsed electric current technology achieved ultra-fast spheroidization of GCr15 bearing steel within 90 min.
基金Supported by National Natural Science Foundation of China(Grant No.52275206).
文摘Grease is extensively used in rolling bearings due to its inherent sealing properties.However,mechanical degradation typically occurs,resulting in a significantly shorter lifespan for the grease compared to the bearing.Investigating aging mechanisms is essential.This study utilized rolling bearings to obtain mechanically aged greases.The aged samples were then subjected to do rheological test,FTIR test and friction test to examine the effects of aging time,radial load,and rotational speed.An innovative disk-ball-disk device was developed to study the friction characteristics of aged grease in rolling bearings.Additionally,a grease lubrication and friction model were proposed to further evaluate the lubrication performance of aged grease,using measured rheological parameters and the kinematic velocities of the disk-ball-disk device as inputs.The calculated friction coefficients matched well with disk-ball-disk experimental results.FTIR analysis revealed that the non-soap thickener’s structure remained stable,but additives depleted at high speeds.The structure of lithium soap thickener decomposed severely,leading to oil bleeding and a shortened replenishment duration.Over aging time,both greases had lower friction and viscosity due to gradual thickener breakdown,releasing bled oil and extending replenishment.Radial load minimally affected the properties of aged grease.This study may provide valuable insights into the aging mechanisms of grease and the enhancement of rolling bearing lubrication.
文摘Full ceramic bearings are mission-critical components in oil-free environments,such as food processing,semiconductor manufacturing,and medical applications.Developing effective fault diagnosis methods for these bearings is essential to ensuring operational reliability and preventing costly failures.Traditional supervised deep learning approaches have demonstrated promise in fault detection,but their dependence on large labeled datasets poses significant challenges in industrial settings where fault-labeled data is scarce.This paper introduces a few-shot learning approach for full ceramic bearing fault diagnosis by leveraging the pre-trained GPT-2 model.Large language models(LLMs)like GPT-2,pre-trained on diverse textual data,exhibit remarkable transfer learning and few-shot learning capabilities,making them ideal for applications with limited labeled data.In this study,acoustic emission(AE)signals from bearings were processed using empirical mode decomposition(EMD),and the extracted AE features were converted into structured text for fine-tuning GPT-2 as a fault classifier.To enhance its performance,we incorporated a modified loss function and softmax activation with cosine similarity,ensuring better generalization in fault identification.Experimental evaluations on a laboratory-collected full ceramic bearing dataset demonstrated that the proposed approach achieved high diagnostic accuracy with as few as five labeled samples,outperforming conventional methods such as k-nearest neighbor(KNN),large memory storage and retrieval(LAMSTAR)neural network,deep neural network(DNN),recurrent neural network(RNN),long short-term memory(LSTM)network,and model-agnostic meta-learning(MAML).The results highlight LLMs’potential to revolutionize fault diagnosis,enabling faster deployment,reduced reliance on extensive labeled datasets,and improved adaptability in industrial monitoring systems.
文摘Clay deposits typically exhibit significant degrees of heterogeneity and anisotropy in their strength and stiffness properties.Such non-monotonic responses can significantly impact the stability analysis and design of overlying shallow foundations.In this study,the undrained bearing capacity of shallow foundations resting on inhomogeneous and anisotropic clay layers subjected to oblique-eccentric combined loading is investigated through a comprehensive series of finite element limit analysis(FELA)based on the well-established lower-bound theorem and second-order cone programming(SOCP).The heterogeneity of normally consolidated(NC)clays is simulated by adopting a well-known general model of undrained shear strength increasing linearly with depth.In contrast,for overconsolidated(OC)clays,the variation of undrained shear strength with depth is considered to follow a bilinear trend.Furthermore,the inherent anisotropy is accounted for by adopting different values of undrained shear strength along different directions within the soil medium,employing an iterative-based algorithm.The results of numerical simulations are utilized to investigate the influences of natural soil heterogeneity and inherent anisotropy on the ultimate bearing capacity,failure envelope,and failure mechanism of shallow foundations subjected to the various combinations of vertical-horizontal(V-H)and vertical-moment(V-M)loads.
文摘Laminated elastomeric bearings used in seismic isolation rely on the mechanical properties of their constituent elastomers to ensure effective performance.However,despite their resistance to temperature fluctuations and environmental aggressors,silicone elastomers exhibit relatively low stiffness,limiting their direct applicability in seismic isolation.This study investigates the effect of fumed silica as a reinforcing filler to enhance the mechanical properties of laminated silicone elastomeric bearings.Elastomeric samples were fabricated with varying fumed silica proportions and subjected to Shore A hardness,uniaxial tensile,and lap shear tests to assess the influence of filler content.Additionally,quasi-static tests were conducted on reduced-scale bearing prototypes under combined vertical compression and cyclic horizontal shear to evaluate their seismic isolation performance.The results demonstrate that fumed silica reinforcement significantly increases stiffness,as evidenced by higher Shore A hardness values.However,a trade-off was observed in tensile properties,with reductions in tensile strength and elongation at break.Despite this,the equivalent elastic modulus did not show substantial variation up to large deformations,indicating that stiffness is preserved under most working conditions.Lap shear tests showed that fumed silica improves shear resistance,while quasi-static tests revealed inelastic behavior with small increases in equivalent shear coefficients but no substantial loss in damping ratios.These findings suggest that fumed silica reinforcement enhances silicone elastomers’stiffness and shear resistance while maintaining moderate damping properties,making it a promising approach for improving the mechanical performance of elastomeric bearings in seismic isolation applications.
基金supported by Young Scholar Program(Category A Continuation Funding)of National Natural Science Foundation of China(No.52525401)General Program of National Natural Science Foundation of China(No.52174125)+4 种基金Outstanding Youth Cultivation Project in Shanxi Province(No.202103021222008)Major Program of National Natural Science Foundation of China(No.52334005)New Cornerstone Science Foundation through the XPLORER PRIZEShanxi-Zheda Institute of Advanced Materials and Chemical Engineering(No.2022SX-TD010)Shanxi Science and Technology Major Project(No.20201102004).
文摘Coal pillars are critical supporting structures between underground coal gasification gasifiers.Its bearing capacity and structural stability are severely threatened by high-temperature environments.To elucidate the high-temperature deterioration mechanism of coal pillars at multiple scales,coal strength features as a function of temperature were investigated via uniaxial compression and acoustic emission equipment.The pyrolysis reaction process and microstructure evolution were characterized via X-ray diffractometer(XRD),scanning electron microscope(SEM),thermogravimetric(TG),Fourier transform infrared spectroscopy(FTIR),and computed tomography(CT)tests.Experimental results reveal a critical temperature threshold of 500℃for severe degradation of the coal bearing capacity.Specifically,both the strength and elastic modulus exhibit accelerated degradation above this temperature,with maximum reductions of 45.53%and 61.34%,respectively.Above 500℃,coal essentially undergoes a pyrolysis reaction under N_(2)and CO_(2)atmospheres.High temperatures decrease the quantity of O_(2)-based functional groups,growing aromaticity and the degree of graphitization.These changes induce dislocation and slip inside the coal crystal nucleus and then lead to deformation of the coal molecular structural units and strain energy generation.This process results in a great increase in porosity.Consequently,the stress deformation of coal increases,transforming the type of failure from brittle to ductile failure.These findings are expected to provide scientific support for UCG rock strata control.
文摘Background:Early weight bearing can accelerate the recovery of ankle function,but the timing of weight bearing has not been clarifi ed.In this study,the effi cacy and safety of weight-bearing at 1 week and 4 weeks after ankle fracture were further investigated.Methods:Forty-six postoperative ankle fracture patients were enrolled and divided into 1-week group(23)and 4-week group(23)according to randomized numerical table method.All patients underwent routine rehabilitation.On this basis,weight-bearing was started at 1 week after surgery in the 1-week group and at 4 weeks after surgery in the 4-week group.Both groups underwent a 6-week trial intervention.Ankle pain and function were assessed by VAS,AOFAS,and OMAS scales at 2,4,and 6 weeks after treatment.Results:There was no statistically signifi cant diff erence in the general data of patients in the 2 groups before surgery(P>0.05).At 2 weeks postoperatively,the VAS of the 1-week group was higher than that of the 4-week group,and the scores of the Pain item in AOFAS and Swelling item in OMAS were lower than that of the 4-week group.At 4 weeks postoperatively,the VAS was higher in the 1-week group than in the 4-week group.At 6 weeks postoperatively,the VAS was lower in the 1-week group than in the 4-week group,and the scores of the Pain,Maximum walking distance,and Sagittal motion items in the AOFAS,and the scores of the Stiff ness and Swelling items in the OMAS were higher than in the 4-week group.Conclusions:A rehabilitation strategy of early weight-bearing implemented 1 week after surgery in patients with ankle fractures can eff ectively reduce the degree of ankle stiff ness and accelerate the recovery of ankle function in patients.
基金The National Natural Science Foundation of China(No.52171274).
文摘Spiral pile foundations,as a promising type of foundation,are of significant importance for the development of offshore wind energy,particularly as it moves toward deeper waters.This study conducted a physical experiment on a three-spiral-pile jacket foundation under deep-buried sandy soil conditions.During the experiment,horizontal displacement was applied to the structure to thoroughly investigate the bearing characteristics of the three-spiral-pile jacket foundation.This study also focused on analyzing the bearing mechanisms of conventional piles compared with spiral piles with different numbers of blades.Three different working conditions were set up and compared,and key data,such as the horizontal bearing capacity,pile shaft axial force,and spiral blade soil pressure,were measured and analyzed.The results show the distinct impacts of the spiral blades on the compressed and tensioned sides of the foundation.Specifically,on the compressed side,the spiral blades effectively enhance the restraint of the soil on the pile foundation,whereas on the tensioned side,an excessive number of spiral blades can negatively affect the structural tensile performance to some extent.This study also emphasizes that the addition of blades to the side of a single pile is the most effective method for increasing the bearing capacity of the foundation.This research aims to provide design insights into improving the bearing capacity of the foundation.
文摘The pitch bearing is a component in wind turbine units used to adjust the angle of the fan blades to adapt to the wind direction,so as to maximize the utilization of wind energy.Due to the different working mode of the pitch bearing itself compared with ordinary small bearings and the harsh working environment,the pitch bearing is prone to faults such as cracking and deformation.In severe cases,it will lead to overall damage to the pitch bearing,causing the blade to fall from a high altitude and even injuring personnel.Therefore,this paper conducts a patent analysis and technical decomposition of the deformation monitoring device for pitch bearings,analyzes and summarizes the development process of existing deformation monitoring devices for pitch bearings.Combined with the TRIZ evolution theory and based on the S-curve,it is concluded that the current deformation monitoring device for pitch bearings is in the transitional stage between the infant period and the growth period,and discusses the possible subsequent evolution directions.Through reviewing relevant literature,it is found that inner ring cracks first appear near the upper and lower surfaces of the bolt holes in the inner ring of the pitch bearing.To this end,a new type of deformation monitoring device for pitch bearings is designed.The fiber optic displacement sensor is used for qualitative monitoring of initial cracks near the surface of the bolt holes in the inner ring of the pitch bearing.After cracks are detected,the eddy current sensor is used for quantitative monitoring of whether there are extended cracks between the cracked bolt holes and adjacent bolt holes.Finally,the work done in this paper is summarized and prospected.
文摘As an important part of offshore wind turbine support and fixed units, the multibucket jacket foundation bears large loads and a complex marine environment. In this paper, the horizontal bearing characteristics of the four-bucket jacket foundation of offshore wind power in sandy soil are studied. Through model tests and numerical simulations, the influence of bucket foundation sealing properties, load application speed, and loading direction on foundation-bearing capacity are discussed. The results show that the horizontal ultimate bearing capacity of the foundation in the nonsealing condition is decreased by 51.3% compared with the sealing condition;therefore, after the foundation penetration construction is completed, the bucket sealing must be ensured to increase the load-bearing performance of the structure. At a loading speed of 3.25 mm/s, the horizontal ultimate bearing capacity of the foundation is increased by 9.4% over the working condition of 1.85 mm/s. The bearing capacity of the foundation is maximized in the loading direction α =45° and is the smallest when α =0°. That is, the foundation can maximize its loadbearing performance under the condition of single-bucket compression/tension. During the design process, the main load of the structure should be loaded in the 45° direction. The contrast error of the experiment and numerical simulation does not exceed 10%. The research results have important guiding importance for designing and constructing the jacket foundation and can be used as a reference for the stable operation and sustainable development of offshore wind power systems.
文摘To enhance the gas-damping effect and improve the bearing performance,a restricted layer is applied on the surface of aerostatic porous bearings.Based on the gas lubrication theory,a mathematical model of an aerostatic porous bearing with a restricted layer is established,and two proportional coefficients,a permeability ratio δ and a thickness ratioγ,are proposed.Critical values of δ and γ are determined through sensitivity analyses of complex restriction-layer parameters.The static characteristics of aerostatic porous bearings with a restricted layer or an unrestricted layer are comparatively analyzed by using Fluent simulation.The results show that when δ≈0.005 and γ≈0.010,the load capacity and static stiffness of the restricted-layer aerostatic porous bearing are high;compared with the unrestricted-layer aerostatic porous bearing,the restricted-layer aerostatic porous bearing has a lower sensitivity to changes in the air supply area.The existence of the restricted layer not only enhances the throttling effect and reduces the mass flow rate,but also effectively improves the static stiffness of the bearing.
基金supported by Handan Science and Technology Research and Development Plan Project under Grant no.23422901031Key Laboratory of Intelligent Industrial Equipment Technology of Hebei Province(Hebei University of Engineering)under Grant no.202206.
文摘Rolling bearings are important parts of industrial equipment,and their fault diagnosis is crucial to maintaining these equipment’s regular operations.With the goal of improving the fault diagnosis accuracy of rolling bearings under complex working conditions and noise,this study proposes a multiscale information fusion method for fault diagnosis of rolling bearings based on fast Fourier transform(FFT)and variational mode decomposition(VMD),as well as the Senet(SE)-TCNnet(TCN)model.FFT is used to transform the original one-dimensional time domain vibration signal into a frequency domain signal,while VMD is used to decompose the original signal into several inherent mode functions(IMFs)of different scales.The center frequency method also determines the number of mode decompositions.Then,the data obtained by the two methods are fused into data containing the bearing fault information of different scales.Finally,the fused data are sent to the SE-TCN model for training.Experimental tests are conducted to verify the performance of this method.The findings reveal that an average accuracy of 98.39%can be achieved when noise is added and can even reach 100%when the signal-to-noise ratio is 6 dB.When the load changes,the accuracy of the model can reach 97.45%.The proposed method has the characteristics of high accuracy and strong generalization ability in bearing fault diagnosis.Furthermore,it can effectively overcome the effects of noise and variable working conditions in actual industrial environments,thus providing some ideas for future practical applications of bearing fault diagnosis.
基金funded by the National Natural Science Foundation of China(grant nos.52475084 and 52375076)the Postdoctoral Fellowship Program of CPSF(grant no.GZC20230202).
文摘Difficulty in extracting nonlinear sparse impulse features due to variable speed conditions and redundant noise interference leads to challenges in diagnosing variable speed faults.Therefore,an improved spectral amplitude modulation(ISAM)based on sparse feature adaptive convolution(SFAC)is proposed to enhance the fault features under variable speed conditions.First,an optimal bi-damped wavelet construction method is proposed to learn signal impulse features,which selects the optimal bi-damped wavelet parameters with correlation criterion and particle swarm optimization.Second,a convolutional basis pursuit denoising model based on an optimal bi-damped wavelet is proposed for resolving sparse impulses.A model regularization parameter selection method based on weighted fault characteristic amplitude ratio assistance is proposed.Then,an ISAM method based on kurtosis threshold is proposed to further enhance the fault information of sparse signal.Finally,the type of variable speed faults is determined by order spectrum analysis.Various experimental results,such as spectral amplitude modulation and Morlet wavelet matching,verify the effectiveness and advantages of the ISAM-SFAC method.
