With the rapid development of the aviation industry,the development of intelligent manufacturing equipment represented by composite robots has been paid close attention by the aviation industry.Based on the analysis o...With the rapid development of the aviation industry,the development of intelligent manufacturing equipment represented by composite robots has been paid close attention by the aviation industry.Based on the analysis of the background and main structure function of composite robots,this paper focuses on the analysis of key technologies such as composite robot hardware design,visual sensing and planning system,integrated control of‘hands,feet,and eyes',multi-robot collaborative operation,and safety.The typical applications of composite robots in aviation intelligent manufacturing such as automatic drilling and connection of aircraft,aircraft surface spraying and finishing,parts handling,aircraft measurement,and inspection are presented.The development trends such as standardization of composite robots,integration of‘5G+cloud computing+AI',and fusion of intelligent sensors are proposed.展开更多
Short and ultrashort pulse lasers offer excellent advantages in laser precision machining mainly because of their high pulse energy and low ablation threshold. The complex process of laser interaction with metals limi...Short and ultrashort pulse lasers offer excellent advantages in laser precision machining mainly because of their high pulse energy and low ablation threshold. The complex process of laser interaction with metals limits the indepth investigation into laser ablation. Numerical simulation is important in the study of fundamental mechanisms. This review explores the start-of-the-art methods for the theoretical simulation of the laser ablation of metals, including plasma formation and expansion. Laser-induced period surface structures are also studied.展开更多
The effect of microstructure and passive film on the corrosion resistance of 2507 super duplex stainless steel(SDSS)in simulated marine environment was investigated by electrochemical measurements,periodic wet–dry cy...The effect of microstructure and passive film on the corrosion resistance of 2507 super duplex stainless steel(SDSS)in simulated marine environment was investigated by electrochemical measurements,periodic wet–dry cyclic corrosion test,scanning Kelvin probe force microscopy,atomic force microscopy,and X-ray photoelectron spectrometry.The results show that the occupation ratio ofγphase increases with the decrease in cooling rate,whereas the content ofαphase reduces gradually.In addition,theσprecipitated phase only emerges in the annealed steel.The pitting sensitivity and corrosion rate of 2507 SDSS reduce first and then increase as the cooling rate decreases.Theσprecipitated phase drastically reduces the protective ability of the passive film and facilitates micro-galvanic corrosion of the annealed steel.For various microstructures,the pits are preferentially distributed within theσandγphases.The corrosion resistance of 2507 SDSS prepared by different cooling methods is closely related to the microstructure and structure(stability and homogeneity)of the passive film.Normalized steel shows an optimal corrosion resistance,followed by the quenched and annealed steels.展开更多
Aerodynamic noise is the dominant noise source of the high-speed train.It not only seriously affects the passenger comfort and people’s normal life along the railway line,but also may cause fatigue damage to the surr...Aerodynamic noise is the dominant noise source of the high-speed train.It not only seriously affects the passenger comfort and people’s normal life along the railway line,but also may cause fatigue damage to the surrounding equipment and buildings.This manuscript carried out the simulation and experimental study on the external aerodynamic noise of high-speed train,in order to increase the understanding of the noise and hence to be better able to control it.The on-line tests were performed to verify that it is reasonable to simplify the high-speed train model.The turbulent air flow model was then developed,and the external steady flow field was computed by Realizable k-εturbulence model.Based on the steady flow field,aerodynamic noise sources on the train surface and the external transient flow field were calculated by broadband acoustics source model and large eddy simulation(LES)respectively.The pressures on the train surface were obtained from the results of the transient model.Considering the transient flow field,the far-field aerodynamic noise generated by the high-speed train was finally obtained based on Lighthill-Curle theory.Through the comparison between simulations and on-line tests,it is shown that the numerical model gives reliable aerodynamic noise predictions.This research is significant to the study and control of the aerodynamic noise of high-speed train.展开更多
Micro milling is a machining method of high precision and efficiency for micro components and features.In order to study the surface quality of single crystal materials in micro milling,the two-edged cemented carbide ...Micro milling is a machining method of high precision and efficiency for micro components and features.In order to study the surface quality of single crystal materials in micro milling,the two-edged cemented carbide tool milling cutter with 0.4 mm diameter was used,and the orthogonal experiment was completed on the micro-milling of single crystal aluminum material.Through the analysis of statistical results,the primary and secondary factor which impacting on surface quality were found as follows:spindle speed,feed rate,milling depth.The ideal combination of optimized process parameters were obtained,when the spindle speed was 36000 r/min,the milling depth was 10μm,the feed rate was 80μm/s,which made the milling surface roughness is 0.782μm and minimal.Single crystal materials removal mechanism were revealed,and the influence of cutting parameters on micro-milling surface were discussed,the reason of tool wear was analyzed.Those provide a certain theoretical and experimental basis for micro milling of single crystal materials.展开更多
To achieve better anti-vibration performance in a low frequency region and expand the range of vibration isolation,a bilateral supported bio-inspired anti-vibration(BBAV)structure composed of purely linear elements is...To achieve better anti-vibration performance in a low frequency region and expand the range of vibration isolation,a bilateral supported bio-inspired anti-vibration(BBAV)structure composed of purely linear elements is proposed,inspired by the motion form of bird legs and the nonlinear extension and compression of muscles and tendons.The kinematic relations and nonlinear dynamic model considering vertical and rotational vibrations are established.The loading capacity and equivalent stiffness are investigated with key parameters.The amplitude-frequency characteristics and force transmissibility are used to evaluate the stability and anti-vibration performance with the effects of the excitation amplitude,rod length,installation angle,and spring stiffness.The results show that the loading requirements and resonant characteristics of the BBAV structure are adjustable,and superior vibration isolation performance can be achieved readily by tuning the parameters.The X-shaped vibration structure is sensitive to the spring stiffness,which exhibits a wider vibration isolation bandwidth with smaller spring stiffness.Besides,depending on the parameters,the nonlinear behavior of the BBAV system can be interconverted between the softening type and the hardening type.The theoretical analysis in this study demonstrates the advantages and effectiveness of the vibration isolation structure.展开更多
This study presents a novel enhanced monostable lever-type electromagnetic energy harvester(L-EEH).According to the positions of the coil and the lever pivot,four configurations are discussed to realize a better harve...This study presents a novel enhanced monostable lever-type electromagnetic energy harvester(L-EEH).According to the positions of the coil and the lever pivot,four configurations are discussed to realize a better harvesting performance of the L-EEHs.On the basis of establishing the theoretical model of the L-EEH,the corresponding analytical solutions can be obtained by applying the harmonic balance method.The effects of the nonlinear coefficient,the lever ratio,the mass ratio,and the circuit parameters on the energy harvesting performance of L-EEHs are analyzed and discussed.The numerical and experimental efforts are carried out to verify the theoretical model and the energy harvesting performance.The results demonstrate that the maximum output voltage can be achieved with an appropriate lever ratio.Furthermore,the L-EEH possesses a considerable energy harvesting performance under a smaller lever ratio compared with the other three configurations.The output power can also be improved by adjusting the tip mass of the lever.The proposed L-EEH has a considerable operating bandwidth and an output power,which can reach 146.6 mW under the excitation amplitude of 0.3 g.展开更多
Gears play an important role in virtual manufacturing systems for digital twins;however,the image of gear tooth defects is difficult to acquire owing to its non-convex shape.In this study,a deep learning network is pr...Gears play an important role in virtual manufacturing systems for digital twins;however,the image of gear tooth defects is difficult to acquire owing to its non-convex shape.In this study,a deep learning network is proposed to detect gear defects based on their point cloud representation.This approach mainly consists of three steps:(1)Various types of gear defects are classified into four cases(fracture,pitting,glue,and wear);A 3D gear dataset was constructed with 10000 instances following the aforementioned classification.(2)Gear-PCNet++introduces a novel Combinational Convolution Block,proposed based on the gear dataset for gear defect detection to effectively extract the local gear information and identify its complex topology;(3)Compared with other methods,experiments show that this method can achieve better recognition results for gear defects with higher efficiency and practicability.展开更多
Composite materials are lightweight structures and have been wildly used in marine applications.A carbon composite structure usually absorbs moisture while in-service,which can significantly affect its properties,and ...Composite materials are lightweight structures and have been wildly used in marine applications.A carbon composite structure usually absorbs moisture while in-service,which can significantly affect its properties,and detriments the overall performance.We perform a detailed study on moisture absorption and diffusion of a carbon fibre reinforced vinyl ester resin composite system.Composite samples are immersed directly in four different solutions at a temperature of 37±0.5℃for 1444h.The moisture diffusion is analysed through the Fickian diffusion model;the diffusion parameters are subsequently determined from the gravimetric data.The moisture absorption and interaction with the composite constituents are then discussed.These indicate the fundamentals of the moisture absorption and diffusion within the carbon composite structure.展开更多
The vibration reduction characteristics of composite beams filled with magnetorheological elastomer core are studied experimentally.The fiber metal laminates with magnetorheological elastomers core is self-designed an...The vibration reduction characteristics of composite beams filled with magnetorheological elastomer core are studied experimentally.The fiber metal laminates with magnetorheological elastomers core is self-designed and prepared.Internal magnetic field is applied to the beam to explore its action of damping vibration performance under the magnetic field for the first time.The composite elements test system with controllable magnetic field intensity is designed and the function of each part is introduced.Then,a set of reasonable and standard vibration test flow of this type of composite beam under different magnetic field intensity is clarified,and the practical test is conducted.It has been found that the composite beam has excellent damping performance with the first 4 damping ratios being greater than 10%.Moreover,after the magnetic field is applied,its damping results can be further improved to meet the active control purpose.展开更多
Existing mobile robots mostly use graph search algorithms for path planning,which suffer from relatively low planning efficiency owing to high redundancy and large computational complexity.Due to the limitations of th...Existing mobile robots mostly use graph search algorithms for path planning,which suffer from relatively low planning efficiency owing to high redundancy and large computational complexity.Due to the limitations of the neighborhood search strategy,the robots could hardly obtain the most optimal global path.A global path planning algorithm,denoted as EDG*,is proposed by expanding nodes using a well-designed expanding disconnected graph operator(EDG)in this paper.Firstly,all obstacles are marked and their corners are located through the map pre-processing.Then,the EDG operator is designed to find points in non-obstruction areas to complete the rapid expansion of disconnected nodes.Finally,the EDG*heuristic iterative algorithm is proposed.It selects the candidate node through a specific valuation function and realizes the node expansion while avoiding collision with a minimum offset.Path planning experiments were conducted in a typical indoor environment and on the public dataset CSM.The result shows that the proposed EDG*reduced the planning time by more than 90%and total length of paths reduced by more than 4.6%.Compared to A*,Dijkstra and JPS,EDG*does not show an exponential explosion effect in map size.The EDG*showed better performance in terms of path smoothness,and collision avoidance.This shows that the EDG*algorithm proposed in this paper can improve the efficiency of path planning and enhance path quality.展开更多
Segment Anything Model(SAM)is a cutting-edge model that has shown impressive performance in general object segmentation.The birth of the segment anything is a groundbreaking step towards creating a universal intellige...Segment Anything Model(SAM)is a cutting-edge model that has shown impressive performance in general object segmentation.The birth of the segment anything is a groundbreaking step towards creating a universal intelligent model.Due to its superior performance in general object segmentation,it quickly gained attention and interest.This makes SAM particularly attractive in industrial surface defect segmentation,especially for complex industrial scenes with limited training data.However,its segmentation ability for specific industrial scenes remains unknown.Therefore,in this work,we select three representative and complex industrial surface defect detection scenarios,namely strip steel surface defects,tile surface defects,and rail surface defects,to evaluate the segmentation performance of SAM.Our results show that although SAM has great potential in general object segmentation,it cannot achieve satisfactory performance in complex industrial scenes.Our test results are available at:https://github.com/VDT-2048/SAM-IS.展开更多
The modeling and self-excited vibration mechanism in the magnetic levitation-collision interface coupling system are investigated.The effects of the control and interface parameters on the system's stability are a...The modeling and self-excited vibration mechanism in the magnetic levitation-collision interface coupling system are investigated.The effects of the control and interface parameters on the system's stability are analyzed.The frequency range of self-excited vibrations is investigated from the energy point of view.The phenomenon of self-excited vibrations is elaborated with the phase trajectory.The corresponding control strategies are briefly analyzed with respect to the vibration mechanism.The results show that when the levitation objects collide with the mechanical interface,the system's vibration frequency becomes larger with the decrease in the collision gap;when the vibration frequency exceeds the critical frequency,the electromagnetic system continues to provide energy to the system,and the collision interface continuously dissipates energy so that the system enters the self-excited vibration state.展开更多
The correlation coefficients of random variables of mechanical structures are generally chosen with experience or even ignored,which cannot actually reflect the effects of parameter uncertainties on reliability.To dis...The correlation coefficients of random variables of mechanical structures are generally chosen with experience or even ignored,which cannot actually reflect the effects of parameter uncertainties on reliability.To discuss the selection problem of the correlation coefficients from the reliability-based sensitivity point of view,the theory principle of the problem is established based on the results of the reliability sensitivity,and the criterion of correlation among random variables is shown.The values of the correlation coefficients are obtained according to the proposed principle and the reliability sensitivity problem is discussed.Numerical studies have shown the following results：（1） If the sensitivity value of correlation coefficient ρ is less than（at what magnitude 0.000 01）,then the correlation could be ignored,which could simplify the procedure without introducing additional error.（2） However,as the difference between ρs,that is the most sensitive to the reliability,and ρR,that is with the smallest reliability,is less than 0.001,ρs is suggested to model the dependency of random variables.This could ensure the robust quality of system without the loss of safety requirement.（3） In the case of ｜Eabs｜ρ0.001 and also ｜Erel｜ρ0.001,ρR should be employed to quantify the correlation among random variables in order to ensure the accuracy of reliability analysis.Application of the proposed approach could provide a practical routine for mechanical design and manufactory to study the reliability and reliability-based sensitivity of basic design variables in mechanical reliability analysis and design.展开更多
In this study,the thermal analysis theory of selective laser melting(SLM)was introduced,and different high-entropy alloy(HEA)specimens were prepared using the SLM technology.The effects of different powder sizes,eleme...In this study,the thermal analysis theory of selective laser melting(SLM)was introduced,and different high-entropy alloy(HEA)specimens were prepared using the SLM technology.The effects of different powder sizes,elemental contents,and process parameters on the microstructure and mechanical properties of FeCoNiCrAl x HEA specimens fabricated using SLM were analyzed.Moreover,hardness and tensile tests of these high-entropy alloys were performed.The results showed that with increasing laser power and hatch spacing,the hardness of the specimens initially increased and subsequently decreased;it also increased with increasing scanning speed.The FeCoNiCrAl 0.5 HEA specimens prepared using fine powder exhibited better tensile properties,followed by FeCoNiCrAl 0.8 HEA.However,the FeCoNiCrAl 0.5 HEA prepared using coarse powder exhibited the poorest tensile properties.A comparison of the tensile properties of the specimens at different heights revealed that the specimens formed at the middle height exhibited improved tensile properties.展开更多
Various ion sources are key components to prepare functional coatings,such as diamond-like carbon(DLC)films.In this article,we present our trying of surface modification on basis of Si-incorporation diamond-like carbo...Various ion sources are key components to prepare functional coatings,such as diamond-like carbon(DLC)films.In this article,we present our trying of surface modification on basis of Si-incorporation diamond-like carbon(Si-DLC)produced by a magnetic field enhanced radio frequency ion source,which is established to get high density plasma with the help of magnetic field.Under proper deposition process,a contact angle of 111°hydrophobic surface was achieved without any surface patterning,where nanostructure SiC grains appeared within the amorphous microstructure.The surface property was influenced by ion flow parameters as well as the resultant surface microstructure.The magnetic field enhanced radio frequency ion source developed in this paper was useful for protective film applications.展开更多
Ti6Al4V alloy manufactured by electron powder bed fusion(EPBF)was separately heat-treated by stress-relief annealing at 600℃,annealing at 800℃,and solid solution at 920℃ for 1 h.Then,the friction and wear tests wer...Ti6Al4V alloy manufactured by electron powder bed fusion(EPBF)was separately heat-treated by stress-relief annealing at 600℃,annealing at 800℃,and solid solution at 920℃ for 1 h.Then,the friction and wear tests were conducted on the samples before and after heat treatment to analyze the properties and mechanism of friction and wear behavior.Results show that the sample annealed at 600℃ for 1 h has the optimal wear resistance,and the wear mass loss reduces by 44%.The sample annealed at 800℃ for 1 h possesses the optimal anti-friction performance,and the coefficient of friction reduces by 14%.This research provides a simple heat treatment method to improve the friction and wear resistance of Ti6Al4V alloy manufactured by EPBF.展开更多
Oil-tea camellia tree is an important oil plant in China that has long flexible branches.The most challenging feature for the mechanized harvest of oil-tea fruits is that its flower and fruit grow synchronously.In ord...Oil-tea camellia tree is an important oil plant in China that has long flexible branches.The most challenging feature for the mechanized harvest of oil-tea fruits is that its flower and fruit grow synchronously.In order to improve the harvesting efficiency and avoid damaging the flower bud,a hand-held fruit harvesting machine with a variable spacing comb brush was proposed.The harvesting machine can generate three kinds of actuation to detach fruit when it runs.The main actuation results from the brushing of multiple comb fingers.The other two kinds of actuation result from the beating of comb fingers on the fruits and the branches.The finger spacing of the comb brush can be adjusted consequently through moving the spacing adjusting crossbar.Hence,when the finger spacing is smaller than the diameter of the oil-tea fruit,the fruit is brushed off,but the flower bud and leaf pass through the finger gap.When the finger spacing is bigger than the fruit diameter,the fruit stuck between the fingers is loosened to ensure the continuous operation of the machine.Nylon was used as the material of the brush finger to avoid damage,which can also reduce the overall weight.The dynamic simulation of the harvesting machine was carried out with ADAMS,and the acceleration of the front end of the comb finger and the variation of the finger spacing were analyzed.The prototype of the harvesting machine was built and tested in the field.Field experiment results showed that when the speed of the comb finger drive shaft was 480 r/min,the average harvesting percentage of oil-tea fruit was 80%,and the flower bud was seldom detached,which met the working requirements of oil-tea fruit harvesting.展开更多
No-tillage seeding has become an important approach to improve crop productivity,which needs colters of high performance to cut the root-stubble-soil composite.However,the difficulty of maize root-stubbles three-dimen...No-tillage seeding has become an important approach to improve crop productivity,which needs colters of high performance to cut the root-stubble-soil composite.However,the difficulty of maize root-stubbles three-dimensional(3D)modeling hinders finite element(FE)simulation to improve development efficiency of such colters because of maize root system complexity and opaque nature of the soil.Fortunately,the non-destructive 3D geometric model of the maize root-stubble in-situ can be established via X-ray computed tomography(CT)following by a systematic procedure.The whole procedure includes CT scanning of the maize root-stubble-soil composite sample,image reconstruction via filtered back-projection(FBP)with the Hanning filter,segmentation of root-stubble via a variational level set method,and post-processing via morphological operations.The 3D reconstruction model of the maize root-stubble in-situ presents a complete,complex and in-situ geometrical morphology,which cannot be realized via other methods,including the destructive modelling after washing via CT.This study is the first to build a 3D geometric model of a maize root-stubble in-situ via CT,which opens up new possibilities for simulation of root-stubble-soil cutting using FEM,and much other research related to plant root-stubbles.展开更多
To obtain the optimal seedling taking trajectory,this study proposed the adjustment of the total transmission ratio curve by using human-computer interaction.On the basis of this design method,a planetary non-circular...To obtain the optimal seedling taking trajectory,this study proposed the adjustment of the total transmission ratio curve by using human-computer interaction.On the basis of this design method,a planetary non-circular gear mechanism was designed that can realize the twice unequal amplitude transmission ratio to meet the seedling harvesting requirements.The cubic non-uniform B-spline curve was used to fit the twice unequal amplitude transmission ratio curve,and the transmission ratio was freely distributed in two levels.The seedling pick-up mechanism was designed by controlling the seedling taking track and the corresponding attitude directly through the local section of the total transmission ratio,and the gear pitch curve was directly controlled by the transmission ratio.The kinematics model of the seedling pick-up mechanism was also established.Furthermore,the influence of the total transmission ratio on the seedling picking track,the ratio of the wave crest to the amplitude,and the mechanism parameters were discussed.A human-computer interactive optimization software was developed using Matlab,and a set of optimal parameters for the seedling pick-up mechanism was obtained to meet the transplanting requirements.By using the Adams software,the virtual prototype simulation of the seedling pick-up mechanism was completed,and the idle experiment for the track and attitude of the prototype was conducted through high-speed camera technology.The theoretical,simulated,and experimental trajectories were consistent with each other.Results revealed that the success rate of the seedling picking exceeded 90%when the rotation speeds were 40 r/min,50 r/min,and 60 r/min,and the qualified rate of the matrix decreased with the increase in rotating speed.Moreover,the number of damaged plants increased with the increase in rotating speed.The experimental results showed that the seedling pick-up mechanism designed using the proposed method demonstrated a good effect and met the required seedling picking performance.展开更多
基金the National Key Research and Development Program of China(No.2022YFB4700400)。
文摘With the rapid development of the aviation industry,the development of intelligent manufacturing equipment represented by composite robots has been paid close attention by the aviation industry.Based on the analysis of the background and main structure function of composite robots,this paper focuses on the analysis of key technologies such as composite robot hardware design,visual sensing and planning system,integrated control of‘hands,feet,and eyes',multi-robot collaborative operation,and safety.The typical applications of composite robots in aviation intelligent manufacturing such as automatic drilling and connection of aircraft,aircraft surface spraying and finishing,parts handling,aircraft measurement,and inspection are presented.The development trends such as standardization of composite robots,integration of‘5G+cloud computing+AI',and fusion of intelligent sensors are proposed.
基金supported by the National Key Research and Development Program of China (2018YFB1107700)the National Natural Science Foundation of China (51705013, 51875313)。
文摘Short and ultrashort pulse lasers offer excellent advantages in laser precision machining mainly because of their high pulse energy and low ablation threshold. The complex process of laser interaction with metals limits the indepth investigation into laser ablation. Numerical simulation is important in the study of fundamental mechanisms. This review explores the start-of-the-art methods for the theoretical simulation of the laser ablation of metals, including plasma formation and expansion. Laser-induced period surface structures are also studied.
基金financially supported by the National Natural Science Foundation of China(No.51871026)the Natural Science Foundation of Zhejiang Province,China(No.LY18E010004)supported by the National Material Environmental Corrosion Infrastructure,China。
文摘The effect of microstructure and passive film on the corrosion resistance of 2507 super duplex stainless steel(SDSS)in simulated marine environment was investigated by electrochemical measurements,periodic wet–dry cyclic corrosion test,scanning Kelvin probe force microscopy,atomic force microscopy,and X-ray photoelectron spectrometry.The results show that the occupation ratio ofγphase increases with the decrease in cooling rate,whereas the content ofαphase reduces gradually.In addition,theσprecipitated phase only emerges in the annealed steel.The pitting sensitivity and corrosion rate of 2507 SDSS reduce first and then increase as the cooling rate decreases.Theσprecipitated phase drastically reduces the protective ability of the passive film and facilitates micro-galvanic corrosion of the annealed steel.For various microstructures,the pits are preferentially distributed within theσandγphases.The corrosion resistance of 2507 SDSS prepared by different cooling methods is closely related to the microstructure and structure(stability and homogeneity)of the passive film.Normalized steel shows an optimal corrosion resistance,followed by the quenched and annealed steels.
基金supported by National Natural Science Foundation of China(51705068)the fundamental research funds for the central universities(N150303003)research initiation funds for the PhD of Liaoning Province(201601005).
文摘Aerodynamic noise is the dominant noise source of the high-speed train.It not only seriously affects the passenger comfort and people’s normal life along the railway line,but also may cause fatigue damage to the surrounding equipment and buildings.This manuscript carried out the simulation and experimental study on the external aerodynamic noise of high-speed train,in order to increase the understanding of the noise and hence to be better able to control it.The on-line tests were performed to verify that it is reasonable to simplify the high-speed train model.The turbulent air flow model was then developed,and the external steady flow field was computed by Realizable k-εturbulence model.Based on the steady flow field,aerodynamic noise sources on the train surface and the external transient flow field were calculated by broadband acoustics source model and large eddy simulation(LES)respectively.The pressures on the train surface were obtained from the results of the transient model.Considering the transient flow field,the far-field aerodynamic noise generated by the high-speed train was finally obtained based on Lighthill-Curle theory.Through the comparison between simulations and on-line tests,it is shown that the numerical model gives reliable aerodynamic noise predictions.This research is significant to the study and control of the aerodynamic noise of high-speed train.
文摘Micro milling is a machining method of high precision and efficiency for micro components and features.In order to study the surface quality of single crystal materials in micro milling,the two-edged cemented carbide tool milling cutter with 0.4 mm diameter was used,and the orthogonal experiment was completed on the micro-milling of single crystal aluminum material.Through the analysis of statistical results,the primary and secondary factor which impacting on surface quality were found as follows:spindle speed,feed rate,milling depth.The ideal combination of optimized process parameters were obtained,when the spindle speed was 36000 r/min,the milling depth was 10μm,the feed rate was 80μm/s,which made the milling surface roughness is 0.782μm and minimal.Single crystal materials removal mechanism were revealed,and the influence of cutting parameters on micro-milling surface were discussed,the reason of tool wear was analyzed.Those provide a certain theoretical and experimental basis for micro milling of single crystal materials.
基金Project supported by the National Natural Science Foundation of China(No.52275091)the Fundamental Research Funds for the Central Universities of China(No.N2103008)the Natural Science Foundation of Liaoning Province of China(No.2020-MS-125)。
文摘To achieve better anti-vibration performance in a low frequency region and expand the range of vibration isolation,a bilateral supported bio-inspired anti-vibration(BBAV)structure composed of purely linear elements is proposed,inspired by the motion form of bird legs and the nonlinear extension and compression of muscles and tendons.The kinematic relations and nonlinear dynamic model considering vertical and rotational vibrations are established.The loading capacity and equivalent stiffness are investigated with key parameters.The amplitude-frequency characteristics and force transmissibility are used to evaluate the stability and anti-vibration performance with the effects of the excitation amplitude,rod length,installation angle,and spring stiffness.The results show that the loading requirements and resonant characteristics of the BBAV structure are adjustable,and superior vibration isolation performance can be achieved readily by tuning the parameters.The X-shaped vibration structure is sensitive to the spring stiffness,which exhibits a wider vibration isolation bandwidth with smaller spring stiffness.Besides,depending on the parameters,the nonlinear behavior of the BBAV system can be interconverted between the softening type and the hardening type.The theoretical analysis in this study demonstrates the advantages and effectiveness of the vibration isolation structure.
基金Project supported by the National Natural Science Foundation of China(No.52175125)。
文摘This study presents a novel enhanced monostable lever-type electromagnetic energy harvester(L-EEH).According to the positions of the coil and the lever pivot,four configurations are discussed to realize a better harvesting performance of the L-EEHs.On the basis of establishing the theoretical model of the L-EEH,the corresponding analytical solutions can be obtained by applying the harmonic balance method.The effects of the nonlinear coefficient,the lever ratio,the mass ratio,and the circuit parameters on the energy harvesting performance of L-EEHs are analyzed and discussed.The numerical and experimental efforts are carried out to verify the theoretical model and the energy harvesting performance.The results demonstrate that the maximum output voltage can be achieved with an appropriate lever ratio.Furthermore,the L-EEH possesses a considerable energy harvesting performance under a smaller lever ratio compared with the other three configurations.The output power can also be improved by adjusting the tip mass of the lever.The proposed L-EEH has a considerable operating bandwidth and an output power,which can reach 146.6 mW under the excitation amplitude of 0.3 g.
基金opening fund of State Key Laboratory of Lunar and Planetary Sciences(Macao University of Science and Technology),No.119/2017/A3the Natural Science Foundation of China,Nos.61572056 and 61872347the Special Plan for the Development of Distinguished Young Scientists of ISCAS,No.Y8RC535018.
文摘Gears play an important role in virtual manufacturing systems for digital twins;however,the image of gear tooth defects is difficult to acquire owing to its non-convex shape.In this study,a deep learning network is proposed to detect gear defects based on their point cloud representation.This approach mainly consists of three steps:(1)Various types of gear defects are classified into four cases(fracture,pitting,glue,and wear);A 3D gear dataset was constructed with 10000 instances following the aforementioned classification.(2)Gear-PCNet++introduces a novel Combinational Convolution Block,proposed based on the gear dataset for gear defect detection to effectively extract the local gear information and identify its complex topology;(3)Compared with other methods,experiments show that this method can achieve better recognition results for gear defects with higher efficiency and practicability.
基金The author would like to acknowledge the Fuzhou University for providing the start-up research funding for Minjiang Scholar Distinguished Professor scheme in Fujian Province,China.Financial support from the National Natural Science Foundation of China(52005108)is also appreciated.
文摘Composite materials are lightweight structures and have been wildly used in marine applications.A carbon composite structure usually absorbs moisture while in-service,which can significantly affect its properties,and detriments the overall performance.We perform a detailed study on moisture absorption and diffusion of a carbon fibre reinforced vinyl ester resin composite system.Composite samples are immersed directly in four different solutions at a temperature of 37±0.5℃for 1444h.The moisture diffusion is analysed through the Fickian diffusion model;the diffusion parameters are subsequently determined from the gravimetric data.The moisture absorption and interaction with the composite constituents are then discussed.These indicate the fundamentals of the moisture absorption and diffusion within the carbon composite structure.
基金This study was supported by the National Natural Science Foundation of China(granted No.51505070)the Fundamental Research Funds for the Central Universities of China(granted No.N160313002,N160312001,N170302001,N180302004,N180703018,N180312012 and N180313006)the National Key Laboratory of Science and Technology on Advanced Composites in Special Environments,Harbin Institute of Technology(granted No.6142905192512).
文摘The vibration reduction characteristics of composite beams filled with magnetorheological elastomer core are studied experimentally.The fiber metal laminates with magnetorheological elastomers core is self-designed and prepared.Internal magnetic field is applied to the beam to explore its action of damping vibration performance under the magnetic field for the first time.The composite elements test system with controllable magnetic field intensity is designed and the function of each part is introduced.Then,a set of reasonable and standard vibration test flow of this type of composite beam under different magnetic field intensity is clarified,and the practical test is conducted.It has been found that the composite beam has excellent damping performance with the first 4 damping ratios being greater than 10%.Moreover,after the magnetic field is applied,its damping results can be further improved to meet the active control purpose.
基金Supported by National Key Research and Development Program of China(Grant No.2022YFB4700402).
文摘Existing mobile robots mostly use graph search algorithms for path planning,which suffer from relatively low planning efficiency owing to high redundancy and large computational complexity.Due to the limitations of the neighborhood search strategy,the robots could hardly obtain the most optimal global path.A global path planning algorithm,denoted as EDG*,is proposed by expanding nodes using a well-designed expanding disconnected graph operator(EDG)in this paper.Firstly,all obstacles are marked and their corners are located through the map pre-processing.Then,the EDG operator is designed to find points in non-obstruction areas to complete the rapid expansion of disconnected nodes.Finally,the EDG*heuristic iterative algorithm is proposed.It selects the candidate node through a specific valuation function and realizes the node expansion while avoiding collision with a minimum offset.Path planning experiments were conducted in a typical indoor environment and on the public dataset CSM.The result shows that the proposed EDG*reduced the planning time by more than 90%and total length of paths reduced by more than 4.6%.Compared to A*,Dijkstra and JPS,EDG*does not show an exponential explosion effect in map size.The EDG*showed better performance in terms of path smoothness,and collision avoidance.This shows that the EDG*algorithm proposed in this paper can improve the efficiency of path planning and enhance path quality.
基金supported by the National Natural Science Foundation of China(51805078)Project of National Key Laboratory of Advanced Casting Technologies(CAT2023-002)the 111 Project(B16009).
文摘Segment Anything Model(SAM)is a cutting-edge model that has shown impressive performance in general object segmentation.The birth of the segment anything is a groundbreaking step towards creating a universal intelligent model.Due to its superior performance in general object segmentation,it quickly gained attention and interest.This makes SAM particularly attractive in industrial surface defect segmentation,especially for complex industrial scenes with limited training data.However,its segmentation ability for specific industrial scenes remains unknown.Therefore,in this work,we select three representative and complex industrial surface defect detection scenarios,namely strip steel surface defects,tile surface defects,and rail surface defects,to evaluate the segmentation performance of SAM.Our results show that although SAM has great potential in general object segmentation,it cannot achieve satisfactory performance in complex industrial scenes.Our test results are available at:https://github.com/VDT-2048/SAM-IS.
基金Project supported by the National Natural Science Foundation of China(No.12372005)。
文摘The modeling and self-excited vibration mechanism in the magnetic levitation-collision interface coupling system are investigated.The effects of the control and interface parameters on the system's stability are analyzed.The frequency range of self-excited vibrations is investigated from the energy point of view.The phenomenon of self-excited vibrations is elaborated with the phase trajectory.The corresponding control strategies are briefly analyzed with respect to the vibration mechanism.The results show that when the levitation objects collide with the mechanical interface,the system's vibration frequency becomes larger with the decrease in the collision gap;when the vibration frequency exceeds the critical frequency,the electromagnetic system continues to provide energy to the system,and the collision interface continuously dissipates energy so that the system enters the self-excited vibration state.
基金supported by Changjiang Scholars and Innovative Research Team in University of China (Grant No. IRT0816)Key National Science & Technology Special Project on "High-Grade CNC Machine Tools and Basic Manufacturing Equipments" of China (Grant No. 2010ZX04014-014)+1 种基金National Natural Science Foundation of China (Grant No. 50875039)Key Projects in National Science & Technology Pillar Program during the 11th Five-year Plan Period of China (Grant No. 2009BAG12A02-A07-2)
文摘The correlation coefficients of random variables of mechanical structures are generally chosen with experience or even ignored,which cannot actually reflect the effects of parameter uncertainties on reliability.To discuss the selection problem of the correlation coefficients from the reliability-based sensitivity point of view,the theory principle of the problem is established based on the results of the reliability sensitivity,and the criterion of correlation among random variables is shown.The values of the correlation coefficients are obtained according to the proposed principle and the reliability sensitivity problem is discussed.Numerical studies have shown the following results：（1） If the sensitivity value of correlation coefficient ρ is less than（at what magnitude 0.000 01）,then the correlation could be ignored,which could simplify the procedure without introducing additional error.（2） However,as the difference between ρs,that is the most sensitive to the reliability,and ρR,that is with the smallest reliability,is less than 0.001,ρs is suggested to model the dependency of random variables.This could ensure the robust quality of system without the loss of safety requirement.（3） In the case of ｜Eabs｜ρ0.001 and also ｜Erel｜ρ0.001,ρR should be employed to quantify the correlation among random variables in order to ensure the accuracy of reliability analysis.Application of the proposed approach could provide a practical routine for mechanical design and manufactory to study the reliability and reliability-based sensitivity of basic design variables in mechanical reliability analysis and design.
基金supported by National Natural Science Foundation of China(Grant No.52275412)Central Universities Fundamental Research Funds of China(Grant No.N2103023).
文摘In this study,the thermal analysis theory of selective laser melting(SLM)was introduced,and different high-entropy alloy(HEA)specimens were prepared using the SLM technology.The effects of different powder sizes,elemental contents,and process parameters on the microstructure and mechanical properties of FeCoNiCrAl x HEA specimens fabricated using SLM were analyzed.Moreover,hardness and tensile tests of these high-entropy alloys were performed.The results showed that with increasing laser power and hatch spacing,the hardness of the specimens initially increased and subsequently decreased;it also increased with increasing scanning speed.The FeCoNiCrAl 0.5 HEA specimens prepared using fine powder exhibited better tensile properties,followed by FeCoNiCrAl 0.8 HEA.However,the FeCoNiCrAl 0.5 HEA prepared using coarse powder exhibited the poorest tensile properties.A comparison of the tensile properties of the specimens at different heights revealed that the specimens formed at the middle height exhibited improved tensile properties.
文摘Various ion sources are key components to prepare functional coatings,such as diamond-like carbon(DLC)films.In this article,we present our trying of surface modification on basis of Si-incorporation diamond-like carbon(Si-DLC)produced by a magnetic field enhanced radio frequency ion source,which is established to get high density plasma with the help of magnetic field.Under proper deposition process,a contact angle of 111°hydrophobic surface was achieved without any surface patterning,where nanostructure SiC grains appeared within the amorphous microstructure.The surface property was influenced by ion flow parameters as well as the resultant surface microstructure.The magnetic field enhanced radio frequency ion source developed in this paper was useful for protective film applications.
基金National Natural Science Foundation of China(51975036)Guangdong Province Key R&D Project(2018B090904004)。
文摘Ti6Al4V alloy manufactured by electron powder bed fusion(EPBF)was separately heat-treated by stress-relief annealing at 600℃,annealing at 800℃,and solid solution at 920℃ for 1 h.Then,the friction and wear tests were conducted on the samples before and after heat treatment to analyze the properties and mechanism of friction and wear behavior.Results show that the sample annealed at 600℃ for 1 h has the optimal wear resistance,and the wear mass loss reduces by 44%.The sample annealed at 800℃ for 1 h possesses the optimal anti-friction performance,and the coefficient of friction reduces by 14%.This research provides a simple heat treatment method to improve the friction and wear resistance of Ti6Al4V alloy manufactured by EPBF.
基金This work was supported by the Zhejiang Provincial Key Research&Development Plan(Grant No.2019C02065)the National Natural Science Foundation of China(Grant No.31971798)+1 种基金the National Key Research and Development Program of China(Grant No.2019YFD1001602)the 521 Talent Plan of Zhejiang Sci-Tech University,and the Cultivation Project for Youth Discipline Leader in Zhejiang Provincial Institute.
文摘Oil-tea camellia tree is an important oil plant in China that has long flexible branches.The most challenging feature for the mechanized harvest of oil-tea fruits is that its flower and fruit grow synchronously.In order to improve the harvesting efficiency and avoid damaging the flower bud,a hand-held fruit harvesting machine with a variable spacing comb brush was proposed.The harvesting machine can generate three kinds of actuation to detach fruit when it runs.The main actuation results from the brushing of multiple comb fingers.The other two kinds of actuation result from the beating of comb fingers on the fruits and the branches.The finger spacing of the comb brush can be adjusted consequently through moving the spacing adjusting crossbar.Hence,when the finger spacing is smaller than the diameter of the oil-tea fruit,the fruit is brushed off,but the flower bud and leaf pass through the finger gap.When the finger spacing is bigger than the fruit diameter,the fruit stuck between the fingers is loosened to ensure the continuous operation of the machine.Nylon was used as the material of the brush finger to avoid damage,which can also reduce the overall weight.The dynamic simulation of the harvesting machine was carried out with ADAMS,and the acceleration of the front end of the comb finger and the variation of the finger spacing were analyzed.The prototype of the harvesting machine was built and tested in the field.Field experiment results showed that when the speed of the comb finger drive shaft was 480 r/min,the average harvesting percentage of oil-tea fruit was 80%,and the flower bud was seldom detached,which met the working requirements of oil-tea fruit harvesting.
基金The work is financially supported by the National Natural Science Foundation of China(Grant No.51705227)University of Science and Technology Liaoning Talent Project Grants(Grant No.601011507-19)+1 种基金and Special Scientific Research Foundation of University of Science and Technology Liaoning(Grant No.2016YY02)We thank Jiuming Su for his lab assistance,and also thank Zong Zhang and Xinrui Xu for their analysis assistance.
文摘No-tillage seeding has become an important approach to improve crop productivity,which needs colters of high performance to cut the root-stubble-soil composite.However,the difficulty of maize root-stubbles three-dimensional(3D)modeling hinders finite element(FE)simulation to improve development efficiency of such colters because of maize root system complexity and opaque nature of the soil.Fortunately,the non-destructive 3D geometric model of the maize root-stubble in-situ can be established via X-ray computed tomography(CT)following by a systematic procedure.The whole procedure includes CT scanning of the maize root-stubble-soil composite sample,image reconstruction via filtered back-projection(FBP)with the Hanning filter,segmentation of root-stubble via a variational level set method,and post-processing via morphological operations.The 3D reconstruction model of the maize root-stubble in-situ presents a complete,complex and in-situ geometrical morphology,which cannot be realized via other methods,including the destructive modelling after washing via CT.This study is the first to build a 3D geometric model of a maize root-stubble in-situ via CT,which opens up new possibilities for simulation of root-stubble-soil cutting using FEM,and much other research related to plant root-stubbles.
基金the National Natural Science Foundation of China(Grant No.52075497,No.51775512)the National Key Research and Development Program of China(Grant No.2017YFD0700800)the Key Research and Development Projects in Zhejiang Province(Grant No.2018C02046).
文摘To obtain the optimal seedling taking trajectory,this study proposed the adjustment of the total transmission ratio curve by using human-computer interaction.On the basis of this design method,a planetary non-circular gear mechanism was designed that can realize the twice unequal amplitude transmission ratio to meet the seedling harvesting requirements.The cubic non-uniform B-spline curve was used to fit the twice unequal amplitude transmission ratio curve,and the transmission ratio was freely distributed in two levels.The seedling pick-up mechanism was designed by controlling the seedling taking track and the corresponding attitude directly through the local section of the total transmission ratio,and the gear pitch curve was directly controlled by the transmission ratio.The kinematics model of the seedling pick-up mechanism was also established.Furthermore,the influence of the total transmission ratio on the seedling picking track,the ratio of the wave crest to the amplitude,and the mechanism parameters were discussed.A human-computer interactive optimization software was developed using Matlab,and a set of optimal parameters for the seedling pick-up mechanism was obtained to meet the transplanting requirements.By using the Adams software,the virtual prototype simulation of the seedling pick-up mechanism was completed,and the idle experiment for the track and attitude of the prototype was conducted through high-speed camera technology.The theoretical,simulated,and experimental trajectories were consistent with each other.Results revealed that the success rate of the seedling picking exceeded 90%when the rotation speeds were 40 r/min,50 r/min,and 60 r/min,and the qualified rate of the matrix decreased with the increase in rotating speed.Moreover,the number of damaged plants increased with the increase in rotating speed.The experimental results showed that the seedling pick-up mechanism designed using the proposed method demonstrated a good effect and met the required seedling picking performance.
