The mechanical behavior of cohesive soil is sensitized to drying-wetting cycles under confinements.However,the hydromechanical coupling effect has not been considered in current constitutive models.A macro-micro analy...The mechanical behavior of cohesive soil is sensitized to drying-wetting cycles under confinements.However,the hydromechanical coupling effect has not been considered in current constitutive models.A macro-micro analysis scheme is proposed in this paper to investigate the soil deformation behavior under the coupling of stress and drying-wetting cycles.A new device is developed based on CT(computerized tomography)workstation to apply certain normal and shear stresses on a soil specimen during drying-wetting cycles.A series of tests are conducted on a type of loess with various coupling of stress paths and drying-wetting cycles.At macroscopic level,stress sensor and laser sensor are used to acquire stress and strain,respectively.The shear and volumetric strain increase during the first few drying-wetting cycles and then become stable.The increase of the shear stress level or confining pressure would cause higher increase rate and the value of shear strain in the process of drying-wetting cycles.At microscopic level,the grayscale value(GSV)of CT scanning image is characterized as the proportion of soil particles to voids.A fabric state parameter is proposed to characterize soil microstructures under the influence of stress and drying-wetting cycle.Test results indicate that the macroand micro-responses show high consistence and relevance.The stress and drying-wetting cycles would both induce collapse of the soil microstructure,which dominants degradation of the soil mechanical properties.The evolution of the macro-mechanical property of soil exhibits a positive linear relationship with the micro-evolution of the fabric state parameter.展开更多
Understanding the physical,mechanical behavior,and seepage characteristics of coal under hydro-mechanical coupling holds significant importance for ensuring the stability of surrounding rock formations and preventing ...Understanding the physical,mechanical behavior,and seepage characteristics of coal under hydro-mechanical coupling holds significant importance for ensuring the stability of surrounding rock formations and preventing gas outbursts.Scanning electron microscopy,uniaxial tests,and triaxial tests were conducted to comprehensively analyze the macroscopic and microscopic physical and mechanical characteristics of coal under different soaking times.Moreover,by restoring the stress path and water injection conditions of the protective layer indoors,we explored the coal mining dynamic behavior and the evolution of permeability.The results show that water causes the micro-surface of coal to peel off and cracks to expand and develop.With the increase of soaking time,the uniaxial and triaxial strengths were gradually decreased with nonlinear trend,and decreased by 63.31%and 30.95%after soaking for 240 h,respectively.Under different water injection pressure conditions,coal permeability undergoes three stages during the mining loading process and ultimately increases to higher values.The peak stress of coal,the deviatoric stress and strain at the permeability surge point all decrease with increasing water injection pressure.The results of this research can help improve the understanding of the coal mechanical properties and seepage evolution law under hydro-mechanical coupling.展开更多
Scientists and engineers are looking forward to new manufacturing technologies to realize the integrated fabrication of macro shape and microstructure for the components with a short production chain, which can also s...Scientists and engineers are looking forward to new manufacturing technologies to realize the integrated fabrication of macro shape and microstructure for the components with a short production chain, which can also save materials and reduce energy consumption. Additive manufacturing (AM) technology is a new fabrication pattern with a character of a lay-by-lay material deposition. The components are fabricated in a bottom-up way, from points, lines, to layers and volume, which provided a capability to solve the impossible integrated fabrication problem for micro- and macro-structure by using conventional manufacturing technologies. Thus, based on integrated fabrication of micro- and macro- structures, research team in Xi’an Jiaotong University has been focusing on technological innovations and applications of advanced additive manufacturing technologies. Novel additive manufacturing principles have been proposed and explored, by which new AM processes and equipment for met- als, composites, ceramics, and biomaterials have been developed to support the industrial applications. Additive manufacturing and cutting-edge applications of advanced composite structure, metamaterials, bio-implants, and monocrystal alloy components have been investigated to push the new development of integrated fabrication of micro- and macro- structures.展开更多
Accurately characterizing the liver's mechanical properties is of paramount importance for disease diagnosis,treatment,surgical prosthetic modeling,and impact injury dummies.However,due to its inherent biological ...Accurately characterizing the liver's mechanical properties is of paramount importance for disease diagnosis,treatment,surgical prosthetic modeling,and impact injury dummies.However,due to its inherent biological soft tissue nature,the characterization of mechanical behavior varies across testing methods and sample types.In this study,we employed transmission electron microscope and Micro CT to observe the morphology of the marginal and center of rat livers and conducted macroscopic mechanical tests to characterize their elasticity and viscoelasticity.The results revealed that the central region displayed higher metabolic levels,elongated mitochondria,and an abundance of rough endoplasmic reticulum at the microscale.At the mesoscale,larger diameter portal veins were mainly distributed in the central region,while smaller diameter arteries were predominantly located at the periphery.At the macroscale,under a strain rate of 0.0167 s^(-1),no significant differences were observed in the elastic properties between the two regions.However,as the strain rate increased up to 0.167 s^(-1),the central region displayed higher porosity,resulting in reduced liquid loss,increased hardness,and higher viscosity compared to the periphery.Consequently,the liver demonstrated overall heterogeneity,with isotropic models suitable for the peripheral region,while more intricate models may be required to capture the complexity of the central region with its intricate vasculature.展开更多
Micro/nano hierarchical structures could endow materials with various surface functions.However,the multilayer and multiscale characteristics of micro/nano hierarchical structures bring difficulties for their one step...Micro/nano hierarchical structures could endow materials with various surface functions.However,the multilayer and multiscale characteristics of micro/nano hierarchical structures bring difficulties for their one step and controllable fabrication.Accordingly,based on tip-based fabrication techniques,this study proposed a micro-amplitude vibration-assisted scratching method by introducing a periodic backward displacement into the conventional scratching process,which enabled the synchronous creation of the microscale V-groove and nanoscale ripples,i.e.a typical micro/nano hierarchical structure.The experiments and finite element modeling were employed to explore the formation process and mechanism of the micro/nano hierarchical structures.Being different from conventional cutting,this method was mainly based on the plow mechanism,and it could accurately replicate the shape of the indenter on the material surface.The microscale V-groove was formed due to the scratching action,and the nanoscale ripple was formed due to the extrusion action of the indenter on the microscale V-groove’s surface.Furthermore,the relationships between the processing parameters and the dimensions of the micro/nano hierarchical structures were established through experiments,and optimized processing parameters were determined to achieve regular micro/nano hierarchical structures.By this method,complex patterns constructed by various micro/nano hierarchical structures were fabricated on both flat and curved surfaces,achieving diverse surface structural colors.展开更多
Micro aerial vehicles(MAVs)have flexibility and maneuverability,which can offer vast potential for applications in both civilian and military domains.Compared to Fixed-wing/Rotor-wing MAVs,Flapping Wing Micro Robots(F...Micro aerial vehicles(MAVs)have flexibility and maneuverability,which can offer vast potential for applications in both civilian and military domains.Compared to Fixed-wing/Rotor-wing MAVs,Flapping Wing Micro Robots(FWMRs)have garnered widespread attention among scientists due to their superior miniaturized aerodynamic theory,reduced noise,and enhanced resistance to disturbances in complex and diverse environments.Flying insects,it not only has remarkable flapping flight ability(wings),but also takeoff and landing habitat ability(legs).If the various functions of flying insects can be imitated,efficient biomimetic FWMRs can be produced.This paper provides a review of the flight kinematics,aerodynamics,and wing structural parameters of insects.Then,the traditional wings and folding wings of insect-inspired FWMRs were compared.The research progress in takeoff and landing of FWMRs was also summarized,and the future developments and challenges for insect-inspired FWMRs were discussed.展开更多
基金funded by National Key R&D Program of China(Grant No.2023YFC3007001)Beijing Natural Science Foundation(Grant No.8244053)China Postdoctoral Science Foundation(Grant No.2024M754065).
文摘The mechanical behavior of cohesive soil is sensitized to drying-wetting cycles under confinements.However,the hydromechanical coupling effect has not been considered in current constitutive models.A macro-micro analysis scheme is proposed in this paper to investigate the soil deformation behavior under the coupling of stress and drying-wetting cycles.A new device is developed based on CT(computerized tomography)workstation to apply certain normal and shear stresses on a soil specimen during drying-wetting cycles.A series of tests are conducted on a type of loess with various coupling of stress paths and drying-wetting cycles.At macroscopic level,stress sensor and laser sensor are used to acquire stress and strain,respectively.The shear and volumetric strain increase during the first few drying-wetting cycles and then become stable.The increase of the shear stress level or confining pressure would cause higher increase rate and the value of shear strain in the process of drying-wetting cycles.At microscopic level,the grayscale value(GSV)of CT scanning image is characterized as the proportion of soil particles to voids.A fabric state parameter is proposed to characterize soil microstructures under the influence of stress and drying-wetting cycle.Test results indicate that the macroand micro-responses show high consistence and relevance.The stress and drying-wetting cycles would both induce collapse of the soil microstructure,which dominants degradation of the soil mechanical properties.The evolution of the macro-mechanical property of soil exhibits a positive linear relationship with the micro-evolution of the fabric state parameter.
基金Project(52225403)supported by the National Natural Science Foundation of ChinaProject(2023YFF0615401)supported by the National Key Research and Development Program of China+1 种基金Projects(2023NSFSC0004,2023NSFSC0790)supported by Science and Technology Program of Sichuan Province,ChinaProject(2021-CMCUKFZD001)supported by the Open Fund of State Key Laboratory of Coal Mining and Clean Utilization,China。
文摘Understanding the physical,mechanical behavior,and seepage characteristics of coal under hydro-mechanical coupling holds significant importance for ensuring the stability of surrounding rock formations and preventing gas outbursts.Scanning electron microscopy,uniaxial tests,and triaxial tests were conducted to comprehensively analyze the macroscopic and microscopic physical and mechanical characteristics of coal under different soaking times.Moreover,by restoring the stress path and water injection conditions of the protective layer indoors,we explored the coal mining dynamic behavior and the evolution of permeability.The results show that water causes the micro-surface of coal to peel off and cracks to expand and develop.With the increase of soaking time,the uniaxial and triaxial strengths were gradually decreased with nonlinear trend,and decreased by 63.31%and 30.95%after soaking for 240 h,respectively.Under different water injection pressure conditions,coal permeability undergoes three stages during the mining loading process and ultimately increases to higher values.The peak stress of coal,the deviatoric stress and strain at the permeability surge point all decrease with increasing water injection pressure.The results of this research can help improve the understanding of the coal mechanical properties and seepage evolution law under hydro-mechanical coupling.
文摘Scientists and engineers are looking forward to new manufacturing technologies to realize the integrated fabrication of macro shape and microstructure for the components with a short production chain, which can also save materials and reduce energy consumption. Additive manufacturing (AM) technology is a new fabrication pattern with a character of a lay-by-lay material deposition. The components are fabricated in a bottom-up way, from points, lines, to layers and volume, which provided a capability to solve the impossible integrated fabrication problem for micro- and macro-structure by using conventional manufacturing technologies. Thus, based on integrated fabrication of micro- and macro- structures, research team in Xi’an Jiaotong University has been focusing on technological innovations and applications of advanced additive manufacturing technologies. Novel additive manufacturing principles have been proposed and explored, by which new AM processes and equipment for met- als, composites, ceramics, and biomaterials have been developed to support the industrial applications. Additive manufacturing and cutting-edge applications of advanced composite structure, metamaterials, bio-implants, and monocrystal alloy components have been investigated to push the new development of integrated fabrication of micro- and macro- structures.
基金supported by the National Natural Science Foundation of China(Grant Nos.U2241273,12172034,U20A20390,and 11827803)the Beijing Municipal Natural Science Foundation(Grant No.7212205)+1 种基金the 111 project(Grant No.B13003)the Fundamental Research Funds for the Central Universities.
文摘Accurately characterizing the liver's mechanical properties is of paramount importance for disease diagnosis,treatment,surgical prosthetic modeling,and impact injury dummies.However,due to its inherent biological soft tissue nature,the characterization of mechanical behavior varies across testing methods and sample types.In this study,we employed transmission electron microscope and Micro CT to observe the morphology of the marginal and center of rat livers and conducted macroscopic mechanical tests to characterize their elasticity and viscoelasticity.The results revealed that the central region displayed higher metabolic levels,elongated mitochondria,and an abundance of rough endoplasmic reticulum at the microscale.At the mesoscale,larger diameter portal veins were mainly distributed in the central region,while smaller diameter arteries were predominantly located at the periphery.At the macroscale,under a strain rate of 0.0167 s^(-1),no significant differences were observed in the elastic properties between the two regions.However,as the strain rate increased up to 0.167 s^(-1),the central region displayed higher porosity,resulting in reduced liquid loss,increased hardness,and higher viscosity compared to the periphery.Consequently,the liver demonstrated overall heterogeneity,with isotropic models suitable for the peripheral region,while more intricate models may be required to capture the complexity of the central region with its intricate vasculature.
基金supported by the Jilin Province Key Research and Development Plan Project(20240302066GX)the National Natural Science Foundation of China(Grant No.52075221)the Fundamental Research Funds for the Central Universities(2023-JCXK-02)。
文摘Micro/nano hierarchical structures could endow materials with various surface functions.However,the multilayer and multiscale characteristics of micro/nano hierarchical structures bring difficulties for their one step and controllable fabrication.Accordingly,based on tip-based fabrication techniques,this study proposed a micro-amplitude vibration-assisted scratching method by introducing a periodic backward displacement into the conventional scratching process,which enabled the synchronous creation of the microscale V-groove and nanoscale ripples,i.e.a typical micro/nano hierarchical structure.The experiments and finite element modeling were employed to explore the formation process and mechanism of the micro/nano hierarchical structures.Being different from conventional cutting,this method was mainly based on the plow mechanism,and it could accurately replicate the shape of the indenter on the material surface.The microscale V-groove was formed due to the scratching action,and the nanoscale ripple was formed due to the extrusion action of the indenter on the microscale V-groove’s surface.Furthermore,the relationships between the processing parameters and the dimensions of the micro/nano hierarchical structures were established through experiments,and optimized processing parameters were determined to achieve regular micro/nano hierarchical structures.By this method,complex patterns constructed by various micro/nano hierarchical structures were fabricated on both flat and curved surfaces,achieving diverse surface structural colors.
基金supported by the National Natural Science Foundation of China(grant numbers 52305321 and 62273246)The Natural Science Foundation of Jiangsu Province(BK20230496)+3 种基金China Postdoctoral Science Foundation Funded Project(2023M732536 and 2024T170630)Jiangsu Province Excellence Postdoctoral Program(2023ZB218)The National Key R&D Program of China(2022YFB4702202)The Jiangsu Provincial Key Technology R&D Program(BE2021009-02).
文摘Micro aerial vehicles(MAVs)have flexibility and maneuverability,which can offer vast potential for applications in both civilian and military domains.Compared to Fixed-wing/Rotor-wing MAVs,Flapping Wing Micro Robots(FWMRs)have garnered widespread attention among scientists due to their superior miniaturized aerodynamic theory,reduced noise,and enhanced resistance to disturbances in complex and diverse environments.Flying insects,it not only has remarkable flapping flight ability(wings),but also takeoff and landing habitat ability(legs).If the various functions of flying insects can be imitated,efficient biomimetic FWMRs can be produced.This paper provides a review of the flight kinematics,aerodynamics,and wing structural parameters of insects.Then,the traditional wings and folding wings of insect-inspired FWMRs were compared.The research progress in takeoff and landing of FWMRs was also summarized,and the future developments and challenges for insect-inspired FWMRs were discussed.
