After millions of years of natural evolution,horsetails have evolved unique stem structures that enable survival in harsh environments.Inspired by the cross-sectional characteristics of horsetail stems,a series of bio...After millions of years of natural evolution,horsetails have evolved unique stem structures that enable survival in harsh environments.Inspired by the cross-sectional characteristics of horsetail stems,a series of bioinspired sandwich structures were designed and fabricated using the laser powder bed fusion(LPBF)process.By combining experimental and finite element simulation methods,the formability,mechanical properties,deformation behavior,and thermal conduction performance of these structures were determined.Results show that the surface morphology of the bioinspired sandwich structures was smooth,with no cracks observed.The bioinspired sandwich structure with an inner tube diameter of 1.9 mm(D_(1.9))exhibited optimal comprehensive mechanical properties,with a specific strength of 64.2 MPa/(g/cm^(3)),and specific energy absorption of 3.3 J/g.Stress distribution results revealed that the D_(1.9)structures had the most uniform stress distribution.Furthermore,increasing the internal conduction paths improved heat transfer;therefore,the thermal conductivities of the D_(1.4),D_(1.9),and D_(2.4)structures were higher than that of the D0 structure.This study demonstrates that a bioinspired design approach,combined with additive manufacturing technology,enables the development of high-performance structures with both load-bearing and thermally insulating capabilities.展开更多
This paper proposes a novel optimization framework in passive control techniques to reduce noise pollution.The geometries of the structures are represented by Catmull-Clark subdivision surfaces,which are able to build...This paper proposes a novel optimization framework in passive control techniques to reduce noise pollution.The geometries of the structures are represented by Catmull-Clark subdivision surfaces,which are able to build gap-free Computer-Aided Design models and meanwhile tackle the extraordinary points that are commonly encountered in geometricmodelling.The acoustic fields are simulated using the isogeometric boundary elementmethod,and a density-based topology optimization is conducted to optimize distribution of sound-absorbing materials adhered to structural surfaces.The approach enables one to perform acoustic optimization from Computer-Aided Design models directly without needingmeshing and volume parameterization,thereby avoiding the geometric errors and time-consuming preprocessing steps in conventional simulation and optimization methods.The effectiveness of the present method is demonstrated by three dimensional numerical examples.展开更多
In order to study current situation of application,recycling and residue pollution of mulching films in Xinjiang,and accurately grasp pollution degree of residue of mulching films,this paper made an empirical analysis...In order to study current situation of application,recycling and residue pollution of mulching films in Xinjiang,and accurately grasp pollution degree of residue of mulching films,this paper made an empirical analysis on residue of mulching films in 31 typical counties and cities in Xinjiang. Results indicate that( i) use of mulching films in Xinjiang is wide and there is great difference in use and residue recycling between cities and counties. Planting area and planting structure jointly influence use of mulching films,and the use of mulching films is significantly correlated with recycling of mulching films,but not correlated with recycling rate of mulching films.( ii) There are significant differences in distribution of residue of mulching films,highest in North Xinjiang and South Xinjiang,followed by East Xinjiang,and the lowest in West Xinjiang.( iii) There are significant differences in distribution of residue of mulching films between different crop fields. Residue of mulching films in cotton field is the key problem of pollution.展开更多
Nine kinds of biodegradable plastic film and one kind of conventional PE film are used to conduct experiment in the field,and study the effect of degradable plastic film on cotton yield. The results show that there is...Nine kinds of biodegradable plastic film and one kind of conventional PE film are used to conduct experiment in the field,and study the effect of degradable plastic film on cotton yield. The results show that there is no difference in cotton yield between Treatment II,III,and ordinary PE film,and other kinds of degradable plastic film significantly reduce yield,with yield reduction of 6. 5%-16. 7%. The yield differences among treatments are mainly affected by the number of plants harvested.展开更多
The advent of laser powder bed fusion(LPBF)has provided an effective solution for fabricating lightweight structures with intricate designs that cannot be realized using other manufacturing methods.Lattice structures,...The advent of laser powder bed fusion(LPBF)has provided an effective solution for fabricating lightweight structures with intricate designs that cannot be realized using other manufacturing methods.Lattice structures,however,which feature unique characteristics,pose greater challenges in the LPBF process than solid structures and exhibit more significant distortion.The underlying mechanisms and influencing factors of this distortion remain unclear,presenting a significant research gap.This study investigates the generation mechanism of residual stress in Ti-6Al-4V lattice structures during LPBF and examines how process and geometric parameters influence residual distortion.Lattice-type cantilever structures with various arm thicknesses and strut diameters were fabricated using different laser powers and scan patterns.The residual distortion after removal from the building substrate was measured using a non-contact coordinate-measuring machine.The results suggest that increasing the arm thickness,reducing the strut diameter,and employing a scanning pattern with interlayer rotation effectively reduce residual distortion.Among these factors,the scanning pattern had the most distinct impact,differing significantly from those affecting solid structures.P2(45°)scanning pattern resulted in the greatest residual distortion,approximately twice that of the least distorted pattern.Meanwhile,the laser power exerted a minor influence on the distortion of the lattice structures.These findings provide insights and guidance for fabricating lattice structures using the LPBF process,broadening its applications in aerospace,automotive,and other weight-sensitive industries.展开更多
The purpose of this work is to develop a new analysis model for angular-contact,ball-bearing systems on the basis of plate theory instead of commonly known approaches that utilize spring elements.Axial and radial stif...The purpose of this work is to develop a new analysis model for angular-contact,ball-bearing systems on the basis of plate theory instead of commonly known approaches that utilize spring elements.Axial and radial stiffness on an annular plate are developed based on plate,Timoshenko beam,and plasticity theories.The model is developed using theoretical and inductive methods and validated through a numerical simulation with the finite element method.The new analysis model is suitable for static and modal analyses of rotor-bearing systems.Numerical examples are presented to reveal the effectiveness and applicability of the proposed approach.展开更多
基金supported by National Key Research and Development Program of China(Grant No.2021YFB1715400)National Natural Science Foundation of China(Grant No.52225503)+3 种基金Key Research and Development Program of Jiangsu Province(Grant Nos.BE2022069,BE2022069-1)Fundamental Research Funds for the Central Universities(Grant No.NI2024003)National Natural Science Foundation of China for Creative Research Groups(Grant No.51921003)the 15th Batch of“Six Talents Peaks”Innovative Talents Team Program(Grant No.TD-GDZB-001).
文摘After millions of years of natural evolution,horsetails have evolved unique stem structures that enable survival in harsh environments.Inspired by the cross-sectional characteristics of horsetail stems,a series of bioinspired sandwich structures were designed and fabricated using the laser powder bed fusion(LPBF)process.By combining experimental and finite element simulation methods,the formability,mechanical properties,deformation behavior,and thermal conduction performance of these structures were determined.Results show that the surface morphology of the bioinspired sandwich structures was smooth,with no cracks observed.The bioinspired sandwich structure with an inner tube diameter of 1.9 mm(D_(1.9))exhibited optimal comprehensive mechanical properties,with a specific strength of 64.2 MPa/(g/cm^(3)),and specific energy absorption of 3.3 J/g.Stress distribution results revealed that the D_(1.9)structures had the most uniform stress distribution.Furthermore,increasing the internal conduction paths improved heat transfer;therefore,the thermal conductivities of the D_(1.4),D_(1.9),and D_(2.4)structures were higher than that of the D0 structure.This study demonstrates that a bioinspired design approach,combined with additive manufacturing technology,enables the development of high-performance structures with both load-bearing and thermally insulating capabilities.
基金We acknowledge the support of the National Natural Science Foundation of China(NSFC)under Grant Nos.51904202 and 11702238Stephane Bordas thanks the financial support of Intuitive modeling and SIMulation platform(IntuiSIM)(PoC17/12253887)grant by Luxembourg National Research Fund.
文摘This paper proposes a novel optimization framework in passive control techniques to reduce noise pollution.The geometries of the structures are represented by Catmull-Clark subdivision surfaces,which are able to build gap-free Computer-Aided Design models and meanwhile tackle the extraordinary points that are commonly encountered in geometricmodelling.The acoustic fields are simulated using the isogeometric boundary elementmethod,and a density-based topology optimization is conducted to optimize distribution of sound-absorbing materials adhered to structural surfaces.The approach enables one to perform acoustic optimization from Computer-Aided Design models directly without needingmeshing and volume parameterization,thereby avoiding the geometric errors and time-consuming preprocessing steps in conventional simulation and optimization methods.The effectiveness of the present method is demonstrated by three dimensional numerical examples.
文摘In order to study current situation of application,recycling and residue pollution of mulching films in Xinjiang,and accurately grasp pollution degree of residue of mulching films,this paper made an empirical analysis on residue of mulching films in 31 typical counties and cities in Xinjiang. Results indicate that( i) use of mulching films in Xinjiang is wide and there is great difference in use and residue recycling between cities and counties. Planting area and planting structure jointly influence use of mulching films,and the use of mulching films is significantly correlated with recycling of mulching films,but not correlated with recycling rate of mulching films.( ii) There are significant differences in distribution of residue of mulching films,highest in North Xinjiang and South Xinjiang,followed by East Xinjiang,and the lowest in West Xinjiang.( iii) There are significant differences in distribution of residue of mulching films between different crop fields. Residue of mulching films in cotton field is the key problem of pollution.
文摘Nine kinds of biodegradable plastic film and one kind of conventional PE film are used to conduct experiment in the field,and study the effect of degradable plastic film on cotton yield. The results show that there is no difference in cotton yield between Treatment II,III,and ordinary PE film,and other kinds of degradable plastic film significantly reduce yield,with yield reduction of 6. 5%-16. 7%. The yield differences among treatments are mainly affected by the number of plants harvested.
基金supported by National Key Research and Development Program of China(Grant No.2021YFB1715400)National Natural Science Foundation of China(Grant No.52105261)High-level Special Funds at the Southern University of Science and Technology(Grant No.G03034K003).
文摘The advent of laser powder bed fusion(LPBF)has provided an effective solution for fabricating lightweight structures with intricate designs that cannot be realized using other manufacturing methods.Lattice structures,however,which feature unique characteristics,pose greater challenges in the LPBF process than solid structures and exhibit more significant distortion.The underlying mechanisms and influencing factors of this distortion remain unclear,presenting a significant research gap.This study investigates the generation mechanism of residual stress in Ti-6Al-4V lattice structures during LPBF and examines how process and geometric parameters influence residual distortion.Lattice-type cantilever structures with various arm thicknesses and strut diameters were fabricated using different laser powers and scan patterns.The residual distortion after removal from the building substrate was measured using a non-contact coordinate-measuring machine.The results suggest that increasing the arm thickness,reducing the strut diameter,and employing a scanning pattern with interlayer rotation effectively reduce residual distortion.Among these factors,the scanning pattern had the most distinct impact,differing significantly from those affecting solid structures.P2(45°)scanning pattern resulted in the greatest residual distortion,approximately twice that of the least distorted pattern.Meanwhile,the laser power exerted a minor influence on the distortion of the lattice structures.These findings provide insights and guidance for fabricating lattice structures using the LPBF process,broadening its applications in aerospace,automotive,and other weight-sensitive industries.
基金The authors would like to thank Professor Hongguang Li of Shanghai Jiao Tong University for his valuable comments on this paper.The authors are grateful for the support of the National Natural Science Foundation of China(Grant Nos.U1637206 and 51705311)the SAST Project(Grant No.SAST2017-079)the State Key Laboratory of Mechanical System and Vibration of Shanghai Jiao Tong University(Grant No.MSVZD201709).
文摘The purpose of this work is to develop a new analysis model for angular-contact,ball-bearing systems on the basis of plate theory instead of commonly known approaches that utilize spring elements.Axial and radial stiffness on an annular plate are developed based on plate,Timoshenko beam,and plasticity theories.The model is developed using theoretical and inductive methods and validated through a numerical simulation with the finite element method.The new analysis model is suitable for static and modal analyses of rotor-bearing systems.Numerical examples are presented to reveal the effectiveness and applicability of the proposed approach.
