The present investigation introduces a composite frequency selective Rasorber(CFSR)that demonstrates a wide−1 dB transmission band,two high absorption bands with absorptivity higher than 90%,and large oblique incidenc...The present investigation introduces a composite frequency selective Rasorber(CFSR)that demonstrates a wide−1 dB transmission band,two high absorption bands with absorptivity higher than 90%,and large oblique incidence angles up to 60°.The CFSR consists of four functional layers separated by three dielectric slabs,which includes lossless metasurface-Ⅰ(MS-Ⅰ),loss metasurface-Ⅱ(MS-Ⅱ),loss metasurface-Ⅲ(MS-Ⅲ),and a three-dimensional metastructure(3D-MS).MS-Ⅰfunctions as a reflector for two absorption bands with a minimal insertion loss transmission window.MS-Ⅱis designed for high-frequency absorption.MS-Ⅲserves as a low-frequency absorption layer for CFSR and an impedance matching layer for MS-Ⅱ.The design methodologies for the transmission window in MS-III and the introduction of 3D-MS are key to achieving high-performance CFSR.The physical mechanisms of CFSR are explained through equivalent circuit model(ECM)analysis and impedance characterization.Finally,measurement results confirm that the proposed CFSR exhibits a−1 dB transmission band ranging from 8.79 to 10.41 GHz with a minimum insertion loss of 0.44 dB at 9.59 GHz;furthermore,the frequency range where reflection coefficient remains below−10 dB is measured to be between 3.33 and 18.00 GHz,aligning well with simulation outcomes.展开更多
Traditional linear vibration isolators struggle to combine high load-bearing capacity with low-frequency vibration isolation, whereas nonlinear metastructure isolators can effectively fulfill both functions. This pape...Traditional linear vibration isolators struggle to combine high load-bearing capacity with low-frequency vibration isolation, whereas nonlinear metastructure isolators can effectively fulfill both functions. This paper draws inspiration from the Quasi-Zero Stiffness (QZS) characteristics resulting from the buckling deformation of beams, and proposes a gear-based QZS structure by arranging beams in a circular array. We investigated the static mechanical behavior under different structural parameters, loading angles, and gear combinations through experiments and simulations, and demonstrated the mechanical performances could be effectively programmed. Subsequent vibration isolation tests on the double gears prove superior vibration isolation performance at low frequency while maintaining high load-bearing capacities. Additionally, a key contribution of our work is the development of a mathematical model to characterize the buckling behavior of the unit beam within the gear structure, with its accuracy validated through finite element analysis and experimental results. The gear’s modulus, number of teeth, and pressure angle are selected according to standard series, allowing the gear can be seamlessly integrated into existing mechanical systems in critical fields such as aerospace, military, and etc.展开更多
Multifunctional metastructure integrated broadband microwave absorption and effective mechanical resistance has attracted much attention.However,multifunctional performance is limited by the lack of theoretical approa...Multifunctional metastructure integrated broadband microwave absorption and effective mechanical resistance has attracted much attention.However,multifunctional performance is limited by the lack of theoretical approaches to integrated design.Herein,a multi-layer impedance gradient honeycomb(MIGH)was designed through theoretical analysis and simulation calculation,and fabricated using 3D printing technique.A theoretical calculation strategy for impedance gradient structure was established based on the electromagnetic parameter equivalent method and the multi-layer finite iterative method.The impedance of MIGH was analyzed by the theoretical calculation strategy to resolve the broadband absorption.Intrinsic loss mechanism of matrix materials and distributions of electric fields,magnetic fields and power loss were analyzed to investigate the absorption mechanism.Experimental results indicated that a 15 mm thick designed metastructure can achieve the absorption more than 88.9%in the frequency range of 2-18 GHz.Moreover,equivalent mechanical parameters of MIGH was calculated by integral method according to the Y-shaped model.Finite Element analysis of stress distributions were carried out to predict the deformation behavior.Mechanical tests demonstrate that MIGH achieved the compression modulus of 22.89 MPa and flexure modulus of 17.05 MPa.The integration of broadband electromagnetic absorption and effective mechanical resistance was achieved by the proposed design principle and fabrication methodology.展开更多
Traditional vibration isolation structures cannot work effectively for low-frequency vibration under heavy loads,due to the inherent contradiction between the high-static and lowdynamic stiffness of these structures.A...Traditional vibration isolation structures cannot work effectively for low-frequency vibration under heavy loads,due to the inherent contradiction between the high-static and lowdynamic stiffness of these structures.Although the challenge can be effectively addressed by introducing a negative stiffness mechanism,the existing structures inevitably have complex configurations.Metastructures,a class of man-made structures with both extraordinary mechanical properties and simple configurations,provide a new insight for low-frequency vibration isolation technology.In this paper,circular metastructure isolators consisting of some simple beams are designed for low-frequency vibration,including a single-layer isolator and a double-layer isolator,and their static and dynamic characteristics are studied,respectively.For the static characteristic,the force–displacement and stiffness–displacement curves are obtained by finite element simulation;for the dynamic characteristic,the vibration transmissibility curves are obtained analytically and numerically.The result shows that the circular nonlinear single-layer isolator has excellent lowfrequency isolation performance,and the isolation frequency band will decrease about 20 Hz when the isolated mass is fixed at 1.535 kg,compared with a similar circular linear isolator.These static and dynamic properties are well verified through experiments.Our work provides an innovative approach for the low-frequency vibration isolation and has wide potential applications in aeronautics.展开更多
A metamaterial vibration isolator,termed as wave-insulating isolator,is proposed,which preserves enough load-bearing capability and offers ultra-low and broad bandgaps for greatly enhanced wave insulation.It consists ...A metamaterial vibration isolator,termed as wave-insulating isolator,is proposed,which preserves enough load-bearing capability and offers ultra-low and broad bandgaps for greatly enhanced wave insulation.It consists of plate-shaped metacells,whose symmetric and antisymmetric local resonant modes offer several low and broad mode bandgaps although the complete bandgap remains high and narrow.The bandgap mechanisms,vibration isolation properties,effects of key parameters,and robustness to complex conditions are clarified.As experimentally demonstrated,the wave-insulating isolator can improve the vibration insulation in the ranges of[50 Hz,180 Hz]and[260 Hz,400 Hz]by 15 dB and 25 dB,respectively,in contrast to the conventional isolator with the same first resonant frequency.展开更多
Combining periodic layered structure with three-dimensional cylindrical local resonators,a hybrid metastructure with improved wave isolation ability was designed and investigated through theoretical and numerical appr...Combining periodic layered structure with three-dimensional cylindrical local resonators,a hybrid metastructure with improved wave isolation ability was designed and investigated through theoretical and numerical approaches.The metastructure is composed of periodic rubber layers and concrete layers embedded with three-dimensional resonators,which can be freely designed with multi local resonant frequencies to attenuate vibrations at required frequencies and widen the attenuation bandgap.The metastructure can also effectively attenuate seismic responses.Compared with layered rubber-based structures,the metastructure has more excellent wave attenuation effects with greater attenuation and wider bandgap.展开更多
Metastructures with unique mechanical properties have shown attractive potential application in vibration and noise reduction.Typically,most of the metastructures deal with the vibration bandgap properties of infinite...Metastructures with unique mechanical properties have shown attractive potential application in vibration and noise reduction.Typically,most of the metastructures deal with the vibration bandgap properties of infinite structures without considering specific boundary condition and dynamic behaviors,which cannot be directly applied to the engineering structures.In this research,we design a Stiffened Plate-type Metastructure(SPM)composed of a plate with periodic stiffeners and cantilever beam-type resonators subjected to general boundary conditions for low-frequency vibration suppression.The effects of boundary conditions and the number and orientation of the stiffeners on Locally Resonant(LR)type bandgap properties in SPM are further investigated.An analytical modeling framework is developed to predict the bandgap formations and vibration behaviors of SPMs in finite-size configuration.The governing equations of the SPM reinforced by various arrangements of stiffeners are derived based on the first-order shear deformation theory and Hamilton’s principle,and a Fourier series combined with auxiliary functions is employed to satisfy the arbitrary boundary conditions.Finite element analysis and experimental investigations of vibration behaviors for the SPM are carried out to validate the accuracy and reliability of the present analytical model.For practical designs of the SPMs with specific boundary conditions,it is found that there exist optimal numbers of stiffeners and resonators which can produce the significant LR-type bandgap behaviors.Furthermore,various arrangements of stiffeners and resonators are explored for different boundary conditions by breaking the requirement of spatially periodicity.It is shown that for the designed SPM,the vibration modes of its host structure should be considered to widen the frequency range in which the resonators transfer and store energy,and hence improve the performance of low-frequency vibration suppression.The present work can provide a significant theoretical guidance for the engineering application of metamaterial stiffened structures。展开更多
Auxetic metastructures have attracted tremendous attention because of their robust multifunctional properties and promising potential industrial applications.This paper studies the in-plane mechanical behaviors of a c...Auxetic metastructures have attracted tremendous attention because of their robust multifunctional properties and promising potential industrial applications.This paper studies the in-plane mechanical behaviors of a chiral S-shaped metastructure subjected to tensile loading in both X-direction and Y-direction and wave propagation properties using the finite element(FE)method.The relationships between structural parameters and elastic behaviors are also discussed.The results indicate that the orientation of chiral S-shaped metastructure under tensile loading in the X-direction exhibits higher auxeticity and stiffness.Then,the band structures and the edge modes of each band gap of the chiral S-shaped metastructure are explored,and the relations between band gap properties and structural parameters are also systematically analyzed.Moreover,we explore the wave mitigation of the chiral S-shaped metastructures by regulating the structural parameters.Finally,the transmission properties of the finite chiral S-shaped periodic metastructures are studied to confirm the results of band gap simulation.This study promotes the engineering application of vibration isolation of chiral structures based on the band gap theory.展开更多
In this communication,we design and analyse Sundoli,a necrobot(a bionically engineered robot using decreased animal parts).Sundoli is manufactured using a crow endoskeleton,supported and rearticulated by a geared mech...In this communication,we design and analyse Sundoli,a necrobot(a bionically engineered robot using decreased animal parts).Sundoli is manufactured using a crow endoskeleton,supported and rearticulated by a geared mechanical metastructure to enable controllable passive deformation.The metastructures and bone braces are designed to affix the femur bone to the tibiotarsus,whilst still permitting kinematic movement between the tibiotarsus and the tarsometatarsus of the crow skeleton.The rearticulated hips function as a fulcrum between the upper and lower body parts,whilst concurrently enabling sagittal rotation of the crow skeleton about the hips.Static compression tests,finite element analyses,and in-situ tests conducted using Sundoli show that the deformation behaviours of metastructures with and without supports are acutely sensitive to the angle of the tarsometatarsus relative to both the ground and the loading direction,highlighting the importance of designing the metastructure holistically and with consideration of the entire skeletal structure.At different loads and angles,the metastructures exhibit variable stiffnesses over their full deformational ranges,demonstrating their effectiveness in protecting the brittle biological bones.Using a metastructure as a mechanism for passive joint rearticulation enables Sundoli to support a payload 8.7 times its body weight without lateral support(an 870%payload ratio)and 14 times its body weight with lateral support(a 1400%payload ratio).This payload capacity is achievable throughout the full range of its upper body movement in the sagittal plane.展开更多
Sonodynamic therapy(SDT)has attracted widespread attention in treatment of implant-associated infections,one of the key factors leading to implant failure.Nevertheless,constructing efficient ultrasound-triggered coati...Sonodynamic therapy(SDT)has attracted widespread attention in treatment of implant-associated infections,one of the key factors leading to implant failure.Nevertheless,constructing efficient ultrasound-triggered coatings on implant surfaces remains a challenge.Herein,an acoustic metastructure Cu-doped defective tita-nium oxide coating(Cu-TiO_(x))with lattice strain was constructed in situ on titanium implant to realize effective sonocatalysis.The redistribution of Cu atoms broke the pristine lattice of TiO_(2)during the thermal reduction treatment to regulate its energy structure,which favored separation of electron-hole pairs generated by ultra-sound radiation to enhance the sonocatalytic generation of reactive oxygen species.In addition,the acoustic metastructure enhanced the absorption of ultrasound by Cu-TiO_(x)metastructure coating,which further promoted its sonocatalytic effect.Thus,Cu-TiO_(x)metastructure coating could efficiently eliminate Staphylococcus aureus and Escherichia coli infections under ultrasonic irradiation in 10 min.Besides,the osteogenic property of implant was significantly improved after infection clearance in vivo.This work provides a fresh perspective on the design of SDT biosurfaces based on metastructure and strain-defect engineering.展开更多
In this study,we fabricated multifunctional metastructures from carbon fiber-reinforced plastic composites using additive manufacturing technology.These metastructures are characterized by their lightweight,load-beari...In this study,we fabricated multifunctional metastructures from carbon fiber-reinforced plastic composites using additive manufacturing technology.These metastructures are characterized by their lightweight,load-bearing capacity,and broadband low-frequency sound absorption properties.The metastructure consists of 36 unit cells,and non-local coupling mechanism was considered for designing the sound absorption performance.We developed an acoustic impedance theory tailored for the metastructure,facilitating an analysis of thermal and viscous dissipation mechanisms.It is proven theoretically and experimentally that the proposed composite metastructure can achieve a noise reduction with an average sound absorption coefficient greater than 0.9 across frequencies in the rage of 330-1500 Hz.We also studied the metastructure’s quasi-static and cyclic compression performance,confirming its efficient absorption capabilities after cyclic compression.The proposed design and additive manufacturing method for composite metastructures provides a novel pathway for creating lightweight,multifunctional structures with diverse applications,such as aerospace engineering.展开更多
Three-dimensional(3D)printing allows for the construction of complex structures.However,3D-printing vertical structures with a high aspect ratio remains a pending challenge,especially when a high lateral resolution is...Three-dimensional(3D)printing allows for the construction of complex structures.However,3D-printing vertical structures with a high aspect ratio remains a pending challenge,especially when a high lateral resolution is required.Here,to address this challenge,we propose and demonstrate micro-3D sculptured metastructures with deep trenches of 1:4(width:height)aspect ratio for sub-10µm resolution.Our construction relies on two-photon polymerization for a 3D-pattern with its trenches,followed by electroplating of a thick metal film and its dry etching to remove the seed layer.To test the proposed fabrication process,we built up three-dimensional RF metastructures showcasing the depth effect as the third dimension.Using the numerical solutions,we custom-tailored these metastructure resonators to fall within a specific resonance frequency range of 4-6 GHz while undertaking comparative analyses regarding overall footprint,quality factor,and resonance frequency shift as a function of their cross-sectional aspect ratio.The proposed process flow is shown to miniaturize metal footprint and tune the resonance frequency of these thick 3Dmetastructures while increasing their quality factor.These experimental findings indicate that this method of producing trenches via 3D-printing provides rich opportunities to implement high-aspect-ratio,complex structures.展开更多
Sic-based composites are widely used as electromagnetic wave absorbers due to their excellent dielectric properties.However,the constraints associated with structural design and the intricacies of the preparation proc...Sic-based composites are widely used as electromagnetic wave absorbers due to their excellent dielectric properties.However,the constraints associated with structural design and the intricacies of the preparation process hinder their broader application.In this study,novel mullite anti-gyroid/SiC gyroid metastructures are designed to integrate the mechanical and electromagnetic wave(EMW)absorption properties of composite materials.Mullite anti-gyroid/SiC gyroid composites are fabricated utilizing a combination of digital light processing(DLP)three-dimensional(3D)printing and precursor infiltration and pyrolysis(PiP)processes.Through the modulation of structural units,the electromagnetic parameters can be effectively regulated,thus improving the impedance matching characteristics of the composites.The structural composites show outstanding EMW absorption properties,with a minimum reflection loss of-54 dB at a thickness of 1.9 mm and an effective absorption bandwidth of 3.20 GHz at a thickness of 2.2 mm.Furthermore,the PIP process significantly enhances the mechanical properties of the composites;compared with those of the mullite/SiC ceramics,the flexural strength of the composites is improved by 3.69-5.85 times(13.28±1.15 MPa vs.(49.05±1.07)-(77.78±3.72)MPa),and the compressive strength is improved by 4.59-13.58 times(8.55±0.90 MPa vs.(39.02±1.63)-(116.13±2.58)MPa).This approach offers a novel and effective method for fabricating structural composites with an expanded range of higher electromagnetic wave absorption properties and improved mechanical properties.展开更多
Seismic metastructures are able to effectively attenuate or convert elastic surface waves,attracting increasing attention in different areas such as civil engineering.However,the effects of the source depth and layere...Seismic metastructures are able to effectively attenuate or convert elastic surface waves,attracting increasing attention in different areas such as civil engineering.However,the effects of the source depth and layered characteristics of viscous soil on metastructures for elastic surface wave reduction with Bragg bandgap mechanism remain challenging,which are the key issues for practical applications.In this work,we calculate the dispersion and transmission of metastructures in layered soil and confirm that the metastructures can effectively attenuate the elastic surface waves within the bandgaps.Then,the influence of the embedded depth of the metastructures,the depth of the vibrating source,layered characteristics of viscous soil on the surface vibration reduction are further discussed.It is found that surface vibration attenuation is enhanced by increasing the embedded depth of the metastructures and the density of the first layer.The width of the bandgap increases with the introduction of soil viscosity.On the contrary,the surface vibration attenuation decreases if the vibrating source is placed at a certain depth which requires the bandgap of bulk waves of the metastructures.This study of the seismic metastructures in layered soil provides a guidance in surface vibration reduction in practice.展开更多
Microwave absorbers(MAs)with broadband and strong microwave absorption capacities are urgently required to meet the demands of complex electromagnetic(EM)environments.Herein,a novel labyrinth multiresonant metastructu...Microwave absorbers(MAs)with broadband and strong microwave absorption capacities are urgently required to meet the demands of complex electromagnetic(EM)environments.Herein,a novel labyrinth multiresonant metastructure composed of a polyether-ether-ketone/flaky carbonyl iron(PEEK/CIP)magnetic composite was proposed and fabricated via 3D printing technology.A complex multiresonant cavity design was introduced,and the resonant loss area was significantly improved.Both broadband and high-efficiency microwave absorption performances were achieved.The multilayer labyrinth multiresonant metastructure was designed with gradient impedance.The effects of structural parameters on the absorbing properties were investigated and optimized.Experiments and simulations demonstrated the effectiveness of the design strategy.The designed metastructure with a 10 mm thickness exhibited a-10 dB absorption bandwidth at a frequency of 3.78–40 GHz and an absorption bandwidth below-15 dB at 7.5–36.5 GHz.Moreover,an excellent wide-angle absorption performance was observed for different polarization states,including transverse electric(TE)and transverse magnetic(TM)modes.The combination of a complex multiresonant metastructure design and 3D printing fabrication provides a facile route to considerably extend the absorption bandwidth and strength of electromagnetic absorbers.This work is expected to provide a promising strategy for further enhancing microwave absorption performance,and the designed metastructure possesses great application potential in stealth and electromagnetic compatibility technologies.展开更多
The narrow attenuation bands of traditional marine structures have long been a challenge in mitigating water waves.In this paper,a metastructure(MS)composed of floating periodic pontoons is proposed for broadband wate...The narrow attenuation bands of traditional marine structures have long been a challenge in mitigating water waves.In this paper,a metastructure(MS)composed of floating periodic pontoons is proposed for broadband water wave attenuation.The interaction of surface gravity waves with the MS is investigated using linear wave theory.The potential solutions of water waves by the MS with a finite array are developed by using the eigenfunction expansion matching method(EEMM),and the band structure of the MS is calculated by the transfer matrix method(TMM),in which the evanescent modes of waves are considered.The solution is verified against the existing numerical result for a special case.Based on the present solution,the association between Bragg resonance reflection and Bloch bandgaps is examined,the effects of pontoon geometry are analyzed,and the comparison between floating MS and bottom-mounted periodic structures is conducted.A computational fluid dynamics(CFD)model is further developed to assess the structures in practical fluid environments,and the floating MS presents excellent wave attenuation performance.The study presented here may provide a promising solution for protecting the coast and offshore structures.展开更多
Recent research activities in elastic metamaterials demonstrate a significant potential for subwavelength wave propagation control owing to their interior locally resonant mechanism. The growing technological developm...Recent research activities in elastic metamaterials demonstrate a significant potential for subwavelength wave propagation control owing to their interior locally resonant mechanism. The growing technological developments in electro/magnetomechanical couplings of smart materials have introduced a controlling degree of freedom for passive elastic metamaterials. Active elastic metamaterials could allow for a fine control of material physical behavior and thereby induce new functional properties that cannot be produced by passive approaches. In this paper, two types of active elastic metamaterials with shunted piezoelectric materials and electrorheological elastomers are proposed. Theoretical analyses and numerical validations of the active elastic metamaterials with detailed microstructures are pre- sented for designing adaptive applications in band gap structures and extraordinary waveguides. The active elastic metamaterial could provide a new design methodology for adaptive wave filters, high signal-to-noise sensors, and structural health monitoring applications.展开更多
Graph convolutional networks(GCNs)have been developed as a general and powerful tool to handle various tasks related to graph data.However,current methods mainly consider homogeneous networks and ignore the rich seman...Graph convolutional networks(GCNs)have been developed as a general and powerful tool to handle various tasks related to graph data.However,current methods mainly consider homogeneous networks and ignore the rich semantics and multiple types of objects that are common in heterogeneous information networks(HINs).In this paper,we present a Heterogeneous Hyperedge Convolutional Network(HHCN),a novel graph convolutional network architecture that operates on HINs.Specifically,we extract the rich semantics by different metastructures and adopt hyperedge to model the interactions among metastructure-based neighbors.Due to the powerful information extraction capabilities of metastructure and hyperedge,HHCN has the flexibility to model the complex relationships in HINs by setting different combinations of metastructures and hyperedges.Moreover,a metastructure attention layer is also designed to allow each node to select the metastructures based on their importance and provide potential interpretability for graph analysis.As a result,HHCN can encode node features,metastructure-based semantics and hyperedge information simultaneously by aggregating features from metastructure-based neighbors in a hierarchical manner.We evaluate HHCN by applying it to the semi-supervised node classification task.Experimental results show that HHCN outperforms state-of-the-art graph embedding models and recently proposed graph convolutional network models.展开更多
基金Project(2021RC3003) supported by the Hunan Science and Technology Innovation Talents Program,China。
文摘The present investigation introduces a composite frequency selective Rasorber(CFSR)that demonstrates a wide−1 dB transmission band,two high absorption bands with absorptivity higher than 90%,and large oblique incidence angles up to 60°.The CFSR consists of four functional layers separated by three dielectric slabs,which includes lossless metasurface-Ⅰ(MS-Ⅰ),loss metasurface-Ⅱ(MS-Ⅱ),loss metasurface-Ⅲ(MS-Ⅲ),and a three-dimensional metastructure(3D-MS).MS-Ⅰfunctions as a reflector for two absorption bands with a minimal insertion loss transmission window.MS-Ⅱis designed for high-frequency absorption.MS-Ⅲserves as a low-frequency absorption layer for CFSR and an impedance matching layer for MS-Ⅱ.The design methodologies for the transmission window in MS-III and the introduction of 3D-MS are key to achieving high-performance CFSR.The physical mechanisms of CFSR are explained through equivalent circuit model(ECM)analysis and impedance characterization.Finally,measurement results confirm that the proposed CFSR exhibits a−1 dB transmission band ranging from 8.79 to 10.41 GHz with a minimum insertion loss of 0.44 dB at 9.59 GHz;furthermore,the frequency range where reflection coefficient remains below−10 dB is measured to be between 3.33 and 18.00 GHz,aligning well with simulation outcomes.
基金supported in part by National Key R&D Program of China under Grant 2024YFB4708600National Natural Science Foundation of China under Grant 52305304+3 种基金Jilin Youth Growth Technology Project under Grant 20230508147RCthe Science and Technology Research Project of Jilin Provincial Education Department(No.JJKH20231193KJ)supported in part by the National Natural Science Foundation of China under Grant 52021003 and Grant 52205565in part by the Natural Science Foundation of Jilin Province under Grant 20210101053JC.
文摘Traditional linear vibration isolators struggle to combine high load-bearing capacity with low-frequency vibration isolation, whereas nonlinear metastructure isolators can effectively fulfill both functions. This paper draws inspiration from the Quasi-Zero Stiffness (QZS) characteristics resulting from the buckling deformation of beams, and proposes a gear-based QZS structure by arranging beams in a circular array. We investigated the static mechanical behavior under different structural parameters, loading angles, and gear combinations through experiments and simulations, and demonstrated the mechanical performances could be effectively programmed. Subsequent vibration isolation tests on the double gears prove superior vibration isolation performance at low frequency while maintaining high load-bearing capacities. Additionally, a key contribution of our work is the development of a mathematical model to characterize the buckling behavior of the unit beam within the gear structure, with its accuracy validated through finite element analysis and experimental results. The gear’s modulus, number of teeth, and pressure angle are selected according to standard series, allowing the gear can be seamlessly integrated into existing mechanical systems in critical fields such as aerospace, military, and etc.
基金supported by the National Natural Science Foundation of China(Grant No.62201352)。
文摘Multifunctional metastructure integrated broadband microwave absorption and effective mechanical resistance has attracted much attention.However,multifunctional performance is limited by the lack of theoretical approaches to integrated design.Herein,a multi-layer impedance gradient honeycomb(MIGH)was designed through theoretical analysis and simulation calculation,and fabricated using 3D printing technique.A theoretical calculation strategy for impedance gradient structure was established based on the electromagnetic parameter equivalent method and the multi-layer finite iterative method.The impedance of MIGH was analyzed by the theoretical calculation strategy to resolve the broadband absorption.Intrinsic loss mechanism of matrix materials and distributions of electric fields,magnetic fields and power loss were analyzed to investigate the absorption mechanism.Experimental results indicated that a 15 mm thick designed metastructure can achieve the absorption more than 88.9%in the frequency range of 2-18 GHz.Moreover,equivalent mechanical parameters of MIGH was calculated by integral method according to the Y-shaped model.Finite Element analysis of stress distributions were carried out to predict the deformation behavior.Mechanical tests demonstrate that MIGH achieved the compression modulus of 22.89 MPa and flexure modulus of 17.05 MPa.The integration of broadband electromagnetic absorption and effective mechanical resistance was achieved by the proposed design principle and fabrication methodology.
基金Supported by Innovation Foundation for Doctor Dissertation of Northwestern Polytechnical University,China(No.CX2024001)National Natural Science Foundation of China(Nos.11972296,12372157)+1 种基金Aeronautical Science Foundation of China(No.20220057053001)Open Project of State Key Laboratory for Strength and Vibration of Mechanical Structures of Xi’an Jiaotong University,China(No.SV2023-KF-19).
文摘Traditional vibration isolation structures cannot work effectively for low-frequency vibration under heavy loads,due to the inherent contradiction between the high-static and lowdynamic stiffness of these structures.Although the challenge can be effectively addressed by introducing a negative stiffness mechanism,the existing structures inevitably have complex configurations.Metastructures,a class of man-made structures with both extraordinary mechanical properties and simple configurations,provide a new insight for low-frequency vibration isolation technology.In this paper,circular metastructure isolators consisting of some simple beams are designed for low-frequency vibration,including a single-layer isolator and a double-layer isolator,and their static and dynamic characteristics are studied,respectively.For the static characteristic,the force–displacement and stiffness–displacement curves are obtained by finite element simulation;for the dynamic characteristic,the vibration transmissibility curves are obtained analytically and numerically.The result shows that the circular nonlinear single-layer isolator has excellent lowfrequency isolation performance,and the isolation frequency band will decrease about 20 Hz when the isolated mass is fixed at 1.535 kg,compared with a similar circular linear isolator.These static and dynamic properties are well verified through experiments.Our work provides an innovative approach for the low-frequency vibration isolation and has wide potential applications in aeronautics.
基金supported by the National Natural Science Foundation of China(Nos.52241103 and 52322505)the Natural Science Fund for Distinguished Young Scholars of Hunan Province of China(No.2023JJ10055)。
文摘A metamaterial vibration isolator,termed as wave-insulating isolator,is proposed,which preserves enough load-bearing capability and offers ultra-low and broad bandgaps for greatly enhanced wave insulation.It consists of plate-shaped metacells,whose symmetric and antisymmetric local resonant modes offer several low and broad mode bandgaps although the complete bandgap remains high and narrow.The bandgap mechanisms,vibration isolation properties,effects of key parameters,and robustness to complex conditions are clarified.As experimentally demonstrated,the wave-insulating isolator can improve the vibration insulation in the ranges of[50 Hz,180 Hz]and[260 Hz,400 Hz]by 15 dB and 25 dB,respectively,in contrast to the conventional isolator with the same first resonant frequency.
基金Supports from National Natural Science Foundation of China(Grant Nos.U20A20286 and 11972184)the Systematic Project of Guangxi Key Laboratory of Disaster Prevention and Engineering Safety(Grant No.2021ZDK006)+1 种基金Natural Science Foundation of Jiangsu Province of China(Grant No.BK20201286)Science and Technology Project of Jiangsu Province of China(Grant No.BE2020716)are gratefully acknowledged.
文摘Combining periodic layered structure with three-dimensional cylindrical local resonators,a hybrid metastructure with improved wave isolation ability was designed and investigated through theoretical and numerical approaches.The metastructure is composed of periodic rubber layers and concrete layers embedded with three-dimensional resonators,which can be freely designed with multi local resonant frequencies to attenuate vibrations at required frequencies and widen the attenuation bandgap.The metastructure can also effectively attenuate seismic responses.Compared with layered rubber-based structures,the metastructure has more excellent wave attenuation effects with greater attenuation and wider bandgap.
基金the National Natural Science Foundation of China(Nos.12102353,11972296 and 12072276)the 111 Project,China(No.BP0719007)the support from Innovation Foundation for Doctor Dissertation of Northwestern Polytechnical University,China(No.CX2022021).
文摘Metastructures with unique mechanical properties have shown attractive potential application in vibration and noise reduction.Typically,most of the metastructures deal with the vibration bandgap properties of infinite structures without considering specific boundary condition and dynamic behaviors,which cannot be directly applied to the engineering structures.In this research,we design a Stiffened Plate-type Metastructure(SPM)composed of a plate with periodic stiffeners and cantilever beam-type resonators subjected to general boundary conditions for low-frequency vibration suppression.The effects of boundary conditions and the number and orientation of the stiffeners on Locally Resonant(LR)type bandgap properties in SPM are further investigated.An analytical modeling framework is developed to predict the bandgap formations and vibration behaviors of SPMs in finite-size configuration.The governing equations of the SPM reinforced by various arrangements of stiffeners are derived based on the first-order shear deformation theory and Hamilton’s principle,and a Fourier series combined with auxiliary functions is employed to satisfy the arbitrary boundary conditions.Finite element analysis and experimental investigations of vibration behaviors for the SPM are carried out to validate the accuracy and reliability of the present analytical model.For practical designs of the SPMs with specific boundary conditions,it is found that there exist optimal numbers of stiffeners and resonators which can produce the significant LR-type bandgap behaviors.Furthermore,various arrangements of stiffeners and resonators are explored for different boundary conditions by breaking the requirement of spatially periodicity.It is shown that for the designed SPM,the vibration modes of its host structure should be considered to widen the frequency range in which the resonators transfer and store energy,and hence improve the performance of low-frequency vibration suppression.The present work can provide a significant theoretical guidance for the engineering application of metamaterial stiffened structures。
基金supported by the National Natural Science Foundation of China under the Grant Number of 12072241 and the Fundamental Research Funds for the Central Universities under the Grant Number of 2042022kf0009.
文摘Auxetic metastructures have attracted tremendous attention because of their robust multifunctional properties and promising potential industrial applications.This paper studies the in-plane mechanical behaviors of a chiral S-shaped metastructure subjected to tensile loading in both X-direction and Y-direction and wave propagation properties using the finite element(FE)method.The relationships between structural parameters and elastic behaviors are also discussed.The results indicate that the orientation of chiral S-shaped metastructure under tensile loading in the X-direction exhibits higher auxeticity and stiffness.Then,the band structures and the edge modes of each band gap of the chiral S-shaped metastructure are explored,and the relations between band gap properties and structural parameters are also systematically analyzed.Moreover,we explore the wave mitigation of the chiral S-shaped metastructures by regulating the structural parameters.Finally,the transmission properties of the finite chiral S-shaped periodic metastructures are studied to confirm the results of band gap simulation.This study promotes the engineering application of vibration isolation of chiral structures based on the band gap theory.
文摘In this communication,we design and analyse Sundoli,a necrobot(a bionically engineered robot using decreased animal parts).Sundoli is manufactured using a crow endoskeleton,supported and rearticulated by a geared mechanical metastructure to enable controllable passive deformation.The metastructures and bone braces are designed to affix the femur bone to the tibiotarsus,whilst still permitting kinematic movement between the tibiotarsus and the tarsometatarsus of the crow skeleton.The rearticulated hips function as a fulcrum between the upper and lower body parts,whilst concurrently enabling sagittal rotation of the crow skeleton about the hips.Static compression tests,finite element analyses,and in-situ tests conducted using Sundoli show that the deformation behaviours of metastructures with and without supports are acutely sensitive to the angle of the tarsometatarsus relative to both the ground and the loading direction,highlighting the importance of designing the metastructure holistically and with consideration of the entire skeletal structure.At different loads and angles,the metastructures exhibit variable stiffnesses over their full deformational ranges,demonstrating their effectiveness in protecting the brittle biological bones.Using a metastructure as a mechanism for passive joint rearticulation enables Sundoli to support a payload 8.7 times its body weight without lateral support(an 870%payload ratio)and 14 times its body weight with lateral support(a 1400%payload ratio).This payload capacity is achievable throughout the full range of its upper body movement in the sagittal plane.
基金support from the National Natural Science Foundation of China(52450110)the“Pioneer”and“Leading Goose”R&D Program of Zhejiang(2024C03080)Science and Technology Commission of Shanghai Municipality(24ZR1475600)are acknowledged.
文摘Sonodynamic therapy(SDT)has attracted widespread attention in treatment of implant-associated infections,one of the key factors leading to implant failure.Nevertheless,constructing efficient ultrasound-triggered coatings on implant surfaces remains a challenge.Herein,an acoustic metastructure Cu-doped defective tita-nium oxide coating(Cu-TiO_(x))with lattice strain was constructed in situ on titanium implant to realize effective sonocatalysis.The redistribution of Cu atoms broke the pristine lattice of TiO_(2)during the thermal reduction treatment to regulate its energy structure,which favored separation of electron-hole pairs generated by ultra-sound radiation to enhance the sonocatalytic generation of reactive oxygen species.In addition,the acoustic metastructure enhanced the absorption of ultrasound by Cu-TiO_(x)metastructure coating,which further promoted its sonocatalytic effect.Thus,Cu-TiO_(x)metastructure coating could efficiently eliminate Staphylococcus aureus and Escherichia coli infections under ultrasonic irradiation in 10 min.Besides,the osteogenic property of implant was significantly improved after infection clearance in vivo.This work provides a fresh perspective on the design of SDT biosurfaces based on metastructure and strain-defect engineering.
基金supported by the National Key R&D Program of China(Grant No.2022YFB4602000)the National Natural Science Foundation of China(Grant No.12272267)+4 种基金the Young Elite Scientists Sponsorship Program by CAST(Grant No.2021QNRC001)Shanghai Science and Technology Committee(Grant Nos.22JC1404100,21JC1405600)the Fundamental Research Funds for the Central Universitiesthe Special Funds of the Tongji University for“Sino-German Cooperation 2.0 Strategy”Shanghai Gaofeng Project for University Academic Program Development.
文摘In this study,we fabricated multifunctional metastructures from carbon fiber-reinforced plastic composites using additive manufacturing technology.These metastructures are characterized by their lightweight,load-bearing capacity,and broadband low-frequency sound absorption properties.The metastructure consists of 36 unit cells,and non-local coupling mechanism was considered for designing the sound absorption performance.We developed an acoustic impedance theory tailored for the metastructure,facilitating an analysis of thermal and viscous dissipation mechanisms.It is proven theoretically and experimentally that the proposed composite metastructure can achieve a noise reduction with an average sound absorption coefficient greater than 0.9 across frequencies in the rage of 330-1500 Hz.We also studied the metastructure’s quasi-static and cyclic compression performance,confirming its efficient absorption capabilities after cyclic compression.The proposed design and additive manufacturing method for composite metastructures provides a novel pathway for creating lightweight,multifunctional structures with diverse applications,such as aerospace engineering.
基金the financial support in part from TUBITAK 20AG001,and 121C266HVD also acknowledges the support from TUBA and TUBITAK 2247-A National Leader Researchers Program(121C266)。
文摘Three-dimensional(3D)printing allows for the construction of complex structures.However,3D-printing vertical structures with a high aspect ratio remains a pending challenge,especially when a high lateral resolution is required.Here,to address this challenge,we propose and demonstrate micro-3D sculptured metastructures with deep trenches of 1:4(width:height)aspect ratio for sub-10µm resolution.Our construction relies on two-photon polymerization for a 3D-pattern with its trenches,followed by electroplating of a thick metal film and its dry etching to remove the seed layer.To test the proposed fabrication process,we built up three-dimensional RF metastructures showcasing the depth effect as the third dimension.Using the numerical solutions,we custom-tailored these metastructure resonators to fall within a specific resonance frequency range of 4-6 GHz while undertaking comparative analyses regarding overall footprint,quality factor,and resonance frequency shift as a function of their cross-sectional aspect ratio.The proposed process flow is shown to miniaturize metal footprint and tune the resonance frequency of these thick 3Dmetastructures while increasing their quality factor.These experimental findings indicate that this method of producing trenches via 3D-printing provides rich opportunities to implement high-aspect-ratio,complex structures.
基金The authors gratefully acknowledged the financial support provided by the National Key R&D Program of China(No.2021YFB3701500)the Program of Shanghai Academic/Technology Research Leader(No.22XD1404000).
文摘Sic-based composites are widely used as electromagnetic wave absorbers due to their excellent dielectric properties.However,the constraints associated with structural design and the intricacies of the preparation process hinder their broader application.In this study,novel mullite anti-gyroid/SiC gyroid metastructures are designed to integrate the mechanical and electromagnetic wave(EMW)absorption properties of composite materials.Mullite anti-gyroid/SiC gyroid composites are fabricated utilizing a combination of digital light processing(DLP)three-dimensional(3D)printing and precursor infiltration and pyrolysis(PiP)processes.Through the modulation of structural units,the electromagnetic parameters can be effectively regulated,thus improving the impedance matching characteristics of the composites.The structural composites show outstanding EMW absorption properties,with a minimum reflection loss of-54 dB at a thickness of 1.9 mm and an effective absorption bandwidth of 3.20 GHz at a thickness of 2.2 mm.Furthermore,the PIP process significantly enhances the mechanical properties of the composites;compared with those of the mullite/SiC ceramics,the flexural strength of the composites is improved by 3.69-5.85 times(13.28±1.15 MPa vs.(49.05±1.07)-(77.78±3.72)MPa),and the compressive strength is improved by 4.59-13.58 times(8.55±0.90 MPa vs.(39.02±1.63)-(116.13±2.58)MPa).This approach offers a novel and effective method for fabricating structural composites with an expanded range of higher electromagnetic wave absorption properties and improved mechanical properties.
基金supported by the National Natural Science Foundation of China(No.12272267,No.52278411)the Young Elite Scientists Sponsorship Program by CAST(2021QNRC001)+1 种基金the Shanghai Science and Technology Commission(Grant No.22JC1404100 and No.21JC1405600)the Fundamental Research Funds for the Central Universities and the Special Funds of the Tongji University for“Sino-German Cooperation 2.0 Strategy”.
文摘Seismic metastructures are able to effectively attenuate or convert elastic surface waves,attracting increasing attention in different areas such as civil engineering.However,the effects of the source depth and layered characteristics of viscous soil on metastructures for elastic surface wave reduction with Bragg bandgap mechanism remain challenging,which are the key issues for practical applications.In this work,we calculate the dispersion and transmission of metastructures in layered soil and confirm that the metastructures can effectively attenuate the elastic surface waves within the bandgaps.Then,the influence of the embedded depth of the metastructures,the depth of the vibrating source,layered characteristics of viscous soil on the surface vibration reduction are further discussed.It is found that surface vibration attenuation is enhanced by increasing the embedded depth of the metastructures and the density of the first layer.The width of the bandgap increases with the introduction of soil viscosity.On the contrary,the surface vibration attenuation decreases if the vibrating source is placed at a certain depth which requires the bandgap of bulk waves of the metastructures.This study of the seismic metastructures in layered soil provides a guidance in surface vibration reduction in practice.
基金supported by the Fundamental Research Funds for the Central Universities (Grant No.xzd012021041)the Analytical&Testing Center of Xi’an Jiaotong University for SEM analysis。
文摘Microwave absorbers(MAs)with broadband and strong microwave absorption capacities are urgently required to meet the demands of complex electromagnetic(EM)environments.Herein,a novel labyrinth multiresonant metastructure composed of a polyether-ether-ketone/flaky carbonyl iron(PEEK/CIP)magnetic composite was proposed and fabricated via 3D printing technology.A complex multiresonant cavity design was introduced,and the resonant loss area was significantly improved.Both broadband and high-efficiency microwave absorption performances were achieved.The multilayer labyrinth multiresonant metastructure was designed with gradient impedance.The effects of structural parameters on the absorbing properties were investigated and optimized.Experiments and simulations demonstrated the effectiveness of the design strategy.The designed metastructure with a 10 mm thickness exhibited a-10 dB absorption bandwidth at a frequency of 3.78–40 GHz and an absorption bandwidth below-15 dB at 7.5–36.5 GHz.Moreover,an excellent wide-angle absorption performance was observed for different polarization states,including transverse electric(TE)and transverse magnetic(TM)modes.The combination of a complex multiresonant metastructure design and 3D printing fabrication provides a facile route to considerably extend the absorption bandwidth and strength of electromagnetic absorbers.This work is expected to provide a promising strategy for further enhancing microwave absorption performance,and the designed metastructure possesses great application potential in stealth and electromagnetic compatibility technologies.
基金Project supported by the National Natural Science Foundation of China(No.12272128)the Natural Science Foundation of Jiangsu Province of China(No.BK20243019)。
文摘The narrow attenuation bands of traditional marine structures have long been a challenge in mitigating water waves.In this paper,a metastructure(MS)composed of floating periodic pontoons is proposed for broadband water wave attenuation.The interaction of surface gravity waves with the MS is investigated using linear wave theory.The potential solutions of water waves by the MS with a finite array are developed by using the eigenfunction expansion matching method(EEMM),and the band structure of the MS is calculated by the transfer matrix method(TMM),in which the evanescent modes of waves are considered.The solution is verified against the existing numerical result for a special case.Based on the present solution,the association between Bragg resonance reflection and Bloch bandgaps is examined,the effects of pontoon geometry are analyzed,and the comparison between floating MS and bottom-mounted periodic structures is conducted.A computational fluid dynamics(CFD)model is further developed to assess the structures in practical fluid environments,and the floating MS presents excellent wave attenuation performance.The study presented here may provide a promising solution for protecting the coast and offshore structures.
基金supported by the Air Force Office of Scientific Research under Grant AF 9550-15-1-0061 with Program Manager Dr. Byung-Lip (Les) Lee
文摘Recent research activities in elastic metamaterials demonstrate a significant potential for subwavelength wave propagation control owing to their interior locally resonant mechanism. The growing technological developments in electro/magnetomechanical couplings of smart materials have introduced a controlling degree of freedom for passive elastic metamaterials. Active elastic metamaterials could allow for a fine control of material physical behavior and thereby induce new functional properties that cannot be produced by passive approaches. In this paper, two types of active elastic metamaterials with shunted piezoelectric materials and electrorheological elastomers are proposed. Theoretical analyses and numerical validations of the active elastic metamaterials with detailed microstructures are pre- sented for designing adaptive applications in band gap structures and extraordinary waveguides. The active elastic metamaterial could provide a new design methodology for adaptive wave filters, high signal-to-noise sensors, and structural health monitoring applications.
基金funded by The Science and Technology Strengthening Police Basic Program of Ministry of Public Security(2018GABJC03)The Technology Research Project Program of Ministry of Public Security(2018JSYJA02).
文摘Graph convolutional networks(GCNs)have been developed as a general and powerful tool to handle various tasks related to graph data.However,current methods mainly consider homogeneous networks and ignore the rich semantics and multiple types of objects that are common in heterogeneous information networks(HINs).In this paper,we present a Heterogeneous Hyperedge Convolutional Network(HHCN),a novel graph convolutional network architecture that operates on HINs.Specifically,we extract the rich semantics by different metastructures and adopt hyperedge to model the interactions among metastructure-based neighbors.Due to the powerful information extraction capabilities of metastructure and hyperedge,HHCN has the flexibility to model the complex relationships in HINs by setting different combinations of metastructures and hyperedges.Moreover,a metastructure attention layer is also designed to allow each node to select the metastructures based on their importance and provide potential interpretability for graph analysis.As a result,HHCN can encode node features,metastructure-based semantics and hyperedge information simultaneously by aggregating features from metastructure-based neighbors in a hierarchical manner.We evaluate HHCN by applying it to the semi-supervised node classification task.Experimental results show that HHCN outperforms state-of-the-art graph embedding models and recently proposed graph convolutional network models.
