Chiral metamaterials have been proven to possess many appealing mechanical phenomena,such as negative Poisson's ratio,high-impact resistance,and energy absorption.This work extends the applications of chiral metam...Chiral metamaterials have been proven to possess many appealing mechanical phenomena,such as negative Poisson's ratio,high-impact resistance,and energy absorption.This work extends the applications of chiral metamaterials to underwater sound insulation.Various chiral metamaterials with low acoustic impedance and proper stiffness are inversely designed using the topology optimization scheme.Low acoustic impedance enables the metamaterials to have a high and broadband sound transmission loss(STL),while proper stiffness guarantees its robust acoustic performance under a hydrostatic pressure.As proof-of-concept demonstrations,two specimens are fabricated and tested in a water-filled impedance tube.Experimental results show that,on average,over 95%incident sound energy can be isolated by the specimens in a broad frequency range from 1 k Hz to 5 k Hz,while the sound insulation performance keeps stable under a certain hydrostatic pressure.This work may provide new insights for chiral metamaterials into the underwater applications with sound insulation.展开更多
Nonlinear elastic metamaterial,a topic which has attracted extensive attention in recent years,can enable broadband vibration reduction under relatively large amplitude.The combination of damping and strong nonlineari...Nonlinear elastic metamaterial,a topic which has attracted extensive attention in recent years,can enable broadband vibration reduction under relatively large amplitude.The combination of damping and strong nonlinearity in metamaterials may entail extraordinary effects and offer the capability for low-frequency and broadband vibration reduction.However,there exists a clear lack of proper design methods as well as the deficiency in understanding properties arising from this concept.To tackle this problem,this paper numerically demonstrates that the nonlinear elastic metamaterials,consisting of sandwich damping layers and collision resonators,can generate very robust hyper-damping effect,conducive to efficient and broadband vibration suppression.The collision-enhanced hyper damping is persistently presented in a large parameter space,ranging from small to large amplitudes,and for small and large damping coefficients.The achieved robust effects greatly enlarge the application scope of nonlinear metamaterials.We report the design concept,properties and mechanisms of the hyper-damping and its effect on vibration transmission.This paper reveals new properties offered by nonlinear elastic metamaterials,and offers a robust method for achieving efficient low-frequency and broadband vibration suppression.展开更多
A periodical composite material pipe is proposed based on the Bragg scattering mechanism of phononic crystals (PCs). The band gap (BG) properties of the flexural wave in this PC pipe under axial load and hydro-pressur...A periodical composite material pipe is proposed based on the Bragg scattering mechanism of phononic crystals (PCs). The band gap (BG) properties of the flexural wave in this PC pipe under axial load and hydro-pressure are calculated using the transfer matrix (TM) method. The frequency response functions (FRFs) of the PC pipe under axial load and hydro-pressure are calculated using the finite element approach, and the mechanism is elucidated to illustrate the phenomenon. The results show that axial load and hydro-pressure and their combination all have a great influence on the flexural vibration proper ties. This research offers theoretical support for research on PC pipes with complex conditions and is of great significance in solving the problem of high pressure.展开更多
基金supported by the National Natural Science Foundation of China(Nos.52171327,11991032,52201386,and 51805537)。
文摘Chiral metamaterials have been proven to possess many appealing mechanical phenomena,such as negative Poisson's ratio,high-impact resistance,and energy absorption.This work extends the applications of chiral metamaterials to underwater sound insulation.Various chiral metamaterials with low acoustic impedance and proper stiffness are inversely designed using the topology optimization scheme.Low acoustic impedance enables the metamaterials to have a high and broadband sound transmission loss(STL),while proper stiffness guarantees its robust acoustic performance under a hydrostatic pressure.As proof-of-concept demonstrations,two specimens are fabricated and tested in a water-filled impedance tube.Experimental results show that,on average,over 95%incident sound energy can be isolated by the specimens in a broad frequency range from 1 k Hz to 5 k Hz,while the sound insulation performance keeps stable under a certain hydrostatic pressure.This work may provide new insights for chiral metamaterials into the underwater applications with sound insulation.
基金supported by the National Natural Science Foundation of China(Grant Nos.11872371,11991032,and 12002371)the Science and Technology Innovation Program of Hunan Province,China(Grant No.2020RC4022)。
文摘Nonlinear elastic metamaterial,a topic which has attracted extensive attention in recent years,can enable broadband vibration reduction under relatively large amplitude.The combination of damping and strong nonlinearity in metamaterials may entail extraordinary effects and offer the capability for low-frequency and broadband vibration reduction.However,there exists a clear lack of proper design methods as well as the deficiency in understanding properties arising from this concept.To tackle this problem,this paper numerically demonstrates that the nonlinear elastic metamaterials,consisting of sandwich damping layers and collision resonators,can generate very robust hyper-damping effect,conducive to efficient and broadband vibration suppression.The collision-enhanced hyper damping is persistently presented in a large parameter space,ranging from small to large amplitudes,and for small and large damping coefficients.The achieved robust effects greatly enlarge the application scope of nonlinear metamaterials.We report the design concept,properties and mechanisms of the hyper-damping and its effect on vibration transmission.This paper reveals new properties offered by nonlinear elastic metamaterials,and offers a robust method for achieving efficient low-frequency and broadband vibration suppression.
基金the National Natural Science Foundation of China (Grant Nos. 51275519 and 11372346).
文摘A periodical composite material pipe is proposed based on the Bragg scattering mechanism of phononic crystals (PCs). The band gap (BG) properties of the flexural wave in this PC pipe under axial load and hydro-pressure are calculated using the transfer matrix (TM) method. The frequency response functions (FRFs) of the PC pipe under axial load and hydro-pressure are calculated using the finite element approach, and the mechanism is elucidated to illustrate the phenomenon. The results show that axial load and hydro-pressure and their combination all have a great influence on the flexural vibration proper ties. This research offers theoretical support for research on PC pipes with complex conditions and is of great significance in solving the problem of high pressure.
