The elastic constants of superconducting MgB2 are calculated using a molecular dynamics method (MD)with shell model. The lattice parameters, five independent elastic constants, equations of state (EOS), Debye temperat...The elastic constants of superconducting MgB2 are calculated using a molecular dynamics method (MD)with shell model. The lattice parameters, five independent elastic constants, equations of state (EOS), Debye temperature, and bulk modulus of MgB2 are obtained. Meanwhile, the dependence of the bulk modulus B, the lattice parameters a and c, and the unit cell volume V on the applied pressure are presented. It is demonstrated that the method introduced here can well reproduce the experimental results with a reasonable accuracy.展开更多
An explicit integration scheme for rate-dependent crystal plasticity （CP） was developed. Additive decomposition of the velocity gradient tensor into lattice and plastic parts is adopted for describing the kinematics...An explicit integration scheme for rate-dependent crystal plasticity （CP） was developed. Additive decomposition of the velocity gradient tensor into lattice and plastic parts is adopted for describing the kinematics; the Cauchy stress is calculated by using a hypo-elastic formulation, applying the Jaumann stress rate. This CP scheme has been implemented into a commercial finite element code （CPFEM）. Uniaxial compression and roiling processes were simulated. The results show good accuracy and reliability of the integration scheme. The results were compared with simulations using one hyper-elastic CPFEM implementation which involves multiplicative decomposition of the deformation gradient tensor. It is found that the hypo-elastic implementation is only slightly faster and has a similar accuracy as the hyper-elastic formulation.展开更多
Metamaterials with higher-order topological band gaps that exhibit topological physics beyond the bulkedge correspondence provide unique application values due to their ability of integrating topological boundary stat...Metamaterials with higher-order topological band gaps that exhibit topological physics beyond the bulkedge correspondence provide unique application values due to their ability of integrating topological boundary states at multiple dimensions in a single chip.On the other hand,in the past decade,micromechanical metamaterials are developing rapidly for various applications such as micro-piezoelectricgenerators,intelligent micro-systems,on-chip sensing and self-powered micro-systems.To empower these cutting-edge applications with topological manipulations of elastic waves,higher-order topological mechanical systems working at high frequencies(MHz)with high quality-factors are demanded.The current realizations of higher-order topological mechanical systems,however,are still limited to systems with large scales(centimetres)and low frequencies(k Hz).Here,we report the first experimental realization of an on-chip micromechanical metamaterial as the higher-order topological insulator for elastic waves at MHz.The higher-order topological phononic band gap is induced by the band inversion at the Brillouin zone corner which is achieved by configuring the orientations of the elliptic pillars etched on the silicon chip.With consistent experiments,theory and simulations,we demonstrate the emergence of coexisting topological edge and corner states in a single silicon chip as induced by the higher-order band topology.The experimental realization of on-chip micromechanical metamaterials with higherorder topology opens a new regime for materials and applications based on topological elastic waves.展开更多
Dynamical cavitation and oscillation of an anisotropic two-family fiber-reinforced incompressible hyper-elastic sphere subjected to a suddenly applied constant boundary dead load are examined within the framework of f...Dynamical cavitation and oscillation of an anisotropic two-family fiber-reinforced incompressible hyper-elastic sphere subjected to a suddenly applied constant boundary dead load are examined within the framework of finite elasto-dynamics.An exact differential equation between the radius of the cavity and the applied load is obtained.The curves for the variation of the maximum radius of the cavity with the load and the phase diagrams are obtained by vibration theories and numerical computation.It is shown that there exists a critical value for the applied load.When the applied load is larger than the critical value,a spherical cavity will suddenly form at the center of the sphere.It is proved that the evolution of the cavity radius with time follows that of nonlinear periodic oscillation,and oscillation of the anisotropic sphere is not the same as that of the isotropic sphere.展开更多
基金中国科学院资助项目，Scientific Research Foundation for Returned Overseas Chinese Scholars，Ministry of Education of China
文摘The elastic constants of superconducting MgB2 are calculated using a molecular dynamics method (MD)with shell model. The lattice parameters, five independent elastic constants, equations of state (EOS), Debye temperature, and bulk modulus of MgB2 are obtained. Meanwhile, the dependence of the bulk modulus B, the lattice parameters a and c, and the unit cell volume V on the applied pressure are presented. It is demonstrated that the method introduced here can well reproduce the experimental results with a reasonable accuracy.
文摘An explicit integration scheme for rate-dependent crystal plasticity （CP） was developed. Additive decomposition of the velocity gradient tensor into lattice and plastic parts is adopted for describing the kinematics; the Cauchy stress is calculated by using a hypo-elastic formulation, applying the Jaumann stress rate. This CP scheme has been implemented into a commercial finite element code （CPFEM）. Uniaxial compression and roiling processes were simulated. The results show good accuracy and reliability of the integration scheme. The results were compared with simulations using one hyper-elastic CPFEM implementation which involves multiplicative decomposition of the deformation gradient tensor. It is found that the hypo-elastic implementation is only slightly faster and has a similar accuracy as the hyper-elastic formulation.
基金supported by the Natural Science Foundation of Guangdong Province(2020A1515010549)China Postdoctoral Science Foundation(2020M672615 and 2019M662885)+1 种基金National Postdoctoral Program for Innovative Talents(BX20190122)the Jiangsu specially-appointed professor funding。
文摘Metamaterials with higher-order topological band gaps that exhibit topological physics beyond the bulkedge correspondence provide unique application values due to their ability of integrating topological boundary states at multiple dimensions in a single chip.On the other hand,in the past decade,micromechanical metamaterials are developing rapidly for various applications such as micro-piezoelectricgenerators,intelligent micro-systems,on-chip sensing and self-powered micro-systems.To empower these cutting-edge applications with topological manipulations of elastic waves,higher-order topological mechanical systems working at high frequencies(MHz)with high quality-factors are demanded.The current realizations of higher-order topological mechanical systems,however,are still limited to systems with large scales(centimetres)and low frequencies(k Hz).Here,we report the first experimental realization of an on-chip micromechanical metamaterial as the higher-order topological insulator for elastic waves at MHz.The higher-order topological phononic band gap is induced by the band inversion at the Brillouin zone corner which is achieved by configuring the orientations of the elliptic pillars etched on the silicon chip.With consistent experiments,theory and simulations,we demonstrate the emergence of coexisting topological edge and corner states in a single silicon chip as induced by the higher-order band topology.The experimental realization of on-chip micromechanical metamaterials with higherorder topology opens a new regime for materials and applications based on topological elastic waves.
基金supported by the National Natural Science Foundation of China (Grant Nos.10772104 and 10872045)the innovation project of Shanghai Municipal Education Commission (Grant No.09YZ12)Shanghai Leading Academic Discipline Project (Grant No.S30106)
文摘Dynamical cavitation and oscillation of an anisotropic two-family fiber-reinforced incompressible hyper-elastic sphere subjected to a suddenly applied constant boundary dead load are examined within the framework of finite elasto-dynamics.An exact differential equation between the radius of the cavity and the applied load is obtained.The curves for the variation of the maximum radius of the cavity with the load and the phase diagrams are obtained by vibration theories and numerical computation.It is shown that there exists a critical value for the applied load.When the applied load is larger than the critical value,a spherical cavity will suddenly form at the center of the sphere.It is proved that the evolution of the cavity radius with time follows that of nonlinear periodic oscillation,and oscillation of the anisotropic sphere is not the same as that of the isotropic sphere.
