A novel elastic metamaterial is proposed with the aim of achieving lowfrequency broad bandgaps and bandgap regulation.The band structure of the proposed metamaterial is calculated based on the Floquet-Bloch theorem,an...A novel elastic metamaterial is proposed with the aim of achieving lowfrequency broad bandgaps and bandgap regulation.The band structure of the proposed metamaterial is calculated based on the Floquet-Bloch theorem,and the boundary modes of each bandgap are analyzed to understand the effects of each component of the unit cell on the bandgap formation.It is found that the metamaterials with a low elastic modulus of ligaments can generate flexural wave bandgaps below 300 Hz.Multi-frequency vibrations can be suppressed through the selective manipulation of bandgaps.The dual-graded design of metamaterials that can significantly improve the bandgap width is proposed based on parametric studies.A new way that can regulate the bandgap is revealed by studying the graded elastic modulus in the substrate.The results demonstrate that the nonlinear gradient of the elastic modulus in the substrate offers better bandgap performance.Based on these analyses,the proposed elastic metamaterials can pave the way for multi-frequency vibration control,low-frequency bandgap broadening,and bandgap tuning.展开更多
Long-distance oil and gas pipelines are important infrastructure for ensuring the security of national energy supply.There is still a certain gap between safety management requirements and systematic construction of r...Long-distance oil and gas pipelines are important infrastructure for ensuring the security of national energy supply.There is still a certain gap between safety management requirements and systematic construction of relevant regulations and standards for long-distance pipelines in China and those of EU countries.By means of literature review and standard comparison,the differences in key indicators such as design coefficient,regional grade classification.展开更多
What is spinal concussion？Spinal cord concussion is a variant of mild spinal cord injury,clinically designated as transient paraplegia or neurapraxia,and characterized by variable degrees of sensory impairment and mo...What is spinal concussion？Spinal cord concussion is a variant of mild spinal cord injury,clinically designated as transient paraplegia or neurapraxia,and characterized by variable degrees of sensory impairment and motor weakness that typically resolve within 24–72 hours without permanent deficits（Del Bigio and Johnson,1989;Zwimpfer and Bernstein,1990;Torg et al.,1997）.展开更多
Light-weight,high-strength metamaterials with excellent specific energy absorption(SEA)capabilities are sig-nificant for aerospace and automobile.The SEA of metamaterials largely depends on the material and structural...Light-weight,high-strength metamaterials with excellent specific energy absorption(SEA)capabilities are sig-nificant for aerospace and automobile.The SEA of metamaterials largely depends on the material and structural design.Herein,inspired by the superior impact resistance of pomelo peel for protecting the pulp and the elevated SEA ability of a functionally graded structure,a graded bionic polyhedron metamaterial(GBPM)was designed and realized by 3D printing using a soft material(photosensitive resin)and a hard material(Ti-6Al-4V).Guided by compression tests and numerical simulations,the elevated SEA ability was independent of the materials.The fluctuation region appeared in hard-material-fabricated bionic polyhedron metamaterial(BPMs)and was absent in soft-material-fabricated BPMs in the stress-strain curves,resulting in the growth rate of the SEA value of the soft-material-fabricated GBPM being enhanced by 5.9 times compared with that of the hard-material-fabricated GBPM.The SEA values of soft-and hard-material-fabricated GBPM were 1.89 and 44.16 J/g,which exceed those of most soft-and hard-material-fabricated metamaterials reported in previous studies.These findings can guide the design of metamaterials with high energy absorption to resist external impacts.展开更多
基金Project supported by the National Natural Science Foundation of China(Nos.11872233,U2341231,and 12102245)。
文摘A novel elastic metamaterial is proposed with the aim of achieving lowfrequency broad bandgaps and bandgap regulation.The band structure of the proposed metamaterial is calculated based on the Floquet-Bloch theorem,and the boundary modes of each bandgap are analyzed to understand the effects of each component of the unit cell on the bandgap formation.It is found that the metamaterials with a low elastic modulus of ligaments can generate flexural wave bandgaps below 300 Hz.Multi-frequency vibrations can be suppressed through the selective manipulation of bandgaps.The dual-graded design of metamaterials that can significantly improve the bandgap width is proposed based on parametric studies.A new way that can regulate the bandgap is revealed by studying the graded elastic modulus in the substrate.The results demonstrate that the nonlinear gradient of the elastic modulus in the substrate offers better bandgap performance.Based on these analyses,the proposed elastic metamaterials can pave the way for multi-frequency vibration control,low-frequency bandgap broadening,and bandgap tuning.
基金Soft Science Research Project of the Special Equipment Safety and Energy Conservation Technology Committee of the State Administration for Market Regulation“Comparative Study of Special Equipment Supervision and Inspection Modes at Home and Abroad(AJW-2024-06)”Scientific Research and Technology Development Project of National Oil and Gas Pipeline Network Group Co.,Ltd.“Benchmarking of Pressure Pipeline(Long-Distance Pipeline)Regulatory System and Research on In-Service Pipeline Safety Management Technology(J-24-D08)”。
文摘Long-distance oil and gas pipelines are important infrastructure for ensuring the security of national energy supply.There is still a certain gap between safety management requirements and systematic construction of relevant regulations and standards for long-distance pipelines in China and those of EU countries.By means of literature review and standard comparison,the differences in key indicators such as design coefficient,regional grade classification.
基金supported by NIH PO1 NS055976Craig H.Neilsen Foundation
文摘What is spinal concussion？Spinal cord concussion is a variant of mild spinal cord injury,clinically designated as transient paraplegia or neurapraxia,and characterized by variable degrees of sensory impairment and motor weakness that typically resolve within 24–72 hours without permanent deficits（Del Bigio and Johnson,1989;Zwimpfer and Bernstein,1990;Torg et al.,1997）.
基金supported by Guangdong Provincial Key-Area Research and Development Program of China(Grant No.2020B090923001)National Natural Science Foundation of China(Grant Nos.51922044,52205358)Central Universities Funda-mental Research Funds of China(Grant No.HUST:2022JYCXJJ021).
文摘Light-weight,high-strength metamaterials with excellent specific energy absorption(SEA)capabilities are sig-nificant for aerospace and automobile.The SEA of metamaterials largely depends on the material and structural design.Herein,inspired by the superior impact resistance of pomelo peel for protecting the pulp and the elevated SEA ability of a functionally graded structure,a graded bionic polyhedron metamaterial(GBPM)was designed and realized by 3D printing using a soft material(photosensitive resin)and a hard material(Ti-6Al-4V).Guided by compression tests and numerical simulations,the elevated SEA ability was independent of the materials.The fluctuation region appeared in hard-material-fabricated bionic polyhedron metamaterial(BPMs)and was absent in soft-material-fabricated BPMs in the stress-strain curves,resulting in the growth rate of the SEA value of the soft-material-fabricated GBPM being enhanced by 5.9 times compared with that of the hard-material-fabricated GBPM.The SEA values of soft-and hard-material-fabricated GBPM were 1.89 and 44.16 J/g,which exceed those of most soft-and hard-material-fabricated metamaterials reported in previous studies.These findings can guide the design of metamaterials with high energy absorption to resist external impacts.
