In this work,we design a twisting metamaterial for longitudinal-torsional(L-T)mode conversion in pipes through exploring the theory of perfect transmodal FabryPerot interference(TFPI).Assuming that the axial and radia...In this work,we design a twisting metamaterial for longitudinal-torsional(L-T)mode conversion in pipes through exploring the theory of perfect transmodal FabryPerot interference(TFPI).Assuming that the axial and radial motions in pipes can be decoupled,we find that the metamaterial can be designed in a rectangular coordinate system,which is much more convenient than that in a cylindrical system.Numerical calculation with detailed microstructures shows that an efficient L-T mode conversion can be obtained in pipes with different radii.In addition,we fabricate mode-converting microstructures on an aluminum pipe and conduct ultrasonic experiments,and the results are in good agreement with the numerical calculations.We expect that the proposed LT mode-converting metamaterial and its design methodology can be applied in various ultrasonic devices.展开更多
There exist strong interests of developing nano-grained steels because of the outstanding properties including high strength/weight ratio, wear resistance, excellent toughness, and favorable cellular activity. This ar...There exist strong interests of developing nano-grained steels because of the outstanding properties including high strength/weight ratio, wear resistance, excellent toughness, and favorable cellular activity. This article reviews the main fabrication process and microstructural control of nano-structured steels over the last decades. Severe plastic deformation is considered as an effective route of obtaining the nano-grained microstructures. The process of cold-rolling and annealing of martensitic steel is a viable method to obtain bulk nano-structured low carbon steel, while the final thickness of the cold-rolling plate is limited. According to the theoretical results of the thermal simulation studies, a novel alloy design combined with the rapid transformation and rolling process is proposed to successfully fabricate nano-grained high strength bulk steel. The refinement mechanisms are expected to be taking advantage of increase in the transformation nucleation sites and inhibiting the grain coarsening. Moreover, corresponding mechanical properties are summarized.展开更多
基金Project supported by the National Natural Science Foundation of China(Nos.U2033208,52192633)the Natural Science Basic Research Plan in Shaanxi Province of China(No.2021JQ-006)+1 种基金the China Postdoctoral Science Foundation(No.2020TQ0241)the Innovative Scientific Program of China Nuclear Power Engineering Co.,Ltd。
文摘In this work,we design a twisting metamaterial for longitudinal-torsional(L-T)mode conversion in pipes through exploring the theory of perfect transmodal FabryPerot interference(TFPI).Assuming that the axial and radial motions in pipes can be decoupled,we find that the metamaterial can be designed in a rectangular coordinate system,which is much more convenient than that in a cylindrical system.Numerical calculation with detailed microstructures shows that an efficient L-T mode conversion can be obtained in pipes with different radii.In addition,we fabricate mode-converting microstructures on an aluminum pipe and conduct ultrasonic experiments,and the results are in good agreement with the numerical calculations.We expect that the proposed LT mode-converting metamaterial and its design methodology can be applied in various ultrasonic devices.
文摘There exist strong interests of developing nano-grained steels because of the outstanding properties including high strength/weight ratio, wear resistance, excellent toughness, and favorable cellular activity. This article reviews the main fabrication process and microstructural control of nano-structured steels over the last decades. Severe plastic deformation is considered as an effective route of obtaining the nano-grained microstructures. The process of cold-rolling and annealing of martensitic steel is a viable method to obtain bulk nano-structured low carbon steel, while the final thickness of the cold-rolling plate is limited. According to the theoretical results of the thermal simulation studies, a novel alloy design combined with the rapid transformation and rolling process is proposed to successfully fabricate nano-grained high strength bulk steel. The refinement mechanisms are expected to be taking advantage of increase in the transformation nucleation sites and inhibiting the grain coarsening. Moreover, corresponding mechanical properties are summarized.
