Over the past decade,multistable mechanical metamaterials have been widely investigated because of their novel shape reconfigurability and programmable energy landscape.The ability to reversibly reshape among diverse ...Over the past decade,multistable mechanical metamaterials have been widely investigated because of their novel shape reconfigurability and programmable energy landscape.The ability to reversibly reshape among diverse stable states with different energy levels represents the most important feature of the multistable mechanical metamaterials.We summarize main design strategies of multistable mechanical metamaterials,including those based on self-assembly scheme,snap-through instability,structured mechanism and geometrical frustration,with a focus on the number and controllability of accessible stable states.Then we concentrate on unusual mechanical properties of these multistable mechanical metamaterials,and present their applications in a wide range of areas,including tunable electromagnetic devices,actuators,robotics,and mechanical logic gates.Finally,we discuss remaining challenges and open opportunities of designs and applications of multistable mechanical metamaterials.展开更多
Thin-walled structures are commonly utilized in aerospace and aircraft structures,which are prone to buckling under axial compression and extremely sensitive to geometric imperfections.After decades of efforts,it stil...Thin-walled structures are commonly utilized in aerospace and aircraft structures,which are prone to buckling under axial compression and extremely sensitive to geometric imperfections.After decades of efforts,it still remains a challenging issue to accurately predict the lower-bound buckling load due to the impact of geometric imperfections.Up to now,the lower-bound curve in NASA SP-8007 is still widely used as the design criterion of aerospace thin-walled structures,and this series of knockdown factors(KDF)has been proven to be overly conservative with the significant promotion of the manufacturing process.In recent years,several new numerical and experimental methods for determining KDF have been established,which are systematically reviewed in this paper.The Worst Multiple Perturbation Load Approach(WMPLA)is one of the most representative methods to reduce the conservatism of traditional methods in a rational manner.Based on an extensive collection of test data from 1990 to 2020,a new lower-bound curve is approximated to produce a series of improved KDFs.It is evident that these new KDFs have an overall improvement of 0.1-0.3 compared with NASA SP-8007,and the KDF predicted by the WMPLA is very close to the front of the new curve.This may provide some insight into future design guidelines of axially compressed cylindrical shells,which is promising for the lightweight design of large-diameter aerospace structures.展开更多
基金supported by the National Natural Science Foundation of China(No.11722217)the Tsinghua University,China Initiative Scientific Research Program(No.2019Z08QCX10)the Institute for Guo Qiang,Tsinghua University,China(No.2019GQG1012)。
文摘Over the past decade,multistable mechanical metamaterials have been widely investigated because of their novel shape reconfigurability and programmable energy landscape.The ability to reversibly reshape among diverse stable states with different energy levels represents the most important feature of the multistable mechanical metamaterials.We summarize main design strategies of multistable mechanical metamaterials,including those based on self-assembly scheme,snap-through instability,structured mechanism and geometrical frustration,with a focus on the number and controllability of accessible stable states.Then we concentrate on unusual mechanical properties of these multistable mechanical metamaterials,and present their applications in a wide range of areas,including tunable electromagnetic devices,actuators,robotics,and mechanical logic gates.Finally,we discuss remaining challenges and open opportunities of designs and applications of multistable mechanical metamaterials.
基金the National Natural Science Foundation of China(Grant Nos.U21A20429,11772078,and 11825202)the National Defense Basic Research Program(Grant No.JCKY2020110).
文摘Thin-walled structures are commonly utilized in aerospace and aircraft structures,which are prone to buckling under axial compression and extremely sensitive to geometric imperfections.After decades of efforts,it still remains a challenging issue to accurately predict the lower-bound buckling load due to the impact of geometric imperfections.Up to now,the lower-bound curve in NASA SP-8007 is still widely used as the design criterion of aerospace thin-walled structures,and this series of knockdown factors(KDF)has been proven to be overly conservative with the significant promotion of the manufacturing process.In recent years,several new numerical and experimental methods for determining KDF have been established,which are systematically reviewed in this paper.The Worst Multiple Perturbation Load Approach(WMPLA)is one of the most representative methods to reduce the conservatism of traditional methods in a rational manner.Based on an extensive collection of test data from 1990 to 2020,a new lower-bound curve is approximated to produce a series of improved KDFs.It is evident that these new KDFs have an overall improvement of 0.1-0.3 compared with NASA SP-8007,and the KDF predicted by the WMPLA is very close to the front of the new curve.This may provide some insight into future design guidelines of axially compressed cylindrical shells,which is promising for the lightweight design of large-diameter aerospace structures.
