A new type of thin-walled circular tubes(CTs),which is inspired by the bamboo with highly-efficient energy absorption(EA)capability,was proposed and designed for the potential application of the energy absorber of rai...A new type of thin-walled circular tubes(CTs),which is inspired by the bamboo with highly-efficient energy absorption(EA)capability,was proposed and designed for the potential application of the energy absorber of rail vehicles in this study.And then,the axial crushing behavior and crashworthiness of the bamboo-inspired bionic tube(BT)were experimentally and numerically investigated,compared with the single CT and foam-filled tube(FT).The typical crushing responses(e.g.,deformation mode,load-displacement response,energy absorption,and strain distribution)and quantitative crashworthiness indicators(EA,SEA,FP,Fm,and CFE)of these three types of CTs were presented and discussed.Effects of impact velocity and foam relative density on the crashworthiness of tested tubes were also explored.The experimental and simulation results show that the BT specimen exhibits the best capability of load-carrying,energy absorption,and crashworthiness among three types of tubes.Compared with the CT specimen,the EA value of BT specimens increased by 93.1%,while the corresponding Fm value raised from 74.2 kN to 143.4 kN.展开更多
High-entropy carbide ceramics(HECCs)are promising ultrahigh-temperature ceramics with exceptional properties,but their brittleness limits their practical application.Inspired by the structure of bamboo,fibrous monolit...High-entropy carbide ceramics(HECCs)are promising ultrahigh-temperature ceramics with exceptional properties,but their brittleness limits their practical application.Inspired by the structure of bamboo,fibrous monolithic high-entropy(Ti_(0.2)Zr_(0.2)Hf_(0.2)Nb_(0.2)Ta_(0.2))C-based ceramics(FMCs)with continuous weak cell boundaries were designed and fabricated through a combination of phase inversion and hot-pressing techniques.By optimizing the composition of the cell boundary,FM721 achieves a high fracture toughness of 8.3±1.5 MPa∙m^(1/2),a 51.9% improvement over(Ti_(0.2)Zr_(0.2)Hf_(0.2)Nb_(0.2)Ta_(0.2))C(HECC),and a work of fracture of 784.0±190.8 J/m^(2),a 1132.7%increase.The toughening mechanisms include crack deflection,crack branching,and load redistribution at the cell boundary,which increase the crack propagation path,consuming more energy.Moreover,the introduction of cell boundaries reduces the defect sensitivity and enhances damage tolerance.For example,FM721 maintains 77.8%of its initial flexural strength even after a 294 N indentation.Moreover,the relatively low density of FMCs and the thermal barrier effect at the cell boundaries significantly enhance the thermal insulation performance.As the temperature increases from room temperature(25℃)to 1000℃,the thermal conductivity of FM721 decreases by 22.9% and 34.5%,respectively,compared with that of the conventional HECC.This work presents a novel strategy for optimizing both the mechanical strength and thermal insulation performance of HECCs,providing insights for the design of thermal protection materials in extreme environments.展开更多
基金This work was supported by the National Natural Science Foundation of China(Grant No.12122211).
文摘A new type of thin-walled circular tubes(CTs),which is inspired by the bamboo with highly-efficient energy absorption(EA)capability,was proposed and designed for the potential application of the energy absorber of rail vehicles in this study.And then,the axial crushing behavior and crashworthiness of the bamboo-inspired bionic tube(BT)were experimentally and numerically investigated,compared with the single CT and foam-filled tube(FT).The typical crushing responses(e.g.,deformation mode,load-displacement response,energy absorption,and strain distribution)and quantitative crashworthiness indicators(EA,SEA,FP,Fm,and CFE)of these three types of CTs were presented and discussed.Effects of impact velocity and foam relative density on the crashworthiness of tested tubes were also explored.The experimental and simulation results show that the BT specimen exhibits the best capability of load-carrying,energy absorption,and crashworthiness among three types of tubes.Compared with the CT specimen,the EA value of BT specimens increased by 93.1%,while the corresponding Fm value raised from 74.2 kN to 143.4 kN.
基金supported by the Shenzhen Science and Technology Program(Nos.202206193000001 and 20220818183014003)the National Natural Science Foundation of China(No.52202126)the Leading Talent Project of the National Special Support Program(No.2022WRLJ003).
文摘High-entropy carbide ceramics(HECCs)are promising ultrahigh-temperature ceramics with exceptional properties,but their brittleness limits their practical application.Inspired by the structure of bamboo,fibrous monolithic high-entropy(Ti_(0.2)Zr_(0.2)Hf_(0.2)Nb_(0.2)Ta_(0.2))C-based ceramics(FMCs)with continuous weak cell boundaries were designed and fabricated through a combination of phase inversion and hot-pressing techniques.By optimizing the composition of the cell boundary,FM721 achieves a high fracture toughness of 8.3±1.5 MPa∙m^(1/2),a 51.9% improvement over(Ti_(0.2)Zr_(0.2)Hf_(0.2)Nb_(0.2)Ta_(0.2))C(HECC),and a work of fracture of 784.0±190.8 J/m^(2),a 1132.7%increase.The toughening mechanisms include crack deflection,crack branching,and load redistribution at the cell boundary,which increase the crack propagation path,consuming more energy.Moreover,the introduction of cell boundaries reduces the defect sensitivity and enhances damage tolerance.For example,FM721 maintains 77.8%of its initial flexural strength even after a 294 N indentation.Moreover,the relatively low density of FMCs and the thermal barrier effect at the cell boundaries significantly enhance the thermal insulation performance.As the temperature increases from room temperature(25℃)to 1000℃,the thermal conductivity of FM721 decreases by 22.9% and 34.5%,respectively,compared with that of the conventional HECC.This work presents a novel strategy for optimizing both the mechanical strength and thermal insulation performance of HECCs,providing insights for the design of thermal protection materials in extreme environments.
