Foamed concrete as energy absorption material for high geo-stress soft rock tunnels has been proven to be feasible due to its high compressibility and lightweight.However,the lengthy curing and defoaming problems caus...Foamed concrete as energy absorption material for high geo-stress soft rock tunnels has been proven to be feasible due to its high compressibility and lightweight.However,the lengthy curing and defoaming problems caused by the cast-in-place method of large-volume foamed concrete remain unsolved.In this study,we propose a novel energy absorber composed of foamed concrete-filled polyethylene(FC-PE)pipe and analyze its deformation and energy absorption capacity via quasi-static lateral compression experiments.Results show that FC-PE pipes exhibit typical three-stage deformation characteristics,comprising the elastic stage,the plastic plateau,and the densification stage.Furthermore,the plateau stress,energy absorption,and specific energy absorption of the specimens are 0.81–1.91 MPa,164–533 J,and 1.4–3.6 J/g,respectively.As the density of the foamed concrete increases,the plateau stress and energy absorption increase significantly.Conversely,the length of the plastic plateau and energy absorption efficiency decrease.Moreover,based on the vertical slice method,progressive compression of core material,and the 6 plastic hinges deformation mechanism of the pipe wall,a theoretical calculation method for effective energy absorption is established and achieves good agreement with experimental results,which is beneficial to the optimization of the composite structure.展开更多
Bimetallic lined steel pipe （LSP） is a new anti-corrosion technology. It is widely used to transport oil, gas, water and corrosive liquid chemicals. At present, the hydroforming pressure for LSP has been investigate...Bimetallic lined steel pipe （LSP） is a new anti-corrosion technology. It is widely used to transport oil, gas, water and corrosive liquid chemicals. At present, the hydroforming pressure for LSP has been investigated theoretically and experimentally by most researchers. However, there are a few reports on the thermal strength of bimetallic LSP. Actually, the bimetallic LSP will be subjected to remarkable thermal load in the process of three layer polyethylene （3PE） external coating. Reverse yielding failure may occur on the inner pipe of the bimetallic LSP when it suffers from remarkable thermal load and residual contact pressure simultaneously. The aim of this paper is to study the thermal load and strength of the bimetallic LSP. A mechanical model, which can estimate the thermal strength of the bimetallic LSP, was established based on the elastic theory and the manufacture of the bimetallic LSP. Based on the model, the correlation between the thermal strength of the bimetallic LSP and residual contact pressure and wall thickness of the inner pipe was obtained. Reverse yielding experiments were performed on the LSP （NT80SS-316L） under different thermal loads. Experiment results are consistent with calculated results from the theoretical model. The experimental and simulation results may provide powerful guidance for the bimetallic LSP production and use.展开更多
The influence of Mo addition on the microstructure and properties of TiNiNb alloy with 4.5 at.% Nb has been investigated systemically. The experimental results indicated that the uniform distribution of Mo depresses t...The influence of Mo addition on the microstructure and properties of TiNiNb alloy with 4.5 at.% Nb has been investigated systemically. The experimental results indicated that the uniform distribution of Mo depresses the appearance of coarse 13-Nb particles at the grain boundaries and short stripped texture consisting of abundant fine disperse Nb-rich particles appears around the grain boundaries. The yield strength of the alloy was enhanced from 450 to 600 MPa due to the solution strengthening of Nb and Mo and the elongation reached 18% when the Mo content is 0.5 at.%. At the same time, the shape memory effect of the alloy also is improved significantly by the Mo addition. The maximum recoverable strain of the alloy with 0.5 at.% Mo is near 8% and has reached the high level of Ni-Ti binary alloys. This novel high- strength alloy is promising to be used for high pressure tube and the macro-scale coupling with higher-quality requirements.展开更多
基金The authors gratefully acknowledge the support of National Natural Science Foundation of China(No.51991392)the Second Tibetan Plateau Scientific Expedition and Research Program(STEP)of China(No.2019QZKK0904)+1 种基金the National Outstanding Youth Science Fund Project of National Natural Science Foundation of China(No.51922104)Youth Innovation Promotion Association CAS.
文摘Foamed concrete as energy absorption material for high geo-stress soft rock tunnels has been proven to be feasible due to its high compressibility and lightweight.However,the lengthy curing and defoaming problems caused by the cast-in-place method of large-volume foamed concrete remain unsolved.In this study,we propose a novel energy absorber composed of foamed concrete-filled polyethylene(FC-PE)pipe and analyze its deformation and energy absorption capacity via quasi-static lateral compression experiments.Results show that FC-PE pipes exhibit typical three-stage deformation characteristics,comprising the elastic stage,the plastic plateau,and the densification stage.Furthermore,the plateau stress,energy absorption,and specific energy absorption of the specimens are 0.81–1.91 MPa,164–533 J,and 1.4–3.6 J/g,respectively.As the density of the foamed concrete increases,the plateau stress and energy absorption increase significantly.Conversely,the length of the plastic plateau and energy absorption efficiency decrease.Moreover,based on the vertical slice method,progressive compression of core material,and the 6 plastic hinges deformation mechanism of the pipe wall,a theoretical calculation method for effective energy absorption is established and achieves good agreement with experimental results,which is beneficial to the optimization of the composite structure.
基金financial support from the National Natural Science Foundation of China (Nos. 51004084, 51274170)the Doctoral Fund of Ministry of Education of China (No. 20105121120002)
文摘Bimetallic lined steel pipe （LSP） is a new anti-corrosion technology. It is widely used to transport oil, gas, water and corrosive liquid chemicals. At present, the hydroforming pressure for LSP has been investigated theoretically and experimentally by most researchers. However, there are a few reports on the thermal strength of bimetallic LSP. Actually, the bimetallic LSP will be subjected to remarkable thermal load in the process of three layer polyethylene （3PE） external coating. Reverse yielding failure may occur on the inner pipe of the bimetallic LSP when it suffers from remarkable thermal load and residual contact pressure simultaneously. The aim of this paper is to study the thermal load and strength of the bimetallic LSP. A mechanical model, which can estimate the thermal strength of the bimetallic LSP, was established based on the elastic theory and the manufacture of the bimetallic LSP. Based on the model, the correlation between the thermal strength of the bimetallic LSP and residual contact pressure and wall thickness of the inner pipe was obtained. Reverse yielding experiments were performed on the LSP （NT80SS-316L） under different thermal loads. Experiment results are consistent with calculated results from the theoretical model. The experimental and simulation results may provide powerful guidance for the bimetallic LSP production and use.
基金financially supported by the National Natural Science Foundation of China (No.51001100)
文摘The influence of Mo addition on the microstructure and properties of TiNiNb alloy with 4.5 at.% Nb has been investigated systemically. The experimental results indicated that the uniform distribution of Mo depresses the appearance of coarse 13-Nb particles at the grain boundaries and short stripped texture consisting of abundant fine disperse Nb-rich particles appears around the grain boundaries. The yield strength of the alloy was enhanced from 450 to 600 MPa due to the solution strengthening of Nb and Mo and the elongation reached 18% when the Mo content is 0.5 at.%. At the same time, the shape memory effect of the alloy also is improved significantly by the Mo addition. The maximum recoverable strain of the alloy with 0.5 at.% Mo is near 8% and has reached the high level of Ni-Ti binary alloys. This novel high- strength alloy is promising to be used for high pressure tube and the macro-scale coupling with higher-quality requirements.
