A finite element program developed elastic-plastic crack propagation simulation using Fortran language. At each propagation step, the adaptive mesh is automatically refined based on a posteriori h-type refinement usin...A finite element program developed elastic-plastic crack propagation simulation using Fortran language. At each propagation step, the adaptive mesh is automatically refined based on a posteriori h-type refinement using norm stress error estimator. A rosette of quarter-point elements is then constructed around the crack tip to facilitate the prediction of crack growth based on the maximum normal stress criterion and to calculate stress intensity factors under plane stress and plane strain conditions. Crack was modelled to propagate through the inter-element in the mesh. Some examples are presented to show the results of the implementation.展开更多
Nested Newmark model(NNM) is a conceptual framework to assessing post-earthquake movements including dispersed shear movements. The original NNM omits that the tensile stresses would be encountered in slopes induced b...Nested Newmark model(NNM) is a conceptual framework to assessing post-earthquake movements including dispersed shear movements. The original NNM omits that the tensile stresses would be encountered in slopes induced by earthquakes. The purpose of this study is to introduce the tensile strength cut-off and the relevant failure mechanism into NNM and conduct the limit analysis to determine the seismic displacement. Parametric studies are carried out to further investigate the influence of the tensile strength and input ground motions on permanent displacement. Neglecting the tensile strength can underestimate the permanent displacements of slopes. As the peak acceleration increases, the underestimation becomes more significant. With the reduction of tensile strength, much larger deformation occurs next to the slope crest. Although the present results are limited to an example, the method is of value in practice to predict the post-earthquake profile of slope.展开更多
The effect of Zn addition on the microstructure, tensile properties and electrochemical properties of as-annealed 3003 Al alloy was investigated through TEM observations, tensile tests and Tafel polarization analysis....The effect of Zn addition on the microstructure, tensile properties and electrochemical properties of as-annealed 3003 Al alloy was investigated through TEM observations, tensile tests and Tafel polarization analysis. High density precipitates are observed in the Zn-containing alloys and the alloy with 1.8% Zn addition also has rod-like precipitates. Tensile test results indicate that Zn has a great effect on tensile strength of 3003 Al alloy. The alloy with 1.5% Zn addition has the highest ultimate tensile strength. The electrochemical results indicate that Zn addition to 3003 Al alloy also has great impact on the corrosion potential of the 3003 A1 alloy in 0.5% NaCl solution and ethylene glycol-water solution. The corrosion potential varies with the Zn content and shifts negatively.展开更多
With the growing tension of port shoreline resource in Three Gorges Reservoir area, many wharfs can only be constructed on slippery stratum with poor geological condition, which means buckling failure occurs easily. F...With the growing tension of port shoreline resource in Three Gorges Reservoir area, many wharfs can only be constructed on slippery stratum with poor geological condition, which means buckling failure occurs easily. FEM strength reduction method is used in analyzing slope stability of a wharf in Chongqing, and its accuracy is verified by comparing the acquired results with the computation of traditional limit equilibrium method. On this basis, the influences of reservoir water level variation, overload and backfill material behind the retaining wall, and soil share strength of wharf slope on slippery stratum are analyzed. Analysis shows that, there＇ s a most adverse water level in wharf slope, and the engineering proposals with a certain practical significance such as improve the drainage behind retaining wall, controll overload and improve the strength of backfill soil and subsoil are suggested.展开更多
Maintaining the safety and reliability of nuclear engineering materials under a neutron irradiation environment is significant. Atomic-scale simulations are conducted to investigate the mechanism of irradiation-induce...Maintaining the safety and reliability of nuclear engineering materials under a neutron irradiation environment is significant. Atomic-scale simulations are conducted to investigate the mechanism of irradiation-induced vacancy formation in CLAM, F82 H and α-Fe with different neutron energies and objective laws of the effect of vacancy concentration on mechanical properties of α-Fe. Damage of these typical metal engineering materials caused by neutrons is mainly displacement damage, while the displacement damage rate and the non-ionizing effect of neutrons decrease with the increase of neutron energy. The elastic modulus, yield strength, and ultimate strength of α-Fe are in the order of magnitude of GPa. However, the elastic modulus is not constant but decreases with the increase of strain at the elastic deformation stage. The ultimate strength reaches its maximum value when vacancy concentration in α-Fe is 0.2%. On this basis, decreasing or increasing the number of vacancies reduces the ultimate strength.展开更多
文摘A finite element program developed elastic-plastic crack propagation simulation using Fortran language. At each propagation step, the adaptive mesh is automatically refined based on a posteriori h-type refinement using norm stress error estimator. A rosette of quarter-point elements is then constructed around the crack tip to facilitate the prediction of crack growth based on the maximum normal stress criterion and to calculate stress intensity factors under plane stress and plane strain conditions. Crack was modelled to propagate through the inter-element in the mesh. Some examples are presented to show the results of the implementation.
基金Projects(41630638,51878248)supported by the National Natural Science Foundation of China
文摘Nested Newmark model(NNM) is a conceptual framework to assessing post-earthquake movements including dispersed shear movements. The original NNM omits that the tensile stresses would be encountered in slopes induced by earthquakes. The purpose of this study is to introduce the tensile strength cut-off and the relevant failure mechanism into NNM and conduct the limit analysis to determine the seismic displacement. Parametric studies are carried out to further investigate the influence of the tensile strength and input ground motions on permanent displacement. Neglecting the tensile strength can underestimate the permanent displacements of slopes. As the peak acceleration increases, the underestimation becomes more significant. With the reduction of tensile strength, much larger deformation occurs next to the slope crest. Although the present results are limited to an example, the method is of value in practice to predict the post-earthquake profile of slope.
文摘The effect of Zn addition on the microstructure, tensile properties and electrochemical properties of as-annealed 3003 Al alloy was investigated through TEM observations, tensile tests and Tafel polarization analysis. High density precipitates are observed in the Zn-containing alloys and the alloy with 1.8% Zn addition also has rod-like precipitates. Tensile test results indicate that Zn has a great effect on tensile strength of 3003 Al alloy. The alloy with 1.5% Zn addition has the highest ultimate tensile strength. The electrochemical results indicate that Zn addition to 3003 Al alloy also has great impact on the corrosion potential of the 3003 A1 alloy in 0.5% NaCl solution and ethylene glycol-water solution. The corrosion potential varies with the Zn content and shifts negatively.
文摘With the growing tension of port shoreline resource in Three Gorges Reservoir area, many wharfs can only be constructed on slippery stratum with poor geological condition, which means buckling failure occurs easily. FEM strength reduction method is used in analyzing slope stability of a wharf in Chongqing, and its accuracy is verified by comparing the acquired results with the computation of traditional limit equilibrium method. On this basis, the influences of reservoir water level variation, overload and backfill material behind the retaining wall, and soil share strength of wharf slope on slippery stratum are analyzed. Analysis shows that, there＇ s a most adverse water level in wharf slope, and the engineering proposals with a certain practical significance such as improve the drainage behind retaining wall, controll overload and improve the strength of backfill soil and subsoil are suggested.
基金supported by the Specialized Research Fund for the Doctoral Program of Higher Education of China(Grant No.20133218110023)China Postdoctoral Science Foundation(Grant No.2014M561642)+2 种基金the Jiangsu Planned Projects for Postdoctoral Research Funds(Grant No.1401091C)the Fundamental Research Funds for the Central Universities(Grant No.3082015NJ20150021)the Priority Academic Program Development of Jiangsu Higher Education Institutions
文摘Maintaining the safety and reliability of nuclear engineering materials under a neutron irradiation environment is significant. Atomic-scale simulations are conducted to investigate the mechanism of irradiation-induced vacancy formation in CLAM, F82 H and α-Fe with different neutron energies and objective laws of the effect of vacancy concentration on mechanical properties of α-Fe. Damage of these typical metal engineering materials caused by neutrons is mainly displacement damage, while the displacement damage rate and the non-ionizing effect of neutrons decrease with the increase of neutron energy. The elastic modulus, yield strength, and ultimate strength of α-Fe are in the order of magnitude of GPa. However, the elastic modulus is not constant but decreases with the increase of strain at the elastic deformation stage. The ultimate strength reaches its maximum value when vacancy concentration in α-Fe is 0.2%. On this basis, decreasing or increasing the number of vacancies reduces the ultimate strength.
