In order to discuss the effect of tectonic stress on the structural evolution of coal, given the importance attached to High-resolution Transmission Electron Microscopy (HTEM), we investigated several aspects of mater...In order to discuss the effect of tectonic stress on the structural evolution of coal, given the importance attached to High-resolution Transmission Electron Microscopy (HTEM), we investigated several aspects of material structures of high-rank Carboniferous period coal, located in the northern foreland basin of the Dabie orogenic belt in eastern China. High powered crystal lattice images of Bright Fields (BF) and Selected Area Diffraction patterns (SAD) of different types of metamorphism in coal were obtained. The results show that the Basic Structural Units (BSU) become increasingly more compact as a function of rising tem-perature and pressure. Under pressure, the local orientation of molecules is strengthened, the arrangement of BSU speeds up and the degree of order is clearly enhanced.展开更多
A new spherical triangular finite element based on shallow shell formulation is developed in this paper. The element has six degrees of freedom at each comer node, five of which are the essential external degrees of f...A new spherical triangular finite element based on shallow shell formulation is developed in this paper. The element has six degrees of freedom at each comer node, five of which are the essential external degrees of freedom and the additional sixth is associated with the in-plane shell rotation. The displacement fields of the element satisfy the exact requirement of rigid body modes of motion. The element is based on independent strain assumption insofar as it is allowed by the compatibility equations. The element developed herein is first validated by applying it to the analysis of a benchmark problem involving a standard spherical shell with simply supported edges. The results of the analysis showed that reasonably accurate results were obtained even when modeling the shells using fewer elements compared to other shell element types. The element is then used in a finite element model to analyze polygon shaped spherical roof structures. The distribution of the various components of deflection and stress is obtained. Furthermore, the effect of introducing circular arched beams as stiffeners spanning the two diagonally opposite end comers is investigated. It is found that the stiffeners reduced the deflections and the stresses in the roof structure by considerable value.展开更多
基金support for this work, provided by the National Natural Science Foundation of China (No40872105)the Scientific Research Foundation of the North China Institute of Science Technology (NoA08002)
文摘In order to discuss the effect of tectonic stress on the structural evolution of coal, given the importance attached to High-resolution Transmission Electron Microscopy (HTEM), we investigated several aspects of material structures of high-rank Carboniferous period coal, located in the northern foreland basin of the Dabie orogenic belt in eastern China. High powered crystal lattice images of Bright Fields (BF) and Selected Area Diffraction patterns (SAD) of different types of metamorphism in coal were obtained. The results show that the Basic Structural Units (BSU) become increasingly more compact as a function of rising tem-perature and pressure. Under pressure, the local orientation of molecules is strengthened, the arrangement of BSU speeds up and the degree of order is clearly enhanced.
文摘A new spherical triangular finite element based on shallow shell formulation is developed in this paper. The element has six degrees of freedom at each comer node, five of which are the essential external degrees of freedom and the additional sixth is associated with the in-plane shell rotation. The displacement fields of the element satisfy the exact requirement of rigid body modes of motion. The element is based on independent strain assumption insofar as it is allowed by the compatibility equations. The element developed herein is first validated by applying it to the analysis of a benchmark problem involving a standard spherical shell with simply supported edges. The results of the analysis showed that reasonably accurate results were obtained even when modeling the shells using fewer elements compared to other shell element types. The element is then used in a finite element model to analyze polygon shaped spherical roof structures. The distribution of the various components of deflection and stress is obtained. Furthermore, the effect of introducing circular arched beams as stiffeners spanning the two diagonally opposite end comers is investigated. It is found that the stiffeners reduced the deflections and the stresses in the roof structure by considerable value.
