دانلود رایگان مقاله استخراج ویژگی و رویکرد مش بندی برای سازه های ورق مانند در سنگ

Abstract

Meshing rock samples with sheet-like structures based their CT scanned volumetric images, is a crucial component for both visualization and numerical simulation. In rocks, fractures and veins commonly exist in the form of sheet-like objects (e.g. thin layers and distinct flat shapes), which are much smaller than the rock mass dimensions. The representations of such objects require high-resolution 3D images with a huge dataset, which are difficult and even impossible to visualize or analyze by numerical methods. Therefore, we develop a microscopic image based meshing approach to extract major sheet-like structures and then preserve their major geometric features at the macroscale. This is achieved by the following four major steps: (1) extracting major objects through extending, separation and recovering operations based on the CT scanned data/microscopic images; (2) simplifying and constructing a simplified centroidal Voronoi diagram on the extracted structures; (3) generating triangular meshes to represent the structure; (4) generating volume tetrahedron meshes constrained with the above surface mesh as the internal surfaces. Moreover, a shape similarity approach is proposed to measure and evaluate how similar the generated mesh models to the original rock samples. It is applied as criteria for further mesh generation to better describe the rock features with fewer elements. Finally, a practical CT scanned rock is taken as an application example to demonstrate the usefulness and capability of the proposed approach.

4. Conclusions

In this paper, a new mesh generation approach for 3D rock images with fractures and veins is proposed to generate both surface and volume meshes for rocks involving complicated sheet-like structures. Comparing with grid models, the proposed algorithm can generate meshes with less element number to approximate internal sheet-like structures within rock samples. For the rock sample, the ratio between the tetrahedral mesh element number and the grid number is 1:6704. A shape similarity measurement is also proposed and the optimal Voronoi cell radius used for generating surface mesh for the rock sample is 7 with the corresponding similarity 64.57%. In practice, surface meshes with shape similarity above 60% are considered as close approximations for the sheet-like structures. Our numerical experiments show that this technique is more effective than the direct resolution reduction with regard to both shape similarity and element quantity. Moreover, the generated surface mesh can be utilized as constraints to generate corresponding volume mesh. The element quality of the volume mesh is high concerning a variety of measurements and the element quantity is reasonable for future finite element simulations. In general, the generated mesh models are competitive with grid models and have wide applications in both visualization and finite element simulation.