Digital Modeling And Algorithm Of Structure

The requirement of3d entity model is not only to describe the structure form，butalso to carry on the numerical analysis with the rapid development of computer aidedengineering technology. For these requirements, the emergence of grid model cansatisfy both of them, but the grid generation technology has always been a bigproblem. How to obtain the grid model quickly and accurately, which have a vital rolein describing the entity model and numerical calculation. Therefore, the developmentof digital modeling software is imperative. The major achievements and researchstatus in this area are studied in this paper. The rapid grid generation and displayalgorithm are proposed. Digital modeling software is developed, it can do quickmodeling for a large-scale complex structure and the size of grid generation is up to10billion. In particular, the main work of this paper is as follows:(1) In terms of entity modeling, the CAD software is adopted to establish thethree-dimensional entity model of complex structure. Then, two common formats ofthe STL files are analyzed and its topology is rebuild for the defect problems ofstandard STL file which generated by CAD software. After that, some commondefects of the model are fixed such as dislocation, hole, crack and overlap. Finally, weobtain the reasonable reconstructing topology structure which is stability and easy togrid computing;(2) In terms of grid generation, the Edge-based integral slicing algorithm isstudied in this paper. In the algorithm，the intersection point are solved between edgesof triangle patch and each slice plane, and then relationship of the intersection isdetermined so that the closed contour of each slice plane can be obtained. The gridsare filled with the aid of the scanning line filling technique of computational graphics.In the process of calculating the intersection points the incremental algorithm isadopted which can avoid repetitive search and judgment effectively and can improvethe speed of grid generation;(3) In terms of grid display, the blanking display algorithm of grid is studied andthe multi-function display technology is designed in this paper. We propose a fast blanking algorithm which can quickly remove the hidden surfaces/lines between gridswithin the three-dimensional entity to obtain the actual effect of three-dimensionalgrid model；The multi-threaded parallel technology is employed to realize thesoftware display module parallelization, which improve the speed of grid displayingand expand the size of the grid generation; The multi-function display technology isdesigned to realize the mesh grid and the wireframes graph display; The CT(Computed Tomography) ideological is employed to display the two-dimensionalslice and three-dimensional cutting anywhere in the X, Y or Z direction after gridgeneration, and detect the quality of grid generation observe entity internal structurebetter;(4) Digital modeling software is employed to do the large-scale complex structureof digital modeling. The software can realize the mesh modeling of all kinds ofancient buildings and can reconstruct their structure on the computer, it can also wellpreserve the data information of cultural relics; The grid model of modern large-scalecomplex structure is obtained to lay a foundation for numerical analysis;(5) The interfaces between the digital modeling software and three dimensionaldynamics software（DYN-3D）and the finite element software ANSYS are reasonablydesigned. The grid model parameters of digital modeling software are employed inthe calculation software to check the reliability and stability of the software. Threeengineering problems are selected for numerical analysis in this paper, the damageeffect of dynamite explosion in the subway(DYN-3D software), the stress of the threegorges dam under hydrostatic pressure state and the influence of seismic waves withinthe mountain bunkers (ANSYS software);(6) There must be some small defects in the digital modeling software which ispowerful scientific software. These defects are random but do not affect the mainfunction of the software and the detection of the defects are very troublesome.Therfore, an improved MDP model in software testing and a new optimizationsoftware testing strategy are proposed to reduce the cost expectation test greatly. Thetesting strategy can reduce the time and cost of the digital modeling software testingand lay the foundation for the next step work.