Based On Csg Structure Of 3 D Meshing Technique In The Application Of Microwave Tube Cad Technology

With rapid development of modern computer technology and numerical simulation method, the technology of computer aided design (CAD) has gradually developed. It has been a testing method for its advantages of production efficiency improving, cost saving and processing cycle reducing. Mesh subdivision is essential to CAD technology and influential to simulated calculation accuracy.The finite element method mainly uses triangle and tetrahedron mesh unit, it is used widely in sorts of engineering design owe to its superior boundary approximation and systematic treatment process. The microwave tube simulator suit (MTSS) is designed with the finite element method by Theory and Computer Simulation Laboratory of University of Electronic Science and Technology, and it has been applied in microwave tube producing institutes of domestic. But in this entire research process, mesh subdivision has negative influence on solution accuracy and calculation velocity. Therefore, liberalization of mesh control becomes extraordinary significant for improving status.The data model with three dimensional is generally divided in three categories: representation based on body (etc. Constructive Solid Geometry (CSG) method), representation based on boundary (etc. B-rep method), representation of decomposition model(etc. model factorization method).In this thesis, mesh subdivision technology which focuses on aspectual CSG is mainly investigated. Traditional CSG composition method uses simple and regular volume elements or their Boolean operation to construct3-D model. However, it’s difficult to construct some entity involves random curved surface (etc. spiral structure in traveling wave tube). Draw lessons from ex-research, an algorithm which uses model compositing with2-D quadratic and3-D quadratic B spline to fit curve and curved surface piecewise. The traditional CSG method is improved by adding two extended basic volume describing curve and curved surface. Finally,3-D structure mesh provided by MTSS is subdivided integrally.The following are the main work of this thesis: 1.3-D Delaunay mesh and AFT mesh subdivision technology are investigated; in addition, basic theory, optimization method, development trend, and research significance of3-D mesh subdivision are summarized.2. CSG composition method research and analysis including the defect of traditional CSG are penetrated; an algorithm with spline fitting curved surface graph is finally opted.3. An algorithm of CSG composition and its corresponding C++algorithm, specific UML graph are represented, file format generated from mesh subdivision software of laboratory is transformed and saved in CSG structure.4.3-D mesh subdivision algorithm is presented based on graph describing pattern of CSG, surface mesh and aspectual mesh are obtained and optimized through AFT method and Delaunay triangulation respectively.5. Sorts of structure involves curved surface(including spiral structure) and mesh subdivision samples of electron gun, collector and cycle frequency structure in microwave field are presented so as to inspect and verify the feasibility of method.