The Research On Machining Simulation Based On Three-dimentinal FEM

As upgrade of products being faster and faster, the enterprises have to speed up the design and manufacture of the products to meet all kinds of demands from consumer. As a result, the theories and the key technology about the virtual manufacturing have been developed and applied by companies from different points. CAD/CAM as the key technology is playing a more and more important role during the product's design and manufacture. But existing machining simulation systems mainly foucs on geometrical simulation, which can not display the physical phenomenon during machining. Also some information after machining can not be sent back to improve the process, to make it faster from design to manufacture. So as to decrease the times of feedback between design and manufacture, a lot of researchers did their best to reflect the machining more veritably, and many models about machining physical simulation were established. Through the analyzing and synthesizing machining simulation at home and abroad, The paper hase done some work on integration of geometrical and physical simulation.In chapter 1, the history of cutting machining simulation is introduced and the present research about the cutting physical simulation is offered and concluded. For the purpose of integration of FEA and machining simulation, in chapter 2 a mechanics model about cutting based on the principles of machining is built applying three-dimensional finite element static method. Tetrahedron element as media, employing working process discretization from geometrical simulation, it removes cutting scrap and analyzes the workpiece using FEM at the same time, and results of the analysis are sent back to the workpiece. The combination of above methods makes the integration of geometrical and physical simulation possible.To realize the model, the related technology is studies in the chapter 3 and 4. The workpiece and scrap are separated by the nodes created from AFT based on the cutting parameters. Taking B-rep solid model as input, the elements used in the finite element analysis can be got by means of Delaunay tetrahedron meshing. In this situation the elements are not broken during cutting scrap. To speed up the solution to finite element equation, the method of Gauss iteration for system of linear equations is modified. The equation modification criterion is confirmed to accelerate the finite element analysis, while the methods of chip separation and boundary conditions application are offered.In the chapter 6, a machining simulation system is offered. Based on the OpenGL. the three-dimensional simulation environment is built using VC++6.0 development tool. Several classes needed in the simulation system are created according to the machining model and related technology. By the system, the follow functions are implemented: displaying a three-dimentional solid, human-computer interaction, the static analysis to solid and the machining simulation. At last, an example about simulating turning a long and thin shaft is given. In addition, machining tolerance model which resulted form cutting force making workpiece deformed during the turning is offered.