Research On Computer Visualization Technologies And Software Development In Three-Dimensional Finite Element Based Numerical Simulation System For Bulk Metal Forming Processes

In the course of industry modernization, progress in technology and innovation in science are the theme of this course. The advanced manufacturing technology represented by computer aided design/ manufacture/ engineering, is the most active part in fields of application and academic research. With the development of computer technology and the metal forming theory, the 3-D FEM (Finite Element Method) based numerical simulation for metal forming processes can be realized on computer. The detailed information in the metal forming processes can be obtained through the numerical simulation. It gives a powerful tool or means for the optimization of process design and die design in bulk metal forming.Pre-processor and post-processor are the most important parts in FEM simulation system. Today, although two-dimensional visualization algorithms have been widely used in engineering software, most of the advanced 3-D methods are still under research because it can hardly meet the real-time requirement of FEM application software due to the complexity and irregularity of 3-D solid FEM models and meshes, especially the visualization research of hexahedral mesh. Therefore, research on computer visualization technologies and software development in three-dimensional finite element based numerical simulation system for bulk metal forming processes is very important for improving the level of domestic engineering software.This paper mainly studied the algorithm about removing hidden lines, contour lines, arbitrary section and data-field visualization after sectioning on the basis of eight-node isoparametric elements. In the part of removing hidden lines, each polygon is outlined in the foreground color, filled with the background color, and then outlined again in the foreground color, and by using polygon offset the visual unpleasantness can be eliminated .The scheme make the hex-mesh and its contourdisplayed on computer more quickly and clearly. The color property of uniform transition makes nephogram easy and possible. OpenGL' pipeline and back-transformation take an XY window coordinate and return the ack-transformed XYZ object coordinate equivalent, then construct a section plane. Thus users can clearly observe the inner data distribution and trend. In the part of contour on three-dimensional FE model, the concept of "visual node" is introduced to surface or arbitrary section of hex-mesh FE model. The contour generation method based on "triangulation" is clearly in principle, simply in programming and accurate in showing. The example for the forging process of an aluminum alloy rear lower arm is illustrated to make the algorithm easier to be understood, especially the method of hexahedral mesh regeneration.Based on the above research, Combined with the knowledge on computer graphics, the Pre-processor and post-processor of CASFORM-3D-a three-dimensional numerical simulation system for metal forming are developed on the windows using Visual C++ and OpenGL. CASFORM-3D has friendly GUI. The characteristics of the Pre-process are automatic generation (regeneration) of hexahedral mesh, automatic transformation the data between new and old mesh system. The post-processor is versatile, including transformed-mesh graph, contour lines, nephogram, velocity vector and load-stroke curve. The effectiveness of the proposed techniques has been confirmed by examples. It can simulate the metal forming process such as forging and extrusion effectively.