Research On Outer Smooth The Flange Of Auto Body Panel And Rapidly Automatic Reverse Normal Of Finite Element

During the automotive design and manufacture period, it is the main factor of auto product development speed and quality that the design and manufacture level of the auto body die especially auto panel die. In our country, rapid development of automobile industry and rapid update of new automobile model provide automotive die with huge market, and bring forward higher request to the die corporation at the same time. The application of CAD technology for auto panel at home is still on the level that the alternant plotting and modeling is done on the popular CAD software system with the designer's experience, which makes CAD software become a drawing board barely. So rapid numerical simulation design of stamping die is very important for quickening the speed of die design, improving the quality of die design , shortening the circle of die debugging and manufacture, reducing the cost of die.CAE technique which provides numerical die of CAD with simulation of stamping process can make die design more reasonable, and reduce the cost of die debugging in CAM. With maturation and application of CAE technique, adopting traditional method of stamping die addendum design must modify the addendum returned to CAD,when the addendum surface need modifying in CAE. Then a series of steps including mesh, fill hole, flange in CAE need doing again, so the efficiency of simulation will be depressed greatly.In order to improve the design quality of die surface and shorten the design circle of die surface, stamping Die-face which integrates CAD of die surface into CAE circumstance can implement die surface CAD connected with CAE without sew. This work not only does good exploration to the design mode of die in future, but also applies powerful support for improving the competition of die corporations. Research on outer smooth the flange of auto body panel based on ACIS and fast automatic reverse normal of finite element are presented in this paper. In contrast with the process of CAD-driving die-face design, there are some special steps for the CAE-driving die-face design. The most obvious difference is that the auto-body part contour needs smoothing earlier than the design of addendum surfaces does. It is helpful to improve the design quality of addendum surface. In spite of extensive researches on smoothing technique, there is still dearth of the published solutions about smoothing the part contour with additional surface. The additional surfaces, which are created by the contour of automobile panel and smoothing curve, have the continuity with the part surfaces at the boundary. The smoothing curve is used to smooth the part contour and created by the algorithm presented in the paper. The aim of smoothing the part contour is to close the open regions on the original part, to change the different drawing depth into an even one, to decrease the quantity and the depth of concave regions on part contour. This paper attempts to analyze the difficulties and provide practical solutions. Main results include the algorithm to calculate the segments needing to be smoothed on boundary, the strategy to create the smoothing curve and the procedure of surface generation. The relevant function modules for parametric design are developed.Based on the forming process simulation, DFE(die face engineering) is die face design development tendency. This article has discussed several outer smoothing essential technologies of outer boundary of auto-body panel, has produced the method of concave region judgement and create the smoothing curve and has developed the corresponding parameter design. Through to massive actual automobiles cover value simulation, has proven:1) technical mentality clear, complex is not high, easy to realize.2) curve describe by NURBS precise expression, the parameter design enable the curve with strongly controllable.3) may effectively enhance the addendum design quality, thus improves the manufacture of auto-body panel.Aim at the surface patch message in finite element , has proposed an rapid automatic reverse normal algorithm base on repair topology of finite element. The main idea origin is healing surface and repair topology in ACIS .Repair the gaps of surfaces for part imported from CAD, it becomes an unidirectional surface. A loop represents a connected portion of the boundary of a face. Loops may be open or closed. A loop is composed by a series of coedges. The normal of surface and coedge conform the right-hand rule. The direction of coedges of neighboring surfaces is opposite. Actually, makes the direction of finite element to be consistent is the same to make the surface to become an unidirectional surface by healing the surface and repairing topology. Each triangle element or quadrangle element can be seen as a small plane and each quadrangle element can be seen as a small surface, the sides of each element can be seen as a Loop. Also, each side of an element can be regarded as a coedge. The direction of a coedge is form the start-point to end-point. If we want to maintain the normal of two neighboring element be consistent , we must guarantee the direction of the coedge of the same side that belongs to the two element is opposite.This algorithm has stronger compatibility. Though the surface has same flaws . For example ,the surface has crack and overlaps. During reverse normal of elements, it can remove the overlap element that has realized to the element preliminary optimization. This algorithm is very importance to judge the contact question in the forming process simulation and judge offset direction in the fast offset algorithm of auto-panel forming surface.A fast and effective normal consistent algorithm base on repair the topology of finite element is an very important step of pre-process of CAE-automatic reverse normal of finite element, and passed massive examination test of complex automobile components. The computed result indicated that this algorithm has following several aspects characteristic:(1) This procedure is very fast and accurate. Because of repairing topology, it can effective avoid the problems of finite element that caused by crack and overlap of surface. (2) this algorithm is easy to realize and effective and occupies the memory few.