Research On Flexible Parametric Die-face Design For Automotive Panels

The design of automotive panel die is the core factor to restrict the rate and quality of automotive products development. As the first link of die design, die-face design directly determines the complexity of die structure and the formability of the die results in a decisive role in die design. With the rapid development of CAD/CAE integrated technology, CAE-oriented parametric die-face design for automotive panel has been extensively researched. At present, some commercial available CAE analysis software packages have introduces corresponding die-face modules. However, these software systems have "shortcomings in editing the section curves and constructing addendum surfaces. Meanwhile, the research on die CAD/CAE integration techniques in China have lagged behind, it is urgent to make effort in the study on CAE-oriented parametric die-face design. For all this, to build a system on CAE-oriented parametric die-face design for automotive panel, NURBS is employed to study some key techniques on that. The main contents of this dissertation are as following:(1) Realize the functions of extracting part edges、hiding flange、determining the stamping direction for parametric die-face design on ACIS platform.(2) To decrease the quantity and the depth of the concave regions for facilitating the addendum-design, a smoothing method for automotive panels based on offset technique of polyline is proposed, and the smoothing curves and surfaces are constructed by NURBS. It shows that our method is robust to accurately find all smoothing regions with no errors and adjustments, which has great applicability and reliability.(3) To enhance the efficiency and stability of die-face design, an editing strategy for2D section feature and its optimization algorithm are proposed based on the template technique, which are conductive to the formation of standardize design habits and could avoid abnormal problems; The covering method is adopted to obtain the original NURBS patch surfaces, and then sub-surface models are merged to generate an overall smooth model. This method could reduce the order of the model、the complexity of algorithm and is convenient to modify the local shape; All of curvilinear and free-formed surfaces are expressed in the same form for the utility of NURBS method, and it is advantage for the flexible editing. Finally, effective and applicability of the proposed method are verified by the front fender part.(4) Aimed at the low/distortion phenomena appearing at the surface, of outer panels during stamping process, a flexible corrective method based on geometry morphing algorithm is proposed. Three corrective approaches:good bearing、holes in blank and die face morphing are tried out by specimens with typical depression features, and laser scanner is performed to measure the surface low/distortion at the corner areas of the depression feature. The experiments results show that die face morphing is a practical and effective method to minimize the occurrence of surface low/distortion.