In a sheet metal forming process, fracture and wrinkle are the most difficult task in new parts launching. The variation in process condition generates the fracture and wrinkle fluctuation. The fracture and wrinkle are very sensitive to the process conditions, then the main effects of the design variables cannot be obtained from the standard mean analysis. Therefore, in order to minimize the fracture and wrinkle in parts of automobile, a special method to counterpart is required. In this study, a new design method to achieve the optimal in the sheet metal forming process is proposed. The effectiveness of the proposed methods is shown with an example of the parts of fracture and wrinkle.
The most time consuming job in the sheet metal forming process is compensating for springback. Factors such as uneven material properties and process conditions generate noise, which in turn create springback. The springback is very sensitive to the process and noise conditions, and the main effects of the design variables cannot be obtained from mean analysis. Therefore, to achieve minimal springback, an effective design countermeasure must be put in place to reduce noise effects. In this study, two robust design methods to achieve minimal springback in U-channel forming, including compensation process, are proposed. The effectiveness of the proposed methods is shown with an example of the sidewall curl springback. The proposed methods consistently outperform our previous work, indicating that the complex method is more preferable to the mean analysis, if there is no evidence of additivity of effects.
The most time consuming operation during the tryout of new parts is the compensation of geometric deviations induced by springback. The variation of springback due to the noise factors such as material properties and forming conditions increase the difficulties of the compensation operation. If the forming process includes a drawing operation followed by a restriking operation, a robust design for springback compensation is needed for both operations. In this study, a new 2-stage procedure for robust springback compensation using Taguchi's orthogonal array experiments combined with the Pick-the-Winner rule and the design space reduction method is proposed. The effectiveness of the proposed method is shown with an example of the sidewall curl springback compensation in U-channel forming.
The flat type automotive cross members with high strength steel have advantages in light weight and fewer parts compared to the hump type cross members. But the complex part shape of the flat type cross member and the poor formability of high strength steel make it difficult to form the parts without forming defects, such as splits and wrinkles. The purpose of this study is to develop the flat type automotive cross member with high strength steel. For that purpose, drawing processes are evaluated using PAM-STAMPTM and proper draw die and blank designs are proposed. Using the proposed die and blank design, the flat type upper and lower cross member could be formed successfully without forming defects.
Increasing needs for light weight and high safety in modern automobiles induced the wide application of high strength steels in automotive body structures. The main difficulty in the forming of sheet metal parts with high strength steel is the large amount of springback including sidewall curl and twist in channel shaped member parts. Among these shape defects, twist occurs frequently and requires numerous reworks on the dies compensate the shape deviation. But until now, it seems to be no effective method to reduce the twist in forming processes. In this study, a new forming process to reduce the twist deformation during the forming of automotive structural member was suggested. This method consists of forming and restriking of embosses on the sidewall around the stretch flanging area of the part. and was applied in the forming process design of an automotive front side inner member with high strength steel. To evaluate the effectiveness of the method, springback analysis using Pamstampa™ was done. Through the analysis results, the suggested method proven to be effective in twist reduction of channel shaped parts with stretch flanging area.
In spite of relatively high prices, aluminum wheels rapidly replace traditional steel wheels because of light weight and stylish design. To cope with expanding aluminum wheel market, steel wheel makers try to produce skeleton typed steel wheels adopting high strength steel which are light, stylish and lowprice compared with conventional steel wheel. But skeleton typed steel wheel disks are difficult to form because of complex shapes and low drawability of high strength steel. This paper presents the drawing process design for 5-spoke skeleton steel wheel disk. Through the finite element simulation of various alternatives for multi stage drawing processes, desirable draw die designs were proposed.