The purpose of this research is the development of technology to make complex-shape closed-section parts directly from sheet blanks (direct sheet forming). Closed-section parts with large expansion of the circumferential length are expected to be formed by direct sheet forming. In this work, first, the deformation type of curved circular tubes is confirmed from the results of FEM analysis. Next, with reference to curved circular tubes, the deformation type of curved conical tubes is discussed. The validity of FEM analysis is confirmed by comparison with experimental results of curved circular tubes. It is clarified that curved circular tubes and curved conical tubes are formed with the same processes and deformation types (bending of sheet, axial bending of U-section, shrink flanging and plane-strain compression). However, in the 2nd process (axial bending of U-section) of forming curved conical tubes, longitudinal strain at the narrower side is greater than that at the wider side.
In the hot rolling process of aluminum, a roll coating is formed on the surface of the work roll. The roll coating consists of particles of aluminum, aluminum oxide, and coolant. When the roll coating is thick or nonuniformly distributed, it detaches from the work roll onto the surface of the rolled material, causing surface defects on aluminum products. Therefore, the condition of the roll coating must be properly managed. However, work roll monitoring techniques applicable in the hot and humid environment of the manufacturing process do not yet exist. To develop such monitoring techniques, we focus on the optical changes of the surface of the work roll and process these optical changes quantitatively by extracting image features from work roll images taken by a camera. The features we designed in this work were found to be effective in capturing the trend of optical changes of the work roll surface.
New formability evaluation methods are investigated for closed section parts manufactured from sheet blanks. New methods are based on an analytical approach and geometrical information. The authors proposed the developmental evaluation method in which in-plane strain is calculated by the development of product shapes. By the double-stage development using principal curvatures and series of tangential planes, the developmental evaluation method becomes applicable to shapes with large curvature. In this paper, the results of calculation by the proposed method are compared with the results of FEM simulation regarding on sheet forming into horn tubes. The horn tube, which consists of circular, conical and transient portions, is one of the typical shapes of automotive parts. The conclusion is that the two sets of calculation results are in good qualitative agreement. For product shapes with widely spread relatively small strain which is introduced in forming processes, the geometrical condition is dominant for the strain distribution and the prediction accuracy of the developmental evaluation method is improved.