Investigation of the Influences on the Indentation of tubes under lateral loads by segmented forming tools using DoE

Making the widely used bending processes with geometry-specific tools, such as compression bending, more flexible in terms of the part geometries that can be produced with a single tool set, is a current challenge as mass customization and small batch sizes demands on manufacturing technologies. One approach is to segment the tools and thus add degrees of freedom that allow the die to adapt to different part geometries. However, the discrete surface can cause part defects such as localized indentations and until now, there has been no design method for segmented surfaces. As a step to close this gap, this study presents a statistical, finite element (FE) simulation-based design of experiments (DoE) to investigate the main influences on the indentation depth in the lateral indentation of circular steel tubes by segmented tool surfaces, considering both tool surface parameters and tube properties. The resulting regression equation is then used to compare the prognosticated indentation depths with those obtained from FE simulations and to develop a first pre-design approach for segmented tool surfaces. The results of the simulation-based DoE show that the segment spacing, the wall thickness factor, the interaction between them, the segment radius and the interaction between the segment radius and the segment spacing are the main influencing parameters and, interestingly, the mechanical tube properties have no significant influence. Finally, it is outlined that the regression equation can be used as a pre-design tool and that refinements are necessary for its usage as a valid design tool.