https://popups.uliege.be/esaform21/index.php?id=3383 Index terms fr 0 https://popups.uliege.be/esaform21/index.php?id=4146 The subjective perception of the quality of sheet metal components mainly depends on geometric characteristics and surface structure. Additionally, particular attention must be paid in this context to avoiding surface defects such as skid lines during the sheet metal forming process. For this reason, current research activities focus on predicting such surface defects as precisely as possible in the early development stages of sheet metal components by using FEM simulation. However, the modelling approaches available today do not yet provide an adequate basis for such a numerical prediction regarding the appearance of surface defects of sheet metal components such as car body outer skin panels, especially of skid lines. Consequently, the research work reported about in this paper concentrates on the development of an empirical methodology for predicting and quantifying the formation of skid lines during deep-drawing processes by using FEM simulation. For this purpose, an experimental tool was developed to produce different skid line formations by using various process parameters and thus to investigate process-influencing factors on the example of the steel sheet material DC06. In principle, the investigations carried out showed that the punch radius and the blank holder force indeed do represent crucial influencing factors for the formation of skid lines. Finally, the results obtained were used to develop a forming simulation criterion, which allows predicting skid lines formations based on calculated strain state variables such as major strain, thinning and unbending strain. Wed, 31 Mar 2021 15:37:04 +0200 Wed, 31 Mar 2021 15:37:09 +0200 https://popups.uliege.be/esaform21/index.php?id=4146 https://popups.uliege.be/esaform21/index.php?id=4131 Niobium is a ductile transition metal of growing interest for several technological applications, thanks to its intriguing characteristics, among them high melting point, moderate density, good ductility, high corrosion resistance and superconductivity. By contrast, its use is limited by some weaknesses lied to the mechanical properties, which can undermine the quality of the surfaces worked by metal forming processes. Sheets of pure Niobium can be used for the manufacture of extremely customized components and a flexible process like the incremental sheet forming fits well with this manufacturing philosophy; in fact, this technique does not require complicated tools and/or dedicated equipment and is capable to respond quickly to the market demands. The scope of this paper is to investigate the influence of the tool/sheet contact conditions on different features like the forming loads, the surface quality and the occurrence of failures, when pure Niobium rolled sheets are formed incrementally. To this aim, the simplest variant of incremental sheet forming, namely single point incremental forming, was considered by using a common fixed end forming tool with hemispherical head. The process was carried out under dry and lubricated tool/sheet contact conditions, following the indications from a preliminary campaign of wear tests conducted by a pin-on-disk apparatus. The experimental campaign highlights the strong influence of the tool/sheet contact conditions and the importance of a correct choice of them on the features investigated, in order to limit the forming forces and the risk of failure, as well as to preserve the surface quality of the components made by incremental sheet forming of Niobium. Wed, 31 Mar 2021 09:09:19 +0200 Wed, 31 Mar 2021 09:09:19 +0200 https://popups.uliege.be/esaform21/index.php?id=4131