https://popups.uliege.be/esaform21/index.php?id=458 Publications of Auteurs Mathias Liewald 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=2824 The research subjects of current investigations at the Institute for Metal Forming Technology (IFU) Stuttgart include the manufacture of face gearings. Usually, gearings are produced by means of a coining process, which causes high process forces that considerably restrict the geometry of the teeth in terms of the height-to-width ratio. In order to avoid these problems, a new forming process has been developed. This technology offers significant advantages, such as the reduction of process forces and the ability to manufacture the required tall and acuminate tooth elements through a cold-forming process. This paper describes the design and functionality of the novel pin-to-gear forming process. In this paper, the operating principle of the method is presented first of all. The new pin-to-gear process is then compared to conventional coining and the free-divided-flow (FDF) process developed at IFU Stuttgart in 2018. This examination takes the form of a numerical simulation using DEFORM-2D software. To investigate the influence of preform parameters on the form filling of the tooth cavities, parameter studies in design and geometry are conducted. Process limits regarding geometric constraints are presented alongside possibilities for increasing process reliability. Through this investigation, the potential and opportunities of the innovative pin-to-gear forming process will be illustrated. Wed, 24 Mar 2021 19:06:51 +0100 Sat, 10 Apr 2021 14:00:48 +0200 https://popups.uliege.be/esaform21/index.php?id=2824 https://popups.uliege.be/esaform21/index.php?id=1954 Shortened product development processes in automotive industry combined with the upcoming lack of experts do challenge sheet metal part production fundamentally. Tryout time and manufacturing costs of large forming dies today are significantly influenced by their digitally supported engineering. The forming process by such tools is beside other influences is affected by elastic deformations of forming dies and press structure as well as contact areas between die and sheet metal part. In deep drawing such contact areas are influenced by the blank properties and the flange behavior in terms of thickening and thinning. Recent developments in sheet metal forming simulation do consider advanced friction models and structural modeling of die and press components improving simulation accuracy. Nevertheless thinning or thickening of sheet metal results into localized surface pressure distribution during deep drawing. For this reason, it is not sufficient to use the currently common practice of homogeneous surface pressure distribution in sheet metal forming simulation. In this respect, this paper presents a numerical approach for consideration of straining effects in the sheet metal part during forming operation. For this purpose, a systematic process improvement was developed in this paper to identify contact areas via a numeric simulation parameter. Validating the numerical investigation, a rectangle cup die is used, considering major strain. The main results of this contribution for that reason show how simulated contact areas can be estimated by reverse engineering of real forming parts. Hereby straining based contact areas lead to a novel contact area design in process planning, resulting in efficient die tryout. Tue, 23 Mar 2021 11:15:03 +0100 Tue, 23 Mar 2021 12:07:12 +0100 https://popups.uliege.be/esaform21/index.php?id=1954 https://popups.uliege.be/esaform21/index.php?id=1931 Cold forging tools become increasingly complex and require enhanced functionality, especially in the context of digitisation. Conventional subtractive manufacturing processes often reach their limits when the geometric complexity of the workpiece increases, hence additive manufacturing processes have become increasingly important in the last decades. Additive manufacturing processes have already been used in many fields of manufacturing technology to produce tool components with promising results, but the potentials of additive manufacturing processes have not yet been applied to cold forging tools. Therefore, the Institute for Metal Forming Technology (IFU) of the University of Stuttgart has developed an additive manufactured cold extrusion tool with integrated functional features. As functional features in the additive manufactured extrusion tool, a close contour glass fiber sensor for temperature measurement, a cooling system and a lubrication system for the controlled injection of minimal lubricant amounts during the forming process were integrated. Due to the integrated functional features, structural degradation appears in the tool, therefore the structural-mechanical tool properties were analyzed numerically with the FE-Software DEFORM 3D™ in this report as well. Furthermore, the additive manufactured cold extrusion tool was experimentally evaluated in sequentially executed extrusion operations. Thereby the integrated functional features were used and gathered data were recorded. As a result of the experimental forming tests, near-contour temperature measurements in the extrusion tool with and without the use of the integrated cooling system as well as the modification of the maximum punch forces by an inline lubricant application were obtained. In addition, the experimentally determined temperature fields in the extrusion die are validated with numerically calculated results. Tue, 23 Mar 2021 10:41:38 +0100 Mon, 12 Apr 2021 10:08:38 +0200 https://popups.uliege.be/esaform21/index.php?id=1931 https://popups.uliege.be/esaform21/index.php?id=455 For economic or process-related reasons, punching of structural sheet metal components often has to be used for car bodies. The difference in angle of attack between punch and sheet metal component is referred to as “slant angle”. However, at the current state of the art, no precise information is available on the characteristics of cutting surfaces in relation to the slant angles. For this reason, cost-intensive slider units are used for comparatively small slant angles of around 10° in order to ensure series suitability of corresponding punching processes. In this respect, recent studies performed by the authors have shown that good cutting surface qualities can also be achieved for slant angles distinctly beyond 10°. This contribution presents an empirical test series for the characterization of cutting surface parameters when punching with a slant angle. Here, the experimental cutting surface analysis showed an asymmetric characteristic of the cutting surface along the hole circumference. Furthermore, the investigated sheet metal materials HC340LA, DP600 and DP800 revealed recurring tendencies regarding the parameters “edge draw-in”, “clean cut”, “fracture surface” and “burr height”, which had been combined to corresponding three-dimensional regression models. With these regression models, cutting simulations could be calibrated, allowing a quality prognosis of cutting surfaces achievable when punching at specific slant angles. Fri, 19 Mar 2021 21:43:42 +0100 Fri, 02 Apr 2021 18:06:22 +0200 https://popups.uliege.be/esaform21/index.php?id=455