https://popups.uliege.be/esaform21/index.php?id=1526 Index terms fr 0 https://popups.uliege.be/esaform21/index.php?id=2129 The measurement of thermoelectric current is a new and effective method for inline wear detection in sheet metal forming. The measuring principle is based on the Seebeck effect, whose characteristic value, the Seebeck coefficient depends on the material composition. In the previous research of the authors, a boundary value of the thermoelectric value that separates the mild and severe wear was identified. Due to the large deviation of the Seebeck coefficient of the material used in sheet metal forming, it is worth discussing the influence of the Seebeck coefficient of the sheet metal material on the effectiveness and boundary value of the thermoelectric current for wear detection. In this paper, the measuring principle is first illustrated using an equation based on thermoelectricity. The Seebeck coefficients of the tools and sheet metals are then determined by a specifically designed device. At the same time, the wear tests for different materials are used to determine the boundary values for different tribological systems. Finally, the obtained Seebeck coefficient and boundary values are compared. From the results it can be concluded that the value of the measured Seebeck coefficients have a discernible effect on the boundary values, which provides a useful insight for inline wear diagnosis for practical applications. Tue, 23 Mar 2021 13:01:48 +0100 Fri, 14 May 2021 14:44:18 +0200 https://popups.uliege.be/esaform21/index.php?id=2129 https://popups.uliege.be/esaform21/index.php?id=2151 Auxiliary systems for sheet forming processes are widely used to improve products accuracy and increase tools life. As example, in blanking hydraulic dampers are widely used to reduce shocks and vibrations; nitrogen springs are often integrated in deep drawing tools to correct the ram tilt or to locally increase the blank-holder force, obtaining geometrical features on the stamped blank with one press pass. In this paper, a Magneto-Rheological (MR) semi-active actuator is developed for sheet forming operations and the interaction between MR fluid and electromagnetic field is investigated by Finite Element (FE) analysis. To overcome the limitations of gas springs and hydraulic actuator, the static electromagnetic circuits is reconfigured with respect of conventional MR actuators known in the state-of-the-art. The novel MR actuator has an inner bore where the electric windings are placed, while the narrow gap, in which the active MR fluid flows, is obtained between the inner bore and the cylinder internal surface. The resulting magnetic fields H and induction fields B, as well as the selection of components materials, are studied through the magneto-static FE model. The results from FE simulations show a longer activation length along the gap resulting in higher controllable forces values, without increasing the overall dimensions of the proposed prototype. Tue, 23 Mar 2021 13:27:28 +0100 Mon, 03 May 2021 11:12:09 +0200 https://popups.uliege.be/esaform21/index.php?id=2151 https://popups.uliege.be/esaform21/index.php?id=1525 The accurate prediction of forming defects is fundamental for the virtual try-out of metallic sheet components. However, the constitutive model can have a strong impact on the numerical predictions, namely the cup earing, the occurrence of wrinkles and the tearing failure. The process conditions considered in this work are the ones established for the “Benchmark 2 – Cup Drawing of Anisotropic Thick Steel Sheet”, proposed under the Numisheet 2018 international conference. The axisymmetric cups are obtained from a steel sheet with 2.8 mm of thickness, resorting to different process conditions to induce different defects. The advanced yield criterion proposed by Cazacu and Barlat is used to define the anisotropic behavior of the blank. The calibration of the material parameters is carried out by fitting the following experimental data from: (i) uniaxial tensile tests performed in every 15º to the rolling direction; (ii) biaxial tension tests to evaluate the directions of the plastic strain rates in the first quadrant of the yield loci. The numerical predictions are compared with the experimental measurements, allowing to assess the accuracy of the finite element model to predict each type of forming defect. The cup earing and the strain localization are accurately predicted, while the wrinkles amplitude is clearly underestimated. Mon, 22 Mar 2021 20:07:36 +0100 Mon, 12 Apr 2021 10:56:43 +0200 https://popups.uliege.be/esaform21/index.php?id=1525 https://popups.uliege.be/esaform21/index.php?id=1887 Polymer coated steels are used in the packaging industry to produce a variety of products, for example cans. During the production of the cans, the steel substrate and the polymer undergo a roughness development. The roughness development is important regarding the product performance and depends (among others) on the original grain size of the steel substrate. The goal of this paper is to investigate the influence of the grain size of the steel substrate on the surface roughness during the production process of the can. For this purpose, 3D topography measurements were performed after several process steps (drawing, redrawing and ironing) of can making. A larger grain size results in a higher roughness increase and a lower minimum coating thickness of the inside of the can. Tue, 23 Mar 2021 10:23:46 +0100 Mon, 12 Apr 2021 10:03:00 +0200 https://popups.uliege.be/esaform21/index.php?id=1887 https://popups.uliege.be/esaform21/index.php?id=3732 High process stability is needed in sheet metal forming industry. This can be achieved by predicting and controlling the transient process and temperature variation, especially at start of production. In this connection, the temperature induced friction changing plays a significant role because it leads to product failures. The handling of the transient friction effects is currently done reactively, based on the individual experience of the machine operators. In future, those transient effects need to be controlled. This paper shows initially an analysis of the temperature induced friction increase in a well-known and proven flat strip drawing test. Different tribological systems were tested at tool temperatures between 20 and 80 °C. The temperature increase results in a higher friction of up to 77 %. Several influences on friction increase will be presented. These friction influences were verified afterwards with a heated forming demonstrator under laboratory conditions. Mon, 29 Mar 2021 14:22:14 +0200 Thu, 08 Apr 2021 20:00:06 +0200 https://popups.uliege.be/esaform21/index.php?id=3732 https://popups.uliege.be/esaform21/index.php?id=2575 Fine blanking is a highly productive process of industrial mass production with which high quality components in particular but not exclusively for the automotive industry are produced. The manufacturing process faces its limits at elevated tensile strengths of the materials to be processed. Consequently, high-strength steels can currently only be fine blanked to a limited extent. This can be overcome by lowering the flow stress of high-strength steels by means of inductive heating. A steel of high importance especially for industries with high hygiene standards such as medical and nutrition production is the stainless steel X5CrNi18-10 (1.4301). As a metastable austenitic steel which can initiate cutting impact on the press through martensitization, fine blanking of stainless steel is a challenge. X5CrNi18-10 is not a high-strength steel per se but becomes difficult to process due to the high hardness of the martensite phase, known as transformation-induced plasticity (TRIP) effect. Thus, in order to combine the possible advantages of the fine blanking process with inductive heating and the important properties of stainless steel, fine blanking of this steel was investigated with inductive heating prior to the fine blanking. The process forces and product quality properties such as die roll were investigated and found to be advantageous in comparison to non-heated fine blanking specimens of the same steel. The process forces and the die roll height decreased due to the heating. Wed, 24 Mar 2021 18:19:07 +0100 Fri, 02 Apr 2021 14:51:13 +0200 https://popups.uliege.be/esaform21/index.php?id=2575 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=2483 Compared to cutting processes such as milling, forming processes like electrohydraulic forming offer advantages regarding resource as well as energy efficiency. Due to high tooling costs, forming technologies are nonetheless considered as economically inefficient for low production quantities. Using a combination of high-speed forming with 3D printing technologies for tool manufacturing, three variants to reduce tooling time and costs for processing sheet metals for small quantities were proposed. Since the dies have to withstand high dynamic loads, 3D-printed low-cost dies made of polylactide (PLA) are limited regarding their form stability, mainly depending on the forming energy and sheet thickness. To enlarge the scope of application for 3D-printed dies a method to reinforce these dies is presented and investigated. Armoring of the dies was achieved by electrohydraulic cladding of the dies with 0.5 mm thick aluminum sheet metals. To characterize and compare the properties of the unarmored and the armored polylactide dies, specific characteristics of the formed sheet metals concerning the die wear and the molding quality were investigated. Polylactide dies enabled embossing of fine structures in addition to the forming of the die shape. Armoring of the dies led to a reduction of the embossed layer structure. Therefore, the armoring can be used as a way to control the characteristics of the formed sheet metals. In a further step, the cladding sheets were produced with copper sheet metals and used as sinking electrode for electric discharge machining of steel dies. Tue, 23 Mar 2021 20:21:45 +0100 Tue, 30 Mar 2021 09:37:17 +0200 https://popups.uliege.be/esaform21/index.php?id=2483