https://popups.uliege.be/esaform21/index.php?id=1463 Publications of Auteurs Marion Merklein fr 0 https://popups.uliege.be/esaform21/index.php?id=3876 Packaging steel is characterized by low thickness (0.1 mm – 0.5 mm) and ferritic microstructure resulting from low carbon contents. In combination with continuous annealing processes and temper rolling, this results in only little elongation observed in tensile tests. However, as in real forming processes much higher deformation occurs, it is important to receive true stress-true strain data up to a highest possible level e.g. to characterize material for finite element analysis. Therefore, tensile tests with three different measuring lengths (80 mm, 50 mm, 20 mm) were conducted for the packaging steel TH415. Likewise, the testing speed was reduced to investigate the possibility to receive more elongation under the condition of a constant stress level. The results revealed a significant increase in elongation when using smaller tensile test geometries. As well, the reduction in testing speed leads to much higher elongation while showing only little strain rate influence. While for the 80 mm geometry and standard speed no homogenous forming condition could be reached due to early failure before Lüders strain, this could be improved by using smaller testing specimens and a lower strain rate. Combining the influence of strain rate and geometry a significant increase of more than ten percentage points in elongation was reached. Mon, 29 Mar 2021 14:53:46 +0200 Thu, 08 Apr 2021 21:13:53 +0200 https://popups.uliege.be/esaform21/index.php?id=3876 https://popups.uliege.be/esaform21/index.php?id=3831 The application of high strength aluminum sheet metal components in automotive and aviation products effectively saves material and thus weight. Material strengthening can be realized by accumulative roll bonding (ARB), which belongs to the severe plastic deformation processes. Through repeated rolling steps a multilayered sheet metal is produced, which possesses increased strength due to its ultra-fine grained microstructure. Prior to each rolling step a surface treatment via wire brushing is mandatory for removing the oxide layer and roughening the sheet surface, which enables the bonding between the unique layers during rolling. The necessary surface treatment of the sheets is not fully understood by the current state of the art. In the past, it was not possible to achieve a defined and stable surface finish, because the brushing operation was done manually. The improvement of the process stability is essential to determine the relationship between the input parameters for brushing and the resulting bond strength of multilayered ARB sheets. For this reason, a robot-controlled surface treatment is introduced. The investigated material is the precipitation-hardened aluminum AA6014 with a sheet thickness of 1 mm. A suitable brushing kinematic under constant load is implemented and its effects on the surface properties are investigated by roughness measurements. The investigation shows, that the parameter combination leads to comparable or even higher roughness values than through manual brushing. Through 16 consecutive brushing paths a homogeneous and sufficient high surface roughness is realized, which enables material bonding in the rolling step. Thus, the research results indicate, that the robot-assisted surface treatment of ARB sheet metal is a promising method for a better automation and reproducibility of the brushing and the overall ARB process. Mon, 29 Mar 2021 14:47:26 +0200 Thu, 08 Apr 2021 20:55:16 +0200 https://popups.uliege.be/esaform21/index.php?id=3831 https://popups.uliege.be/esaform21/index.php?id=3826 Steel fibers as concrete reinforcement improve the building material’s mechanical properties and enlarges its field of application. The production of steel fibers by the process chain notch rolling and cyclic bending promises energetic improvement compared to the conventional manufacturing process wire drawing. The innovative procedure is not yet researched extensively and modelling of the material behavior brings with it many challenges. Different stress states of both process steps require various material models and material failure must be considered. The study brings an appropriate modelling of the test sheet metal DP600 with a thickness of t0=0.8 mm for the second process step into focus. The wire strip’s notches are exposed to a cyclic tension-compression load for which high strength steel exhibits early yielding and a distinct transient region of the stress-strain curve after load reversal. For this reason, the isotropic-kinematic hardening model by Chaboche and Rousselier determined in tension-compression tests is validated by cyclic bending tests. For considering crack initiation, an appropriate ductile damage model for depicting material fatigue is identified. To allow practical realization of the process and validation of the material model, an experimental test method for manufacturing wire strip samples by notch stamping is introduced. Mon, 29 Mar 2021 14:45:38 +0200 Thu, 08 Apr 2021 20:53:00 +0200 https://popups.uliege.be/esaform21/index.php?id=3826 https://popups.uliege.be/esaform21/index.php?id=3673 Due to the ongoing technological development, the demand for geometrically complicated high performance parts with great functional density is increasing. Often, the use of sheet metal is a beneficial approach in manufacturing technology to meet the requirements on components regarding material strength and lightweight construction goals. The forming of therefore required complex sheet metal part geometries with integrated functional elements cause the need for a three dimensional material flow. Sheet-bulk metal forming, characterized by the application of bulk forming operations on sheet metals, is a suitable approach to produce such components. A challenge is the material flow control, resulting in an insufficient die filling of the functional elements. The use of tailored blanks with a defined sheet thickness distribution is an auspicious approach to face this challenge in subsequent forming processes. In the presented work, semi-finished products with a continuous thickness profile manufactured by orbital forming are applied in a full forward extrusion process. By an additional implementation of a heat treatment, the tailored blanks undergo a recrystallization process that causes a softening of the strain hardened material. In this paper, the potential of a heat treatment in the process class of sheet-bulk metal forming is shown by characterizing the geometrical and mechanical properties of the functional components by applying the mild deep drawing steel DC04 with an initial sheet thickness of t0 = 2.0 mm. Mon, 29 Mar 2021 14:01:44 +0200 Thu, 08 Apr 2021 19:12:57 +0200 https://popups.uliege.be/esaform21/index.php?id=3673 https://popups.uliege.be/esaform21/index.php?id=2124 Additive manufacturing (AM) has many advantages compared to conventional processes. Of particular interest is the tool-less manufacturing of components, which allows one component to differ from the next completely and has the possibility of producing complex geometries. At the same time, however, AM has deficits such as long production times, low production tolerances and low surface qualities compared to conventional processes. Therefore, a finishing process using machining is often necessary, which extends the manufacturing time and produces waste. Thus, the avoidance of machining rework is of high interest, especially with expensive materials such as stainless steel or titanium. One approach to avoid machining processes is to use forming technology. By applying a forming operation, surfaces can be smoothened and geometrical aspects can be defined more sharply. Especially for functional surfaces, this procedure is favorable because of the work hardening, which in turn increases the strength of the material. Using the example of laser-based powder bed fusion (PBF-LB) followed by a cup backward extrusion process, two materials, which are frequently used in AM are investigated. On the one hand, the titanium alloy Ti-6Al-4V, as a material with low machinability and low formability at room temperature, and the stainless steel 316 L. Compared to Ti-6Al-4V, 316 L has a higher formability. Cylinders are built using PBF-LB and then formed to smoothen the surface and achieve a higher geometrical accuracy concerning edges. Formed, additively made parts have a more defined geometry, namely sharp edges and a surface roughness reduced by up to 90 %. Tue, 23 Mar 2021 12:56:32 +0100 Mon, 12 Apr 2021 10:35:39 +0200 https://popups.uliege.be/esaform21/index.php?id=2124 https://popups.uliege.be/esaform21/index.php?id=1911 The use of high-strength steel and aluminium is rising due to the intensified efforts being made in lightweight design, and self-piercing riveting is becoming increasingly important. Conventional rivets for self-piercing riveting differ in their geometry, the material used, the condition of the material and the coating. To shorten the manufacturing process, the use of stainless steel with high strain hardening as the rivet material represents a promising approach. This allows the coating of the rivets to be omitted due to the corrosion resistance of the material and, since the strength of the stainless steel is achieved by cold forming, heat treatment is no longer required. In addition, it is possible to adjust the local strength within the rivet. Because of that, the authors have elaborated a concept for using high nitrogen steel 1.3815 as the rivet material. The present investigation focusses on the joint strength in order to evaluate the capability of rivets in high nitrogen steel by comparison to conventional rivets made of treatable steel. Due to certain challenges in the forming process of the high nitrogen steel rivets, deviations result from the targeted rivet geometry. Mainly these deviations cause a lower joint strength with these rivets, which is, however, adequate. All in all, the capability of the new rivet is proven by the results of this investigation. Tue, 23 Mar 2021 10:35:05 +0100 Mon, 12 Apr 2021 10:05:15 +0200 https://popups.uliege.be/esaform21/index.php?id=1911