https://popups.uliege.be/esaform21/index.php?id=89 Coordinators: Prof. Giusy Ambrogio and Prof. Mihaela (Miki) Banu Co-organisers: Prof. Beatriz Silva, Prof. Katia Mocellin, Prof. Torgeir Welo and Prof. Carpoforo (Foro) Vallellano Description: This mini-symposium focuses on contributions that detail new developments and enhance the understanding of incremental and sheet metal forming processes. The topics of interest include (but are not limited to) novel process designs, in-process measurement techniques, innovative tooling, methods for the analysis and modeling of friction phenomena and methods for the optimization, robust design and control of incremental and sheet forming processes. Mini Symposia fr Wed, 03 Mar 2021 09:37:52 +0100 Wed, 14 Apr 2021 09:58:36 +0200 https://popups.uliege.be/esaform21/index.php?id=89 0 https://popups.uliege.be/esaform21/index.php?id=331 Harmonic decomposition is an analytical technique that is able to express a manifold surface as the sum of a number of simple surface harmonic components. By reconstructing the initial geometry using a reduced number of components, a similar surface is obtained with a lower level of geometric detail. Because small features are filtered out and the resulting surface lies equal parts above and below the original surface, a tailored multi-step SPIF (Single Point Incremental Forming) processing strategy can be devised. This sequential SPIF strategy uses three processing passes to form a workpiece. The first step is a regular SPIF operation using a conventional toolpath strategy to form the reduced geometry. Two finishing steps are then needed, one from the same side to form the smaller features that lies deeper than the reduced geometry and one backwards pass from the other side of the sheet. To add features that need to be shallower than the reduced geometry, the part is flipped around. The used sequence of these finishing steps and the toolpath strategy used significantly influence the final part accuracy and surface quality. The advantages and disadvantages of four of these combined strategies are examined and compared to regular SPIF. Fri, 19 Mar 2021 15:38:57 +0100 https://popups.uliege.be/esaform21/index.php?id=331 https://popups.uliege.be/esaform21/index.php?id=419 Accurate prediction of the defects occurring in incrementally formed parts has been gaining attention in recent years. This interest is because accurate predictions can overcome the limitation in the advancement of incremental forming in industrial-scale implementation, which has been held back by the increase in the cost and development time due to trial and error methods. The finite element method has been widely utilized to predict the defects in the formed part, e.g., bulge. However, the computation time of running these models and their mesh-size dependency in predicting the forming defects represent barriers in adopting these models as part of CAD-FEM-CAE platforms. Thus, robust analytical and data-driven algorithms must be developed for a cost-effective design of complex parts. In this paper, a new analytical model is proposed to predict the bulge location and geometry in two point incremental forming of an aerospace aluminum alloy AA7075-O for a 67° truncated cone. First, the algorithm calculates the region of interest based on the part geometry. A novel shape function and weighted summation method are then utilized to calculate the amplitude of the instability produced by material accumulation during forming, leading to a bulge on the unformed portion of the sample. It was found that the geometric profile of the part influences the shape function, which is a function created to incorporate the effects of process parameter and boundary condition. The calculated profile in each direction is finalized into one 3-dimensional profile, compared with the experimental results for validation. The proposed model has proven to predict an accurate bulge profile with 95% accuracy comparing with experiments with less than 5% computational cost of FEM modeling. Fri, 19 Mar 2021 18:47:41 +0100 https://popups.uliege.be/esaform21/index.php?id=419 https://popups.uliege.be/esaform21/index.php?id=468 The use of high-speed forming technologies can contribute to satisfying current social and political demands on production technology such as sustainability and climate protection in manufacturing. These technologies have a very high potential for shaping complex, sharp-edged parts and constitute a key means of reducing a component’s weight. One exemplary high-speed forming technology is electromagnetic forming. It uses the energy density of pulsed magnetic fields to impose forces on electrically conductive materials, which leads to plastic deformation when reaching the yield stress of the material. However, for very thin sheet materials this effect can result in an uncontrolled deformation of the work piece. In order to overcome this effect, electromagnetically driven tools the use of can be appropriate. An additional benefit is that this process is no longer restricted to electrically highly conductive work piece materials. This paper describes a media-based process using electromagnetically driven tools to form micro-flow channels, which are often used in bipolar plates, into thin sheet metals. The principles are explained and first results are shown. Fri, 19 Mar 2021 22:10:43 +0100 https://popups.uliege.be/esaform21/index.php?id=468 https://popups.uliege.be/esaform21/index.php?id=1237 The rubber and elastomer molding process has been used for many years in the aviation industry for piece production, small series. Due to the current development of plastics in the field of polyurethane, it is possible to obtain a plate hardness of 40-95 SHA, which allows for deep drawing of containers of various purposes. An additional argument is the price of the material, which is several times lower in relation to rubber or fibroflex products. This allows the flexible punch forming method to be used for special or prototype applications, where the costs and time of tool production are the main argument. The paper presents one geometric model of a container, but formed from different materials, i.e. steel with a high content of chromium, aluminum alloy, copper, in order to compare the differences in their intended use, as well as the production method. Mon, 22 Mar 2021 15:41:42 +0100 https://popups.uliege.be/esaform21/index.php?id=1237 https://popups.uliege.be/esaform21/index.php?id=1464 During forming operations, the microstructure of metal parts is usually changed. Effects of cold hardening result in different mechanical properties, whereas the deformed microstructure also changes the electromechanical properties. The latter is responsible inter alia for the chemical corrosion behavior in terms of breakdown potential. In this study, the principle of corrosion resistance of steel E355 (EN 10305-1) was analyzed after rotary swaging with the same nominal strain but different process settings. Especially higher feed rates (forming increments per stroke) and the additional application of shear strain by eccentric rotary swaging increased the pitting potential significantly and thus the corrosion resistance. The introduced methods are assumed as prospective candidates for industrial production of parts that provide higher durability without further anti-corrosion treatment. Mon, 22 Mar 2021 19:56:49 +0100 https://popups.uliege.be/esaform21/index.php?id=1464 https://popups.uliege.be/esaform21/index.php?id=1544 Recently, hole-flanging by single-stage incremental forming (SPIF) has been proposed as a suitable process to perform hole flanges for small- and medium-sized batches with high flexibility in shape. However, this incremental forming has many differences compared with the conventional press working operation in terms of strain and thickness distributions, failure mechanisms and flangeability measures. In fact, regarding the evaluation of the formability of the flanges, the classical Forming Limit Ratio (LFR) should be used with care to quantify this property in hole-flanging by SPIF. Additionally, the FLC (Forming Limit Curve for necking) and FFL (Fracture Forming Limit) curves, powerful tools for analysing sheet failure in practice, may also yield erroneous prediction of necking in conventional press working or fracture in SPIF. The aim of this work is to present a comparison and analysis of the formability of hole flanges performed by SPIF and press working in AA7075-O sheets. Two complementary parameters to the LFR to compare the flangebility in both operations are discussed, along with the influence of bending induced by the forming tool and the stress triaxiality in the evolution of the principal strains during the forming process. The results point out the limitations in the current practice. Mon, 22 Mar 2021 20:10:02 +0100 https://popups.uliege.be/esaform21/index.php?id=1544 https://popups.uliege.be/esaform21/index.php?id=1555 Lightweight alloys can be considered among the most promising materials thanks to their capability to reduce the environmental impact, without affecting mechanical properties. In addition, when very complex shapes are required, a viable strategy could be represented by the adoption of non-conventional forming processes applied to tailored blanks that allow to obtain local variation of the material properties. In fact, referred to the Mg alloys, both grain size and temperature strongly influence the deformation behavior, as well as the mechanical properties. In this work, the effects of a selective Laser Heat Treatment (LHT) on a Mg AZ31B-H24 alloy sheet were investigated both numerically and experimentally. Experimental tests were performed, using a Diode laser source and keeping a square spot stationary in the center of the sample. The microstructure evolution was evaluated by means of light microscopy. Subsequently, the heat-treated samples were subjected to bulge tests under superplastic conditions (450°C) and using pressurized argon gas. The experimental microstructure distributions obtained were used for the numerical bulge tests analyses performed in the same conditions of the experimental trials. Experimental LHT results showed the capability to locally modify the microstructure when suitable temperatures and interaction times are selected. Regarding the bulge tests, the obtained results showed the possibility to effectively affect the thickness distribution of the final shapes. Mon, 22 Mar 2021 20:11:00 +0100 https://popups.uliege.be/esaform21/index.php?id=1555 https://popups.uliege.be/esaform21/index.php?id=1870 In a modern production environment, flexible manufacturing methods are important because an overall trend towards mass customization and on-demand production is observed. Kinematic and incremental forming methods with generic tools can provide a large product variation but a deeper understanding of the forming mechanisms is required for process modelling, e.g. Incremental Swivel Bending (ISB). Particularly crucial is to identify the influences on the forming zone in order to purposefully control the material flow of a forming process. For a bending process where the bending moment is transmitted by clamping tools, this paper presents a method to alter the contact pressure distribution in order to affect the angular size and strain gradient of the forming zone. In the light of these results, the presented method can be deployed for a tooling with adaptive contact pressure to directly influence material flow, in particular using generic tools to overall provide a better control of flexible forming methods. Tue, 23 Mar 2021 10:02:38 +0100 https://popups.uliege.be/esaform21/index.php?id=1870 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 https://popups.uliege.be/esaform21/index.php?id=1887 https://popups.uliege.be/esaform21/index.php?id=2043 The acquisition and evaluation of process data in production engineering holds great potential. This allows detecting faulty processes at an early stage and processes to be optimized even more efficiently. However, the use of technologies for data acquisition in the manufacturing industry is far less widespread than the mentioned potential implies. This paper presents an Internet of Things approach by means of which production environments can be retrofitted easily and cost-effectively. Tue, 23 Mar 2021 12:32:00 +0100 https://popups.uliege.be/esaform21/index.php?id=2043 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 https://popups.uliege.be/esaform21/index.php?id=2151 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 https://popups.uliege.be/esaform21/index.php?id=2483 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 https://popups.uliege.be/esaform21/index.php?id=2575 https://popups.uliege.be/esaform21/index.php?id=2715 The purpose of this paper is to simulate a complex forming process with parameters identified from tensile and shear tests. An elastic-plastic model is retained which combines a Hill’s 1948 anisotropic criterion and plastic potential using a non-associated flow rule. Firstly, a mechanical characterization is made with homogenous tests like tensile and shear tests [1]. On the other hand a process of micro Single Point Incremental forming is simulated [2]. It consists in deforming a clamped blank using a hemispherical punch which has a small diameter compared to the blank dimensions. From a small-size sheet of 0.2 mm thick, a square-based pyramid is obtained incrementally, with a define height path and advanced speed, by a tool instrumented to measure the forming force, which deforms locally the material. It is shown that the non-associated flow plasticity model leads to a good agreement between experimental and numerical results for the evolution of the punch force during the process. Wed, 24 Mar 2021 18:49:56 +0100 https://popups.uliege.be/esaform21/index.php?id=2715 https://popups.uliege.be/esaform21/index.php?id=2759 One of the main objectives of production engineering is to reproducibly manufacture (complex) defect-free parts. To achieve this, it is necessary to employ an appropriate process or tool design. While this will generally prove successful, it cannot, however, offset stochastic defects with local variations in material properties. Closed-loop process control represents a promising approach for a solution in this context. The state of the art involves using this approach to control geometric parameters such as a length. So far, no research or applications have been conducted with closed-loop control for microstructure and product properties. In the project on which this paper is based, the local martensite content of parts is to be adjusted in a highly precise and reproducible manner. The forming process employed is a special, property-controlled flow-forming process. A model-based controller is thus to generate corresponding correction values for the tool-path geometry and tool-path velocity on the basis of online martensite content measurements. For the controller model, it is planned to use a special process or microstructure (correlation) model. The planned paper not only describes the experimental setup but also presents results of initial experimental investigations for subsequent use in the closed-loop control of α’-martensite content during flow-forming. Wed, 24 Mar 2021 18:56:43 +0100 https://popups.uliege.be/esaform21/index.php?id=2759 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 https://popups.uliege.be/esaform21/index.php?id=3673 https://popups.uliege.be/esaform21/index.php?id=3788 Flowforming is an advanced forming technique to produce net shape axisymmetric components, with high dimensional accuracy, based on the simultaneous action of a rotating mandrel and multiple translational rollers. The deformation mechanism has great influence on the uniformity of microstructure, with a gradient in the grain size from the inner to the outer portion of the component cross section, with elongated grains in the rollers feed direction. The highly directional deformation of the microstructure, both along the radial and axial direction, may reach extreme values in the case of large reduction and this aspect may introduce significant uncertainties in the evaluation of the mechanical properties of the final parts (i.e. microhardness, maximum elongation, yield strength) due to the computational methodologies used to estimate the average grain size. The paper focuses on the most frequently used measurement methods to assess the measurement accuracy for the correlation with the local variations of mechanical properties. The reference case for the investigations is the flowforming of AA6082 tubes, processed at different process parameters to change the shape of the grain and the gradient along the radius. Comparisons were carried out with regards to methods that allow measuring the grain size using zero-dimensional features (points), one-dimensional features (lines), and two-dimensional features (areas), respectively with the triple-point count method, the Heyn intercept method and the Jeffries planimetric method. Mon, 29 Mar 2021 14:32:44 +0200 https://popups.uliege.be/esaform21/index.php?id=3788 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 https://popups.uliege.be/esaform21/index.php?id=3826 https://popups.uliege.be/esaform21/index.php?id=3969 Stretch forming process is primarily used for generating curved structures from sheet metals such as car body panels or aircraft fuselage panels. Although there are large number of studies about stretch forming, these investigations focus mainly on flat sheet metals. However, various parts especially in the automotive industry, such as passenger car fenders are first preformed to a profile and afterwards stretch formed to generate desired final geometry. Moreover, as a consequence of weight reduction activities, these fender parts are usually made of ultra-high strength steels (UHSS) in the last two years. In the current study, stretch forming characteristics of an open profile made of martensitic UHSS (MS1500) are investigated using finite elements method (FEM). Used geometry was an asymmetrical hat profile which was preformed using roll forming prior to stretch forming. Mechanical properties of the material used is characterized using tensile test and modeled using Swift isotropic strain hardening rule. Strain and stress distribution along the bend section, geometry and springback in the final part as well as forming force have been investigated using finite element (FE) simulations. A twist has been observed in the final product along its longitudinal axis. To validate the FE results, experiments have been conducted. Twist problem is also detected in the manufactured samples. The amount of springback in produced part was similar to the experiments. It is found that FE simulations can model stretch forming process of open profiles accurately. Tue, 30 Mar 2021 09:16:31 +0200 https://popups.uliege.be/esaform21/index.php?id=3969 https://popups.uliege.be/esaform21/index.php?id=4225 While the majority of industrial sheet bending processes consist of conventional air bending, more complex bending processes such as multi-point bending are also utilized. Multi-point bending involves forming several bends simultaneously with changing contact conditions. Of the various models that may be employed to simulate such processes, analytic models are most attractive for industrial applications as they are time-efficient, strongly theoretically supported and easily extended to a wide range of dies layouts without the need of additional experimental data. In this paper a new analytic model is presented to predict the forming forces, the deformation of the sheet and the springback. The model is based on the literature around large-radius air bending. The geometry of the sheet is determined at each moment as a function of the tool’s positions. The reaction forces are calculated based on the equilibrium of forces and moments and the springback is calculated based on the elastic unloading of the internal bending forces. The model has been compared with a more time consuming finite element (FE) model and the geometry of the sheet has been experimentally verified by means of digital processing of video images. The proposed analytic model shows good agreement with the computational FE model and it is demonstrated to be a robust tool for calculation of the bending characteristics. Thu, 01 Apr 2021 16:33:09 +0200 https://popups.uliege.be/esaform21/index.php?id=4225 https://popups.uliege.be/esaform21/index.php?id=4315 Putting in place Circular Economy strategies is an urgent action to be undertaken. Manufacturing processes play a relevant role as efficient material reuse enabler. Scientists have to make an effort either to find new process or to rethink old process to reprocess End-of-life (EoL) components to recover both material and functions. In this paper, Single Point Incremental Forming (SPIF) process is used for reshaping sheet metal EoL components. Deep drawing process as well as uniaxial pre-straining (to imitate the End-of-Life component) followed by SPIF operations (to obtain the reshaped components) are set- up and implemented to form and reform aluminum sheet metal components. As the authors have already proved the technical feasibility of such an approach, the present paper aims at a better understanding of the formability and geometrical accuracy performance of SPIF process as used to reform components. Specifically, an experimental campaign varying kind and extent of restraining is developed and the formability and geometrical accuracy of the subsequent SIPF operations is analyzed. Results proves that SPIF process is a promising approach for reshaping purpose. Thu, 01 Apr 2021 18:04:29 +0200 https://popups.uliege.be/esaform21/index.php?id=4315