https://popups.uliege.be/esaform21/index.php?id=94 Index terms fr 0 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=437 The current market requirements are increasingly pushing the industry towards the manufacturing of highly customized products. Tailored blanks are a class of sheet metals characterized by the local variation of properties, attributable to the presence of different materials, different thickness distribution, and thermal treatments. In the manufacturing of tailored welded blanks, welding and forming processes cover a central role. In this framework, friction stir welding demonstrated to be a suitable candidate technology for the production by joining of tailored blanks. Indeed, sheet metals welded by this solid-state welding process typically exhibit high formability when compared to the conventional welding methods. Due to the improved formability, a good deal of attention has been recently given toward the single point incremental forming (SPIF) process and its integration with FSW. Remarkable efforts have been dedicated to the numerical modeling of the SPIF of metallic alloy sheets jointed by FSW. The main criticisms in these models are related to the definition of the mechanical properties of the materials, which are affected by the structural alteration induced by the FSW. The present work aims to model the local alterations in the mechanical properties and to analyze how these local characteristics affect the formability of the blanks. With this purpose, a 20 mm wide sample collected from a FS welded blank of aluminum alloy AA6082 has been modeled using the mechanical properties variation achieved in a previous work. The influence of this local variation in properties has been assessed using a Finite Element Model Updating strategy. Fri, 19 Mar 2021 19:38:16 +0100 Mon, 12 Apr 2021 09:13:32 +0200 https://popups.uliege.be/esaform21/index.php?id=437 https://popups.uliege.be/esaform21/index.php?id=2611 The present paper offers a FE modeling strategy to predict the stress state in carbon fiber reinforced plastic (CFRP) plate material after installing a Blind Rivet Nut (BRN). In industry, a BRN is a permanent mechanical fastener used to equip plate material with a threaded part. Analogue to the installing process of the more common blind rivet, the BRN deforms plastically in such a way a counter head is formed on the underside of the plate. Simultaneously, the upper side of the deformation chamber expands in the radial direction creating an interference fit. The interference fit together with the counter head units the nut to the plate. However, the high contact forces between the BRN and the plate often cause damage in the CFRP material compromising the integrity of the joint. The latter observation implies that while setting a BRN in CFRP, the detrimental contact forces must be controlled to guarantee a qualitative joint. The necessary understanding of the stress distribution in the plate material is numerically investigated in two steps. In the first step, a computational efficient axisymmetric model is used to reveal the contract pressure between the BRN and the plate during the setting process. In the second step, the contact pressures are transferred to a 3D model of the plate. In this stage, the orthotropic properties of the composite are assigned to the plate material and an adequate failure criterion is adopted. The result is compared to a full 3D model using the Tsai – Wu failure criterion. Wed, 24 Mar 2021 18:30:23 +0100 Sat, 10 Apr 2021 13:16:47 +0200 https://popups.uliege.be/esaform21/index.php?id=2611 https://popups.uliege.be/esaform21/index.php?id=3605 The study assesses feasibility of hot extrusion of a large seamless hexagonal 9%Cr-1%Mo steel tube. The manufacturing chain starts from a pierced cylindrical billet, hot extruded and to be further cold drawn in several passes. Preliminary industrial tests have shown thickness reduction in extrusion limited by a huge initial force peak (+25 %) reaching the press capacity. To understand this force peak, thermomechanical numerical simulation (ForgeNxt®) of the furnace-press transfer and extrusion stages is carried out. Constitutive model at high temperature, high strain and strain rate has been selected from literature. Surface properties, namely Heat Transfer Coefficient (HTC) and friction coefficient, have been made space- and time-dependent to represent glass lubrication. Numerical results are qualitatively compared to industrial experimental values to evaluate the prediction of the model. It suggests that the difficult start of the glass melting and flow along a cooled die affects the force peak. Practical improvements are suggested on this basis, together with possible refinements of the simulation for more precision and insight into extruded tube quality. Mon, 29 Mar 2021 13:33:17 +0200 Thu, 08 Apr 2021 21:46:35 +0200 https://popups.uliege.be/esaform21/index.php?id=3605 https://popups.uliege.be/esaform21/index.php?id=3869 The integration of forming in the fatigue modelling of cold-formed components significantly improves the predictive accuracy of the estimated life. The current study investigated the fatigue behaviour of a bent specimen made from a 5 mm thick, S900MC high strength steel plate. Because of its superior static and dynamic strength, this grade is progressively used for hollow cold-formed sections in mobile applications. However, it exhibits a strong stress saturation as well as limited formability. In this regard, a finite element modelling framework was adopted from previous research and further developed to integrate bending in the fatigue modelling and life estimation procedure. However, this framework currently ignores the possible influence of kinematic hardening and associated Bauschinger effect. For this reason, a numerical study was performed that compares isotropic with kinematic hardening for this specific application. First, the characteristic behaviour of these models was verified in a virtual tension-compression test. Subsequently, they were implemented in forming simulation followed by fatigue loading. Herein, the stress-strain evolution was investigated and a multi-axial fatigue criteria was used to map the sensitivity of the estimated life to the type of hardening. In general, the stress that entered the fatigue calculation was at least 21% lower for the kinematic model. As a result, a significant increase of 65% was observed for the estimated fatigue life, yielding a better comparison with experimental data. Mon, 29 Mar 2021 14:52:43 +0200 Thu, 08 Apr 2021 21:11:43 +0200 https://popups.uliege.be/esaform21/index.php?id=3869 https://popups.uliege.be/esaform21/index.php?id=1621 Among processes involving plastic deformation, sheet metal forming requires a most accurate description of plastic anisotropy. One of the main sources of mechanical anisotropy is the intrinsic anisotropy of the constituent crystals. In this paper, we present the single-crystal yield criterion recently developed by Cazacu et al. [1] and its application to the prediction of anisotropy in uniaxial tension of strongly textured polycrystalline sheets. Namely, it is shown that using this single crystal yield criterion the Lankford coefficients exist and have finite values for all loading orientations. Moreover, the variation of both the yield stress and Lankford coefficients with the crystallographic direction can be expressed analytically. An application of this criterion to forming a cylindrical cup from a single crystal of (100) orientation is presented. Finally, we show that using this single-crystal model, one can describe well the effect of the spread around an ideal texture component on the anisotropy in uniaxial tensile properties of a polycrystal. Mon, 22 Mar 2021 20:18:49 +0100 Mon, 05 Apr 2021 18:23:38 +0200 https://popups.uliege.be/esaform21/index.php?id=1621 https://popups.uliege.be/esaform21/index.php?id=756 Additive manufacturing has proven to be a very beneficial production technology in the medical and healthcare industries. While existing for over four decades, recent work has seen great improvements in the quality of products; particularly in medical devices such as implants. Improved customization reduced operating time and increased cost-effectiveness associated with Metal AM for these products offers a new value proposition.  This paper investigates and evaluates modelling methods for the zygoma bone (human jawbone) and explores the most suitable material and optimum design for this critical biomedical implant. This paper proposes an innovative and efficient pre-process methodology that includes modelling, design validation, topological optimization, and numerical analysis. The method includes the generation of the model using reverse engineering of CT scan data and a topology optimization technique which makes the implant lightweight without causing excessive stress concentration. Static structural Finite Element Analysis was conducted to test three different biocompatible materials (Ti6Al4V, stainless steel 316L and CoCr alloys) which are commonly available for metal additive manufacturing. The stresses and conditions in the analysis were that of the human mastication process and all the implant design were tested with the three material types. The Taguchi method was used to determine the optimum design which was found to result in the highest mass reduction of 25% with Ti6Al4V as the implant material. Sun, 21 Mar 2021 13:01:12 +0100 Fri, 02 Apr 2021 17:42:14 +0200 https://popups.uliege.be/esaform21/index.php?id=756 https://popups.uliege.be/esaform21/index.php?id=883 Finite element (FE) forming simulation offers the possibility of a detailed analysis of the deformation behaviour of engineering textiles during forming processes, to predict possible manufacturing effects such as wrinkling or local changes in fibre volume content. The majority of macroscopic simulations are based on conventional two-dimensional shell elements with large aspect ratios to model the membrane and bending behaviour of thin fabrics efficiently. However, a three-dimensional element approach is necessary to account for stresses and strains in thickness direction accurately, which is required for processes with a significant influence of the fabric’s compaction behaviour, e.g. wet compression moulding. Conventional linear 3D-solid elements that would be commercially available for this purpose are rarely suitable for high aspect ratio forming simulations. They are often subjected to several locking phenomena under bending deformation, which leads to a strong dependence of the element formulation on the forming behaviour [1]. Therefore, in the present work a 3D hexahedral solid-shell element, based on the initial work of Schwarze and Reese [2,3], which has shown promising results for the forming of thin isotropic materials [1], is extended for highly anisotropic materials. The advantages of a locking-free element formulation are shown through a comparison to commercially available solid and shell elements in forming simulations of a generic geometry. Additionally, first ideas for an approach of a membrane-bending-decoupling based on a Taylor approximation of the strain are discussed, which is necessary for an accurate description of the deformation behaviour of thin fabrics. Mon, 22 Mar 2021 09:49:49 +0100 Tue, 30 Mar 2021 09:49:12 +0200 https://popups.uliege.be/esaform21/index.php?id=883 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 Tue, 30 Mar 2021 09:16:31 +0200 https://popups.uliege.be/esaform21/index.php?id=3969