References of "Duflou, Joost"
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See detailNumerical simulation of a pyramid steel sheet formed by single point incremental forming using solid-shell finite elements
Duchene, Laurent ULg; Guzmán Inostroza, Carlos Felipe ULg; Behera, Amar Kumar et al

in Key Engineering Materials [=KEM] (2013)

Single Point Incremental Forming (SPIF) is an interesting manufacturing process due to its dieless nature and its increased formability compared to conventional forming processes. Nevertheless, the ... [more ▼]

Single Point Incremental Forming (SPIF) is an interesting manufacturing process due to its dieless nature and its increased formability compared to conventional forming processes. Nevertheless, the process suffers from large geometric deviations when compared to the original CAD profile. One particular example arises when analyzing a truncated two-slope pyramid. In this paper, a finite element simulation of this geometry is carried out using a newly implemented solid-shell element, which is based on the Enhanced Assumed Strain (EAS) and the Assumed Natural Strain (ANS) techniques. The model predicts the shape of the pyramid very well, correctly representing the springback and the through thickness shear (TTS). Besides, the effects of the finite element mesh refinement, the EAS and ANS techniques on the numerical prediction are presented. It is shown that the EAS modes included in the model have a significant influence on the accuracy of the results. [less ▲]

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See detailExperimental Characterisation of Damage Occuring during Single Point Incremental Forming of a Ferritic Steel
Mertens, Anne ULg; Guzmán Inostroza, Carlos Felipe ULg; Habraken, Anne ULg et al

Poster (2012, September)

Single Point Incremental Forming (SPIF) has been developed as a new dieless process for forming metal sheets. This technique appears very promising in view of the current requirements for rapid ... [more ▼]

Single Point Incremental Forming (SPIF) has been developed as a new dieless process for forming metal sheets. This technique appears very promising in view of the current requirements for rapid prototyping and/or small series production [1]. However, inaccuracies in the shape of the processed part and material failure constitute important limiting factors for applications. In the present research, a numerical approach, based on the damage model proposed by Gurson [2], has been chosen to analyse and optimise the process, predict the material rupture and the process limit. From experimental observations of plastic deformation and ductile fracture, damage is related to the nucleation, growth and coalescence of microvoids [3]. Gurson’s model uses the volume fraction of these voids as a main variable. Hence the determination of this value is a key factor for a correct identification and validation of the model. More particularly, the present work focuses on two different methods used to experimentally characterise damage occurring during single point incremental forming of a ferritic steel. Void measurements carried out by optical microscopy combined with image analysis have been compared with porosity values obtained from density measurements based on the Archimedes’ principle [4], so as to assess the feasibility of using this method for a quick characterisation of the damage. [less ▲]

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See detailStudy of the geometrical inaccuracy on a SPIF two-slope pyramid by finite element simulations
Guzmán Inostroza, Carlos Felipe ULg; Gu, Jun; Duflou, Joost et al

in International Journal of Solids and Structures (2012), 49(25), 3594-3604

Single Point Incremental Forming (SPIF) is a recent manufacturing process which can give a symmetrical or asymmetrical shape to an undeformed metal sheet by using a relative small tool. In this article, a ... [more ▼]

Single Point Incremental Forming (SPIF) is a recent manufacturing process which can give a symmetrical or asymmetrical shape to an undeformed metal sheet by using a relative small tool. In this article, a two-slope SPIF pyramid with two different depths, which suffers from large geometric deviations when comparing the intended and final shapes, is studied. The article goal is to detect if these divergences are due to new plastic strain while forming the second angle pyramid by using finite elements simulations. To validate the numerical results, both the shape and the forces are compared with experimental measurements. Then, an analysis of the material state is carried out taking the equivalent plastic strain, von Mises effective stress and yield stress distribution through a cut in the mesh. It is noticed that there is plastic deformation in the center of the pyramid, far from the tool neighbourhood. Also, high values of stresses are observed under the yield stress in other parts of the sheet. As a strong bending behaviour plus membrane tension is found in some sheet elements, these elastic stresses are due to a bending action of the tool. It is concluded that the main shape deviations come from elastic strains due to structural elastic bending, plus a minor contribution of localized springback, as no plastic deformation is observed in the angle change zone. Future developments in toolpath designs should eventually consider these elastic strains in order to achieve the intended geometry. [less ▲]

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See detailAdaptive remeshing for incremental forming simulation
Lequesne, Cédric ULg; Henrard, Christophe ULg; Bouffioux, Chantal ULg et al

in Pavel, H. (Ed.) Proceedings of the 7th International Conference and Workshop on Numerical Simulation od 3D Sheet Metal Forming Processes (NUMISHEET 2008) (2008)

Incremental forming of aluminium sheets has been modelled by finite element simulations. However the computation time was prohibitive because the tool deforms every part of the sheet and the mesh along ... [more ▼]

Incremental forming of aluminium sheets has been modelled by finite element simulations. However the computation time was prohibitive because the tool deforms every part of the sheet and the mesh along the tool path must be very fine. Therefore, an adaptive remeshing method has been developed. The elements that are close to the tool are divided into smaller elements in order to have a fine mesh where high deformations occur. Consequently, some new nodes become inconsistent with the non-refined neighbouring elements. To overcome that problem, their displacements are constrained, i.e. dependent on their master nodes displacements. The data concerning these new nodes and elements are stored in a linked list, which is a fundamental data structure. It consists of a sequence of cells, each containing data fields and a pointer towards the next cell. The goal of this article is to explain the developments performed in the finite element code, to validate the adaptive remeshing technique and to measure its efficiency using the line test simulation. During this test, which is a simple incremental forming test, a clamped sheet is deformed by a spherical tool moving along a linear path. [less ▲]

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See detailDevelopment of an inverse method for identification of materials parameters in the single point incremental sheet forming process
Bouffioux, Chantal ULg; Henrard, Christophe ULg; Gu, Jun et al

in Tisza, M. (Ed.) Proceedings of the IDDRG 2007 International Conference (2007)

The purpose of this article is to develop an inverse method for adjusting the material parameters during single point incremental forming. The main idea consists in simulating tests performed on the same ... [more ▼]

The purpose of this article is to develop an inverse method for adjusting the material parameters during single point incremental forming. The main idea consists in simulating tests performed on the same machine as the one used for the process itself. This reduces the costs of the equipment since no specific and costly standard test equipment is needed. Moreover, it has the advantage that the material parameters are fitted for a heterogeneous stress and strain state occurring during the real process. Before using the inverse method, the numerical results must be compared with the experimental ones. Several boundary conditions will be tested. [less ▲]

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