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Estimation of joint contact forces in the equine digit Noble, Prisca ; Collin, Bernard ; et al in ISB proceedings (2009, July) Detailed reference viewed: 117 (29 ULg)Viscoelastic Modeling of Brain Tissue: A Fractional Calculus-Based Approach Libertiaux, Vincent ; Pascon, Frédéric in Ganghoffer, Jean-François; Pastrone, Franco (Eds.) Mechanics of Microstructured Solids Cellular Materials, Fibre Reinforced Solids and Soft Tissues (2009) In recent years, the mechanical study of the brain has become a major topic in the field of biomechanics. A global biomechanical model of the brain could find applications in neurosurgery and haptic ... [more ▼] In recent years, the mechanical study of the brain has become a major topic in the field of biomechanics. A global biomechanical model of the brain could find applications in neurosurgery and haptic device design. It would also be useful for car makers, who could then evaluate the possible trauma due to impact. Such a model requires the design of suitable constitutive laws for the different tissues that compose the brain (i.e. for white and for gray matters, among others). Numerous constitutive equations have already been proposed, based on linear elasticity, hyperelasticity, viscoelasticity and poroelasticity. Regarding the strong strain-rate dependence of the brain’s mechanical behaviour, we decided to describe the brain as a viscoelastic medium. The design of the constitutive law was based on the Caputo fractional derivation operator. By definition, it is a suitable tool for modeling hereditary materials. Indeed, unlike integer order derivatives, fractional (or real order) operators are non-local, which means they take the whole history of the function into account when computing the derivative at current time t. The model was calibrated using experimental data on simple compression tests performed by Miller and Chinzei. A simulated annealing algorithm was used to ensure that the global optimum was found. The fractional calculus-based model shows a significant improvement compared to existing models. This model fits the experimental curves almost perfectly for natural strains up to − 0.3 and for strain-rates from 0.64s − 1 to 0.64 10− 2 s − 1. [less ▲] Detailed reference viewed: 112 (12 ULg)Modelling the vertical spincasting of large bimettalic rolling mill rolls Studer, Léo ; Detrembleur, Sylvain ; Habraken, Anne et al in Proceedings of the Second International Conference on Advances in Solidification Processes (ICASP-2) (2008) In order to take into account the dynamic effects of molten metal during solidification, a methodology is presented to interface a metal solidification solver with a specifically developped flow dynamics ... [more ▼] In order to take into account the dynamic effects of molten metal during solidification, a methodology is presented to interface a metal solidification solver with a specifically developped flow dynamics solver. [less ▲] Detailed reference viewed: 59 (13 ULg)On the evaluation of the through thickness residual stresses distribution of cold formed profiles Rossi, Barbara ; Habraken, Anne ; Pascon, Frédéric in 10th International ESAFORM Conference on Material Forming : ESAFORM, Zaragoza, 18-20 April 2007 (2007) The aim of this research is to evaluate the through thickness residual stresses distribution in the walls and in the corners of a cold-formed open section made of a material presenting a non linear ... [more ▼] The aim of this research is to evaluate the through thickness residual stresses distribution in the walls and in the corners of a cold-formed open section made of a material presenting a non linear hardening behaviour. To get results as close as possible to the reality, the complete process is modeled, including coiling and uncoiling of the sheet before the cold bending of the corner itself. The elastic springback after flattening as well as after final shaping are also taken into account. In order to validate the model in predicting the residual stresses distribution, the presented results are confronted to experimental measurements and FE results collected from the literature. [less ▲] Detailed reference viewed: 90 (30 ULg)Modelling the vertical centrifugal casting of large bimetallic rolling mills Studer, Léo ; Habraken, Anne ; Pirotton, Michel et al in Onate, E.; Papadrakis, M.; Schrefler, B. (Eds.) Proceedings of the Conference of Computational Methods for Coupled Problems in Science and Engineering 2 (2007) In order to take into account the dynamical effects of molten metal during solidification, we want to interface a metal solidification solver with a flow dynamics solver. Detailed reference viewed: 97 (9 ULg)Finite element study of the effect of some local defects on the risk of transverse cracking in continuous casting of steel slabs Pascon, Frédéric ; Habraken, Anne in Computer Methods in Applied Mechanics & Engineering (2007), 196 This paper introduces a numerical 2.5D model of continuous casting of steel slabs. This model is based on the finite element method and it has been applied to the study of some local defects in a ... [more ▼] This paper introduces a numerical 2.5D model of continuous casting of steel slabs. This model is based on the finite element method and it has been applied to the study of some local defects in a continuous caster, such as partial blockage of nozzles (leading to a local reduction of secondary cooling rate), locking or misalignment of rolls. The purpose of the study was the evaluation of the effect of such defects on the risk of transverse cracking during bending and unbending operations. To do so, the simulation at macro-scale of the complete process has been first performed in standard conditions to get reference values and then each defect has been introduced. Defining two indexes (indicators) of the risk of transverse cracking, it has been possible to classify the defects in terms of risk increase, helping steel producers to focus on the most critical problems. [less ▲] Detailed reference viewed: 87 (6 ULg)A 2.5 D finite element model for bending and straightening in continuous casting of steel slabs Pascon, Frédéric ; Cescotto, Serge ; Habraken, Anne in International Journal for Numerical Methods in Engineering (2006), (68), 125-149 This paper presents a bi-dimensional slice model of the continuous casting process developed to focus on the risk of transverse cracking during bending and straightening of steel slabs. The model is based ... [more ▼] This paper presents a bi-dimensional slice model of the continuous casting process developed to focus on the risk of transverse cracking during bending and straightening of steel slabs. The model is based on the finite element method and it integrates both thermal and mechanical aspects: temperature evolution, solidification, stress and strain developments. Generalized plain strain conditions are applied in the casting direction, allowing taking account of the extraction force applied to the slab as well as strains in this direction. The model also includes an original solution to counteract the generally wrong modelling of slab bulging with such slice models. The model has been applied to an industrial case of slab casting. Some numerical results illustrate the accuracy of the model compared to results of other models, measurements and observations on the caster. Transverse cracks are predicted to be the most likely to occur at the edge on the upper face, at the end of straightening of the slab. This is due to the combination of low ductility of the material with tensile stress and elongation in the casting direction in the straightening zone. This conclusion has been confirmed by the examination of slabs that present transverse cracks. [less ▲] Detailed reference viewed: 133 (5 ULg)Modelling of semi-continuous casting of cupro-nickel alloys Pascon, Frédéric ; Pecquet, Etienne ; Zhang, Lihong et al in Papadrakakis, M.; Onate, E.; Schrefler, B. (Eds.) Proceedings of the International Conference on Computational Methods for Coupled Problems in Science and Engineering (2005) This research developed at University of Liege aims to optimize the complete semi-continuous casting process at LBP Company, a producer of copper-nickel alloys (or cupro-nickels). The process consists in ... [more ▼] This research developed at University of Liege aims to optimize the complete semi-continuous casting process at LBP Company, a producer of copper-nickel alloys (or cupro-nickels). The process consists in vertical casting of 7m long ingots. Some problems recurrently occur during casting process: formation of oscillations (wave length of about 500 mm), unsuitable concave cross-sections or internal cracks. In order to reduce the occurrence of such defects and to better understand their formation, we have been asked to develop a finite element model. The research focuses on two main topics: identification of material properties through laboratory tests and literature survey and the development of the numerical tool. The laboratory tests provide thermal and mechanical properties of the ingot and the mould, as well as heat transfer coefficients between the ingot and its surroundings (mould, air and water). These parameters are required for the numerical simulations of the process. In the second part of the research, numerical calculations have been performed using finite element method. Two types of 2D models have already been studied: horizontal slice and vertical slice. This first choice has been guided by the high coupling between thermal and mechanical aspects of the problem, leading to highly complex systems of equations and subsequent long CPU times. However, due to the limitations of such 2D models, a 3D formulation has then been considered and it is still in progress. [less ▲] Detailed reference viewed: 110 (9 ULg)Development of a neural network to predict the final geometry of forged rings after cooling ; ; Pascon, Frédéric et al in Banabic, D. (Ed.) Proceedings of the 8th ESAFORM Conference on Material Forming (Vol. 2) (2005) The paper deals with an application of Artificial Neural Networks (ANNs) to predict the geometry of hot forged pieces after cooling. Different ANNs have been considered and evaluated; then a network with ... [more ▼] The paper deals with an application of Artificial Neural Networks (ANNs) to predict the geometry of hot forged pieces after cooling. Different ANNs have been considered and evaluated; then a network with two hidden layers has been set up. Training and testing data have been obtained through calibrated numerical simulations of the cooling phase carried out with a finite element (F.E.) code. The good agreement between predicted and numerical results confirms the possibility of using well-trained neural network to foresee final dimensions of pieces after hot forging operations. [less ▲] Detailed reference viewed: 45 (7 ULg)Thermo-mechanical-metallurgical model to predict geometrical distortions of rings during cooling phase after ring rolling operations ; Pascon, Frédéric ; Habraken, Anne et al in International Journal of Machine Tools & Manufacture (2005), 45(6), 657-664 The paper presents a validated numerical model able to predict geometrical distortions of rings during cooling phase after hot ring rolling operations. The model is capable to take into account the ... [more ▼] The paper presents a validated numerical model able to predict geometrical distortions of rings during cooling phase after hot ring rolling operations. The model is capable to take into account the effects of all the phenomena resulting from the coupling of thermal, mechanical and metallurgical events. As simulation results strongly depend on the accuracy of input data, physical simulation experiments on real-material samples are developed and carried out to characterize material behaviour during phase transformation. The numerical model is then validated by an industrial case proving its effectiveness in predicting final ring distortions at room temperature. [less ▲] Detailed reference viewed: 107 (14 ULg)Developments in finite element simulations of continuous casting ; Pascon, Frédéric ; et al in Journal de Physique IV (2004), 120 Two complementary approaches of steel continuous casting modelling using the finite element code LAGAMINE have been developed in the M&S Department. We propose here a description of the context in which ... [more ▼] Two complementary approaches of steel continuous casting modelling using the finite element code LAGAMINE have been developed in the M&S Department. We propose here a description of the context in which the study started, then a description of both macroscopic and mesoscopic approaches. The first one describes the whole continuous casting process, from the free surface in the mould and through the entire machine, including thermal and mechanical behaviour of the steel. The second approach focuses on the prediction of cracks and is developed at the grain scale. Some results are also presented for both models. [less ▲] Detailed reference viewed: 76 (11 ULg)Mesoscopic model of intergranular cracks in low carbon steel during cooling of continuous casting ; Pascon, Frédéric ; Lecomte-Beckers, Jacqueline et al in Lamberigts, M. (Ed.) Proceedings of the 2nd international conference of thermomechanical processing of steels (TMP 2004) (2004) This paper addresses the problem of transverse cracking during the continuous casting of low carbon steel. The damage mechanisms occurring at high temperature during this process are identified and a ... [more ▼] This paper addresses the problem of transverse cracking during the continuous casting of low carbon steel. The damage mechanisms occurring at high temperature during this process are identified and a numerical approach for the modelling of these phenomena at the grain scale is proposed. Experiments allowing the identification of the model’s parameters are described. Finally, the first results obtained with the model are presented. [less ▲] Detailed reference viewed: 53 (5 ULg)Prediction of distortion during cooling of steel rolled rings using thermal-mechanical-metallurgical finite element model Pascon, Frédéric ; ; Bouffioux, Chantal et al in Steel Grips 2 (2004), Supplement Metal Forming 1-3 This work takes place in the framework of a CRAFT European project gathering three universities, three companies who produce rings through the ring rolling process and a manufacturer of temperature and ... [more ▼] This work takes place in the framework of a CRAFT European project gathering three universities, three companies who produce rings through the ring rolling process and a manufacturer of temperature and dimension measurement devices. The final goal of the project is to develop and set up a system, integrated in the industrial process, capable of predicting the geometrical characteristics of final pieces just after the ring rolling stage and to allow the rolling process to avoid dimensional defects through online adaption. In fact, ring rolling production does not imply only the rolling process, but also the cooling and quench stages of steel rings. During all these phases, the dimensions of the pieces change dramatically. In particular, due to the lack of symmetry in the cooling conditions, ring distortions include contraction and rotation of the ring section. The modeling of the cooling phase requires taking into account a large number of phenomena resulting from the coupling of thermal, mechanical and metallurgical effects. A numerical model has been implemented in the non-linear finite element code LAGAMINE, developed by the University of Liège. Such a model can help to better understand the evolution of the geometry during the cooling phase and also the effects of each physical and microstructural parameter implemented in the model on the ring final shape. Effectively, several parameters can affect the ring distortions and the model should take them into account; in particular, the mechanical and thermal behavior of each phase present in the material (metastable austenite, ferrite, pearlite, bainite and martensite). Phase transformation modeling implies the integration of a wide data base of material properties (thermo-physical and mechanical properties of the phases, TTT and CCT diagrams, enthalpy and strain of phase transformation, strain of transformation plasticity…) but only a few of these data are available in literature. Some of them have been found for the reference material (42CrMo4 steel), but additional laboratory experiments have been performed at the Universities of Padua and Liège in order to characterize thermal, mechanical and plastic behaviour of phases. Finally, this paper presents the model validation on an industrial case (measurements of temperature and dimensions of rings have been provided by the manufacturer). Then, some applications are presented, demonstrating the importance of some factors such as some material properties, the shape of the rings, the type of cooling (and the cooling rate) or the symmetry of the cooling scheme on final ring distortion. [less ▲] Detailed reference viewed: 119 (14 ULg)2D1/2 thermo-mechanical model of continuous casting using FEM Pascon, Frédéric ; Habraken, Anne in Brucato, V. (Ed.) Proceedings of the 6th International ESAFORM Conference on Material Forming (2003) Two complementary approaches of steel continuous casting modelling using the finite element code LAGAMINE have been developed in the M&S Department. The first one (at a macroscopic scale) describes the ... [more ▼] Two complementary approaches of steel continuous casting modelling using the finite element code LAGAMINE have been developed in the M&S Department. The first one (at a macroscopic scale) describes the whole continuous casting process, from the free surface in the mould and through the entire machine, including thermal and mechanical behaviour of the steel. The second approach focuses on the prediction of cracks and is developed at grain scale. We present in this paper a description of the context in which the study started, the description of the macroscopic approach and some results. [less ▲] Detailed reference viewed: 72 (7 ULg)Finite element analysis of continuous steel casting ; Pascon, Frédéric ; et al in Proceedings of the First International Conference Finite element for process analysis (2003) In order to analyse the behaviour of steel during continuous casting and to improve the process, two complementary models of steel continuous casting using the finite element code LAGAMINE have been ... [more ▼] In order to analyse the behaviour of steel during continuous casting and to improve the process, two complementary models of steel continuous casting using the finite element code LAGAMINE have been developed. We propose here a description of both macroscopic and mesoscopic approaches. The first one describes the whole continuous casting process, from the free surface in the mould and through the entire machine, including thermal and mechanical behaviour of the steel. The second approach focuses on the prediction of cracks and is developed at the grain scale. Results concerning the optimisation of the mould taper and the analysis of transverse cracks initiation are presented as industrial applications. [less ▲] Detailed reference viewed: 208 (5 ULg)Developments in finite element simulations of continuous casting ; Pascon, Frédéric ; et al in Proceedings of the 2nd International Conference on Thermal Process Modelling and Computer Simulations (ICTPMCS) (2003) Two complementary approaches of steel continuous casting modelling using the finite element code LAGAMINE have been developed in the M&S Department. We propose here a description of the context in which ... [more ▼] Two complementary approaches of steel continuous casting modelling using the finite element code LAGAMINE have been developed in the M&S Department. We propose here a description of the context in which the study started, then a description of both macroscopic and mesoscopic approaches. The first one describes the whole continuous casting process, from the free surface in the mould and through the entire machine, including thermal and mechanical behaviour of the steel. The second approach focuses on the prediction of cracks and is developed at the grain scale. Some results are also presented for both models. [less ▲] Detailed reference viewed: 46 (5 ULg)Numerical modelling of metal forming - current practice and advanced applications Cescotto, Serge ; Duchene, Laurent ; Pascon, Frédéric et al in Iu, V. P.; Lamas, L. N.; Li, Y. P. (Eds.) et al Computational Methods in Engineering and Science, lu et al. (eds), Proceedings of the 9th International Conference of enhancement and Promotion of Computing Methods for Engineering and Science (2003) This paper first summarizes the current possibilities and the perspectives of effective modeling of metal forming processes. Practical considerations on manpower requirement and data availability are ... [more ▼] This paper first summarizes the current possibilities and the perspectives of effective modeling of metal forming processes. Practical considerations on manpower requirement and data availability are included in the discussion. Then, two examples of advanced applications are presented: the micro-macro approach for the modeling of sheet metal forming and the modeling of continuous casting. [less ▲] Detailed reference viewed: 38 (5 ULg)Lingopti project: semi-continuous casting process of coper-nickel alloys Pecquet, Etienne ; Pascon, Frédéric ; Lecomte-Beckers, Jacqueline et al in Dick, E.; Vierendeels, J.; Cantrijn, F. (Eds.) et al Proceedings of the 6th national congress on theoretical and applied mechanics (2003) Lingopti project is a First Europe project. It treats semi-continuous casting of copper-nickel alloys ingots. The research, performed in the University of Liège, consists in the optimisation of the mould ... [more ▼] Lingopti project is a First Europe project. It treats semi-continuous casting of copper-nickel alloys ingots. The research, performed in the University of Liège, consists in the optimisation of the mould and the whole casting process of the LBP S.A. company (Chênée – Liège) to obtain better cast products. In fact, cast products sometimes present long oscillation marks (λ ≈ 500mm) and some ingots have many internal cracks. The semi-continuous process consists in the vertical casting of 7m height ingots. The goal is also to test different chemical compositions of the material and to predict what happens on the casting process. [less ▲] Detailed reference viewed: 116 (6 ULg)2D1/2 Thermal-Mechanical Model of Continuous Casting of Steel Using Finite Element Method Pascon, Frédéric Doctoral thesis (2002) The thesis deals with a numerical model based on the finite element method applied to the continuous casting of steel. The model is developed using the LAGAMINE finite element code and two industrial ... [more ▼] The thesis deals with a numerical model based on the finite element method applied to the continuous casting of steel. The model is developed using the LAGAMINE finite element code and two industrial applications of steel casting are presented to illustrate the capabilities of the model. The first chapter introduces the continuous casting process, defining the essential terminology and the industrial challenges. Then, the objectives of the model are detailed: the model is applied to the upper part of the caster (in the mould region) as well as to the bending and straightening zones. Chapters two, three and four are dedicated to the theoretical developments of thermal aspects (phase transformations, thermal contraction, heat flow and thermal boundary conditions), mechanical aspects (generalized plain strain state, material constitutive law, ferrostatic pressure and mechanical contact) and the staggered analysis used for thermal / mechanical coupling. In the two next chapters, some numerical results are presented. The model has been first applied to a 125mm square billet in the mould region. The industrial goal is to evaluate the effect of the mould taper on the cooling of the billet (temperature evolution, solid shell growing, stress and strain development). The second application focuses on the risk of transverse cracking during straightening of steel slabs and the effect of some local defects (reduction of secondary cooling, locking or misalignment of rolls). The thesis ends with some concluding remarks and perspectives for the model. [less ▲] Detailed reference viewed: 129 (21 ULg)Finite element thermo-mechanical model of continuous steel casting Pascon, Frédéric ; Habraken, Anne in Kiuchi, M.; Nishimura, H.; Yanagimoto, J. (Eds.) Proceedings of the 7th International Conference on Advanced Technology of Plasticity (2002) Problems in continuous casting of steel are numerous and have been leading producers to find ever more efficient solutions. Wa have developed a thermomechanical model of continuous casting, using a non ... [more ▼] Problems in continuous casting of steel are numerous and have been leading producers to find ever more efficient solutions. Wa have developed a thermomechanical model of continuous casting, using a non-linear finite element code. Since a complete 3D discretization seemed impossible, the model has been based on a generalized plane strain state (2D1/2) and it includes at the same time thermal exchanges, mechanical behaviour of steel at very high temperature, the ferrostatic pressure and contact between the strand and the machine. This paper presents some results of two industrial applications. First results tend to prove the importance of some process factors (such as the mould taper) and local defects of the machine on the quality of cast products, according with observations. [less ▲] Detailed reference viewed: 58 (5 ULg) |
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