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See detailNumerical investigation of impact of non lethal kinetic projectiles onto human thorax
Nsiampa Ndompetelo, ULg; Robbe, Cyril ULg; Papy, Alexandre

in 6th European Symposium on Non-Lethal Weapons 2011 proceedings (2011, May 16)

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See detailNumerical investigation of photonic crystal fibers by spectral and multipole methods
Nicolet, A.; Guenneau, S.; Zolla, F. et al

in Asymptotics, Singularities and Homogenisation in Problems of Mechanics, Proceedings of the IUTAM Symposium (Liverpool, July 2002) (2003)

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See detailNumerical investigations on web panels stiffened by one or two trapezoidal stiffeners
Degée, Hervé ULg; Boissonnade, N.; Maquoi, René ULg

in Proceedings of the 5th International Conference on Coupled Instabilities in Metal Structures (2008)

This paper focuses on the behaviour of I-girder web panels subjected to combined bending and shear and stiffened by longitudinal trapezoidal stiffeners. This implies to account for the coupling between ... [more ▼]

This paper focuses on the behaviour of I-girder web panels subjected to combined bending and shear and stiffened by longitudinal trapezoidal stiffeners. This implies to account for the coupling between local panel buckling between stiffeners and global buckling of the whole stiffened panel. The study is restricted to panels with one or two longitudinal stiffeners, for which the well-known orthotropic plate approach may not be relevant. For such configurations, the most recent design rules available may either not address this specific problem or be too conservative. This contribution provides information on the behaviour of such girders based on numerical simulations. Results of extensive non-linear FEM calculations are presented and discussed. The effects of aspect ratio, web slenderness and position of stiffeners are studied. Numerical results are compared to design loads obtained according to Eurocode 3 Part 1.5. The parameter study shows that several aspects of the code may be improved and proposals in this respect are given and validated through the numerical results. In particular, the beneficial effect of closed longitudinal stiffeners is highlighted. It is shown that the high level of torsional rigidity exhibited by welded trapezoidal stiffeners may significantly increase the overall resistance of the web panel. [less ▲]

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See detailNumerical mdeling of hydro-mechanical fracture behaviour
Guiducci, Chiara; Collin, Frédéric ULg; Radu, Jean-Pol ULg et al

Conference (2003)

A numerical approach for modeling coupled Hydro-Mechanical fracture behavior in 2D is presented in this paper. This approach accounts for the strong dependence of the flow characteristics on fracture ... [more ▼]

A numerical approach for modeling coupled Hydro-Mechanical fracture behavior in 2D is presented in this paper. This approach accounts for the strong dependence of the flow characteristics on fracture apertures and offers an anisotropic description of the flow propagation in the fracture. An interface finite element and a constitutive model are developed . In order to validate the applicability of the model to general geomechanic problems, 2D simulations were performed. Results show the good application of the mathematical model and the fundamental hydraulic role played by the fractures. [less ▲]

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See detailNumerical Methods for the Lubricated Contact Between Solids in Metal Forming Processes
Boman, Romain ULg; Ponthot, Jean-Philippe ULg

in ECCM’99, European Conference on Computational Mechanics (1999, August)

In this paper, the lubrication problem in numerical simulation of forming processes is presented. In the case of the rolling process, the recent and complex model of Marsault for the solution of the mixed ... [more ▼]

In this paper, the lubrication problem in numerical simulation of forming processes is presented. In the case of the rolling process, the recent and complex model of Marsault for the solution of the mixed lubrication regime has been implemented and tested. This model needs the use of the finite difference method to work properly. We will discuss the advantages and the difficulties encountered when trying to solve the same problem with the finite element method in a general frame. Finally, a finite element formulation for the solution of the time dependant Reynolds’ equation coupled with the deformation of the workpiece is proposed. [less ▲]

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See detailA numerical model for ground-borne vibrations from underground railway traffic based on a periodic finite element–boundary element formulation
Degrande, Geert; Clouteau, Didier; Othman, Ramzi et al

in Journal of Sound & Vibration (2006), 293(3-5), 645-666

A numerical model is presented to predict vibrations in the free field from excitation due to metro trains in tunnels. The three-dimensional dynamic tunnel–soil interaction problem is solved with a ... [more ▼]

A numerical model is presented to predict vibrations in the free field from excitation due to metro trains in tunnels. The three-dimensional dynamic tunnel–soil interaction problem is solved with a subdomain formulation, using a finite element formulation for the tunnel and a boundary element method for the soil. The periodicity of the geometry in the longitudinal direction of the tunnel is exploited using the Floquet transform, limiting the discretization to a single-bounded reference cell. The responses of two different types of tunnel due to a harmonic load on the tunnel invert are compared, both in the frequency–wavenumber and spatial domains. The first tunnel is a shallow cut-and-cover masonry tunnel on the Paris metro network, embedded in layers of sand, while the second tunnel is a deep bored tunnel of London Underground, with a cast iron lining and embedded in the London clay. [less ▲]

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See detailA numerical model of the evolution of ocean sulfate and sedimentary sulfur during the last 800 million years
François, Louis ULg; Gérard, Jean-Claude ULg

in Geochimica et Cosmochimica Acta (1986), 50

A reservoir model describing the time evolution of the sedimentary cycle of sulfur over the past 800 my has been developed. As a first approximation, the ocean sulfate concentration is assumed to be time ... [more ▼]

A reservoir model describing the time evolution of the sedimentary cycle of sulfur over the past 800 my has been developed. As a first approximation, the ocean sulfate concentration is assumed to be time-independent. With this assumption, the model is integrated backward in time and a new initialization procedure is derived in order to calculate the present state of the system which must be compatible with both observational data and model equations. The effects of a variation of the present state of the cycle on its past evolution are investigated. It is found that, when the present gypsum reservoir content is too low or when the weathering rate constants are too high, no acceptable solution can be obtained for the evolution of the cycle, since one reservoir is forced to depletion. The sensitivity of the model to the mean isotopic composition of the sedimentary system and to the fractionation factor during pyrite formation is also studied. Moreover, a model with time-dependent ocean sulfate concentration was developed. The existence of an acceptable solution appears to be linked to the steady state hypothesis for ocean sulfate, since a model with no acceptable steady state solution may be integrated until t = -800 my without any problem of reservoir depletion when the time-dependent equations are used. A tentative evolution of the ocean sulfate concentration is calculated. It is shown that this concentration is negatively correlated to the 34 S of seawater sulfate. The carbon cycle is modelled in order to compare the calculated 13 C of carbonate deposits to the observational data. [less ▲]

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See detailNumerical modeling and digital image correlation strain measurements of coated metal sheets submitted to large bending deformation
Duchene, Laurent ULg; Ben Bettaieb, Amine ULg; Tuninetti Vásquez, Victor ULg et al

in Proceedings of the 16th ESAFORM conference on Material Forming (2013)

The recently developed SSH3D solid-shell element, which is based on the Enhanced Assumed Strain (EAS) and the Assumed Natural Strain (ANS) techniques, is utilized for the modeling of a severe bending ... [more ▼]

The recently developed SSH3D solid-shell element, which is based on the Enhanced Assumed Strain (EAS) and the Assumed Natural Strain (ANS) techniques, is utilized for the modeling of a severe bending sheet forming process. To improve the element's ability to capture the through thickness gradients, a specific integration scheme was developed. In this paper, the performances of this element for the modeling of the T-bent process were assessed thanks to comparison between experimental and numerical results in terms of the strain field at the outer surface of the sheet. The experimental results were obtained by Digital Image Correlation. It is shown that a qualitative agreement between experimental and numerical results is obtained but some numerical parameters should be optimized to improve the accuracy of the simulation predictions. In this respect, the influence of the penalty coefficient of the contact modeling was analyzed. [less ▲]

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See detailThe Numerical Modeling and Measurement of Demagnetization Effect in Bulk YBCO Superconductors Subjected to Transverse Field
Hong, Z.; Vanderbemden, Philippe ULg; Pei, R. et al

in IEEE Transactions on Applied Superconductivity (2008), 18(2), 1561-1564

In this paper, the crossed field demagnetization effect of the bulk type-II superconducting materials in a variety of external magnetic field condition has been investigated both numerically and ... [more ▼]

In this paper, the crossed field demagnetization effect of the bulk type-II superconducting materials in a variety of external magnetic field condition has been investigated both numerically and experimentally. A melt-textured YBCO bulk sample was magnetized along the axial direction and after that a transverse field perpendicular to the central axis applied. The collapse of the original trapped field was measured using a Quantum Design Physical Property Measurement System. A numerical solver based on critical state model is proposed to simulate the measured results. (C) 2008 IEEE. [less ▲]

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See detailNumerical modeling of a 3 point bending test of a reinforced concrete beam using a second gradient theory
Jouan, Gwendal ULg; Kotronis, Panagiotis; Collin, Frédéric ULg

in Eberhardsteiner, J. (Ed.) ECCOMAS 2012 - European Congress on Computational Methods in Applied Sciences and Engineering, e-Book Full Papers (2012)

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See detailNumerical modeling of building structures in fire conditions
Binh, Chu Thi; Dotreppe, Jean-Claude ULg; Franssen, Jean-Marc ULg

in Van Lien, Nguyen; Duc, Do Dinh (Eds.) Proceedings of the workshop on “Construction under Exceptional Condition – CEC2010” (2010, October 29)

Numerical modelling is a very useful tool to predict the fire resistance of a structure, or to reproduce artificially what has happened during a real fire. SAFIR, a non linear computer code developed at ... [more ▼]

Numerical modelling is a very useful tool to predict the fire resistance of a structure, or to reproduce artificially what has happened during a real fire. SAFIR, a non linear computer code developed at the university of Liege-Belgium, is specifically written for modeling the behavior of structures subjected to fire. It allows a determination of the temperatures in the structure esulting from the fire and, in a subsequent analysis, determination of the successive positions of equilibrium of the structure until collapse. SAFIR program accommodates various elements for different idealizations, different calculation procedures and several material models incorporating stress-strain behaviour. The elements include 2-D SOLID, 3-D SOLID, BEAM, SHELL and TRUSS elements. The stress-strain material laws are generally linear-elliptic for steel and nonlinear for concrete. This paper introduces the main hypotheses, the possibilities and the validity of this program. Comparisons of test results and simulated results by SAFIR program for concrete structures, steel structures and concrete-steel composite structures are presented. [less ▲]

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See detailNumerical modeling of damage evolution of DP steels on the basis of X-ray tomography measurements
Ben Bettaieb, Mohamed ULg; Lemoine, Xavier; Bouaziz, O. et al

in Mechanics of Materials (2011), 43(3), 139-156

In order to couple the damage evolution and the stress state of DP steel grades, a new advanced GTN (Gurson-Tvergaard-Needleman) model was developed and implemented into a finite element code. This model ... [more ▼]

In order to couple the damage evolution and the stress state of DP steel grades, a new advanced GTN (Gurson-Tvergaard-Needleman) model was developed and implemented into a finite element code. This model is an extension of the original one. It takes into account the plastic anisotropy and the mixed (isotropic+ kinematic) hardening of the matrix. Two different methods to compute the void volume fraction were developed and used within the constitutive equations. The first method is new and allows the accurate modeling of the observations of damage initiation and growth in DP steels measured using high-resolution X-ray absorption tomography (Bouaziz et al., 2008; Maire et al., 2008). The second method is classic and assumes the additive decomposition of the total void volume fraction into a nucleation and a growth part. A parametric study is carried out to assess the effect of the kinematic hardening on some mechanical parameters such as the equivalent plastic strain, the triaxiality and the porosity. The numerical predictions are favorably compared to the experimental results. [less ▲]

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See detailNumerical modeling of hydro-mechanical fracture behavior
Guiducci, Chiara; Pellegrino, Antonio; Radu, Jean-Pol ULg et al

in Pande, G. N.; Pietruszczak, S. (Eds.) Numerical models in Geomechanics (2002)

A numerical approach for modeling coupled hydro-mechanical fracture behavior is proposed. The movement of fluids through rock fractures is important in many engineering areas of practical interest such as ... [more ▼]

A numerical approach for modeling coupled hydro-mechanical fracture behavior is proposed. The movement of fluids through rock fractures is important in many engineering areas of practical interest such as those ones of petroleum and mining engineering. In that context, one of the most investigated and complex subjects is the effect on well productivity due to changes in hydraulic conductivity both on the matrix rock and on its main fractures. It is well known, that these flow characteristics are strongly controlled by fracture apertures. Recent investigations on the distribution of the apertures in natural fractures suggest that the cubic law can, better than the Darcy law, predict the fluid flux through rough walled fractures as long as the appropriate average fracture aperture is used. A finite element code is developed to predict the influence that the stresses variation in the soil has on the distributed hydraulic conductivity field. The proposed model combines the stochastic cubic law with a non-linear deformation function (hyperbolic) that is suggested to describe the stress-closure/opening curves of the joints and that allows to couple together the hydraulic and the mechanic fracture behavior. The relationships used and the validity of the present model are tested through comparison between experimental data and numerical predictions (Bart 2000) in various boundary and loading conditions. Comparison between the Darcy model governing fluid flow equation and linear stress-closure/opening relation has also been performed showing the differences and the better de-scription given by the proposed new model. [less ▲]

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See detailNumerical modeling of relativistic shock acceleration
Meli, Athina ULg

in Astrophysics & Space Sciences Transactions : ASTRA (2011)

The shock acceleration mechanism is invoked to explain non-thermal cosmic rays in Supernova Remnants, Active Galactic Nuclei and Gamma Ray Bursts jets. Especially, the importance of relativistic shock ... [more ▼]

The shock acceleration mechanism is invoked to explain non-thermal cosmic rays in Supernova Remnants, Active Galactic Nuclei and Gamma Ray Bursts jets. Especially, the importance of relativistic shock acceleration in extragalactic sources is a recurring theme raising a significant interest in the research community. We will briefly discuss the shock acceleration mechanism and we will address the properties of non-relativistic and relativistic shocks, particularly focusing on relativistic numerical Monte Carlo studies. [less ▲]

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See detailNumerical Modeling of Representative Cells of Ti-5553 Using Periodic Homogenization Technique
Gerday, Anne-Françoise ULg; Ben Bettaieb, Mohamed ULg; Pascon, Frédéric ULg et al

in Oñate, E.; Owen, D. R. J. (Eds.) Computational plasticity X. Fundamentals and applications (2009, September)

This article focuses on the modeling of representative cells of Ti-5553 using the periodic homogenization theory and a microscopic constitutive law.

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See detailNumerical modeling of the deep Black Sea ecosystem functioning during the late 80’s (eutrophication phase)
Grégoire, Marilaure ULg; Raick, Caroline ULg; Soetaert, Karline

in Progress in Oceanography (2008), 76(9), 286-333

A one-dimensional coupled physical–biogeochemical model has been developed to simulate the ecosystem of the central Black Sea at the end of the 1980s when eutrophication and invasion by gelatinous ... [more ▼]

A one-dimensional coupled physical–biogeochemical model has been developed to simulate the ecosystem of the central Black Sea at the end of the 1980s when eutrophication and invasion by gelatinous organisms seriously affected the stability and dynamics of the system. The physical model is the General Ocean Turbulence Model (GOTM) and the biogeochemical model describes the foodweb from bacteria to gelatinous carnivores through 24 state variables including three groups of phytoplankton: diatoms, small phototrophic flagellates and dinoflagellates, two zooplankton groups: micro- and mesozooplankton, two groups of gelatinous zooplankton: the omnivorous and carnivorous forms, an explicit representation of the bacterial loop: bacteria, labile and semi-labile dissolved organic matter, particulate organic matter. The model simulates oxygen, nitrogen, silicate and carbon cycling. In addition, an innovation of this model is that it explicitly represents processes in the anoxic layer. Biogeochemical processes in anaerobic conditions have been represented using an approach similar to that used in the modeling of diagenetic processes in the sediments lumping together all the reduced substances in one state variable [Soetaert, K., Herman, P., 1996. A model of early diagenetic processes from the shelf to abyssal depths. Geochimica et Cosmochimica Acta 60 (6) 1019–1040]. In this way, processes in the upper oxygenated layer are fully coupled with anaerobic processes in the deep waters, allowing to perform longterm simulations. The mathematical modeling of phytoplankton and zooplankton dynamics, detritus and the microbial loop is based on the model developed by Van den Meersche et al. [Van den Meersche, K., Middelburg, J., Soetaert, K., van Rijswijk P.H.B., Heip, C., 2004. Carbon–nitrogen coupling and algal–bacterial interactions during an experimental bloom: Modeling a 13c tracer experiment. Limnology and Oceanography 49 (3), 862–878] and tested in the modeling of mesocosm experiments and of the Ligurian sea ecosystem [Raick, C., Delhez, E., Soetaert, K., Gregoire, M., 2005. Study of the seasonal cycle of the biogeochemical processes in the Ligurian sea using an 1D interdisciplinary model. Journal of Marine Systems 55 (3–4) 177–203]. This model has been extended to simulate the development of top predators, the aggregation of detritus as well as the degradation and chemical processes in suboxic/anoxic conditions (e.g. denitrification, anoxic remineralization, redox reactions). The coupled model extends down to the sediments (’2000 m depth) and is forced at the air–sea interface by the 6 hourly ERA-40 reanalysis of ECMWF data. The model has been calibrated and validated using a large set of data available in the Black Sea TU Ocean Base. The biogeochemical model involves some hundred parameters which are first calibrated by hand using published values. Then, an identifiability analysis has been performed in order to determine a subset of identifiable parameters (i.e. ensemble of parameters that can be together estimated from the amount of data we have at our disposal, see later in the text). Also a subset of 10 identifiable parameters was isolated and an automatic calibration subroutine (Levenberg Marquart) has been used to fine tune these parameters. Additionally, in order to assess the sensitivity of model results to the parameterization of the two gelatinous groups, Monte Carlo simulations were performed perturbing all the parameters governing their dynamics. In order to calibrate the particle dynamics and export, the chemical model was run off-line with the particle and microbial loop model in order to check its capacity of simulating anoxic waters. After a 104 year run, the model simulated NH4 and H2S profiles similar to observations but steady state was not reached suggesting that the Black Sea deep waters are not at steady state. The fully coupled model was then used to simulate the period 1988–1992 of the Black Sea ecosystem. The model solution exhibits a complex dynamics with several years of transient adjustment. This complexity is imparted by the explicit modeling of top predators. The integrated chlorophyll and phytoplankton biomasses, the maximum concentration and depth of maximum, mesozooplankton biomass, depth of oxycline, primary production, bacterial production, surface concentrations of nutrients and plankton simulated by the model and obtained from available data analysis were compared and showed a satisfactory agreement. Also, as in the data, the model shows a continuous development of phytoplankton throughout the year, with an intense spring bloom dominated by diatoms and a fall bloom dominated by dinoflagellates. Dinoflagellates dominate from summer until late fall while small phototrophic flagellates are never dominant in terms of biomass, but are present almost throughout the year except in winter. The model simulates an intense silicate removal associated to increased diatoms blooms which were promoted by increased nutrient conditions, and by the presence of gelatinous zooplankton. This silicate pumping leads to silicate limitation of diatoms development in summer allowing the development of dinoflagellates. [less ▲]

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See detailNumerical modeling of the hydro-mechanical behaviour of a large slope movement: the Triesenberg landslide
François, Bertrand ULg; Bonnard, Christophe; Laloui, Lyesse et al

in Zimmermann, T.; Truty, A. (Eds.) Numerics in geotechnics and structures (2006)

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See detailNumerical Modeling of Tribological Devices Using Various Contact Algorithms
CHABRAND, P.; DUBOIS, F.; GRAILLET, D. et al

in Proceedings of “NUMIFORM’98, Simulation of Materials Processing: Theory, Methods and Applications (1998, June)

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