Browsing by Author "Cruchaga, Marcela"

Now showing 1 - 9 of 9
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    A formulation for fluid-structure interaction problems with immersed flexible solids: Application to splitters subjected to flow past cylinders with different cross-sections
    (2024) Cruchaga, Marcela; Ancamil, Pablo; Celentano, Diego
    In the finite element method framework, a fluid-structure formulation is developed by coupling an Eulerian fixed-mesh fluid approach with a Lagrangian deforming-mesh description for a flexible solid. The coupled formulation is solved using a staggered scheme during time. For the fluid solution stage, the solid walls are considered as a time-variable internal boundary. The velocity and pressure fields are obtained by solving the weak form of the fluid dynamic equations in which the solid velocity is imposed on the internal boundary via a penalization term. For the solid solution stage, the displacement field is obtained by solving the discrete solid dynamic equations which consider traction forces computed by integrating pressures and viscous stresses on the nodes belonging to the solid walls. This novel technique is firstly applied to analyze a flexible splitter under the shedding of a flow past square cylinder due to this problem is considered as a benchmark in the literature. The present solutions agree with those computed using body-fitted techniques, thus validating the proposal. Secondly, flexible splitter motions under the shedding of flow past cylinders with different cross-sections and splitter lengths are comprehensively studied. Overall, the computed results confirmed that the hydrodynamic coefficients on the cylinders were reduced because of the presence of the splitter.
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    A surface remeshing technique for a Lagrangian description of 3D two-fluid flow problems
    (2010) Cruchaga, Marcela; Celentano, Diego J.; Breitkopf, Piotr; Villon, Pierre; Rassineux, Alain
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    Characterization of the Elastoplastic Response of Low Zn-Cu-Ti Alloy Sheets Using the CPB-06 Criterion
    (2019) Alister, Francisco; Celentano, Diego; Signorelli, Javier; Bouchard, Pierre-Olivier; Pino, Daniel; Cruchaga, Marcela
    Unlike other HCP metals such as titanium and magnesium, the behavior of zinc alloys has only been modeled in the literature. For the low Zn-Cu-Ti alloy sheet studied in this work, the anisotropy is clearly seen on the stress-strain curves and Lankford coefficients. These features impose a rigorous characterization and an adequate selection of the constitutive model to obtain an accurate representation of the material behavior in metal forming simulations. To describe the elastoplastic behavior of the alloy, this paper focuses on the material characterization through the application of the advanced Cazacu-Plunket-Barlat 2006 (CPB-06 for short) yield function combined with the well-known Hollomon hardening law. To this end, a two-stage methodology is proposed. Firstly, the material characterization is performed via tensile test measurements on sheet samples cut along the rolling, diagonal and transverse directions in order to fit the parameters involved in the associate CPB-06/Hollomon constitutive model. Secondly, these material parameters are assessed and validated in the simulation of the bulge test using different dies. The results obtained with the CPB-06/Hollomon model show a good agreement with the experimental data reported in the literature. Therefore, it is concluded that this model represents a consistent approach to estimate the behavior of Zn-Cu-Ti sheets under different forming conditions.
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    Damage Prediction in the Wire Drawing Process
    (2024) Gonzalez, Alvaro; Cruchaga, Marcela; Celentano, Diego; Ponthot, Jean-Philippe
    In this study, the prediction of damage in the wire drawing process of 2011 aluminum alloy was investigated through both experimental and numerical methods. A comprehensive experimental setup was designed involving 20 cases of wire drawing with varying die angles (10 degrees, 15 degrees, 21 degrees, 27 degrees, and 34 degrees) and reductions (21%, 29%, 31%, and 38%). Each case was tested three times, and the drawing forces, as well as occurrences of wire breakage, were recorded. The mechanical behavior of the material was firstly characterized using uniaxial tensile tests, whose results were used to determine the material parameters of both the hardening Voce law and those of uncoupled and coupled damage models. Then, the numerical simulations of the wire drawing process were performed using a finite element model, accounting for axisymmetric conditions and mesh convergence analysis to ensure accuracy. The previously characterized damage models were applied to evaluate their fracture prediction capabilities. A novel presentation method using three-dimensional graphs was employed to indicate the level of damage for each angle and reduction, providing greater sensitivity and insight into the damage values. Good agreement between the experimental and numerical data was demonstrated for the bilinear coupled damage model, validating its effectiveness. This study contributes to a better understanding of damage prediction in the wire drawing process, with implications for improving industrial practices and material performance evaluations.
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    Elastoplastic Characterization of Zn-Cu-Ti Alloy Sheets: Experiments, Modeling, and Simulation
    (2021) Alister, Francisco ; Celentano, Diego ; Nicoletti, Emanuel ; Signorelli, Javier ; Bouchard, Pierre-Olivier ; Pino, Daniel ; Pradille, Christophe ; Cruchaga, Marcela
    In this work, the elastoplastic behavior of Zn20 alloy sheets is characterized via a methodology that encompasses experiments, modeling, and numerical simulations. The experimental campaign includes tensile, compression, shear, and bulge tests. The modeling is based on the Cazacu-Plunket-Barlat 2006 yield criterion and the Swift hardening law, adjusted only from experimental data from the tensile and compression tests. The corresponding material parameters are obtained with a calibration procedure that accounts for the tensile stress-strain curves and Lankford coefficients, along with five directions regarding the sheet's rolling direction. Besides, compression tests were performed to search for evidence of asymmetric behavior. The numerical simulation, carried out with the finite element method (FEM), is used to validate the previous characterization with the shear and bulge tests models. The experimental force-displacement curve and the shear strain contours are the comparison basis for the shear test. For the bulge test, considering different mask geometries (minor to major axis length ratios), plots of the major-minor strain paths and thickness reduction in terms of the dome height are also used to assess the model's predictive capabilities. In general, the obtained numerical results show a good description of the material behavior in the shear and bulge tests. The evolution of the strain field in the bulge test is well represented by the model regardless of the sample orientation and mask configuration. It is finally concluded that the proposed methodology provides a robust model to describe the elastoplastic response of Zn-Cu-Ti (Zn20) alloy sheets subject to different proportional loading conditions.
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    Experimental and numerical analysis of a sphere falling into a viscous fluid
    (2012) Cruchaga, Marcela; Löhner, Rainald; Celentano, Diego J.
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    Numerical simulation of natural convection and phase-change in a horizontal Bridgman apparatus
    (2011) Celentano, Diego; Cruchaga, Marcela; Romero, Jorge; El Ganaoui, Mohammed
    Purpose - The purpose of this paper is to present a 2D numerical simulation of natural convection and phase-change of succinonitrile in a horizontal Bridgman apparatus. Three different heat transfer mechanisms are specifically studied: no growth, solidification and melting.
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    The Triaxiality Effect on Damage Evolution in Al-2024 Tensile Samples
    (2024) Gonzalez, Alvaro; Celentano, Diego; Cruchaga, Marcela; Ponthot, Jean-Philippe
    The effect of triaxiality on the evolution of damage in Al-2024 aluminum cylindrical specimens is studied in this work. Uncoupled and coupled damage models, all of them explicitly dependent on triaxiality, are assessed and compared. These models are characterized by tensile tests on cylindrical specimens without notches, to obtain the material parameters for each model. The capability of each model to predict fracture when different positive triaxial conditions evolve is then evaluated through tensile tests on notched cylindrical specimens. In particular, the damage index, evaluated at the fracture strain level, is compared with the experimental results validating the models. Moreover, the triaxiality evolution in the different specimens is studied in order to assess its effect on damage, demonstrating that the fracture strain decreases at greater triaxiality values. Observations through scanning electron microscopy confirm this pattern; i.e., an increase in triaxiality reveals a shift in the fracture mechanism from a more ductile condition in the original specimens to a more brittle one as the notch radius decreases. In addition, bilinear damage evolution is proposed to describe the physical behavior of the material when the Lemaitre coupled model is considered. In such a case, special attention must be devoted to the material characterization since coupling between hardening material parameters and damage affects the results.
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    Viscoplastic and Temperature Behavior of Zn-Cu-Ti Alloy Sheets: Experiments, Characterization, and Modeling
    (2021) Alister, Francisco ; Celentano, Diego ; Signorelli, Javier ; Bouchard, Pierre-Olivier ; Pino Muñoz, Daniel ; Cruchaga, Marcela
    It has been experimentally observed that the Zn-Cu-Ti zinc alloy shows a strong influence of strain rate and temperature on its plastic behavior. A significant change in the material response is seen with relatively small strain rate variations or temperature. In this work, these effects are addressed through the Cazacu-Plunket-Barlat 2006 (CPB-2006) yield criterion and the Johnson-Cook hardening law. The tests were carried out over the three main directions: rolling, diagonal, and transversal. Three strain rate conditions (0.002, 0.02, and 0.2 s(-1)) and three temperatures (20, 60, and 80 degrees C) were tested. Although the experi-mental results exhibit a significant influence of the strain rate and temperature on stress-strain curves for all tested directions, such two variables do not practically affect the Lankford coefficients. The proposed model calibration procedure is found to describe the material responses properly under the studied conditions. (C) 2021 The Author(s). Published by Elsevier B.V.