Papers by Javier Signorelli
Metals
The forming limit diagrams (FLDs) characterizing the formability of sheet metals are usually obta... more The forming limit diagrams (FLDs) characterizing the formability of sheet metals are usually obtained by applying proportional loadings. Nevertheless, the industrial processes involve strain path changes that can modify the limit-strain values. In addition, for strongly anisotropic sheet metals such as the Zn-Cu-Ti zinc alloy, large differences in forming limit curves (FLCs) with respect to the sheet rolling direction are observed. In the present work, the analysis of the effect of bilinear strain paths on the FLC is addressed by both experimental measurements and numerical simulations. For this purpose, a miniature testing device was used that allows evaluation of the influence of strain path changes on the limit strain on samples at 0°, 45° and 90° with respect to the sheet rolling direction cut from non-standard large samples previously subjected to a prestrain along the RD up to an early deformation of ~0.12. Numerical simulations were carried out using the well-known Marciniak ...
El codigo TELAGEN v.0.1 vincula las propiedades del cristal simple con propiedades macroscopicas ... more El codigo TELAGEN v.0.1 vincula las propiedades del cristal simple con propiedades macroscopicas homogeneizadas de solidos policristalinos como el tensor de constantes elasticas y el de dilatacion termica, utilizando informacion microestructural del material como la textura cristalografica y morfologica. Este se utiliza para ajustar modelos fenomenologicos macroscropicos mas simples que dependen de variables del reactor. Estas propiedades se obtienen por medio de metodos de homogeneizacion como Hashin Strikman (Z, Hashin, S. Shtrikman, S J. Mech. Phys. Solids. 11:127-140 (1963)) y autoconsistente, vease Ponte Castaneda y Willis (P. Ponte Castaneda y J. Willis, J. Mech. Phys. Solids. 43(12):1919-1951 (1995)). El paso limitante, respecto al costo computacional, es el computo del tensor de Hill (R.Hill, J. Mech. Phys. Solids. 13:89-101 (1965)) efectivo. Las expresiones clasicas del tensor de Hill involucran el computo de una integral doble. Aplicando un cambio de variable adecuado se p...
En el presente trabajo se describe la implementacion numerica y la aplicacion del criterio CPB06 ... more En el presente trabajo se describe la implementacion numerica y la aplicacion del criterio CPB06 para estimar el comportamiento elastoplastico de laminas de zinc. Este criterio se caracteriza por representar la asimetria en solicitacion a traccion-compresion (denominado efecto SD o “Strength Differential”) tipica de metales con estructura HCP. El criterio CPB06 hace uso de un tensor de anisotropia de segundo orden conformado por 9 parametros, una constante de asimetria “k” y el grado de homogeneidad “a”. Para un valor fijo de “a”, la relacion “k” es estimada a partir del esfuerzo de fluencia a traccion y compresion de la muestra. La implementacion de este modelo, en un codigo de elementos finitos propio, contempla la evolucion de los parametros de anisotropia basados en diferentes rangos de deformacion plastica para 3 direcciones de probetas (0°, 45° y 90°) en el ensayo de traccion. Los valores intermedios de dichos parametros seran establecidos por una interpolacion lineal de los v...
Estudio de la Subestructura de Granos Individuales en Chapas de Acero Laminadas Mediante un Modelo de Endurecimiento Basado en Densidad de Dislocaciones
La textura final que presentan las chapas de acero de bajo carbono depende tanto de su composicio... more La textura final que presentan las chapas de acero de bajo carbono depende tanto de su composicion quimica como de la microestructura que desarrollan. En el presente trabajo se muestran detalles de la implementacion numerica de una ley de endurecimiento/ablandamiento siguiendo el trabajo de Peeters et al. (Acta mater. Vol. 48, 2000, pp. 2123). El analisis original, basado en una transicion de escala con condiciones totalmente impuestas (limite superior), se extiende al caso de una homogeneizacion de tipo autoconsistente. La microestructura intragranular se describe en base a mecanismos fisicos elementales de creacion, acumulacion y aniquilacion de dislocaciones: densidades de dislocaciones que representan a paredes de celda, paredes de bloques de celda y de polarizacion. Se estudia la evolucion de las diferentes densidades de dislocaciones sobre la fibra γ ({111} a {111} en direccion // ND, ND: direccion normal) caracteristica de materiales BCC laminados en frio. Se encuentra que la...
Viscoplastic and temperature behavior of Zn–Cu–Ti alloy sheets: experiments, characterization, and modeling
Journal of Materials Research and Technology, 2021
Matéria (Rio de Janeiro), 2018
RESUMEN Los Diagramas Límite de Conformado (DLC), frecuentemente utilizados para caracterizar la ... more RESUMEN Los Diagramas Límite de Conformado (DLC), frecuentemente utilizados para caracterizar la formabilidad de chapas metálicas, se determinan asumiendo trayectorias de carga proporcionales hasta la ocurrencia de la inestabilidad plástica. Sin embargo, las deformaciones límite son afectadas significativamente por los cambios en los caminos de deformación, práctica muy usual en procesos reales de conformado de metales. El objetivo de este trabajo es analizar el efecto de la trayectoria de carga sobre el DLC de chapas de acero DP-780 de 0,9 mm de espesor y zinc Zn20 de 0,65 mm de espesor utilizando ensayos en dos etapas. Se estudiaron las deformaciones límite bajo tracción uniaxial para los materiales pre-deformados bajo carga equibiaxial. El DLC de referencia se obtuvo a través de ensayos de acopado hidráulico y de tracción uniaxial en probetas con diferentes geometrías de entalla. Las deformaciones límite obtenidas en la chapa DP-780 pre-deformada se encuentran por encima del diag...
Journal of Materials Processing Technology, 2019
This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Materials, 2019
Unlike other HCP metals such as titanium and magnesium, the behavior of zinc alloys has only been... more 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/Hollomo...
Journal of Materials Processing Technology, 2019
The formability of sheet metals is frequently characterized by the forming limit curve (FLC), whi... more The formability of sheet metals is frequently characterized by the forming limit curve (FLC), which is determined by applying proportional loading paths until the onset of necking. However, metal forming processes usually involve strain-path changes that can affect the limit strains. The purpose of the present work is to study the consequence of strain path changes on the formability of a 0.65 mm thick Zn-Cu-Ti sheet, by means of tests carried out in bi-linear stages. For this propose, tensile limit strains were determined by uniaxial deformation of biaxially pre-strained specimens. The FLC was first determined for six strain paths, obtained from hydraulic bulge and uniaxial tests with diverse specimen geometries. For the bi-linear strain paths, the tensile limit strains of the biaxially pre-deformed zinc sheet are significantly higher than the FLC of non pre-strained samples for the three orientations studied, revealing interdependence between the material's formability, the loading history and microstructure evolution.
Effect of the cube orientation on formability for FCC materials: A detailed comparison between full-constraint and self-consistent predictions
International Journal of Mechanical Sciences, 2014
ABSTRACT A rate-dependent self-consistent (VPSC) polycrystal-plasticity model, in conjunction wit... more ABSTRACT A rate-dependent self-consistent (VPSC) polycrystal-plasticity model, in conjunction with the MK approach, has been used successfully to address and explain plastic deformation features and localization conditions that cannot be treated with the full-constraint (FC) Taylor scheme. Signorelli and Bertinetti [On the role of constitutive model in the forming limit of FCC sheet metal with cube orientations, International Journal of Mechanical Sciences, 51: 473–480, 2009] investigated FCC sheet-metal formability, focusing on how the cube texture affects localized necking. In the present work, we extent this research to include two types of textures experimentally observed in aluminum alloys: the {1 0 0}<0 0 1> Cube orientation rotated 45° with respect to the sheet normal direction; and the {1 0 0} orientations. The effect of these orientations on the FLD is studied numerically, and a detailed comparison between MK-FC and MK-VPSC, derived from orientation stability and geometrical hardening, is made. The classical MK model, based on strain-rate imposed boundary conditions, was generalized in order to explicitly and correctly includes stress boundary conditions for materials with changes in anisotropy during deformation. In plane-strain stretching, the enhanced formability of the rotated 45°{1 0 0}<0 0 1> orientations has been correlated with texture evolution. In equi-biaxial stretching, the MK-FC approach predicted greater limit-strain values than did the MK-VPSC model. Qualitative differences in geometrical hardening/softening were also found.
Journal of Materials Engineering and Performance, 2015
The objective of this work is to experimentally and numerically determine the influence of plasti... more The objective of this work is to experimentally and numerically determine the influence of plastic anisotropy on the forming limit curve (FLC) for a heat-treated (300°C-1 h) AA1100 aluminum alloy sheet. The FLCs were obtained by the Nakajima test, where the anisotropy effect on the FLC was evaluated using hourglass-type samples taken at 0°, 45°, and 90°with respect to the sheet rolling direction. The effect of crystal orientations on the FLC is investigated using three micro-macro averaging schemes coupled to a Marciniak and Kuczynski (MK) analysis: the tangent viscoplastic self-consistent (VPSC), the tuned strength aVPSC, and the full-constraint Taylor model. The predicted limit strains in the left-hand side of the FLC agree well with experimental measurements along the three testing directions, while differences are found under biaxial stretching modes. Particularly, MK-VPSC predicts an unexpected limit strain profile in the right-hand side of the FLC for samples tested along the transverse direction. Only MK-aVPSC, with a tuning factor of 0.2, predicts satisfactorily the set of FLC measurements. Finally, the correlation of the predicted limit strains with the predicted yield surface by each model was also discussed.
Experimental and Visco-Plastic Self-Consistent evaluation of forming limit diagrams for anisotropic sheet metals: An efficient and robust implementation of the M-K model
International Journal of Plasticity, 2015
ABSTRACT In the present work, an efficient formulation for the prediction of forming-limit diagra... more ABSTRACT In the present work, an efficient formulation for the prediction of forming-limit diagrams (FLDs) based on the well-known Marciniak and Kuczynski (M-K) theory using a Visco-Plastic Self-Consistent (VPSC) crystal-plasticity model has been detailed. The present model extends the previous MK-VPSC implementation (Signorelli et al., Predictions of forming limit diagrams using a rate-dependent polycrystal self-consistent plasticity model, International Journal of Plasticity 25 (2009) 1-25) based on the Newton-Raphson (N-R) method, which gives no guarantee of a robust iterative procedure. In order to avoid convergence problems and to reduce the computational cost of the coupled MK-VPSC scheme, a direct approach (DA) is proposed. The DA eliminates the need of the Jacobian evaluation associated with the N-R method as well as the iterative procedure tied to other possible minimization techniques. Moreover, the mechanical states outside and inside the groove are solved in the sample reference frame, avoiding the need to rotate the crystallographic orientations and the internal variables to the current band reference frame at each increment. In this way, only two calls to the material law are required per M-K increment, obtaining a more robust numerical procedure with a significant computational cost reduction. Interestingly, the requirement of more complex boundary conditions does not substantially increase the number of internal VPSC iterations to achieve a given tolerance. Simulation results show that the direct MK-VPSC approach is consistent with that based on the N-R method. The generalized boundary conditions in the polycrystal model allowed us to calculate either strain-rate ratio or stress ratio based FLDs. The effect of using either strain-rate ratio or stress ratio paths on the FLDs has been investigated by imposing three types of pre-straining on the sheet metals. Formability predictions for a randomly-textured FCC material and for textured FCC, BCC and HCP polycrystals are presented and discussed. Finally, by considering dissimilar metals – extra deep-drawing quality steel (EDDQ), dual-phase steel (DP-780) and pure zinc (Zn20) ‒ we evaluated the MK-VPSC model’s ability to predict forming-limit strains irrespective of microstructure and crystallography. The predicted results have been compared with experimental data and good agreement was found.
Explicit method for calculating the effective properties and micromechanical stresses: An application to an alumina-SiC composite
Philosophical Magazine A, 1999
ABSTRACT High-temperature processing induces large internal stresses at room temperature in compo... more ABSTRACT High-temperature processing induces large internal stresses at room temperature in composites because of the difference between the thermal coefficients of the matrix and of the reinforcing particles. In this work we develop a theoretical scheme to calculate the strains in the particles by using the Eshelby equivalent method. The interaction between the inhomogeneous inclusions (fibres) is evaluated by means of a mean-field model given by Mori and Tanaka, and full anisotropy of fibres and matrix is taken into account within an explicit approach by which the problem is solved as a function of the deformation field instead of the thermoelastic properties. The model is applied to the thermoelastic moduli and residual stresses in biphase composites. We analyse the influence of the orientation distribution function of fibres, its volume fraction and elastic inhomogeneity factor on Young's modulus, Poisson's ratio and the thermal coefficients. We calculate the thermal residual stresses in an Al2O3-SiC composite as a function of direction, and the results are compared with the neutron measurements made by Majundar et al. As the non-uniform crystal structure of SiC whiskers complicates the interpretation of experimental data collected from whisker-reinforced composites, a general equation based on the fractions of cubic and hexagonal polytypes is incorporated in the model. We demonstrate that the residual stresses cannot easily be explained on the basis of elastic interactions and distribution of fibre orientations, even accounting for the elastic and thermal anisotropy of fibres. Correct interpretation and comparison of residual stresses with the measured values requires analysis of the peak shift and broadening stemming from the residual stresses.
Residual Strains in Al-Mg Composites Deformed by Extrusion. Experimental Data and Simulations
Materials Science Forum, 2000
All rights reserved. No part of contents of this paper may be reproduced or transmitted in any fo... more All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of TTP, www.ttp.net. (ID: 66.249.66.172-19/05/11,20:03:14) ... European Powder Diffraction 6 doi:10.4028/www. ...
K-S Relationship Identification Technique by EBSD
Key Engineering Materials, 2011
This paper focuses on the identification of activated slip system in flat specimens of hot- and c... more This paper focuses on the identification of activated slip system in flat specimens of hot- and cold-rolled UNS S32750 DSS plates subjected to low-cycle fatigue, paying particular attention on the existence of the K-S relationship. Electron Backscattered Diffraction (EBSD) technique was used to determine the local crystallographic properties of both phases. Although 27182 couples of α/γ grains were analyzed, the crystallographic K-S relationships were rarely observed between them. As a conclusion, it was observed that microcracks were mostly nucleated at grain boundaries and rarely at the extrusions.
ECAP of Fe. Experiments and simulations of the in-elbow textures
Zeitschrift für Kristallographie Supplements, 2009
ABSTRACT The study of deformation properties of low carbon steels is of particular interest becau... more ABSTRACT The study of deformation properties of low carbon steels is of particular interest because of their many technological applications. Obtaining fine grained Fe based materials can be approached by one of the several available Severe Plastic Deformation (SPD) techniques. The current paper shows experimental data and simulations of the deformation process of iron samples by Equal Channel Angular Extrusion (ECAE). The samples were extruded in a 120 degrees channel die either by one or a few passes. The heterogeneity and local development of the deformation on the elbow of the channel has been studied by X-ray measuring and simulation of the texture evolution. The Self Consistent models used for simulation allowed the calculation of the spin of the main texture components which agreed pretty well with the experiments.
Numerical Simulation of the Forming Limit Curves of a Heat Treated AA110-H14 Aluminium Alloy Sheet Using an Efficient Implementation of a VPSC Based MK Model
International audienc
Metal Forming - Process, Tools, Design, 2012
Why Spin Sharing Seems to be Successful in Texture Simulations?
Materials Science Forum, 2002
All rights reserved. No part of contents of this paper may be reproduced or transmitted in any fo... more All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of TTP, www.ttp.net. (ID: 66.249.66.172-07/05/11,18:56:23) ... Textures of Materials - ICOTOM 13 ...
Estudio De Texturas De Transformación De Fase De Aceros De Bajo Carbono
Uploads
Papers by Javier Signorelli