The Experts below are selected from a list of 219 Experts worldwide ranked by ideXlab platform
Kjell Mattiasson - One of the best experts on this subject based on the ideXlab platform.
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On the Modeling of the Unloading Modulus for Metal Sheets
International Journal of Material Forming, 2010Co-Authors: Per-anders Eggertsen, Kjell MattiassonAbstract:The springback phenomenon is defined as the elastic recovery of the residual stresses produced during the forming of a material. An accurate prediction of springback puts high demands on the constitutive modeling. A constitutive model for springback prediction should of course be able to accurately predict the stress state after the forming phase. However, it should also be able to predict the material behavior during the unloading phase. In Classical Plasticity Theory, the unloading of a material after plastic deformation is assumed to be linearly elastic with the stiffness constantly equal to Young’s modulus. However, several experimental investigations have revealed that this is an incorrect assumption.
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On the Modeling of the Unloading Modulus for Metal Sheets
International Journal of Material Forming, 2010Co-Authors: Per-anders Eggertsen, Kjell MattiassonAbstract:The springback phenomenon is defined as the elastic recovery of the residual stresses produced during the forming of a material. An accurate prediction of springback puts high demands on the constitutive modeling. A constitutive model for springback prediction should of course be able to accurately predict the stress state after the forming phase. However, it should also be able to predict the material behavior during the unloading phase. In Classical Plasticity Theory, the unloading of a material after plastic deformation is assumed to be linearly elastic with the stiffness constantly equal to Young’s modulus. However, several experimental investigations have revealed that this is an incorrect assumption. The main purpose of the present work has been to formulate a constitutive model that can accurately predict the unloading behavior of a sheet metal material. The new model is based on a Classical elasticplastic framework, and is totally independent on the choice of yield criterion and hardening evolution law.
Paolo Lonetti - One of the best experts on this subject based on the ideXlab platform.
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Interlaminar damage model for polymer matrix composites
Journal of Composite Materials, 2020Co-Authors: Paolo Lonetti, Raffaele Zinno, Fabrizio Greco, Ever J. BarberoAbstract:A constitutive model for fiber-reinforced composite materials with damage and unrecoverable deformation, which for the first time accounts for interlaminar damage, is presented. The formulation is based on Continuous Damage Mechanics coupled with Classical Plasticity Theory in a consistent thermodynamic framework using internal state variables. In-plane damage and novel formulation of interlaminar damage are included in order to describe the main failure modes of laminates structures. A novel implementation of the constitutive model into a finite element formulation incorporating geometric nonlinearity is presented. The model uses a small number of adjustable parameters, which are identified from available experimental data. Comparisons with experimental data for composite laminates under torsion loading are shown to validate the model for interlaminar damage. Coupled material and geometrical nonlinear analysis with simultaneous in-plane and interlaminar damage is demonstrated. The effect of warping on in...
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Three-Dimensional Continuum Damage Model for Polymer Matrix Composites
Materials, 2004Co-Authors: Ever J. Barbero, Joan A. Mayugo, Paolo LonettiAbstract:A constitutive model for fiber reinforced composite materials with damage and unrecoverable deformation, which for the first time accounts for thru-the-thickness damage, is presented. The formulation is based on Continuous Damage Mechanics coupled with Classical Plasticity Theory in a consistent thermodynamic framework using internal state variables. A novel formulation of the parameter identification is included in order to describe the main failure modes of polymer matrix composite laminae. The new parameter identification is simpler than those available in the literature. It is also more sensitive and allows for better control of material behavior to match experimental data. Furthermore, it uses material properties that are simpler to test than previous models. The model uses a small number of adjustable parameters, which are identified from available experimental data. Comparisons with experimental data for composite laminates under in plane and torsion loading are shown to validate the model. The new model, although simpler than previous ones, is able to model all experimentally observed behavior of laminates that were previously modeled with more complex models.Copyright © 2004 by ASME
Ever J. Barbero - One of the best experts on this subject based on the ideXlab platform.
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Interlaminar damage model for polymer matrix composites
Journal of Composite Materials, 2020Co-Authors: Paolo Lonetti, Raffaele Zinno, Fabrizio Greco, Ever J. BarberoAbstract:A constitutive model for fiber-reinforced composite materials with damage and unrecoverable deformation, which for the first time accounts for interlaminar damage, is presented. The formulation is based on Continuous Damage Mechanics coupled with Classical Plasticity Theory in a consistent thermodynamic framework using internal state variables. In-plane damage and novel formulation of interlaminar damage are included in order to describe the main failure modes of laminates structures. A novel implementation of the constitutive model into a finite element formulation incorporating geometric nonlinearity is presented. The model uses a small number of adjustable parameters, which are identified from available experimental data. Comparisons with experimental data for composite laminates under torsion loading are shown to validate the model for interlaminar damage. Coupled material and geometrical nonlinear analysis with simultaneous in-plane and interlaminar damage is demonstrated. The effect of warping on in...
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Three-Dimensional Continuum Damage Model for Polymer Matrix Composites
Materials, 2004Co-Authors: Ever J. Barbero, Joan A. Mayugo, Paolo LonettiAbstract:A constitutive model for fiber reinforced composite materials with damage and unrecoverable deformation, which for the first time accounts for thru-the-thickness damage, is presented. The formulation is based on Continuous Damage Mechanics coupled with Classical Plasticity Theory in a consistent thermodynamic framework using internal state variables. A novel formulation of the parameter identification is included in order to describe the main failure modes of polymer matrix composite laminae. The new parameter identification is simpler than those available in the literature. It is also more sensitive and allows for better control of material behavior to match experimental data. Furthermore, it uses material properties that are simpler to test than previous models. The model uses a small number of adjustable parameters, which are identified from available experimental data. Comparisons with experimental data for composite laminates under in plane and torsion loading are shown to validate the model. The new model, although simpler than previous ones, is able to model all experimentally observed behavior of laminates that were previously modeled with more complex models.Copyright © 2004 by ASME
Seung Song - One of the best experts on this subject based on the ideXlab platform.
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on an implementation of the strain gradient Plasticity with linear finite elements and reduced integration
Finite Elements in Analysis and Design, 2012Co-Authors: Moon Shik Park, Seung SongAbstract:The size effects exhibited in the structural behaviors of micro-sized loading components cannot be described with Classical Plasticity Theory alone. Thus, strain gradient Plasticity together with appropriate experiments has been used to account for this size effect. In previous implementations of strain gradient Plasticity into finite element code, low order displacement elements with reduced integration, despite their versatility for solving various structural problems, have been excluded because of their inability to yield the strain gradient inside the element. In this work, a new method of evaluating the plastic strain gradient with linear displacement elements via an isoparametric interpolation of the averaged-at-nodal plastic strain is proposed. Rate-independent yield conditions are satisfied accurately by the Taylor dislocation hardening model with Abaqus UHARD subroutine. To verify the suggested approach, the structural behaviors of micro-sized specimens subjected to bending, twisting, and nano-indentation tests were modeled and analyzed. The predicted size effects are generally in good agreement with previously published experimental results. Computational efforts are minimized and user versatilities are maximized by the proposed implementation.
Moon Shik Park - One of the best experts on this subject based on the ideXlab platform.
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Hardness estimation for pile-up materials by strain gradient Plasticity incorporating the geometrically necessary dislocation density
Journal of Mechanical Science and Technology, 2013Co-Authors: Moon Shik ParkAbstract:A plastic strain gradient Theory incorporating the geometrically necessary dislocation density based on the low order displacement finite element method is proposed for calculation of the hardness value by Berkovich indentation. The obtained analysis results by this work are found to be in good agreement with the experimental data. Three-dimensional modeling technique of Berkovich indentation is also suggested. An empirical coefficient that includes the strain gradient effect into the yield stress formula is introduced and determined by reviewing area factors and hardness curves generated from the analyses. As pile-up occurs, Classical Plasticity Theory gives a higher area factor and lower hardness value than those from experiment. However the strain gradient Plasticity Theory used in this work gives corrected area factor and hardness values. Dislocation density plots are generated that can explain the size effect during indentation and the availability of the three-dimensional modeling of Berkovich indentation.
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on an implementation of the strain gradient Plasticity with linear finite elements and reduced integration
Finite Elements in Analysis and Design, 2012Co-Authors: Moon Shik Park, Seung SongAbstract:The size effects exhibited in the structural behaviors of micro-sized loading components cannot be described with Classical Plasticity Theory alone. Thus, strain gradient Plasticity together with appropriate experiments has been used to account for this size effect. In previous implementations of strain gradient Plasticity into finite element code, low order displacement elements with reduced integration, despite their versatility for solving various structural problems, have been excluded because of their inability to yield the strain gradient inside the element. In this work, a new method of evaluating the plastic strain gradient with linear displacement elements via an isoparametric interpolation of the averaged-at-nodal plastic strain is proposed. Rate-independent yield conditions are satisfied accurately by the Taylor dislocation hardening model with Abaqus UHARD subroutine. To verify the suggested approach, the structural behaviors of micro-sized specimens subjected to bending, twisting, and nano-indentation tests were modeled and analyzed. The predicted size effects are generally in good agreement with previously published experimental results. Computational efforts are minimized and user versatilities are maximized by the proposed implementation.