The Experts below are selected from a list of 795 Experts worldwide ranked by ideXlab platform
Jacques Besson - One of the best experts on this subject based on the ideXlab platform.
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Ductile-Brittle Transition in Charpy and CT tests/Experiments and Modelling
2013Co-Authors: Benoit Tanguy, Roland Piques, Jacques Besson, André PineauAbstract:The objective of this paper is to study Charpy–V notch and CT testsin the ductile–brittle transition range from both an experimental and numericalaspects. Tests were carried out between..165C and 100C on Charpy–Vspecimens using an instrumented pendulum and between..60C and 0C onCT30 sidegrooved specimens. Numerical simulations of both tests are presentedwhere ductile damage is simulated by Rousselier model and cleavage fracture usingBeremin model. Differences between the stress field ahead of a propagating ductilecrack in both specimen geometry are underlined. Calculations are then post–processed to determine the failure probability in the transition temperature rangeunder investigation.
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numerical simulation of ductile fracture with the Rousselier constitutive law
Computer Methods in Applied Mechanics and Engineering, 2008Co-Authors: E Lorentz, Jacques Besson, V CanoAbstract:This contribution aims at developing robust and reliable tools dedicated to predictive numerical simulation of ductile fracture. Description of damage mechanisms relies here on the Rousselier constitutive law. To achieve robustness and objectivity, several points need then to be addressed: reduction of the set of internal variables so as to recast the model into the framework of generalised standard materials; proper expression of the normal plastic flow rule at the vertex of the yield surface; finite strain formulation based on a multiplicative split of the deformation gradient; fully implicit integration of the constitutive equations leading to a single scalar equation that admits a unique root; use of mixed finite elements to avoid volumetric locking; strain gradient-based nonlocal model to control strain localisation and remedy spurious mesh dependency. The capabilities of the resulting numerical formulation are demonstrated through simulating the cup–cone fracture of a notched tensile specimen.
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ductile to brittle transition of an a508 steel characterized by charpy impact test part ii modeling of the charpy transition curve
Engineering Fracture Mechanics, 2005Co-Authors: Benoit Tanguy, Roland Piques, Jacques Besson, A PineauAbstract:Abstract A finite element simulation of the Charpy test is developed in order to model the ductile to brittle transition curve of a pressure vessel steel. The material (an A508 steel) and the experimental results are presented in a companion paper (Part I [Engng. Fract. Mech.]). The proposed simulation includes a detailed description of the material viscoplastic behavior over a wide temperature range. Ductile behavior is modeled using modified Rousselier model. The Beremin model is used to describe brittle fracture. The Charpy test is simulated using a full 3D mesh and accounting for adiabatic heating and contact between the specimen, the striker and the anvil. The developed model is well suited to represent ductile tearing. Using brittle failure parameters identified below −150 °C, it is possible to represent the transition curve up to −80 °C assuming that the Beremin stress parameter σu is independent of temperature. Above this temperature, a temperature dependent Beremin stress parameter, σu, must be used to correctly simulate the transition curve. Quasi-static and dynamic tests can then be consistently modeled.
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Ductile to brittle transition of an A508 steel characterized by Charpy impact test: Part II: modeling of the Charpy transition curve
Engineering Fracture Mechanics, 2005Co-Authors: Benoit Tanguy, Roland Piques, Jacques Besson, A PineauAbstract:Abstract A finite element simulation of the Charpy test is developed in order to model the ductile to brittle transition curve of a pressure vessel steel. The material (an A508 steel) and the experimental results are presented in a companion paper (Part I [Engng. Fract. Mech.]). The proposed simulation includes a detailed description of the material viscoplastic behavior over a wide temperature range. Ductile behavior is modeled using modified Rousselier model. The Beremin model is used to describe brittle fracture. The Charpy test is simulated using a full 3D mesh and accounting for adiabatic heating and contact between the specimen, the striker and the anvil. The developed model is well suited to represent ductile tearing. Using brittle failure parameters identified below −150 °C, it is possible to represent the transition curve up to −80 °C assuming that the Beremin stress parameter σu is independent of temperature. Above this temperature, a temperature dependent Beremin stress parameter, σu, must be used to correctly simulate the transition curve. Quasi-static and dynamic tests can then be consistently modeled.
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modeling of plane strain ductile rupture
International Journal of Plasticity, 2003Co-Authors: Jacques Besson, D Steglich, Wolfgang BrocksAbstract:Abstract The formation of slanted fracture under plane strain conditions is studied using the finite Element (FE) method. Constitutive models proposed by Rousselier and by Gurson are used. Rice's condition for localization is checked at every point of the FE mesh for each time step. The role of mesh design (element size, element aspect ratio, symmetry) is first studied. The different constitutive models are then compared. It is in particular shown that the use of the f ★ function in the Gurson model favors flat fracture.
V Cano - One of the best experts on this subject based on the ideXlab platform.
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1 A GRADIENT DAMAGE MODEL FOR DUCTILE FRACTURE
2016Co-Authors: E Lorentz, V CanoAbstract:The void growth responsible for ductile fracture is described by the Rousselier model. It has been revisited so that it reduces to a standard plastic law where the void effect is taken into account through the total volume change. Thanks to a specific finite strain description, the constitutive law is expressed as a minimisation problem. Therefore, it can fully benefit from a variational formulation dedicated to gradient constitutive laws. The introduction of the gradient of the cumulated plasticity field into the constitutive equations efficiently controls the localisation process, as demonstrated by the numerical simulation of a notched specimen.
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numerical simulation of ductile fracture with the Rousselier constitutive law
Computer Methods in Applied Mechanics and Engineering, 2008Co-Authors: E Lorentz, Jacques Besson, V CanoAbstract:This contribution aims at developing robust and reliable tools dedicated to predictive numerical simulation of ductile fracture. Description of damage mechanisms relies here on the Rousselier constitutive law. To achieve robustness and objectivity, several points need then to be addressed: reduction of the set of internal variables so as to recast the model into the framework of generalised standard materials; proper expression of the normal plastic flow rule at the vertex of the yield surface; finite strain formulation based on a multiplicative split of the deformation gradient; fully implicit integration of the constitutive equations leading to a single scalar equation that admits a unique root; use of mixed finite elements to avoid volumetric locking; strain gradient-based nonlocal model to control strain localisation and remedy spurious mesh dependency. The capabilities of the resulting numerical formulation are demonstrated through simulating the cup–cone fracture of a notched tensile specimen.
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Numerical simulation of ductile fracture with the Rousselier constitutive law
Computer Methods in Applied Mechanics and Engineering, 2008Co-Authors: E Lorentz, J. Besson, V CanoAbstract:International audienceThis contribution aims at developing robust and reliable tools dedicated to predictive numerical simulation of ductile fracture. Description of damage mechanisms relies here on the Rousselier constitutive law. To achieve robustness and objectivity, several points need then to be addressed: reduction of the set of internal variables so as to recast the model into the framework of generalised standard materials; proper expression of the normal plastic flow rule at the vertex of the yield surface; finite strain formulation based on a multiplicative split of the deformation gradient; fully implicit integration of the constitutive equations leading to a single scalar equation that admits a unique root; use of mixed finite elements to avoid volumetric locking; strain gradient-based nonlocal model to control strain localisation and remedy spurious mesh dependency. The capabilities of the resulting numerical formulation are demonstrated through simulating the cup–cone fracture of a notched tensile specimen
Wolfgang Brocks - One of the best experts on this subject based on the ideXlab platform.
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Damage and Fracture
Plasticity and Fracture, 2017Co-Authors: Wolfgang BrocksAbstract:Micromechanical aspects, mechanisms and models of fracture are addressed, which have become increasingly topical since the 1990s though the basic ideas and perceptions date back to the early years of fracture mechanics. The characteristics of brittle and ductile damage on the micro-scale and the respective fractographic appearance are outlined and the implications on local criteria of fracture are specified. Two approaches for establishing constitutive equations of damage are distinguished, namely micro-mechanical models which aim at describing the physical processes of damage on the micro-scale following the concept of representative volume elements and phenomenological constitutive equations for stresses and strains describing macroscopically observable effects of degradation based on thermodynamical principles. Two particular models of major significance, the Gurson and the Rousselier yield function are described. A brief introduction to parameter identification ends the chapter.
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Journal Citation (to be inserted by the publisher) Copyright by Trans Tech Publications Damage Models for Cyclic Plasticity
2016Co-Authors: Wolfgang Brocks, D SteglichAbstract:Abstract. The process of void growth in ductile materials under alternating plastification is studied by means of unit-cell calculations. Constitutive models for damage evolution in ductile materials as the micromechanical model by Gurson, Tvergaard and Needleman and the continuum damage model by Rousselier are systematically investigated with respect to their ability of describing this process. Nonlinear kinematic hardening effects are taken into account and a respective extension of the GTN model is presented. The models are finally applied for simulating the mechanical behaviour of tensile specimens under cyclic loading, and the results are compared with experimental results
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modeling of plane strain ductile rupture
International Journal of Plasticity, 2003Co-Authors: Jacques Besson, D Steglich, Wolfgang BrocksAbstract:Abstract The formation of slanted fracture under plane strain conditions is studied using the finite Element (FE) method. Constitutive models proposed by Rousselier and by Gurson are used. Rice's condition for localization is checked at every point of the FE mesh for each time step. The role of mesh design (element size, element aspect ratio, symmetry) is first studied. The different constitutive models are then compared. It is in particular shown that the use of the f ★ function in the Gurson model favors flat fracture.
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Damage Models for Monotonous and Cyclic Loading
PAMM, 2002Co-Authors: Wolfgang Brocks, D SteglichAbstract:Constitutive models for describing damage evolution in ductile materials have found increasing application, mainly the micromechanical model by Gurson, Tvergaard and Needleman, and a continuum damage mechanics approach by Rousselier. Both models modify the von Mises yield potential by incorporating the effects of the hydrostatic stress and damage. The latter is introduced by means of a single scalar damage quantity, the porosity or void volume fraction, which acts as an internal variable aditionally to the plastic equivalent strain. Several examples for the capabilities of these models beyond common applications are given. In particular, their ability to represent cup-cone fracture of round bars and shear fracture of plane strain specimens as well as their behaviour under cyclic loading are studied.
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modeling of crack growth in round bars and plane strain specimens
International Journal of Solids and Structures, 2001Co-Authors: Jacques Besson, D Steglich, Wolfgang BrocksAbstract:The formation of cup-cone fracture in round bars and of slant fracture in plane strain specimens is studied using the finite element (FE) method. Constitutive models proposed by Rousselier [Nucl. Engng. Des. 105 (1987) 97] and by Gurson [Acta Metall. 32 (1984) 157] are used. The analysis takes into account viscoplasticity and void nucleation. Different indicators of localization are computed during FE calculations. The analysis shows that cup-cone is more easily formed using the Rousselier model than the Gurson model. Cup-cone fracture is inhibited in highly viscous materials. The use of the f* function in the Gurson model favors flat fracture. The crack path (flat or cup-cone/slant) can be correlated to the size of the localization zone which is formed ahead of the central penny shaped crack.
E Lorentz - One of the best experts on this subject based on the ideXlab platform.
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1 A GRADIENT DAMAGE MODEL FOR DUCTILE FRACTURE
2016Co-Authors: E Lorentz, V CanoAbstract:The void growth responsible for ductile fracture is described by the Rousselier model. It has been revisited so that it reduces to a standard plastic law where the void effect is taken into account through the total volume change. Thanks to a specific finite strain description, the constitutive law is expressed as a minimisation problem. Therefore, it can fully benefit from a variational formulation dedicated to gradient constitutive laws. The introduction of the gradient of the cumulated plasticity field into the constitutive equations efficiently controls the localisation process, as demonstrated by the numerical simulation of a notched specimen.
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numerical simulation of ductile fracture with the Rousselier constitutive law
Computer Methods in Applied Mechanics and Engineering, 2008Co-Authors: E Lorentz, Jacques Besson, V CanoAbstract:This contribution aims at developing robust and reliable tools dedicated to predictive numerical simulation of ductile fracture. Description of damage mechanisms relies here on the Rousselier constitutive law. To achieve robustness and objectivity, several points need then to be addressed: reduction of the set of internal variables so as to recast the model into the framework of generalised standard materials; proper expression of the normal plastic flow rule at the vertex of the yield surface; finite strain formulation based on a multiplicative split of the deformation gradient; fully implicit integration of the constitutive equations leading to a single scalar equation that admits a unique root; use of mixed finite elements to avoid volumetric locking; strain gradient-based nonlocal model to control strain localisation and remedy spurious mesh dependency. The capabilities of the resulting numerical formulation are demonstrated through simulating the cup–cone fracture of a notched tensile specimen.
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Numerical simulation of ductile fracture with the Rousselier constitutive law
Computer Methods in Applied Mechanics and Engineering, 2008Co-Authors: E Lorentz, J. Besson, V CanoAbstract:International audienceThis contribution aims at developing robust and reliable tools dedicated to predictive numerical simulation of ductile fracture. Description of damage mechanisms relies here on the Rousselier constitutive law. To achieve robustness and objectivity, several points need then to be addressed: reduction of the set of internal variables so as to recast the model into the framework of generalised standard materials; proper expression of the normal plastic flow rule at the vertex of the yield surface; finite strain formulation based on a multiplicative split of the deformation gradient; fully implicit integration of the constitutive equations leading to a single scalar equation that admits a unique root; use of mixed finite elements to avoid volumetric locking; strain gradient-based nonlocal model to control strain localisation and remedy spurious mesh dependency. The capabilities of the resulting numerical formulation are demonstrated through simulating the cup–cone fracture of a notched tensile specimen
Siegfried Schmauder - One of the best experts on this subject based on the ideXlab platform.
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3D optical measurement and numerical simulation of the fracture behavior of Al6061 laser welded joints
Engineering Fracture Mechanics, 2019Co-Authors: Siegfried SchmauderAbstract:Abstract In this paper, the fracture behavior of an aluminum laser welded butt joint was studied numerically and experimentally. With the assistance of a digital image correlation (DIC) system, the strain variation of the flat specimen under deformation is obtained. Void sheeting mechanism and shear bands are found on the surface of the specimen to precede rupture. Although initial pores are found in the fusion zone, good predictions are obtained with respect to stress-strain, F-COD as well as fracture resistance JR curves for flat and compact tension (C(T)) specimens, confirming the Rousselier model can predict the fracture behavior of aluminum laser welded joint well, with the Rousselier parameters calibrated from simulation of fracture behavior of notched round specimens.
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Simulation the crack front in a thin sheet specimen obtained from steel S355
2016Co-Authors: Siegfried Schmauder, Ulrich Weber, Yin Cheng, Thilo F MorgeneyerAbstract:Ductile crack initiation and propagation in steel S355 sheet specimen have been investigated with synchrotron radiation computed laminography (SRCL). The influence of non-metallic inclusions on the damage evolution of crack initiation and propagation is discussed. After the reconstruction of the laminography data, void initiation, growth and coalescence from elongated and localized particles are visualized in 2D and 3D images. The 3D Rousselier model is used to predict the crack fronts before shear crack propagation happens. When defining the elements in front of the initial notch with the true f 0 -values obtained from laminography data, the crack front in front of the notch can be predicted with the Rousselier model very well.
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Simulation of the fracture behavior of Al6061 laser welded joints with the Rousselier model
Computational Materials Science, 2016Co-Authors: Siegfried Schmauder, Ulrich WeberAbstract:Abstract Ductile fracture behavior of an aluminum laser beam welded joint is investigated experimentally and numerically. Based on the hardness test across the welded joints, the dimensions of different weld regions are fixed. Tensile tests of flat specimens extracted from the base material, from the fusion zone and from the heat affected zone are made. The mechanical properties of the different weld regions are used as finite element model input in the simulation work. Fracture toughness tests are performed on compact tension specimens with the initial crack located in the base material, and in the center of the fusion zone, respectively. The tensile test results of compact tension specimens are shown in the form of force vs. crack opening displacement and fracture resistance curves. Based on the numerical calibration of the Rousselier parameters on notched round specimens, the Rousselier model is used to investigate the crack propagation of the compact tension specimen. Good agreement between the numerical and experimental results is obtained from compact tension specimens with the initial crack located at different positions of the weld region.
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Prediction of macroscopic damage behaviour of precipitation strengthened steels via multiscale simulations
GAMM-Mitteilungen, 2015Co-Authors: David Molnar, Ulrich Weber, Peter Binkele, Dennis Rapp, Siegfried SchmauderAbstract:A multiscale modelling approach is presented that sequentially connects in total five simulation methods via parameter transfers in order to capture the macroscopic damage behaviour due to an underlying nano structure of copper precipitates in bcc iron. In this multiscale approach, information on precipitation states is taken from kinetic Monte-Carlo and Phasefield simulations as well as from experimental data. Based on a calibration of Dislocation Dynamics by Molecular Dynamics simulations as well as on testing conditions known from experiments, Dislocation Dynamics simulations with an infinite dislocation on a single glide plane provide strengthening levels which are related to a reference stress-strain curve obtained from experiments. Subsequently, the macroscopic damage behaviour is simulated with the Finite-Element-Method including the Rousselier Damage Model for the reference state as well as for the virtually aged states. The results are validated by comparison with experimental results and predictions are made with respect to specific precipitation cases. (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
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Numerical Simulation and Experimental Investigation of Damage Behaviour on Al6061 Laser Welded Joints
Key Engineering Materials, 2014Co-Authors: Siegfried Schmauder, Ulrich WeberAbstract:The ductile damage behaviour of an aluminium laser welded joint is studied experimentally and numerically. The dimensions of the weld regions are fixed by hardness tests. Fracture toughness tests of Al6061 laser beam welded joints were performed with the compact tension (C(T)) specimens. The Rousselier model is used and the parameters: initial void volume fraction (f0) and average void distance (lc) are identified by metallographic investigations, for the BM, the FZ and the HAZ. Numerical calibration of the Rousselier parameters is performed on notched round specimens. The same Rousselier parameters are used to predict force vs. Crack Opening Displacement (COD) of C(T) specimens.
