Enhanced CDM model accounting of stress triaxiality and Lode angle for ductile damage prediction in metal forming

2020 ◽  
pp. 105678952095804
Author(s):  
Kai Zhang ◽  
Houssem Badreddine ◽  
Naila Hfaiedh ◽  
Khemais Saanouni ◽  
Jianlin Liu
Keyword(s):  
Constitutive Equations ◽  
Damage Model ◽  
Stress Triaxiality ◽  
Ductile Damage ◽  
Irreversible Processes ◽  
State Variables ◽  
Damage Prediction ◽  
Proposed Model ◽  
Lode Angle ◽  
Fully Coupled

This paper deals with the prediction of ductile damage based on CDM approach fully coupled with advanced elastoplastic constitutive equations. This fully coupled damage model is developed based on the total energy equivalence assumption under the thermodynamics of irreversible processes framework with state variables. In this model, the damage evolution is enhanced by accounting for both stress triaxiality and Lode angle. The proposed constitutive equations are implemented into Finite Element (FE) code ABAQUS/Explicit through a user material subroutine (VUMAT). The material parameters are determined by the hybrid experimental-numerical method using various tensile and shear tests. Validation of the proposed model has been done using different tests of two aluminum alloys (Al6061-T6 and Al6014-T4). Through comparisons of numerical simulations with experimental results for different loading paths, the predictive capabilities of the proposed model have been shown. The model is found to be able to capture the initiation as well as propagation of macro-crack in sheet and bulk metals during their forming processes.

An Anisotropic Damage Model for Ductile Metals

2002 ◽  
Author(s):  
Youssef Hammi ◽  
Mark F. Horstemeyer ◽  
Doug J. Bammann
Keyword(s):  
Damage Model ◽  
Ductile Damage ◽  
Damage Effect ◽  
Irreversible Processes ◽  
Plastic Strain Rate ◽  
Fracture Mechanisms ◽  
Anisotropic Damage ◽  
Strain Rate Tensor ◽  
State Variables ◽  
Rate Dependent

An anisotropic ductile damage description is motivated from fracture mechanisms and physical observations in Al-Si-Mg aluminum alloys with second phases. Ductile damage is induced by the classical process of nucleation of voids at inclusions, followed by their growth and coalescence. These mechanisms are related to different microstructural and length scale parameters like the fracture toughness, the void size, the intervoid ligament distance, etc. The classical thermodynamic constraints of irreversible processes with material state variables are used to model the tensorial damage evolution coupled to the Bammann-Chiesa-Johnson (BCJ) rate-dependent plasticity. The damage-plasticity coupling is based on the effective stress concept, assuming the total energy equivalence, and written through a deviatoric damage effect tensor on the deviatoric part and through the trace of the second rank damage tensor on the hydrostatic part. The damage rate tensor is additively decomposed into a nucleation rate tensor, a void growth rate scalar, and a coalescence rate tensor. The induced damage anisotropy is mainly driven by the nucleation, which evolves as a function of the absolute value of the plastic strain rate tensor. Finally, some experimental data of cast A356 aluminum alloy are correlated with predictive void-crack evolution to illustrate the applicability of the anisotropic damage model.

Non-Associative Finite Strain Plasticity Coupled With Anisotropic Ductile Damage for Metal Forming

2012 ◽  
Author(s):  
T. Dung Nguyen ◽  
Houssem Badreddine ◽  
Khémais Saanouni
Keyword(s):  
Strong Coupling ◽  
Constitutive Equations ◽  
Damage Mechanics ◽  
Yield Criterion ◽  
Plastic Anisotropy ◽  
Continuum Damage Mechanics ◽  
Ductile Damage ◽  
Damage Effect ◽  
Irreversible Processes ◽  
State Variables

This paper presents the formulation of an advanced mechanical model describing a wide class of anisotropic elastoplastic constitutive equations accounting for the strong coupling with the anisotropic ductile damage. This model is developed within the framework of thermodynamics of irreversible processes with state variables and the continuum damage mechanics. The plastic anisotropy is accounted for through a non-associative theory for which a plasticity yield criterion and the plastic potential are defined separately but considering the strong coupling between both phenomena. The damage anisotropy is defined by using a second rank tensor. The effect of damage on the mechanical fields (stress, hardening, plastic strain, etc…) is described by a fourth rank damage effect operator that is defined in the context of the hypothesis of total energy equivalence. A rotating frame formulation is used to fulfil the objectivity of the constitutive equations under finite transformation. Finally, in order to illustrate the predictive capabilities of the model, the parametric studies with some simple loading case are investigated and the results discussed on the light of the anisotropic character of the ductile damage and its interaction with the anisotropy of plastic flow.

scholarly journals A fully coupled damage model with stress triaxiality and Lode dependence

2020 ◽  
Vol 967 ◽  
pp. 012051
Author(s):  
K Zhang ◽  
H Badreddine ◽  
N Hfaiedh ◽  
K Saanouni ◽  
J Liu
Keyword(s):  
Damage Model ◽  
Stress Triaxiality ◽  
Lode Dependence ◽  
Fully Coupled

Numerical Design of Extrusion Process Using Finite Thermo-Elastoviscoplasticity with Damage. Prediction of Chevron Shaped Cracks

2009 ◽  
Vol 424 ◽  
pp. 265-272 ◽  
Author(s):  
Carl Labergère ◽  
Khemais Saanouni ◽  
Philippe Lestriez
Keyword(s):  
Constitutive Equations ◽  
Thermal Effects ◽  
Initial Temperature ◽  
Kinematic Hardening ◽  
Extrusion Process ◽  
Main Process ◽  
Damage Prediction ◽  
User Subroutine ◽  
Micro Cracks ◽  
Fully Coupled

The influence of the initial temperature and its evolution with large plastic deformation on the formation of the fully coupled chevron shaped cracks in extrusion is numerically investigated. Fully coupled thermo-elasto-viscoplastic constitutive equations accounting for thermal effects, mixed and nonlinear isotropic and kinematic hardening, isotropic ductile damage with micro-cracks closure effects are used. These constitutive equations have been implemented in Abaqus/Explicit code thanks to the user subroutine vumat and used to perform various numerical simulations needed to investigate the problem. It has been shown that the proposed methodology is efficient to predict the chevron shaped cracks in extrusion function of the main process parameters including the temperature effect.

Advances in Virtual Metal Forming Including the Ductile Damage Occurrence: Application to 3D Sheet Metal Deep Drawing

2008 ◽  
Vol 130 (2) ◽  
Author(s):  
K. Saanouni ◽  
H. Badreddine ◽  
M. Ajmal
Keyword(s):  
Sheet Metal ◽  
Constitutive Equations ◽  
Deep Drawing ◽  
Metal Forming ◽  
Ductile Damage ◽  
Classical Dynamic ◽  
Damage Initiation ◽  
Integration Schemes ◽  
Local Integration ◽  
Fully Coupled

An advanced numerical methodology to simulate virtually any sheet or bulk metal forming including various kinds of initial and induced anisotropies fully coupled to the isotropic ductile damage is presented. First, the fully coupled anisotropic constitutive equations in the framework of continuum damage mechanics under large plastic deformation are presented. Special care is paid to the strong coupling between the main mechanical fields such as elastoplasticity, mixed nonlinear isotropic and kinematic hardenings, ductile isotropic damage, and contact with friction in the framework of nonassociative and non-normal formulation. The associated numerical aspects concerning both the local integration of the coupled constitutive equations as well as the (global) equilibrium integration schemes are presented. The local integration is outlined, thanks to the Newton iterative scheme applied to a reduced system of ordinary differential equations. For the global resolution of the equilibrium problem, the classical dynamic explicit (DE) scheme with an adaptive time step control is used. This fully coupled procedure is implemented into the general purpose finite element code for metal forming simulation, namely, ABAQUS/EXPLICIT. This gives a powerful numerical tool for virtual optimization of metal forming processes before their physical realization. This optimization with respect to the ductile damage occurrence can be made either to avoid the damage occurrence to have a nondamaged part as in forging, stamping, deep drawing, etc., or to favor the damage initiation and growth for some metal cutting processes as in blanking, guillotining, or machining by chip formation. Two 3D examples concerning the sheet metal forming are given in order to show the capability of the proposed methodology to predict the damage initiation and growth during metal forming processes.

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