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.

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.

Damage mechanics characterization on the fatigue behaviour of a solder joint material

2001 ◽  
Vol 215 (8) ◽  
pp. 883-892 ◽  
Author(s):  
C. L. Chow ◽  
F Yang ◽  
H. E. Fang
Keyword(s):  
Solder Joint ◽  
Fatigue Damage ◽  
Damage Mechanics ◽  
Internal State ◽  
Damage Effect ◽  
Irreversible Processes ◽  
State Variables ◽  
Solder Material ◽  
Damage Initiation ◽  
Joint Material

This paper presents the first part of a comprehensive mechanics approach capable of predicting the integrity and reliability of solder joint material under fatigue loading without viscoplastic damage considerations. A separate report will be made to present the comprehensive damage model describing life prediction of the solder material under thermomechanical fatigue (TMF) loading. The method is based on the theory of damage mechanics, which makes possible a macroscopic description of the successive material deterioration caused by the presence of microcracks/voids in engineering materials. A damage mechanics model based on the thermodynamic theory of irreversible processes with internal state variables is proposed and used to provide a unified approach in characterizing the cyclic behaviour of a typical solder material. With the introduction of a damage effect tensor, the constitutive equations are derived to enable the formulation of a fatigue damage dissipative potential function and a fatigue damage criterion. The fatigue evolution is subsequently developed on the basis of the hypothesis that the overall damage is induced by the accumulation of fatigue and plastic damage. This damage mechanics approach offers a systematic and versatile means that is effective in modelling the entire process of material failure, ranging from damage initiation and propagation leading eventually to macrocrack initiation and growth. As the model takes into account the load history effect and the interaction between plasticity damage and fatigue damage, with the aid of a modified general-purpose finite element program, the method can readily be applied to estimate the fatigue life of solder joints under different loading conditions.

Modelling and numerical simulation of thick sheet double slitting process using continuum damage mechanics

2014 ◽  
Vol 23 (8) ◽  
pp. 1150-1167 ◽  
Author(s):  
Yosr Ghozzi ◽  
Carl Labergere ◽  
Khemais Saanouni ◽  
Anthony Parrico
Keyword(s):  
Numerical Simulation ◽  
Constitutive Equations ◽  
Damage Mechanics ◽  
Continuum Damage Mechanics ◽  
Thick Sheet ◽  
Technological Parameters ◽  
Strongly Coupled ◽  
Mixed Hardening ◽  
Elasto Plasticity ◽  
Fully Coupled

This work concerns the modelling and numerical simulation of specific thick sheet cutting process using advanced constitutive equations accounting for elasto-plasticity with mixed hardening fully coupled with isotropic ductile damage. First, the complex kinematics of the different tools is modelled with specific boundary conditions. Second, the fully and strongly coupled constitutive equations are summarized and the associated numerical aspects are shortly presented. An inverse material identification procedure is used to determine the convenient values of the material parameters. Finally, the double slitting process is numerically simulated and the influence of the main technological parameters studied focusing on the cutting forces.

Finite Element Simulation of the Creep Behavior of 2.25Cr-1Mo-0.25V Steel Based on Continuum Damage Mechanics

2015 ◽  
Vol 750 ◽  
pp. 266-271 ◽  
Author(s):  
Yu Zhou ◽  
Xue Dong Chen ◽  
Zhi Chao Fan ◽  
Yi Chun Han
Keyword(s):  
Genetic Algorithm ◽  
Finite Element ◽  
Creep Behavior ◽  
Constitutive Equations ◽  
Damage Evolution ◽  
Damage Mechanics ◽  
Creep Damage ◽  
Continuum Damage Mechanics ◽  
Continuum Damage ◽  
Element Simulation

The creep behavior of 2.25Cr-1Mo-0.25V ferritic steel was investigated using a set of physically-based creep damage constitutive equations. The material constants were determined according to the creep experimental data, using an efficient genetic algorithm. The user-defined subroutine for creep damage evolution was developed based on the commercial finite element software ANSYS and its user programmable features (UPFs), and the numerical simulation of the stress distribution and the damage evolution of the semi V-type notched specimen during creep were studied. The results showed that the genetic algorithm is a very efficient optimization approach for the parameter identification of the creep damage constitutive equations, and finite element simulation based on continuum damage mechanics can be used to analyze and predict the creep damage evolution under multi-axial stress states.

Continuum damage mechanics modelling incorporating stress triaxiality effect on ductile damage initiation

2020 ◽  
Vol 43 (8) ◽  
pp. 1755-1768 ◽  
Author(s):  
Nicola Bonora ◽  
Gabriel Testa ◽  
Andrew Ruggiero ◽  
Gianluca Iannitti ◽  
Domenico Gentile
Keyword(s):  
Damage Mechanics ◽  
Stress Triaxiality ◽  
Continuum Damage Mechanics ◽  
Ductile Damage ◽  
Continuum Damage ◽  
Damage Initiation

Study of Damage in the Medium Density Polyethylene Using Digital Image Correlation

2016 ◽  
Vol 869 ◽  
pp. 356-360
Author(s):  
Lindemberg Ferreira dos Santos ◽  
Rodrigo Nogueira de Codes ◽  
Erijanio Nonato Silva ◽  
Rodrigo Amaral de Codes
Keyword(s):  
Digital Image Correlation ◽  
Digital Image ◽  
Damage Mechanics ◽  
Region Of Interest ◽  
Continuum Damage Mechanics ◽  
Gauge Length ◽  
Image Correlation ◽  
Irreversible Processes ◽  
Medium Density ◽  
Material Stiffness

The non-linear response of solids is an expression of irreversible processes that originate in microdefects, which are understood as initial material damage. This work aims to analyze the degradation of the mechanical properties of medium density polyethylene through continuum damage mechanics using Digital Image Correlation (DIC). With this technique, displacement and strain fields are obtained throughout the specimen gauge length and therefore optical gauges in any region of interest can measure the strain. Mechanical testing with successive loading and unloading were performed in order to obtain the actual magnitude of the material stiffness in certain strains. Finally, through the damage versus strain diagrams, the results showed that the damage in medium density polyethylene increases from a certain deformation.

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