Modeling of Anisotropic Damage for Ductile Materials in Metal Forming Processes

2002 ◽  
Author(s):  
Youssef Hammi ◽  
Mark F. Horstemeyer ◽  
Doug J. Bammann
Keyword(s):  
Metal Forming ◽  
Ductile Damage ◽  
Fracture Mechanisms ◽  
Anisotropic Damage ◽  
Ductile Metals ◽  
Explicit Finite Element ◽  
Microstructural Parameters ◽  
Fully Implicit ◽  
Rate Dependent ◽  
Second Phases

The primary goal of this study is to model the anisotropic effect of ductile damage in metal forming processes. To represent the ductile metals, an anisotropic ductile plasticity/damage formulation is considered within the framework of continuum mechanics. The formulation is motivated from fracture mechanisms and physical observations in Al-Si-Mg aluminum alloys with second phases. The ductile damage mechanisms are represented by the classical ductile process of nucleation of voids at inclusions, followed by their growth and coalescence. Functions of each mechanism evolution are related to different microstructural parameters. The damage, represented by a second rank tensor, is coupled to the Bammann-Chiesa-Johnson (BCJ) rate-dependent plasticity using the effective stress concept. The constitutive equations are integrated using a fully implicit scheme and implemented into a explicit finite element code. This implementation is used to predict damage during the forward axisymmetric extrusion of an aluminum bar. This example illustrates the applicability of the model to predict the initiation and the evolution of anisotropic damage in metal 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.

Application of an efficient anisotropic damage model to the prediction of the failure of metal forming processes

2019 ◽  
Vol 28 (10) ◽  
pp. 1556-1579 ◽  
Author(s):  
Ali Salehi Nasab ◽  
Mohammad Mashayekhi
Keyword(s):  
Constitutive Equations ◽  
Metal Forming ◽  
Kinematic Hardening ◽  
Ductile Damage ◽  
Irreversible Processes ◽  
Anisotropic Damage ◽  
Mapping Algorithm ◽  
Return Mapping ◽  
Integration Schemes ◽  
Return Mapping Algorithm

The main objective of this study is the numerical implementation of an advanced elastic–plastic model fully coupled with anisotropic ductile damage. The implemented formulation has been defined in the framework of thermodynamics of irreversible processes and a symmetric second-order tensor is adopted to describe the anisotropic damage state variable. After a summary of the main constitutive equations is given, the numerical integration of constitutive equations is performed using implicit and asymptotic integration schemes. Finite element simulation is performed using ABAQUS/Explicit software and the developed VUMAT subroutine. Next, the application of the developed model to T-shaped hydroforming of tubes and square-cup deep drawing metal forming processes is thoroughly discussed and failure onset zones due to anisotropic ductile damage growth are predicted and the results were consistent with the literature. Finally, by making an assumption that kinematic hardening can be ignored, an elastic predictor/plastic corrector algorithm requiring the solution of one equation is introduced. The assessment of the developed one-equation return-mapping algorithm is carried out by applying it to the simulation of the tensile test of a pre-notched bar. The Central Prossessing Unit time decreases noticeably using one-equation return mapping algorithm compared to the conventional return mapping algorithm and the numerical results are in good agreement with previous numerical simulations and experiments.

Anisotropic ductile damage fully coupled with anisotropic plastic flow: Modeling, experimental validation, and application to metal forming simulation

2014 ◽  
Vol 23 (8) ◽  
pp. 1211-1256 ◽  
Author(s):  
W Rajhi ◽  
K Saanouni ◽  
H Sidhom
Keyword(s):  
Plastic Flow ◽  
Metal Forming ◽  
Kinematic Hardening ◽  
Ductile Damage ◽  
Damage Effect ◽  
Anisotropic Damage ◽  
State Variables ◽  
Energy Equivalence ◽  
Anisotropic Plastic ◽  
Equivalence Assumption

The main goal of this paper is the modeling, numerical simulation, and experimental validation of the anisotropic ductile damage effects on initially anisotropic plastic flow with mixed (isotropic and kinematic) nonlinear hardening under large plastic strains for metal forming processes simulation. A symmetric second-rank damage tensor together with a symmetrized fourth-rank damage-effect tensor is used to describe the anisotropic ductile damage evolution and its effect on the large plastic flow with hardening. Following the concept of effective state variables in the framework of the total energy equivalence assumption, the “Murakami” fourth-rank damage-effect tensor is chosen to describe the anisotropic damage effect on the elastic-plastic behavior including the mixed hardening. The “Lemaitre” ductile anisotropic damage evolution relationships, where the principal directions of the damage rate tensor are governed by those of the plastic strain rate tensor, are used. As difference with the works cited above, the nonlinear mixed isotropic and kinematic hardening is taken into account considering the full and strong damage effects through the effective state variables deduced from the total energy equivalence assumption initially proposed by Saanouni et al. The non-associative plasticity theory is considered, and the “ Hill 1948 ” quadratic (equivalent) stress norm is used to describe the large plastic anisotropic flow accounting for mixed isotropic and kinematic hardening with anisotropic damage effects. The formulation is performed assuming finite plastic strains and small elastic strains through the so-called rotated frame formulation. The obtained model was implemented into ABAQUS/Explicit® FE software thanks to the user’s developed subroutine VUMAT. The numerical aspects related to the time discretization of the fully coupled anisotropic constitutive equations are carefully described. Finally and for the validation purpose, the model is identified using an appropriate experimental data base concerning the grade 316L stainless steel to simulate numerically some metal forming processes.

Modeling of Solder Fatigue Failure due to Ductile Damage

2010 ◽  
Vol 26 (4) ◽  
pp. N23-N27 ◽  
Author(s):  
K. Aluru ◽  
F.-L. Wen ◽  
Y.-L. Shen
Keyword(s):  
Numerical Study ◽  
Fatigue Cracks ◽  
Damage Model ◽  
Quantitative Information ◽  
Ductile Damage ◽  
Element Analysis ◽  
Cyclic Shear ◽  
Rate Dependent ◽  
Solder Fatigue ◽  
Temporal And Spatial

ABSTRACTA numerical study is undertaken to simulate failure of solder joint caused by cyclic shear deformation. A progressive ductile damage model is incorporated into the rate-dependent elastic-viscoplastic finite element analysis, resulting in the capability of simulating damage evolution and eventual failure through crack formation. It is demonstrated that quantitative information of fatigue life, as well as the temporal and spatial evolution of fatigue cracks, can be explicitly obtained.

scholarly journals Predicting the onset of cracks in bulk metal forming by ductile damage criteria

2017 ◽  
Vol 207 ◽  
pp. 2048-2053 ◽  
Author(s):  
Peter Christiansen ◽  
Chris V. Nielsen ◽  
Paulo A.F. Martins ◽  
Niels Bay
Keyword(s):  
Metal Forming ◽  
Ductile Damage ◽  
Bulk Metal ◽  
Bulk Metal Forming ◽  
Damage Criteria

A Micro-Damage Model for High Velocity Impact Using Combined Viscosity and Gradient Localization Limiters

2005 ◽  
Author(s):  
Rashid K. Abu Al-Rub ◽  
George Z. Voyiadjis ◽  
Anthony N. Palazotto
Keyword(s):  
High Strain ◽  
Broad Class ◽  
Damage Model ◽  
Mesh Size ◽  
Damage Mechanism ◽  
Strain Rates ◽  
Ductile Metals ◽  
Physical Description ◽  
Rate Dependent ◽  
Nonlinear Continuum

During dynamic loading processes, large inelastic deformation associated with high strain rates leads, for a broad class of ductile metals, to degradation and failure by strain localization. However, as soon as material failure dominates a deformation process, the material increasingly displays strain softening and the finite element computations are considerably affected by the mesh size and alignment. This gives rise to a non-physical description of the localized regions. This paper presents theoretical and computational frameworks to solve this problem with the aid of nonlocal gradient-enhanced theory coupled to visco-inelasticity. Constitutive equations for anisotropic thermo-viscodamage (rate-dependent damage) mechanism coupled with thermo-hypoelasto-viscoplastic deformation are developed in this work within the framework of thermodynamic laws, nonlinear continuum mechanics, and nonlocal continua. Explicit and implicit micro-structural length scale measures, which preserve the well-posedness of the differential equations, are introduced through the use of the viscosity and gradient localization limiters.

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