A MULTISCALE FRAMEWORK FOR CHARACTERIZATION AND MODELING DUCTILE FRACTURE IN HETEROGENEOUS ALUMINUM ALLOYS

2009 ◽  
Vol 01 (01) ◽  
pp. 21-55 ◽  
Author(s):  
SOMNATH GHOSH ◽  
D. M. VALIVETI ◽  
CHAO HU ◽  
JIE BAI
Keyword(s):  
Aluminum Alloys ◽  
Ductile Fracture ◽  
Multiscale Modeling ◽  
Damage Model ◽  
Ductile Failure ◽  
Matrix Cracking ◽  
Anisotropic Plasticity ◽  
Gtn Model ◽  
Statistical Homogeneity ◽  
Heterogeneous Microstructures

This paper develops three components contributing to the overall framework of multiscale modeling of ductile fracture in aluminum alloys. The first module is morphology-based domain partitioning (MDP) as a pre-processor to the multiscale modeling. This module delineates regions of statistical homogeneity and inhomogeneity with a systematic three-step process that is based on geometric features of morphology. The second module is detailed micromechanical analysis of particle fragmentation and matrix cracking of heterogeneous microstructures. A locally enriched VCFEM or LE-VCFEM is developed to incorporate ductile failure through matrix cracking in the form of void growth and coalescence using nonlocal Gurson–Tvergaard–Needleman (GTN) model. The third module develops a homogenized anisotropic plasticity-damage model in the form of GTN model for macroscopic analysis. Parameters in this GTN model are calibrated from results of homogenization of microstructural variables obtained from microstructural RVE. Numerical examples elucidate the strength of components of the overall framework.

Characterization of Notched Ductile Failure With Continuum Damage Mechanics

1990 ◽  
Vol 112 (4) ◽  
pp. 412-421 ◽  
Author(s):  
C. L. Chow ◽  
K. Y. Sze
Keyword(s):  
Ductile Fracture ◽  
Circular Hole ◽  
Damage Mechanics ◽  
Damage Model ◽  
Ductile Failure ◽  
Continuum Damage Mechanics ◽  
Thin Plates ◽  
Continuum Damage ◽  
Anisotropic Model ◽  
Aluminum Alloy 2024

A recently developed anisotropic model of continuum damage mechanics has been applied successfully to characterize ductile fracture of cracked plates under mode I and mixed mode failures. The damage model is further extended in this investigation to examine its applicability to include notch ductile fracture of thin plates containing a circular hole. Two hole sizes of 16 mm and 24 mm diameters are chosen and the specimen material is aluminum alloy 2024-T3. Fracture loads of the plates are predicted by the damage model and compared satisfactorily with those determined experimentally. This investigation provides an important confirmation that not only the anisotropic model of continuum damage mechanics but also the same failure criterion developed can be effectively employed to characterize both ductile fracture for plates containing an isolated macro-crack or circular hole which would otherwise not be possible using the conventional theory of fracture mechanics. The successful development of the unified approach to characterize ductile failure provides a vital impetus for design engineers in the general application of the theory of continuum damage mechanics to solve practical engineering problems.

A Micromechanical Model for Ductile Fracture of API X65

2006 ◽  
Vol 321-323 ◽  
pp. 43-47
Author(s):  
Chang Kyun Oh ◽  
Yun Jae Kim ◽  
Jong Hyun Baek ◽  
Young Pyo Kim ◽  
Woo Sik Kim
Keyword(s):  
Experimental Data ◽  
Ductile Fracture ◽  
Mechanical Model ◽  
Micromechanical Model ◽  
Ductile Failure ◽  
Experimental Tests ◽  
Gtn Model ◽  
Deformation And Fracture ◽  
Api X65 Steel ◽  
X65 Steel

This paper presents a micro-mechanical model of ductile fracture for the API X65 steel, using the Gurson-Tvergaard-Needleman (GTN) model. Experimental tests and FE damage simulations using the GTN model are performed for smooth and notched tensile bars with three different notch radii, from which micromechanical parameters in the GTN model are calibrated. The calibrated micro-mechanical model is applied to quantify pre-strain effects on plastic deformation and fracture of the API X65 steel. Good agreements of the FE damage results with experimental data suggest confidence in the use of the proposed micro-mechanical model to simulate ductile failure of pipelines made of API X65 steels.

Influence of Ductile Damage Evolution on the Collapse Load of Frames

2010 ◽  
Vol 77 (3) ◽  
Author(s):  
Edwin L. Chica ◽  
Antolín L. Ibán ◽  
José M. G. Terán ◽  
Pablo M. López-Reyes
Keyword(s):  
Ductile Fracture ◽  
Damage Evolution ◽  
Damage Model ◽  
Ductile Failure ◽  
Ductile Material ◽  
Collapse Load ◽  
Local Criterion ◽  
Solid Materials ◽  
Damage Models ◽  
Isotropic Damage

In this note we analyze the influence of four damage models on the collapse load of a structure. The models considered here have been developed using the hypothesis based on the concept of effective stress and the principle of strain equivalence and they were proposed by Lemaitre and Chaboche (1990, Mechanics of Solid Materials), Wang (1992, “Unified CDM Model and Local Criterion for Ductile Fracture—I. Unified CDM Model for Ductile Fracture,” Eng. Fract. Mech., 42, pp. 177–183), Chandrakanth and Pandey (1995, “An Isotropic Damage Model for Ductile Material,” Eng. Fract. Mech., 50, pp. 457–465), and Bonora (1997, “A Nonlinear CDM Model for Ductile Failure,” Eng. Fract. Mech., 58, pp. 11–28). The differences between them consist mainly in the form of the dissipative potential from which the kinetic law of damage is derived and also in the assumptions made about some parameters of the material.

Meshless Analysis of Ductile Failure

2011 ◽  
Author(s):  
J. Li
Keyword(s):  
Finite Element ◽  
Crack Propagation ◽  
Ductile Fracture ◽  
Reproducing Kernel ◽  
Ductile Failure ◽  
Finite Element Simulations ◽  
Experimental Results ◽  
Gtn Model ◽  
Reproducing Kernel Particle

We study ductile fracture using Reproducing Kernel Particle Interpolation and the Gurson-Tvergaard-Needleman (GTN) model. The meshless simulations are compared with the available experimental results and previous finite element simulations for crack propagation. The results agree well with experimental results, and it is confirmed that the proposed method provides a convenient and yet accurate means for simulation of ductile fracture.

A new microvoid-damage model for ductile fracture

1986 ◽  
Vol 25 (3) ◽  
pp. 377-384 ◽  
Author(s):  
Wei Hua Tai ◽  
Bing Xian Yang
Keyword(s):  
Ductile Fracture ◽  
Damage Model

Numerical Investigation of Ductile Fracture in Pipelines Under Complex Loading Using a Phenomenological Damage Model

2021 ◽  
Author(s):  
Iago S. Santos ◽  
Diego F. B. Sarzosa
Keyword(s):  
Ductile Fracture ◽  
Mechanical Response ◽  
Numerical Study ◽  
Damage Model ◽  
Stress Triaxiality ◽  
Numerical Procedure ◽  
Complex Loading ◽  
Experimental Tests ◽  
Compact Tension ◽  
Axial Tensile

Abstract This paper presents a numerical study on pipes ductile fracture mechanical response using a phenomenological computational damage model. The damage is controlled by an initiation criterion dependent on the stress triaxiality and the Lode angle parameter, and a post-initiation damage law to eliminate each finite element from the mesh. Experimental tests were carried out to calibrate the elastoplastic response, damage parameters and validate the FEM models. The tested geometries were round bars having smooth and notched cross-section, flat notched specimens under axial tensile loads, and fracture toughness tests in deeply cracked bending specimens SE(B) and compact tension samples C(T). The calibrated numerical procedure was applied to execute a parametric study in pipes with circumferential surface cracks subjected to tensile and internal pressure loads simultaneously. The effects of the variation of geometric parameters and the load applications on the pipes strain capacity were investigated. The influence of longitudinal misalignment between adjacent pipes was also investigated.

Applying Gurson Type of Damage Models to Low Constraint Tests of High Strength Steels and Welds

2006 ◽  
Author(s):  
Ming Liu ◽  
Yong-Yi Wang
Keyword(s):  
Damage Mechanics ◽  
Ductile Failure ◽  
High Strength Steels ◽  
High Strength ◽  
Crack Tip Opening Displacement ◽  
Opening Displacement ◽  
Critical Crack ◽  
Gtn Model ◽  
Strain Capacity ◽  
Low Constraint

Pipelines experiencing displacement-controlled loading need to have adequate strain capacity. Large tensile strain capacity can only be achieved when the failure processes are ductile. In ductile failure analyses, the strain capacity may be determined by two approaches. The first approach uses the conventional fracture mechanics criteria, such as the attainment of the critical crack tip opening displacement, to assess the onset of the crack propagation. The other approach uses damage mechanics models in which the onset and propagation of cracks are controlled by the nucleation, growth, and coalescence of voids in the material. The damage mechanics models can provide some insights of the ductile failure processes as they have more physical mechanisms built in the constitutive model. In this paper, the Gurson-Tvergaard-Needleman (GTN) model is applied to two types of low-constraint tests: curved wide plates and back-bend specimens. The wide plate test is considered more representatives of full-scale pipes than the conventional laboratory-sized specimens, but requires large-capacity machines. The back-bend test is a newly developed low-constraint laboratory-sized test specimen. A relatively simple approach to determine the damage parameters of the GTN model is discussed and the transferability of damage parameters between those two test types is also analyzed.

Failure Predictions for DP Steel Cross-die Test using Anisotropic Damage

2011 ◽  
Vol 21 (5) ◽  
pp. 713-754 ◽  
Author(s):  
M. S. Niazi ◽  
H. H. Wisselink ◽  
T. Meinders ◽  
J. Huétink
Keyword(s):  
Strain Rate ◽  
Damage Evolution ◽  
Damage Model ◽  
Anisotropic Damage ◽  
Continuum Damage ◽  
Anisotropic Plasticity ◽  
Continuum Damage Model ◽  
Damage Models ◽  
Isotropic Damage ◽  
Failure Predictions

The Lemaitre's continuum damage model is well known in the field of damage mechanics. The anisotropic damage model given by Lemaitre is relatively simple, applicable to nonproportional loads and uses only four damage parameters. The hypothesis of strain equivalence is used to map the effective stress to the nominal stress. Both the isotropic and anisotropic damage models from Lemaitre are implemented in an in-house implicit finite element code. The damage model is coupled with an elasto-plastic material model using anisotropic plasticity (Hill-48 yield criterion) and strain-rate dependent isotropic hardening. The Lemaitre continuum damage model is based on the small strain assumption; therefore, the model is implemented in an incremental co-rotational framework to make it applicable for large strains. The damage dissipation potential was slightly adapted to incorporate a different damage evolution behavior under compression and tension. A tensile test and a low-cycle fatigue test were used to determine the damage parameters. The damage evolution was modified to incorporate strain rate sensitivity by making two of the damage parameters a function of strain rate. The model is applied to predict failure in a cross-die deep drawing process, which is well known for having a wide variety of strains and strain path changes. The failure predictions obtained from the anisotropic damage models are in good agreement with the experimental results, whereas the predictions obtained from the isotropic damage model are slightly conservative. The anisotropic damage model predicts the crack direction more accurately compared to the predictions based on principal stress directions using the isotropic damage model. The set of damage parameters, determined in a uniaxial condition, gives a good failure prediction under other triaxiality conditions.

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