scholarly journals A Modified Phase-Field Damage Model for Metal Plasticity at Finite Strains: Numerical Development and Experimental Validation

Metals ◽  
2020 ◽  
Vol 11 (1) ◽  
pp. 47
Author(s):  
Jelena Živković ◽  
Vladimir Dunić ◽  
Vladimir Milovanović ◽  
Ana Pavlović ◽  
Miroslav Živković
Keyword(s):  
Phase Field ◽  
Damage Evolution ◽  
Deformation Gradient ◽  
Damage Model ◽  
Steel Structures ◽  
Plasticity Model ◽  
Metal Plasticity ◽  
Damage And Fracture ◽  
Von Mises ◽  
Von Mises Plasticity

Steel structures are designed to operate in an elastic domain, but sometimes plastic strains induce damage and fracture. Besides experimental investigation, a phase-field damage model (PFDM) emerged as a cutting-edge simulation technique for predicting damage evolution. In this paper, a von Mises metal plasticity model is modified and a coupling with PFDM is improved to simulate ductile behavior of metallic materials with or without constant stress plateau after yielding occurs. The proposed improvements are: (1) new coupling variable activated after the critical equivalent plastic strain is reached; (2) two-stage yield function consisting of perfect plasticity and extended Simo-type hardening functions. The uniaxial tension tests are conducted for verification purposes and identifying the material parameters. The staggered iterative scheme, multiplicative decomposition of the deformation gradient, and logarithmic natural strain measure are employed for the implementation into finite element method (FEM) software. The coupling is verified by the ‘one element’ example. The excellent qualitative and quantitative overlapping of the force-displacement response of experimental and simulation results is recorded. The practical significances of the proposed PFDM are a better insight into the simulation of damage evolution in steel structures, and an easy extension of existing the von Mises plasticity model coupled to damage phase-field.

scholarly journals Two-Intervals Hardening Function in a Phase-Field Damage Model for the Simulation of Aluminum Alloy Ductile Behavior

Metals ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 1685
Author(s):  
Vladimir Dunić ◽  
Jelena Živković ◽  
Vladimir Milovanović ◽  
Ana Pavlović ◽  
Andreja Radovanović ◽  
...  
Keyword(s):  
Phase Field ◽  
Damage Model ◽  
Uniaxial Tensile ◽  
Plasticity Model ◽  
Engineering Structures ◽  
Plastic Domain ◽  
Loading Tests ◽  
Ductile Behavior ◽  
Von Mises ◽  
Von Mises Plasticity

The aluminum alloys (AA) are among the most utilized materials in engineering structures, which induces the need for careful investigation, testing, and possibilities for accurate simulation of the structure’s response. AA 5083-H111 specimens were used to investigate the possibility of employing a Phase-Field Damage Model (PFDM) for the simulation of AA structures’ behavior. The specimens were mechanically tested by uniaxial tensile loading tests. Based on the obtained results, the PFDM was employed with a von Mises plasticity model, implemented in the Finite Element Method software. The plasticity model was extended by modification of the hardening function defined in two-intervals: a linear hardening and a Simo-type hardening. An excellent superposition of the simulation and experimental force-displacement response was recorded. These findings suggest that the AA structures’ response can be successfully simulated in the elastic-plastic domain, as well as its failure by damage being controlled.

A General Orthotropic von Mises Plasticity Material Model With Mixed Hardening: Model Definition and Implicit Stress Integration Procedure

1996 ◽  
Vol 63 (2) ◽  
pp. 376-382 ◽  
Author(s):  
M. Kojic´ ◽  
N. Grujovic´ ◽  
R. Slavkovic´ ◽  
M. Zˇivkovic´
Keyword(s):  
Equivalent Stress ◽  
Parameter Method ◽  
Plasticity Model ◽  
Integration Procedure ◽  
Mixed Hardening ◽  
Tangent Moduli ◽  
Stress Integration ◽  
Mises Plasticity ◽  
Von Mises ◽  
Von Mises Plasticity

A general orthotropic von Mises plasticity model, with an extension of the Hill’s yield criterion to include mixed hardening, is introduced in the paper. Material constants and equivalent stress-equivalent plastic strain curves are defined in a way to suggest their experimental determination. The model represents a special case of a general anisotropic metal plasticity model proposed by the authors. An implicit stress integration procedure, representing an application of the governing parameter method (GPM) introduced by the first author, is presented. The GPM is briefly described, and the computational procedure, together with calculation of the consistent tangent moduli, are given in some detail for a general three-dimensional deformation, with direction of application to plane stress/shell conditions. Numerical examples illustrate applicability of the model and effectiveness of the computational algorithm.

A gradient-enhanced damage model motivated by engineering approaches to ductile failure of steels

2019 ◽  
Vol 28 (8) ◽  
pp. 1261-1296 ◽  
Author(s):  
Andreas Seupel ◽  
Meinhard Kuna
Keyword(s):  
Damage Evolution ◽  
Damage Model ◽  
High Stress ◽  
Stress Triaxiality ◽  
Material Behavior ◽  
Pressure Vessel Steel ◽  
Vessel Steel ◽  
Damage Initiation ◽  
Gradient Enhancement ◽  
Von Mises Plasticity

Material models for ductile damage, crack initiation, and crack growth are of high interest, e.g. for metal forming simulations. Empirical engineering approaches are often applied, but the numerical results are sensitive to the discretization if no method is utilized to prevent ill-posedness of the underlying boundary value problem due to strain softening. In order to face this issue, an empirical damage model is equipped with a gradient-enhancement which introduces an additional length scale parameter. Until the initiation of damage, the material is modeled with standard von Mises plasticity. Damage initiation is taken into account by an uncoupled failure indicator. After damage initiation, material degradation is assumed to be driven by a non-local quantity, which depends on plastic deformation and stress triaxiality. During damage evolution, the macroscopic material behavior becomes dependent on hydrostatic stress, which is motivated by well known void growth and coalescence mechanisms. A calibration strategy is developed to determine the parameters of strain hardening, damage initiation, and damage evolution as well as the internal length step-by-step. The proposed model is calibrated to experimental data of a pressure vessel steel. Reasonable predictions of smooth and notched tensile tests as well as a small punch test show the validity of the model for loadings from moderate to high stress triaxialities.

Effect of Triaxiality and Lode Angle on the Plasticity Behaviour of a Ti-6Al-4V Titanium Alloy

2013 ◽  
Vol 577-578 ◽  
pp. 413-416
Author(s):  
Andrea Gilioli ◽  
Andrea Manes ◽  
Marco Giglio ◽  
Nima Allahverdizadeh
Keyword(s):  
Titanium Alloy ◽  
Tensile Tests ◽  
Constitutive Law ◽  
Plasticity Model ◽  
Virtual Test ◽  
Test Methodology ◽  
Lode Angle ◽  
Mises Plasticity ◽  
Von Mises ◽  
Von Mises Plasticity

The widespread Von Mises plasticity model fails to take the hydrostatic and the Lode angle effects into account and the assumption of this model is not valid for all types of metallic alloys. Hence in the present work the applicability of the Von Mises plasticity model in applications on a Ti-6Al-4V Titanium alloy have been analysed. A virtual test methodology, combination of experiments and numerical analysis have been developed. For this purpose various tensile tests on different specimen shapes have been carried out experimentally. These tests have been subsequently numerically reproduced to calibrate a constitutive law which fits every single test best, highlighting the possible effect of triaxiality and Lode angle on plasticity (strain hardening behaviour). An analysis of the specimen fracture surfaces have been carried out to evaluate possible effect of triaxiality and Lode angle down to a microscopic level.

Numerical Modelling of Damage Evolution in Ingot Forging

2015 ◽  
Vol 651-653 ◽  
pp. 237-242
Author(s):  
Peter Christiansen ◽  
Paulo Martins ◽  
Niels Bay ◽  
Jesper Hattel
Keyword(s):  
Numerical Modelling ◽  
Damage Evolution ◽  
Damage Model ◽  
Plasticity Model ◽  
Damage Criterion ◽  
Forging Process ◽  
Porous Plasticity ◽  
Simulation Results

The ingot forging process is numerically simulated applying both the Shima-Oyane porous plasticity model as a coupled damage model and the uncoupled normalized Cockcroft & Latham criterion. Four different cases including two different lower die angles (120oand 180o) and two different sizes of feed (400mm and 800mm) are analysed. Comparison of the simulation results with recommendations in literature on ingot forging, indicates the normalized Cockcroft & Latham damage criterion to be the most realistic of the two.

A hybrid method to update stress for perfect von-Mises plasticity coupled with Lemaitre damage mechanics

2019 ◽  
Vol 37 (2) ◽  
pp. 705-729
Author(s):  
Maliheh Tavoosi ◽  
Mehrdad Sharifian ◽  
Mehrzad Sharifian
Keyword(s):  
Hybrid Method ◽  
Damage Mechanics ◽  
Damage Model ◽  
Internal Variables ◽  
Content Type ◽  
Efficient Integration ◽  
Mises Plasticity ◽  
Lemaitre Damage Model ◽  
Von Mises ◽  
Von Mises Plasticity

Purpose The purpose of this paper is to suggest a robust hybrid method for updating the stress and plastic internal variables in plasticity considering damage mechanics. Design/methodology/approach By benefiting the properties of the well-known explicit and implicit integrations, a new mixed method is derived. In fact, the advantages of the mentioned techniques are used to achieve an efficient integration. Findings The numerical studies demonstrate the high precision and robustness of the suggested algorithm. Research limitations The perfect von-Mises plasticity together with Lemaitre damage model is considered within the realm of small deformations. Practical implications Updating stress and plastic internal variables are of utmost importance in elastoplastic analyses of structures. The accuracy and efficiency of stress-updating methods significantly affect the final outcomes of nonlinear analyses. Originality/value The idea which is used to derive the hybrid method leads to an efficient integration method for updating the constitutive equations of the damage mechanics.

Modeling and Experimental Validation of Superconductor Tape Rolling

2000 ◽  
Vol 123 (4) ◽  
pp. 665-673 ◽  
Author(s):  
M. Pandheeradi ◽  
S. P. Vaze ◽  
D.-W. Yuan ◽  
H. A. Kuhn
Keyword(s):  
Electrical Power ◽  
Three Dimensional ◽  
Element Model ◽  
Rolling Process ◽  
Isotropic Hardening ◽  
Plasticity Model ◽  
Cross Sectional ◽  
Manufacturing Operations ◽  
Von Mises ◽  
Von Mises Plasticity

Efficient, defect-free manufacturing of high-temperature superconducting (HTS) wires and tapes is critical to a variety of defense and electrical power applications. To contribute to the improvement of these manufacturing operations, an analytical and experimental study of the early stages of the multipass rolling process for transforming HTS wires into tapes was conducted. The rolling process was simulated by a three-dimensional (3D) finite element model that uses the Drucker-Prager Cap plasticity model to represent the powder core and a Von-Mises plasticity model with isotropic hardening to represent the silver sheath. The predicted cross-sectional geometry of the tapes is compared with experiments. The results show that the tape cross-sectional geometry and powder core sizes can be predicted accurately. Further, alternate boundary conditions were found to have minimal effect on the predicted cross-sectional geometry for the range of reductions considered, even though the frictional shear stress distributions were significantly different.

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