scholarly journals Finite element simulation of ductile fracture in polycrystalline materials using a regularized porous crystal plasticity model

2021 ◽  
Vol 228 (1) ◽  
pp. 15-31
Author(s):  
Mikhail Khadyko ◽  
Bjørn Håkon Frodal ◽  
Odd Sture Hopperstad
Keyword(s):  
Finite Element ◽  
Ductile Fracture ◽  
Crystal Plasticity ◽  
Large Scale ◽  
Plasticity Model ◽  
Critical Porosity ◽  
Explicit Analytical Solution ◽  
Crystal Plasticity Model ◽  
Proposed Model ◽  
Porous Crystal

AbstractIn the present study, a hypoelastic–plastic formulation of porous crystal plasticity with a regularized version of Schmid’s law is proposed. The equation describing the effect of the voids on plasticity is modified to allow for an explicit analytical solution for the effective resolved shear stress. The regularized porous crystal plasticity model is implemented as a material model in a finite element code using the cutting plane algorithm. Fracture is described by element erosion at a critical porosity. The proposed model is used for two test cases of two- and three-dimensional polycrystals deformed in tension until full fracture is achieved. The simulations demonstrate the capability of the proposed model to account for the interaction between different modes of strain localization, such as shear bands and necking, and the initiation and propagation of ductile fracture in large scale polycrystal models with detailed grain description and realistic boundary conditions.

scholarly journals Investigation of Yield Surfaces Evolution for Polycrystalline Aluminum after Pre-Cyclic Loading by Experiment and Crystal Plasticity Simulation

Materials ◽  
2020 ◽  
Vol 13 (14) ◽  
pp. 3069
Author(s):  
Damin Lu ◽  
Keshi Zhang ◽  
Guijuan Hu ◽  
Yongting Lan ◽  
Yanjun Chang
Keyword(s):  
Finite Element ◽  
Cyclic Loading ◽  
Crystal Plasticity ◽  
Yield Surface ◽  
Plasticity Model ◽  
Anisotropic Hardening ◽  
Polycrystalline Aluminum ◽  
Crystal Plasticity Model ◽  
Subsequent Yield Surface ◽  
Definition Of

This study aims at introducing the back stress of anisotropic strain-hardening into the crystal plasticity theory and demonstrating the rationality of this crystal plasticity model to describe the evolution of the subsequent yield surface of polycrystalline aluminum at the mesoscopic scale under complex pre-cyclic loading paths. By using two different scale finite element models, namely a global finite element model (GFEM) as the same size of the thin-walled tube specimen used in the experiments and a 3D cubic polycrystalline aggregate representative volume element (RVE) model, the evolution of the subsequent yield surface for different unloading cases after 30 pre-cycles is further performed by experiments and numerical simulations within a crystal plasticity finite element (CPFE) frame. Results show that the size and shape of the subsequent yield surfaces are extremely sensitive to the chosen offset strain and the pre-cyclic loading direction, which present pronounced anisotropic hardening through a translation and a distortion of the yield surface characterized by the obvious “sharp corner” in the pre-deformation direction and “flat” in the reverse direction by the definition of small offset strain, while the subsequent yield surface exhibits isotropic hardening reflected by the von Mises circle to be distorted into an ellipse by the definition of large offset strain. In addition, the heterogeneous properties of equivalent plastic strain increment are further discussed under different offset strain conditions. Modeling results from this study show that the heterogeneity of plastic deformation decreases as a law of fraction exponential function with the increasing offset strain. The above analysis indicates that anisotropic hardening of the yield surface is correlated with heterogeneous deformation caused by crystal microstructure and crystal slip. The crystal plasticity model based on the above microscopic mechanism can accurately capture the directional hardening features of the yield surface.

Analysis of the Necking Behaviors with the Crystal Plasticity Model Using 3-Dimensional Shaped Grains

2013 ◽  
Vol 684 ◽  
pp. 357-361 ◽  
Author(s):  
Jong Bong Kim ◽  
Jeong Whan Yoon
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Crystal Plasticity ◽  
Void Nucleation ◽  
Damage Model ◽  
Initial Imperfection ◽  
Plasticity Model ◽  
Element Analysis ◽  
3 Dimensional ◽  
Crystal Plasticity Model

Without initial imperfection and damage evolution model, it is difficult to analyze the necking behavior by finite element analysis with continuum theory. Moreover, the results are greatly dependent on the size of the initial imperfection. In order to predict necking phenomenon without geometric imperfection, in this study, a crystal plasticity model was introduced in the 3-dimensional finite element analysis of tensile test. Grains were modeled by an octahedron and different orientations were allocated to each grain. Damage model was also used to predict the sudden drop of load carrying capacity after necking and to reflect the void nucleation and growth on the severely deformed region. Well-known Cockcroft-Latham damage model was used. Void nucleation, growth and coalescence behavior during necking were predicted reasonably.

scholarly journals A porous crystal plasticity constitutive model for ductile deformation and failure in porous single crystals

2018 ◽  
Vol 28 (2) ◽  
pp. 233-248 ◽  
Author(s):  
Amir Siddiq
Keyword(s):  
Porous Materials ◽  
Crystal Plasticity ◽  
Stress Triaxiality ◽  
Ductile Deformation ◽  
Plasticity Model ◽  
Single Crystalline ◽  
Deformation And Failure ◽  
Crystal Plasticity Model ◽  
Porous Crystal ◽  
As Stress

This work presents a porous crystal plasticity model which incorporates the necessary mechanisms of deformation and failure in single crystalline porous materials. Such models can play a significant role in better understanding the behaviour of inherently porous materials which could be an artefact of manufacturing process viz. 3D metal printing. The presented model is an extension of the conventional crystal plasticity model. The proposed model includes the effect of mechanics-based quantities, such as stress triaxiality, initial porosity, crystal orientation, void growth and coalescence, on the deformation and failure of a single crystalline material. A detailed parametric assessment of the model has been presented to assess the model behaviour for different material parameters. The model is validated using uniaxial data taken from literature. Lastly, model predictions have been presented to demonstrate the model’s ability in predicting deformation and failure in polycrystalline sheet materials.

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