scholarly journals Examination of crystal plasticity in cold drawn tube forming using FEM and Voronoi tessellation

2021 ◽  
Vol 1050 ◽  
pp. 012011
Author(s):  
M Necpal ◽  
M Martinkovič ◽  
M Kuruc
Keyword(s):  
Crystal Plasticity ◽  
Voronoi Tessellation ◽  
Tube Forming

Evolution of Crystal Orientations in Plastically Deformed Steels: Role of Constitutive Models Used in Finite Element Simulations

2013 ◽  
Author(s):  
Samir El Shawish ◽  
Leon Cizelj ◽  
Igor Simonovski
Keyword(s):  
Finite Element ◽  
Stainless Steel ◽  
Plastic Strain ◽  
Crystal Plasticity ◽  
Power Plants ◽  
Voronoi Tessellation ◽  
Finite Element Simulations ◽  
Plasticity Model ◽  
Crystal Orientations ◽  
Individual Grains

Stainless steel is a commonly used material in safety-important components of nuclear power plants. In order to study degradation mechanisms in stainless steels, like crack initiation and propagation, it is important to characterize the degree of plastic strain on microstructural level. One way to estimate local plastic strain is by measuring local crystal orientations of the scanned surfaces: the electron backscatter diffraction (EBSD) measurements on stainless steel revealed a strong correlation between the spread of crystal orientations within the individual grains and the imposed macroscopic plastic strain. Similar behavior was also reproduced by finite element simulations where stainless steel was modeled by an anisotropic elasto-plastic constitutive model. In that model the anisotropic Hill’s plasticity function for yield criteria was used and calibrated against the EBSD measurements and macroscopic tensile curve. In this work the Hill’s phenomenological model is upgraded to a more sophisticated crystal plasticity model where plastic deformation is assumed to be a sum of crystalline slips in all activated slip systems. The hardening laws of Peirce, Asaro and Needleman and of Bassani and Wu are applied in crystal plasticity theory and implemented numerically within the user subroutine in ABAQUS. The corresponding material parameters are taken from literature for 316L stainless steel. Finite element simulations are conducted on the analytical Voronoi tessellation with 100 grains and initial random crystallographic orientations. From the simulations, crystal and modified crystal deformation parameters are calculated, which quantify mean and median spread of crystal orientations within individual grains with respect to central grain orientation. The results are compared to EBSD measurements and previous simulations performed with Hill’s plasticity model.

Crystal Plasticity Simulation of the Bauschinger Effect of Polycrystalline AA7075 through a Texture-Based Representative Volume Element Model

2014 ◽  
Vol 553 ◽  
pp. 22-27
Author(s):  
Ling Li ◽  
Lu Ming Shen ◽  
Gwénaëlle Proust
Keyword(s):  
Finite Element ◽  
Representative Volume Element ◽  
Crystal Plasticity ◽  
Bauschinger Effect ◽  
Voronoi Tessellation ◽  
Strain Curve ◽  
Element Model ◽  
Volume Element ◽  
Model Parameters ◽  
Representative Volume

A texture-based representative volume element (TBRVE) model is developed for the three-dimensional crystal plasticity (CP) finite element simulations of the Bauschinger effect (BE) of polycrystalline aluminium alloy 7075 (AA7075). In the simulations, the grain morphology is created using the Voronoi tessellation method with the material texture systematically discretised from experiment. A modified CP constitutive model, which takes into account the backstress, is used to simulate the BE during cyclic loading. The model parameters are calibrated using the first cycle stress-strain curve and used to predict the mechanical response to the cyclic saturation of AA7075. The results indicate that the proposed TBRVE CP finite element model can effectively capture the BE at the grain level.

A Computational Simulation of Martensitic Transformation in Polycrystal TRIP Steel by Crystal Plasticity FEM with Voronoi Tessellation

2019 ◽  
Vol 794 ◽  
pp. 71-77 ◽  
Author(s):  
Truong Duc Trinh ◽  
Takeshi Iwamoto
Keyword(s):  
Grain Size ◽  
Martensitic Transformation ◽  
Crystal Plasticity ◽  
Trip Steel ◽  
Deformation Behavior ◽  
Voronoi Tessellation ◽  
Computational Simulation ◽  
High Strength ◽  
Transformation Strain ◽  
Kinetics Modelling

TRIP steel shows excellent mechanical properties such as greatly high strength, ductility and toughness by means of the appropriate combination of the strain-induced martensitic transformation (SIMT) behavior and the deformation behavior of each phase at crystal scale. In the past, the effect of grain size in the austenite on the deformation behavior of TRIP steel is investigated by introducing the grain size into a generalized model for the kinetics of SIMT. In order to validate the size-dependent kinetics modelling, it is necessary to simulate the deformation and SIMT behavior of the polycrystalline for the different grain size at the crystal scale. This study focuses on an investigation of SIMT behavior in polycrystalline TRIP steel by finite element simulation. The constitutive formula for monocrystalline TRIP steel including transformation strain in each variant system derived on the basis of the continuum crystal plasticity theory is applied. For the polycrystalline model, Voronoi tessellation is employed. The deformation behavior with a patterning process of martensitic phase in two different numbers of grains with initial crystal orientations for describing the deformation-related length scale is simulated under plane strain condition with two planar slip systems by a cellular automata approach.

Crystal Plasticity Finite-Element Simulation of Single Phase Titanium Alloy with 3D Polycrystalline Models

2014 ◽  
Vol 789 ◽  
pp. 608-615
Author(s):  
Shao Xie ◽  
Bin Tang ◽  
Yi Liu ◽  
Feng Bo Han ◽  
Hong Chao Kou ◽  
...  
Keyword(s):  
Finite Element ◽  
Crystal Plasticity ◽  
Voronoi Tessellation ◽  
Three Dimensional ◽  
Local Stress ◽  
Strain Response ◽  
Stress Strain ◽  
Β Phase ◽  
Crystallographic Slip ◽  
Mesh Density

Based on the rate-dependent crystal plasticity theory, a finite element code which considers crystallographic slip as deformation mechanism of material was developed to investigate the stress–strain response of the β phase of Ti-5553 during uniaxial tension. Three dimensional models with random grain shapes generated by Voronoi tessellation were used for simulations, and two discretization methods were used to disperse the models. Firstly, the parameters of material were identified by fitting simulation stress-strain curves with experimental data. Then the global stress-strain curves were calculated, and effects of mesh type and mesh density were discussed. Results show that mesh type has a relatively significant influence on overall responses, whereas the influence of mesh density is slight. Investigate of local stress-strain response in each grain was also conducted, and obvious inter-granular heterogeneities were observed. Quantitative analysis indicates that the range of stress and strain variations is affected by mesh type.

An Integrated Approach for Virtual Microstructure Generation and Micro-Mechanics Modelling for Micro-Forming Simulation

2007 ◽  
Author(s):  
Kar Cheong Ho ◽  
Nan Zhang ◽  
Jianguo Lin ◽  
Trevor Anthony Dean
Keyword(s):  
Probability Theory ◽  
Crystal Plasticity ◽  
Voronoi Tessellation ◽  
Control Variable ◽  
Integrated Approach ◽  
Physical Parameters ◽  
Micro Forming ◽  
Forming Simulation ◽  
Grain Structures ◽  
Fcc Materials

To aid FE simulation for forming micro-components, an integrated approach is proposed to generate virtual microstructure for micro-mechanics modelling. Based on Voronoi tessellation and the probability theory, a VGRAIN system is created for the generation of grains and grain boundaries for micro-materials. The input data of the system are physical parameters of a material, including average, minimum and maximum grain sizes. Numerical procedures have been established to link the physical parameters of a material to the control variable in a gamma distribution equation and a method has been developed to solve the probability equation. These are the basis for the development of the VGRAIN system, which can be used to generate different grain structures and shapes that follow a certain pattern according to the probability theory. Statistical analyses have been carried out to investigate the distribution of generated virtual grains. The generated virtual microstructure is then implemented in the commercial FE code, ABAQUS, for mesh generation and micro-mechanics analysis using crystal plasticity equations for FCC materials. The crystal plasticity model is implemented in the commercial FE code, ABAQUS, through the used-defined subroutine, UMAT. FE analyses have been carried out to investigate size effects and localised necking encountered in micro-forming processes.

A high-fidelity crystal-plasticity finite element methodology for low-cycle fatigue using automatic electron backscatter diffraction scan conversion: Application to hot-rolled cobalt–chromium alloy

2021 ◽  
pp. 146442072110108
Author(s):  
Yuhui Tu ◽  
Seán B Leen ◽  
Noel M Harrison
Keyword(s):  
Finite Element ◽  
Fatigue Crack ◽  
Crack Initiation ◽  
Crystal Plasticity ◽  
Electron Backscatter Diffraction ◽  
Voronoi Tessellation ◽  
Fatigue Crack Initiation ◽  
Crystal Plasticity Finite Element ◽  
Electron Backscatter ◽  
Backscatter Diffraction

The common approach to crystal-plasticity finite element modeling for load-bearing prediction of metallic structures involves the simulation of simplified grain morphology and substructure detail. This paper details a methodology for predicting the structure–property effect of as-manufactured microstructure, including true grain morphology and orientation, on cyclic plasticity, and fatigue crack initiation in biomedical-grade CoCr alloy. The methodology generates high-fidelity crystal-plasticity finite element models, by directly converting measured electron backscatter diffraction metal microstructure grain maps into finite element microstructural models, and thus captures essential grain definition for improved microstructure–property analyses. This electron backscatter diffraction-based method for crystal-plasticity finite element model generation is shown to give approximately 10% improved agreement for fatigue life prediction, compared with the more commonly used Voronoi tessellation method. However, the added microstructural detail available in electron backscatter diffraction–crystal-plasticity finite element did not significantly alter the bulk stress–strain response prediction, compared to Voronoi tessellation–crystal-plasticity finite element. The new electron backscatter diffraction-based method within a strain-gradient crystal-plasticity finite element model is also applied to predict measured grain size effects for cyclic plasticity and fatigue crack initiation, and shows the concentration of geometrically necessary dislocations around true grain boundaries, with smaller grain samples exhibiting higher overall geometrically necessary dislocations concentrations. In addition, minimum model sizes for Voronoi tessellation–crystal-plasticity finite element and electron backscatter diffraction–crystal-plasticity finite element models are proposed for cyclic hysteresis and fatigue crack initiation prediction.

Boundary Element Crystal Plasticity Method

2017 ◽  
Vol 08 (03n04) ◽  
pp. 1740003
Author(s):  
Ivano Benedetti ◽  
Vincenzo Gulizzi ◽  
Vincenzo Mallardo
Keyword(s):  
Grain Boundary ◽  
Boundary Element ◽  
Crystal Plasticity ◽  
Boundary Integral Equations ◽  
Voronoi Tessellation ◽  
Three Dimensional ◽  
Boundary Integral ◽  
Integral Approach ◽  
Rate Dependent ◽  
Individual Grains

A three-dimensional (3D) boundary element method for small strains crystal plasticity is described. The method, developed for polycrystalline aggregates, makes use of a set of boundary integral equations for modeling the individual grains, which are represented as anisotropic elasto-plastic domains. Crystal plasticity is modeled using an initial strains boundary integral approach. The integration of strongly singular volume integrals in the anisotropic elasto-plastic grain-boundary equations are discussed. Voronoi-tessellation micro-morphologies are discretized using nonstructured boundary and volume meshes. A grain-boundary incremental/iterative algorithm, with rate-dependent flow and hardening rules, is developed and discussed. The method has been assessed through several numerical simulations, which confirm robustness and accuracy.

AN INTEGRATED CRYSTAL PLASTICITY FE SYSTEM FOR MICROFORMING SIMULATION

2009 ◽  
Vol 01 (01) ◽  
pp. 107-124 ◽  
Author(s):  
J. CAO ◽  
W. ZHUANG ◽  
S. WANG ◽  
K. C. HO ◽  
N. ZHANG ◽  
...  
Keyword(s):  
Probability Theory ◽  
Crystal Plasticity ◽  
Voronoi Tessellation ◽  
Control Variable ◽  
Integrated System ◽  
Physical Parameters ◽  
Face Centered Cubic ◽  
Grain Structures ◽  
Face Centered ◽  
Fcc Materials

Based on Voronoi tessellation and the probability theory, a VGRAIN system is created for the generation of grains and grain boundaries for micromaterials. This system requires physical parameters obtained from microstructures of materials, such as the average, minimum and maximum grain sizes. Numerical procedures have been established to link the physical parameters of a material to the control variable in a gamma distribution equation and a method has been developed to solve the probability equation. These are the basis for the development of the VGRAIN system, which can be used to generate different grain structures and shapes that follow a certain pattern according to the probability theory. Statistical analyses have been carried out to investigate the distribution of generated virtual grains. The generated virtual microstructure is then implemented in the commercial FE code, ABAQUS, for mesh generation and micromechanics analysis using crystal plasticity (CP) equations for face-centered cubic (FCC) materials, which are implemented in the commercial FE solver, ABAQUS, through the user-defined subroutines, VUMAT/UMAT. FE analyses have been carried out to demonstrate the effectiveness of the integrated system for the investigation of localized straining and necking, encountered in microforming processes, such as extrusion of micropins, deformation of microfilms and hydroforming of microtubes.

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