Relaxation in crystal plasticity with three active slip systems

2016 ◽  
Vol 28 (5) ◽  
pp. 1477-1494 ◽  
Author(s):  
Sergio Conti ◽  
Georg Dolzmann
Keyword(s):  
Crystal Plasticity ◽  
Slip Systems ◽  
Active Slip

Temperature Dependence of the Yield Stress in α-Titanium Investigated with Crystal Plasticity Analysis

2018 ◽  
Vol 941 ◽  
pp. 1474-1478
Author(s):  
Yelm Okuyama ◽  
Masaki Tanaka ◽  
Tetsuya Ohashi ◽  
Tatsuya Morikawa
Keyword(s):  
Finite Element ◽  
Temperature Dependence ◽  
Yield Stress ◽  
Crystal Plasticity ◽  
Slip Systems ◽  
Temperature Dependent ◽  
Element Analysis ◽  
Pyramidal Slip ◽  
Active Slip ◽  
Lattice Friction

The effect of the activated slip systems on the temperature dependence of yield stress was investigated in α-Ti by using crystal plasticity finite element method. A model for finite element analysis (FEA) was constructed based on experimental results. The displacement in FEA was applied up to the nominal strain of 4% which is the same strain as the experimental one. Stress-strain curves were obtained, which corresponds to experimental data taken every 50 K between 73 K and 673 K. The used material constants which are temperature dependent were elastic constants, and lattice friction stresses. The lattice friction stresses of basal slip systems were set to be higher than that of pyramidal slip systems at 73 K. Then, the lattice friction stresses were set to be closer as the temperature increases. It was found that the activation of slip systems is strong temperature dependent, and that the yield stress depends on the number of active slip systems.

On the Selection of Active Slip Systems in Rate Independent Crystal Plasticity

2013 ◽  
Vol 554-557 ◽  
pp. 1147-1156
Author(s):  
Markus Orthaber ◽  
Thomas Antretter ◽  
Hans Peter Gänser
Keyword(s):  
Crystal Plasticity ◽  
Dislocation Dynamics ◽  
Slip Systems ◽  
Rate Dependency ◽  
Low Viscosity ◽  
Rate Dependent ◽  
Cross Hardening ◽  
The Individual ◽  
Active Slip ◽  
Regularized Model

Non-uniqueness of the set of active slip systems is a crucial issue in crystal plasticity. To avoid this problem one may perform viscoplastic regularization. This introduces a certain rate dependency, while many crystals are known to behave rate independently. One would require very low viscosity parameters in the regularized model to resemble the experimental behavior of rate independent crystals, which in turn entails numerical difficulties. Furthermore, no direct approach is known to model deformation banding using viscoplastically regularized models. Hence, to adequately treat rate independent crystal plasticity an alternative method is needed. The proposed method, Maximum Dissipation Crystal Plasticity (MDCP), achieves uniqueness by selecting the set of active slip systems according to its dissipation. In a finite element calculation, a system of coupled quadratic equations is solved at every integration point to define the material behaviour. This approach is formally equal to the method of incremental energy minimization recently proposed by Petryk et al. It can be shown that a viscoplastically regularized model is a limiting case of MDCP, giving similar results when cross hardening becomes negligible. Nevertheless, recent 3D dislocation dynamics calculations by Devrince et al. show that cross hardening in fcc crystals is far more important than self hardening. In such cases MDCP gives results distinctly different from its rate dependent counterpart. Fewer slip systems are selected by MDCP, resulting in more slip on the individual active systems. The proposed method is numerically implemented as an Abaqus user material subroutine within the large deformation framework, such that the simulation of arbitrary load cases is possible.

scholarly journals Infinite-order laminates in a model in crystal plasticity

2009 ◽  
Vol 139 (4) ◽  
pp. 685-708 ◽  
Author(s):  
Nathan Albin ◽  
Sergio Conti ◽  
Georg Dolzmann
Keyword(s):  
Energy Density ◽  
Lower Bounds ◽  
Crystal Plasticity ◽  
Infinite Order ◽  
Two Dimensions ◽  
Upper And Lower Bounds ◽  
Geometrically Nonlinear ◽  
Slip Systems ◽  
Quasiconvex Envelope ◽  
Active Slip

We consider a geometrically nonlinear model for crystal plasticity in two dimensions, with two active slip systems and rigid elasticity. We prove that the rank-1 convex envelope of the condensed energy density is obtained by infinite-order laminates, and express it explicitly via the 2F1 hypergeometric function. We also determine the polyconvex envelope, leading to upper and lower bounds on the quasiconvex envelope. The two bounds differ by less than 2%.

Crystal Plasticity Analysis of Change in Active Slip Systems of α-Phase of Ti-6Al-4V Alloy under Cyclic Loading

2016 ◽  
Vol 725 ◽  
pp. 183-188
Author(s):  
Yoshiki Kawano ◽  
Tsuyoshi Mayama ◽  
Ryouji Kondou ◽  
Tetsuya Ohashi
Keyword(s):  
Slip System ◽  
Crystal Plasticity ◽  
Basal Slip ◽  
Slip Systems ◽  
Cyclic Plastic ◽  
Loading Direction ◽  
Α Phase ◽  
Primary Slip System ◽  
Active Slip ◽  
Plastic Loading

In this paper, we investigated changes in active slip systems of α-phase of Ti-6Al-4V alloy under a cyclic plastic loading using a crystal plasticity finite element method. In the analyses, a bicrystal model was employed, and the crystallographic orientations were set so as that prismatic <a> or basal slip system was the primary slip system in each grain. The results showed that there was a mechanism where the basal slip systems could reach the stage of activation under the cyclic plastic loading even though the condition was that the prismatic <a> slips initially operate. The reason for the activity changes was due to the changes in the incompatibility between the grains by the work hardening, and the effect of the incompatibility on activities of slip systems appeared even in the perpendicular arrangements of the grains to the loading direction.

On the selection of active slip systems in crystal plasticity

2005 ◽  
Vol 21 (11) ◽  
pp. 2212-2231 ◽  
Author(s):  
Esteban P. Busso ◽  
Georges Cailletaud
Keyword(s):  
Crystal Plasticity ◽  
Slip Systems ◽  
Selection Of ◽  
Active Slip

scholarly journals Deformation Texture Evolution in Flat Profile AlMgSi Extrusions: Experiments, FEM, and Crystal Plasticity Modeling

2021 ◽  
Vol 8 ◽  
Author(s):  
Tomas Manik ◽  
Knut Marthinsen ◽  
Kai Zhang ◽  
Arash Imani Aria ◽  
Bjørn Holmedal
Keyword(s):  
Strain Rate ◽  
Strain Rate Sensitivity ◽  
Crystal Plasticity ◽  
Texture Evolution ◽  
Rate Sensitivity ◽  
Deformation Texture ◽  
Fiber Texture ◽  
Electron Back Scatter Diffraction ◽  
Slip Systems ◽  
Flat Profile

In the present work, the deformation textures during flat profile extrusion from round billets of an AA6063 and an AA6082 aluminium alloy have been numerically modeled by coupling FEM flow simulations and crystal plasticity simulations and compared to experimentally measured textures obtained by electron back-scatter diffraction (EBSD). The AA6063 alloy was extruded at a relatively low temperature (350°C), while the AA6082 alloy, containing dispersoids that prevent recrystallization, was extruded at a higher temperature (500°C). Both alloys were water quenched at the exit of the die, to maintain the deformation texture after extrusion. In the center of the profiles, both alloys exhibit a conventional β-fiber texture and the Cube component, which was significantly stronger at the highest extrusion temperature. The classical full-constraint (FC)-Taylor and the Alamel grain cluster model were employed for the texture predictions. Both models were implemented using the regularized single crystal yield surface. This approach enables activation of any number and type of slip systems, as well as accounting for strain rate sensitivity, which are important at 350°C and 500°C. The strength of the nonoctahedral slips and the strain-rate sensitivity were varied by a global optimization algorithm. At 350°C, a good fit could be obtained both with the FC Taylor and the Alamel model, although the Alamel model clearly performs the best. However, even with rate sensitivity and nonoctahedral slip systems invoked, none of the models are capable of predicting the strong Cube component observed experimentally at 500°C.

Simulation of Thermally Activated Metal Forming Process With Meso-Scale Crystal Plasticity

2003 ◽  
Author(s):  
Suhui Wang ◽  
Chunlei Xie ◽  
Le Ye ◽  
Xin Wu
Keyword(s):  
Strain Rate ◽  
Crystal Plasticity ◽  
Metal Forming ◽  
High Strain ◽  
Material Behavior ◽  
Slip Systems ◽  
Forming Process ◽  
Forming Simulation ◽  
Thermally Activated ◽  
Von Mises

Under thermally activated deformation conditions many engineering metals (steels, aluminum and magnesium alloys) exhibit much enhanced formability; thus, thermal forming has received increasing interests by automotive industries. The thermally activated material constitutive behaviors are not only strain dependent, but also strain rate and temperature dependent, and it is sensitive to in-situ microstructure evolution. In addition, non-steady-state deformation at a high strain rate (in the order of 10−2s−1 or above) introduces additional challenges in forming simulation. In this case, von Mises based macroscopic plasticity are often not sufficient to describe material behaviors with complex thermomechanical history. In this paper, the rate-dependent crystal plasticity model [1] was applied to the high temperature and high strain rate deformation that is dominated by dislocation creep. A user material subroutine was developed and used for FEA metal forming simulation using commercial ABAQUS/Dynamic code. In the simulation, material behavior was computed based on crystal plasticity at each strain increment without using von-Mises equation or a look-up table of material testing data. By inputting different slip systems or their combinations, and by matching the predicted crystallographic textures with experimentally obtained ones, the active slip systems responsible for the deformation was identified. Then, the material parameters were best fitted to the tensile curves obtained at various strain rates and temperatures. The model was applied for more complex multi-axial metal forming processes. The material behavior, along with its crystallographic texture development, was obtained and validated. As a demonstration, this paper also provides an analysis of a newly developed thrmal forming process [2] with this meso-scale crystal plasticity approach. This forming process involves diameter expansion of a tubular workpiece under combined internal pressure and axial loading and at elevated temperatures.

Multiscale Crystal Plasticity Simulation with Pseudo-Three-Dimensional Model on Ultrafine-Graining Based on Evolution of Dislocation Structures

2008 ◽  
Vol 584-586 ◽  
pp. 1057-1062 ◽  
Author(s):  
Yoshiteru Aoyagi ◽  
Naohiro Horibe ◽  
Kazuyuki Shizawa
Keyword(s):  
Slip System ◽  
Dislocation Structure ◽  
Crystal Plasticity ◽  
Three Dimensional ◽  
Slip Rate ◽  
Dislocation Cell ◽  
Reaction Diffusion Equations ◽  
Slip Systems ◽  
Dimensional Model ◽  
Three Dimensional Model

In this study, we develop a multiscale crystal plasticity model that represents evolution of dislocation structure on formation process of ultrafine-grained metal based both on dislocation patterning and geometrically necessary dislocation accumulation. A computation on the processes of ultrafine-graining, i.e., generation of dislocation cell and subgrain patterns, evolution of dense dislocation walls, its transition to micro-bands and lamellar dislocation structure and formation of subdivision surrounded by high angle boundaries, is performed by use of the present model. Dislocation patterning depending on activity of slip systems is reproduced introducing slip rate of each slip system into reaction-diffusion equations governing self-organization of dislocation structure and increasing immobilizing rate of dislocation with activation of the secondary slip system. In addition, we investigate the effect of active slip systems to the processes of fine-graining by using the pseudo-three-dimensional model with twelve slip systems of FCC metal.

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