Multi Scale Modeling of Microstructure Deformation in Material Processing: Session II
Sponsored by: MS&T Organization
Program Organizers: Lukasz Madej, AGH University of Science and Technology
Tuesday 8:00 AM
October 18, 2011
Room: C211
Location: Greater Columbus Convention Center
Session Chair: Mark Tschopp, Center for Advanced Vehicular Systems Mississippi State University
8:00 AM Cancelled
Simulation of Dynamic Recrystallization for Ultrahigh Strength Steel Using Cellular Automation: Huang quan1; Yi ping1; 1School of Mechanical and Electrical Engineering, Central South University
23Co13Ni11Cr3Mo is ultrahigh strength steel with high properties demands. Refining austenitic grain through dynamic recrystallization (DRX) during hot deformation is an important measure to improve microstructure of the material. However, physical fields vary non-linearly in a large range during deformation. It makes huge difficulty in prediction of austenitic grain evolution on varied deformation parameters. In this paper, a cellular automaton (CA) model, which is a multi-scale model coupling macro deformation parameters with micro dynamic microstructure evolution model, was established to simulate DRX during hot deformation. Austenitic grain evolution, such as DRX nucleation and DRX grain growth, was determined by dislocation energy according to CA rules. The material constants in CA models, including dislocation density, nucleation rate and grain growth, were determined by the isothermal compression tests. The metallographic examination of compressed samples was utilized to confirm the model predictions. A reasonable agreement was achieved in recrystallized fraction and grain size.
8:20 AM
Statistical Approaches Applied to Failure of Isotropic Materials with Random Cracks: Ozgur Keles1; Edwin Garcia1; Keith Bowman1; 1Purdue University
Statistical approaches are often used to estimate failure probability of brittle materials based on the weakest link theory suggested by Weibull. In this model, the largest flaw in the component is considered as the strength-determining factor. This and other similar models that include flaw size distributions assume that there is no interaction between cracks. In accord with this, the finite element method was utilized to investigate effect of stress interactions on failure probability in the presence of a flaw size distribution. Interactions were observed by object oriented finite element (OOF) program for isotropic materials with a distribution of crack sizes under various loading conditions. Physical parameters such as Young Modulus and Poisson’s Ratio are used as input parameters. Deviations from Weibull statistics for microstructures having cracks that are randomly generated from a log normal distribution were shown.
8:40 AM
Development of finite element procedures to model the behavior of ultra fine-grained and nanocrystalline grain structures during Equal-Channel Angular Press (ECAP) processing of metals: Kazeem Sanusi1; Gert Oosthuizen1; Pieter Eksteen1; 1University of Stellenbosch
In this paper, the effects of grain size and misorientation angle on the deformation are examined in order to see how microstructural features might explain the observed increase in strength of ultra-fine-grained and nanocrystalline metals and alloys using ECAP technique. The study investigates the behavior of grain structures during ECAP process using the commercial two-dimensional elastic-plastic finite element code (Abaqus/explicit.) with the Arbitrarily Lagrangian Eulerian (ALE) and re-meshing method in the software. The paper successfully demonstrated efficient finite element technique which makes the stress field dependent on the grain size and angle of misorientation between the grains. This approach is much more simple and easier to relate the model to real material as it offers a simple method of including grain size effects and grain misorientation to which we could add additional phenomena through developing the material model used to describe the anisotropy and techniques that would automatically re-mesh the refined grain structure produced under severe plastic deformation. This study will form a foundation for future studies to describe the behaviors of ultra-fine-grained and nanocrystalline metals and alloys.
9:00 AM
Multiscale Modeling of the Deformation Inhomogeneity in the Angular Accumulative Drawing Process: Krzysztof Muszka1; J. Majta1; K. Doniec1; D. Dziedzic1; 1AGH Univeristy of Science and Technology
Multiscale finite element model of Angular Accumulative Drawing (AAD) process is proposed as a tool to optimize the deformation process and to predict a level of strain and stress inhomogeneity in the drawn wire. This recently developed deformation method is proposed as a way to produce wires with high plastic strain inhomogeneity, what in consequence leads to increased deformation energy accumulated in the drawn product and, in turn, to much higher tensile strength and ductility. In the presented model, non-linear hardening rule was applied to capture strain path effects that play major role in this deformation process. Strain and the stress distributions that exist in the drawn wire were predicted using multiscale approach that combined together with properly chosen hardening rule significantly improved the accuracy of the results. It is shown that the effect of strain path in the AAD process can be effectively controlled using computer simulation.
9:20 AM
Three-Phase Regions with the Reaction Type Changing: Vasily Lutsyk1; Vladimir Savinov2; 1Buryat State University; 2Institute of Physical Materials Science
Alternative principles of the phase diagrams (PD) design have been offered (Lutsyk V.I. et al. Z. Naturforsch. A, 2008, 63a, 513; Crystallography Reports, 2009, 54, 1300 & 2011, 56; J. Thermal Analysis & Calorimetry, 2010, 101, 25): 1) the assembly of whole diagram starts with the space scheme of monovariant reactions; 2) contours of the surfaces with the unruled nature are to be closed and data of thermodynamical calculations are used on this stage; 3) surfaces should be approximated as the minimal ones; 4) all geometrical elements are designated, and these “names” contain their meaning; 5) after the computer assembling the PD space model changes into a useful tool to solve different fundamental and applied tasks. New idea for the two-phase tie-lines calculation is used. Most comprehensive investigation of the crystallization processes occurring in the system with the transition from the syntectic equilibrium to the monotectic ones have been fulfilled.