crushing analysis of pebbles in a pebble assembly using dem
DESCRIPTION
Crushing Analysis of Pebbles in a Pebble Assembly using DEM. Ratna Kumar Annabattula, Shuo Zhao, Yixiang Gan and Marc Kamlah. Outline. Introduction Model Results Summary Outlook. Introduction. Pebble Assembly and Pebble-Pebble Interactions. Idealizations: - PowerPoint PPT PresentationTRANSCRIPT
KIT – University of the State of Baden-Wuerttemberg and National Research Center of the Helmholtz Association
Institute for Applied Materials (IAM-WBM)
www.kit.edu
Crushing Analysis of Pebbles in a Pebble Assembly using DEMRatna Kumar Annabattula, Shuo Zhao, Yixiang Gan and Marc Kamlah
CBBI-16 Meeting, Portland, OR, USA
8-10 September 2011.
2 09/09/11Ratna Kumar Annabattula, Karlsruhe Institute of Technology
Outline
Introduction
Model
Results
Summary
Outlook
CBBI-16 Meeting, Portland, OR, USA
8-10 September 2011.
3 09/09/11Ratna Kumar Annabattula, Karlsruhe Institute of Technology
Introduction
Pebble Assembly and Pebble-Pebble Interactions
Assumptions:Pebble shape: sphericalPebble size: uniform, rs = rg= 0.25 mm
Y. Gan et. Al, JMPS 2010
Idealizations:A unit cell of interest from a large assembly
Periodic boundary conditions
CBBI-16 Meeting, Portland, OR, USA
8-10 September 2011.
4 09/09/11Ratna Kumar Annabattula, Karlsruhe Institute of Technology
Introduction
Crush tests on single Li2SiO4 pebbles
Fc – Crush loadFu - 3.03F0 - 3.18 Fitting Parametersm - 2.50
The fit parameters depend on plate materialPhd Thesis, ShuoZhao, 2010 and FML at KIT
Different contact states
CBBI-16 Meeting, Portland, OR, USA
8-10 September 2011.
5 09/09/11Ratna Kumar Annabattula, Karlsruhe Institute of Technology
Introduction
Failure criterion for Osi Pebbles
Failure criterion based on maximum stress in the pebble.
Failure criterion based on the energy absorbed by the pebble.
Failure criterion based on maximum stress in the pebble.
Failure criterion based on the energy absorbed by the pebble.
Phd Thesis, ShuoZhao, 2010
These parameters depend on the plate material
CBBI-16 Meeting, Portland, OR, USA
8-10 September 2011.
6 09/09/11Ratna Kumar Annabattula, Karlsruhe Institute of Technology
Model
Macroscopic Average Stress
Average normal contact force (fave) and hydrostatic pressure (p)
An assembly of 5000 pebbles in a box with periodic boundary conditions.
Uni-axial compression to 3% strain and then unloading to stress-free state.
CBBI-16 Meeting, Portland, OR, USA
8-10 September 2011.
7 09/09/11Ratna Kumar Annabattula, Karlsruhe Institute of Technology
Model
Damage Criterion and simulation flow chart
Φ: Stored elastic energyΦcr: Critical failure energyD: Damage variable
E = (1-D)*E0, if E >= 1 kPaE = 1 kPa if E < 1 kPa
CBBI-16 Meeting, Portland, OR, USA
8-10 September 2011.
8 09/09/11Ratna Kumar Annabattula, Karlsruhe Institute of Technology
Results
Damaged Pebbles
ε33 = 0% ε33 = 1.65% ε33 = 3%
No Damage Localization
CBBI-16 Meeting, Portland, OR, USA
8-10 September 2011.
9 09/09/11Ratna Kumar Annabattula, Karlsruhe Institute of Technology
Results
Stress-Strain Response
Effect of packing factor Effect of damage criterion
CBBI-16 Meeting, Portland, OR, USA
8-10 September 2011.
10 09/09/11Ratna Kumar Annabattula, Karlsruhe Institute of Technology
Results
Damaged Pebbles
Effect of random energy distribution
Effect of packing factor Effect of damage criterion
CBBI-16 Meeting, Portland, OR, USA
8-10 September 2011.
11 09/09/11Ratna Kumar Annabattula, Karlsruhe Institute of Technology
Results
Damaged Pebles: Effect of damage law
CBBI-16 Meeting, Portland, OR, USA
8-10 September 2011.
12 09/09/11Ratna Kumar Annabattula, Karlsruhe Institute of Technology
Results
Damage Histograms: Effect of packing factor
350230
CBBI-16 Meeting, Portland, OR, USA
8-10 September 2011.
13 09/09/11Ratna Kumar Annabattula, Karlsruhe Institute of Technology
Summary
Crushing analysis of pebbles in the frame work of damage mechanics A mere 0.2% of failed pebbles in the assembly ceases the further load
carrying capacity of the assembly. An assembly with high packing factor is prone to more total damage. A sudden damage law exhibits a higher flow stress than gradual
damage. The fraction of critical pebbles to failure is independent of damage
accumulation law. The stress plateau after the critical number of failed pebbles indicate a
creep like behavior.
CBBI-16 Meeting, Portland, OR, USA
8-10 September 2011.
14 09/09/11Ratna Kumar Annabattula, Karlsruhe Institute of Technology
Outlook
Implementation of pebble failure into small particles. The present damage law is heuristic and a damage law with a
physical basis based on experiments to be developed. Extend the analysis to polydisperse pebble assembly.
CBBI-16 Meeting, Portland, OR, USA
8-10 September 2011.
15 09/09/11
Acknowledgments
Regina Knitter for Pebbles and Crush load data.
European Fusion Development Agreement (EFDA) for funding.
Ratna Kumar Annabattula, Karlsruhe Institute of Technology
CBBI-16 Meeting, Portland, OR, USA
8-10 September 2011.
16 09/09/11Ratna Kumar Annabattula, Karlsruhe Institute of Technology
Thank you for your attention!
Questions?
CBBI-16 Meeting, Portland, OR, USA
8-10 September 2011.
17 09/09/11
Backup slides
Ratna Kumar Annabattula, Karlsruhe Institute of Technology
CBBI-16 Meeting, Portland, OR, USA
8-10 September 2011.
18 09/09/11
Backup Slides
Ratna Kumar Annabattula, Karlsruhe Institute of Technology