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Crushing Analysis of Pebbles in a Pebble Assembly using DEM

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:

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Crushing Analysis of Pebbles in a Pebble Assembly using DEM

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  1. Crushing Analysis of Pebbles in a Pebble Assembly using DEM Ratna Kumar Annabattula, Shuo Zhao,Yixiang Gan and Marc Kamlah

  2. Ratna Kumar Annabattula, Karlsruhe Institute of Technology Outline Introduction Model Results Summary Outlook

  3. Ratna Kumar Annabattula, Karlsruhe Institute of Technology Introduction Pebble Assembly and Pebble-Pebble Interactions Idealizations: A unit cell of interest from a large assembly Periodic boundary conditions Assumptions: Pebble shape: spherical Pebble size: uniform, rs = rg= 0.25 mm Y. Gan et. Al, JMPS 2010

  4. Ratna Kumar Annabattula, Karlsruhe Institute of Technology Introduction Crush tests on single Li2SiO4 pebbles Different contact states Fc – Crush load Fu - 3.03 F0 - 3.18Fitting Parameters m - 2.50 The fit parameters depend on plate material Phd Thesis, ShuoZhao, 2010 and FML at KIT

  5. Ratna 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. These parameters depend on the plate material Phd Thesis, ShuoZhao, 2010

  6. Ratna 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.

  7. Ratna Kumar Annabattula, Karlsruhe Institute of Technology Model Damage Criterion and simulation flow chart Φ: Stored elastic energy Φcr: Critical failure energy D: Damage variable E = (1-D)*E0, if E >= 1 kPa E = 1 kPaif E < 1 kPa

  8. Ratna Kumar Annabattula, Karlsruhe Institute of Technology Results Damaged Pebbles ε33 = 0% ε33 = 1.65% ε33 = 3% No Damage Localization

  9. Ratna Kumar Annabattula, Karlsruhe Institute of Technology Results Stress-Strain Response Effect of packing factor Effect of damage criterion

  10. Ratna Kumar Annabattula, Karlsruhe Institute of Technology Results Damaged Pebbles Effect of random energy distribution Effect of packing factor Effect of damage criterion

  11. Ratna Kumar Annabattula, Karlsruhe Institute of Technology Results Damaged Pebles: Effect of damage law

  12. Ratna Kumar Annabattula, Karlsruhe Institute of Technology Results Damage Histograms: Effect of packing factor 350 230

  13. Ratna 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.

  14. Ratna 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.

  15. Ratna Kumar Annabattula, Karlsruhe Institute of Technology Acknowledgments Regina Knitter for Pebbles and Crush load data. European Fusion Development Agreement (EFDA) for funding.

  16. Ratna Kumar Annabattula, Karlsruhe Institute of Technology Thank you for your attention!Questions?

  17. Ratna Kumar Annabattula, Karlsruhe Institute of Technology Backup slides

  18. Ratna Kumar Annabattula, Karlsruhe Institute of Technology Backup Slides

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