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Material Point Method Simulations of Fragmenting Cylinders. Biswajit Banerjee Department of Mechanical Engineering University of Utah 17th ASCE Engineering Mechanics Conference, 2004. Outline. Scenario Material Point Method (MPM) Approach Validation Simulations of fragmentation. - PowerPoint PPT Presentation
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Material Point Method Simulations of Fragmenting Cylinders
Biswajit BanerjeeDepartment of Mechanical Engineering
University of Utah
17th ASCE Engineering Mechanics Conference, 2004
Outline
• Scenario
• Material Point Method (MPM)
• Approach
• Validation
• Simulations of fragmentation
Scenario
What happens to the container ?
Simulation Requirements
• Fire-container interaction
• Large deformations
• Strain-rate/temperature dependence
• Failure due to void growth/shear bands
The Material Point Method (MPM)(Sulsky et al.,1994)
Why MPM ?
• Tightly-coupled fluid-structure interaction.
• No mesh entanglement.• Convenient contact
framework.• Mesh generation trivial.• Easily parallelized.• No tensile instabilities.
• First-order accuracy.• High particle density for
tension dominated problems.
• Computationally more expensive than FEM.
Advantages Disadvantages
Stress update
• Hypoelastic-plastic material• Corotational formulation (Maudlin & Schiferl,1996)
• Semi-implicit (Nemat-Nasser & Chung, 1992)
• Stress tensor split into isotropic/deviatoric
• Radial return plasticity
• State dependent elastic moduli, melting temperature
Plasticity modeling
• Isotropic stress using Mie-Gruneisen Equation of State.
• Deviatoric stress :• Flow stress : Johnson-Cook, Mechanical Threshold
Stress, Steinberg-Cochran-Guinan• Yield function : von Mises, Gurson-Tvergaard-
Needleman, Rousselier
• Temperature rise due to plastic dissipation• Associated flow rule
Damage/Failure modeling
• Damage models:• Void nucleation/growth (strain-based)• Porosity evolution (strain-based)• Scalar damage evolution: Johnson-Cook/Hancock-
MacKenzie
• Failure• Melt temperature exceeded• Modified TEPLA model (Addessio and Johnson, 1988)
• Drucker stability postulate• Loss of hyperbolicity (Acoustic tensor)
Fracture Simulation
• Particle mass is removed.
• Particle stress is set to zero.
• Particle converted into a new material that interacts with the rest of the body via contact.
Validation: Plasticity Models
6061-T6 Aluminum EFC Copper
JC MTS SCG JC MTS SCG
635 K 194 m/s
655 K 354 m/s
718 K 188 m/s
727 K 211 m/s
Validation: Mesh dependence
OFHC Copper298 K 177 m/sMTS
6061-T6 Al655 K 354 m/sJC
1,200,000 cells151,000 cells18,900 cells
735,000 cells91,800 cells11,500 cells
Validation: Penetration/Failure
Validation: Penetration/Failure
160,000 cells 1,280,000 cells
Validation: Erosion Algorithm
Validation: Impact
Validation: Impact Results
Validation: 2D Fragmentation
Validation: 2D Fragmentation
Gurson-Tvergaard-Needleman yield, Drucker stability, Acoustic tensor, Gaussian porosity, fragments match Grady equation, gases with ICE-CFD code.
JC (steel), ViscoScram (PBX 9501)
MTS (steel), ViscoScram (PBX 9501)
Simulations: 3D Fragmentation
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Simulation: Container in Fire
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Questions ?