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ANSYS Explicit Dynamics
Peng Yuan, PhD
Senior Mechanical Specialist ANSYS, Inc.
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• Explicit Dynamics Introduction
• Comparison between the Explicit and Implicit Dynamics
• R14 new features
Presentation Outline
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Application range: from low to hyper velocity
Application area: consumer products, aerospace, defense, heavy equipment, oil and gas, automotive, turbo-machinery, …
ANSYS edge: a result of the focus on productivity, ease of use, and one integrated platform.
Many customers: over 800 customers using the ANSYS Explicit Dynamics worldwide
ANSYS Explicit Dynamics Introduction
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Formulation: Implicit vs. Explicit
t t t tM U C U K U R
Implicit
2
2 2 2
2 2 2
2
t t t t t tM C t K t M M C tU R U U
t t t
Leapfrog method
Explicit Eq. 1 is solved at time t to get U(t+∆t)
Eq. 1 is solved at time t+∆t to get U(t+∆t)
Equation of motion (1)
(2)
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Explicit Solution (Explicit Dynamics)
– Focus on local response and wave propagation
– Well suited to simulate short dynamic events
Implicit Solution (Structural Dynamics, aka Mechanical)
– Focus more on global response
– Suitable for static analysis, slower process or linear dynamics such as modal, harmonic…
Dynamics: Explicit vs. Implicit
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Implicit Solution
• Convergence controls.
- NR Iterations at t
• Solution time is unknown.
Explicit Solution
• Time step size controls.
- The CFL condition
- No iteration at t
• Solution time can be
predicted.
Computational Efficiency
Divergence
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Explicit Application Areas
Rapid loading
Strong coupling between fluid and structure
Shock wave propagation
Explosion / blast
Impact / penetration
Fragmentation / spallation
Spallation due to impact
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Explicit Dynamics Examples
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• Problems including complex contacts
– Difficult converging
• Problems with sophisticated material damage and failure
– Multiphysics
• Load limit analysis
– Highly nonlinear
• Metal forming
– Mesh distortion
• Hyper speed dynamic analyses
– Failure, hydrodynamic
Extending ANSYS Dynamics Capabilities
Crimping analysis
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Consistent GUI with Mechanical
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• New TET element
• 2D capability
• Reaction force trackers
• Composite shell with variable thickness
• Direct access to result database
New Features in New Release R14
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Nodal Based Strain (NBS) formulation with
isotropic elasticity and plasticity including failure
• Overcomes both shear and volume locking
• Particularly valuable in:
- Low velocity applications involving complex geometries
- Bending dominant simulations
*No longer beta in Release 14
New Tetrahedral Element*
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NBS TET Accuracy – Beam Bending
Case Average End Deflection
Error %
ANP TET -0.178 21.1%
NBS TET -0.146 -0.7%
MAPDL -0.147 0.0%
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Plain Strain/Stress or
Axisymmetrical
- About Y-Axis, consistent with ANSYS Mechanical
- 2D results 3D expansion
Solutions Using 2D Models
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• Scoped to boundary conditions
– Supports, velocity, remote displacement
• Scoped to geometry selections
– Contact forces, FSI coupling forces
Force Reaction Tracker
Fluid impact force time-history filtered
at 1.0E4 Hz
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Can import thickness from External Data and Polyflow
Variable Thickness of Composite Shells
Data Integration with ACP
- the ANSYS Composite Pre/Post Processing tool
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Design Assessment
• Customize post-processing of Mechanical systems
• Scriptable means to access results
Linked to Design Assessment
Fragment Volume
Linking DA
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ANSYS Explicit Dynamics:
• Extends the power of structural dynamics for problems that were difficult or impossible to tackle
• R14 provides productivity improvements on
– Solver speed
– Model settings
– Pre/Post processing
Summary
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Questions?
Thank you