ANSYS Explicit Dynamics
Update
Mai Doan
[email protected] +1 512‐687‐9523
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© 2011 ANSYS, Inc.
February 24, 2012
ANSYS Explicit Dynamics Update ‐ Outline
• Introduction • Solve Problems that were Difficult or Impossible in the Past
– Structural Dynamics and Explicit Dynamics
– Complex Interactions (Contact)
• Enhanced Productivity with Release 14
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Speed Improvements – 2D Problems in Workbench
Easier Meshing – New TET element
Better Insight Into Results
Automation
New Physics
© 2011 ANSYS, Inc.
February 24, 2012
Problems Addressed by Explicit Dynamics
Complex reality made easy through simulation
Damage to products from impact
Consumer or commercial product drop
Manufacturing process with large plastic deformation
High speed fragment or object impact
High speed collision of large objects
Cracking of brittle materials in products
Explosion near structures
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February 24, 2012
Nature of Explicit Dynamics Problems
• Short duration localized phenomena
• Transient dynamic wave propagation
Gases, Liquids, Solids and their Interaction (FSI)
• Nonlinear
o Material behavior
o Contact/Interaction
• Large deformations
o Large strains & strain rates
• Material failure
o
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What is ANSYS Explicit Dynamics
Explicit Dynamics, (like Structural Dynamics) models the response of structures: from quasi static to severe loadings
Applications in: Manufacturing, Consumer Products, Aerospace, Defense, Heavy Equipment, Oil and Gas, Turbo‐machinery, …
ANSYS Edge: User Productivity, Ease of Use, Seamless CAD to Solution Environment (ANSYS Workbench)
Used by small and large organization world wide, over 800 ANSYS Explicit Dynamics customers.
Used to design products, protect products, improve processes 5/32
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February 24, 2012
Solution Methods Compared
Explicit Solution (Explicit Dynamics)
• Time is an independent variable that is "explicitly" advanced according to a stability criteria limited by the speed of shock waves in the smallest element
– Local Response
• From shock waves created by impact or other loadings
• Resulting in deformation and material failure
Implicit Solution (Structural Dynamics, aka Mechanical)
• Time is not an independent variable and is "implicitly" advanced according to convergence criteria
– State variables being computed are not time dependent
• Collection of equations represent the relationship of all elements in the problem
• Equations solved “implicitly” with advanced matrix solutions
– Global Response
• From loads applied mostly uniformly to the whole system.
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February 24, 2012
Factors Influencing Calculation Times
For Implicit Solutions
For Explicit Solution
• model size (number of DOF)
• size of the critical time step
• size respectively grade of nonlinearity
• number of time steps to simulate
‐ characteristic element length
‐ sound of speed in materials (Young’s moduli & density)
• model size (number of elements)
• Length of the physical time to be simulated
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© 2011 ANSYS, Inc.
February 24, 2012
New Uses of Explicit Solver
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No convergence problems in highly nonlinear problems
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No equilibrium iteration needed
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Material failure and erosion easy to model
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High frequencies are naturally resolved because of small time steps
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Implicit‐explicit switching capability for efficiency
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Suited to a wide range of complex nonlinear problems
© 2011 ANSYS, Inc.
February 24, 2012
Explicit GUI is the Same as Structural
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February 24, 2012
Extend the Range of Structural Problems
• Drop test simulations –
(short time dynamic range, high frequencies)
• Problems including complex contact situations –
(large geometrical nonlinearities)
• Problems including sophisticated material damage and failure –
(large nonlinearities, element erosion)
• Load limit analyses –
(large deformations, large nonlinearities)
• Manufacturing simulations –
(large deformations, large nonlinearities)
• High‐speed Dynamic analyses
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(failure, fragmentation, blast wave‐structure interaction)
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Complex Contact Example – Crimping Equivalent Stress
Crimping process of seven wires. Changing contact surfaces
Self contact
Severe deformation
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February 24, 2012
Effective Plastic Strain
Complex Contact – Failing Window Crank
Window Crank Mechanism
Effective Plastic Strain
Equivalent Stress
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February 24, 2012
Non‐linear Material Response
Hyper‐elastic CV Boot
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February 24, 2012
Material Failure and Complex Contact
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© 2011 ANSYS, Inc.
February 24, 2012
Productivity Further Enhanced with R14
• Painless problem setup
– Complex geometries easier to mesh with TET elements
• New NBS TET avoids shear locking
• Fast solutions using 2‐D
• Insight into part interactions
– Reaction force trackers implemented • Generalized Shell
– Discrete element, variable thickness shells
– Import Polyflow and other forming simulation results
• Direct Access to results for convenient analysis and processing
• Composites
– Layered composites (shells)
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© 2011 ANSYS, Inc.
February 24, 2012
Painless problem setup
New Tetrahedral Element
Nodal Based Strain (NBS) formulation
• Overcomes both volume and shear locking
• Particularly valuable in low velocity applications involving complex geometry (consumer drops like mobile phones, nuclear equipment drops)
– Low deformations and bending dominates problems
– Isotropic elasticity, plasticity including failure
– Testing has shown that an Hourglass coefficient (Puso factor) of 0.1 should be used
• No longer Beta in Release 14
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February 24, 2012
NBS TET Accuracy – Beam Bending
Case Average End %
Deflection ANP Tet ‐0.178
‐21.1%
NBS Tet ‐0.146
0.7%
MAPDL ‐0.147
0.0%
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February 24, 2012
NBS TET Example – Self Piercing Rivet
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February 24, 2012
NBS TET Example – Drop Test, Tablet PC
Stress Contours Front View
Stress Contours Rear View, Cover Invisible
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February 24, 2012
Fast solutions using 2‐D
2D Plain Strain and Axisymmetric solid analyses supported for Explicit Dynamics
• 2D pre‐ and post‐processing exposed
• Plain Strain
• Axisymmetric axis of symmetry now in y‐direction to be consistent with other ANSYS analysis types
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February 24, 2012
Fast solutions using 2‐D – Bullet Example
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February 24, 2012
Insight into part interactions
Direct and quick results of reaction forces
• Allows capture of high frequency content in response
• Scoped to Boundary Condition
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– Fixed, Displacement, Velocity, Remote Displacement
Scoped to Geometry Selection
– Reaction Forces, Contact Forces, Euler/Lagrange Coupling forces
• Results can be filtered
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February 24, 2012
Example – Boundary Reaction Tracker
Force reaction at each of 4 supports of component subject to impact loading
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February 24, 2012
Example – FSI Force Tracker
External force time history due to fluid jet impinging on deformable surface (filtered at 10,000Hz)
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February 24, 2012
Generalized Shell – Discrete Thickness
Import Shell Thickness from External Data
Example – Import from ANSYS Polyflow
• Polyflow is a Finite Element based CFD tool used for simulating the processing of materials such as polymers, glass, metals and concrete
• Processes modeled include extrusion, blow molding, thermoforming, fibre drawing
• Polyflow results (of predicted thickness) can now be exported to Mechanical and Explicit Dynamics
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February 24, 2012
Blow Molding with Polyflow
• Initial polymer J shape (above)
• Final thickness (below)
Discrete Thickness Example
Import from Polyflow
Complete Virtual Prototyping and Testing capability in ANSYS Workbench for packaging manufacturing:
• Simulate blow molding or thermal forming process to get final thickness distribution
• Perform stress and deformation analysis with the variable thickness map (top load, crush, drop etc.)
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February 24, 2012
Discrete Thickness Shell Example
Complete Virtual Prototyping in ANSYS Workbench
• Simulate blow molding or thermal forming process to get final thickness distribution with POLYFLOW • Perform drop test of product filled with water
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© 2011 ANSYS, Inc.
February 24, 2012
Direct Access to Results
Design Assessment
• Introduced in Workbench to enable customized post‐processing of Mechanical systems
• Programmable/scriptable means to access results
• Explicit Dynamics can now be an upstream system for Design Assessment
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February 24, 2012
Design Assessment – Display Fragments
Equivalent plastic strain
Fragment Volume
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February 24, 2012
Composites
Data Integration with ACP
ACP: Built upon a documented Workbench SDK, EVEN has developed addins to introduce ACP as a component system inside Workbench
Typical Workbench system: file management and standard actions like Update, Duplicate
Consume materials from Engineering Data
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February 24, 2012
ACP Workflow Example
Insertion into schematic flow
Explicit * (Autodyn)
Implicit (MAPDL)
Parameter Support
Allows for inclusion as part of Design Exploration
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February 24, 2012
Composite Example
CFRP Baseball bat with spiral CRFP reinforcement
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© 2011 ANSYS, Inc.
February 24, 2012
Summary
ANSYS Explicit Dynamics • Extends the power of Structural Dynamics for Problems that were Difficult or Impossible in the Past
• Release 14 Provides Further Productivity Enhancements
– Speed Improvements – Easier Problem Setup
– Better Insight Into Simulated Results
– Improved Automated Use
– Convenient Composite Modeling
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© 2011 ANSYS, Inc.
February 24, 2012