Autodyn New Features

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ANSYS® AUTODYN® Explicit Software for Nonlinear Dynamics

ANSYS® AUTODYN® version 11.0

What’s New?

AUTODYN® version 11.0, What’s New?

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TABLE OF CONTENTS 1. Introduction 2. ANSYS AUTODYN and ANSYS Workbench

2.1. ANSYS AUTODYN 2.2. Meshing and ANSYS AUTODYN 2.3. Advanced Meshing and ANSYS AUTODYN 2.4. FEModeler and ANSYS AUTODYN

3. Solver Enhancements 3.1. Trajectory Contact (BETA Option) 3.2. Group Contact 3.3. Automatic Mass Scaling 3.4. New Multi-material Pressure Equilibrium Option 3.5. Enhancements to the ANP Tetrahedral Element 3.6. HP-MPI for Parallel Processing on Linux

4. Material Modelling Enhancements 4.1. Hyperelasticity

4.1.1. Introduction to Hyperelastic Material Models 4.1.2. Neo-Hookean 4.1.3. Mooney-Rivlin

4.1.3.1. 2-Parameter Mooney-Rivlin Model 4.1.3.2. 3-Parameter Mooney-Rivlin Model 4.1.3.3. 5-Parameter Mooney-Rivlin Model 4.1.3.4. 9-Parameter Mooney-Rivlin Model

4.1.4. Yeoh 4.1.4.1. Yeoh 1st order 4.1.4.2. Yeoh 2nd order 4.1.4.3. Yeoh 3rd order

4.1.5. Ogden 4.1.5.1. Ogden 1st Order 4.1.5.2. Ogden 2nd Order 4.1.5.3. Ogden 3rd Order

4.1.6. Arruda-Boyce 4.1.7. Material Data and Examples

4.2. Compaction model enhancements 4.3. New Powder Burn Model

4.3.1. Theory 4.3.2. Material Data Input 4.3.3. Example

4.4. JWL, Miller extension 4.5. Time Dependant Energy Deposition Extension to JWL Equation of State 4.6. Lee-Tarver Enhancement

4.6.1. Improved Stability for Multi-material Euler Applications 4.6.2. Improved Post-burn behavior for all Solvers

5. Pre- and Post- Processing 5.1. Improved Memory Management During Pre-processing 5.2. Results Files 5.3. Improved Compression for Save Files 5.4. Unstructured Parts to initialize 3D Multi-material Euler


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5.5. Unstructured Parts to initialize SPH 5.6. Interactive Selection of Parts 5.7. Highlight Parts 5.8. Interactive Selection of Gauges 5.9. Group Operations

5.9.1. Delete Elements 5.9.2. Split Nodes

5.10. Automatic parallel decomposition of Euler-FCT parts 6. Extended Unit Systems

6.1. US Customary Units 6.2. Micron Unit System

7. Supported Operating Systems and Compilers 8. Installation

8.1. Windows 32-bit 8.2. Windows 64-bit (Limitations) 8.3. Linux Installation

9. Licensing


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1. INTRODUCTION ANSYS AUTODYN release 11.0 is the first release of the ANSYS AUTODYN software within the ANSYS Workbench framework. ANSYS Workbench brings many new possibilities to the ANSYS AUTODYN user in terms of CAD geometry import, complex geometry generation, meshing and ease of use. To complement the significantly enhanced model generation capabilities, a range of new solver, material modeling and post-processing features enable larger simulations to be solved in a faster time. The main new features of the ANSYS AUTODYN 11.0 release are

• ANSYS AUTODYN and ANSYS Workbench o Meshing (for each ANSYS AUTODYN-3D licensee)

Robust and Easy to use meshing tool 3D Tetrahedral, Hexahedral, Quad and Tri meshing Geometry import capabilities from DesignModeler for

an extensive list of third party CAD systems o FEModeler (for each ANSYS AUTODYN-3D licensee)

Links to Finite Element Meshes • ANSYS CDWRITE, ABAQUS, NASTRAN

o Design Modeler (Optional) Geometry editor for existing CAD models Parametric feature-based solid modeler

o Advanced Meshing (Optional) Hexahedral meshing for complex geometries Advanced mesh controls

• Solvers

o New trajectory based 3D contact algorithm Increased flexibility (no external gap) Significant efficiency improvements

o Contact selection by group o Extended material modeling capabilities for ANP-Tet o Automatic mass scaling o New pressure equilibrium option for Euler

• Materials o Hyperelasticity o New Powder Burn model o Extended Granular strength model o JWL-Miller o Simple thermobaric representation

• Pre- and Post-processing o Improved memory management for pre- and post-processing o Results files for more efficient post-processing o Better compression of binary data files o Extended unit systems


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o Interactive selection of Parts o Interactive selection of Gauges o Multi-material Euler Fill using Unstructured Parts o Initialize SPH regions using Unstructured Parts

These and other new features are now described in detail. 2. ANSYS AUTODYN AND ANSYS WORKBENCH The ANSYS AUTODYN 11.0 software is supplied as an integral part of the ANSYS Workbench environment. The ANSYS Workbench, together with the Workbench projects and tabs, provides a unified working environment for developing and managing a variety of CAE information and makes it easier for you to set up and work with data at a high level. Typical tasks you can perform in Workbench are:

• Creating models using DesignModeler or importing models from a variety of CAD systems.

• Generating a numerical mesh suitable for a variety of FE and CFD methods using Meshing or Advanced Meshing

• Performing implicit finite element analyses using Simulation for structural, thermal, and electromagnetic simulations.

• Performing explicit transient nonlinear dynamics simulations of solids, fluids, gases, and their interaction using ANSYS AUTODYN

• Optimizing designs using DesignXplorer or DesignXplorer VT, and implementing a chosen design back into the original model.

Additionally, Workbench includes the following modules:

• Engineering Data: A repository of material data for use by a selection of other Workbench applications.

• FE Modeler: Uses input from NASTRAN, ABAQUS, or Simulation, and allows navigating and visualizing of the finite element model for downstream analysis in ANSYS or ANSYS AUTODYN.

• Other modules for use in specialized applications such as Computational Fluid Dynamics (CFD) simulations.

With the ANSYS AUTODYN 11.0 release, four typical work flows are available to the user. These are described below. 2.1. ANSYS AUTODYN


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ANSYS AUTODYN can be launched from the start of the Workbench (Start, Programs, ANSYS 11.0, ANSYS Workbench).

ANSYS AUTODYN Icon on start page of ANSYS Workbench

The ANSYS AUTODYN application will appear inside the Workbench. The integrated capabilities of ANSYS AUTODYN can be used to setup models, run simulations, post-process results. 2.2. MESHING AND ANSYS AUTODYN The new Meshing application in the ANSYS Workbench is available to ANSYS AUTODYN-3D licensees. This application provides robust, powerful and easy to use mesh generation capabilities. This includes automated meshing methods for

• Hexahedral elements (sweepable geometries) • Tetrahedral meshing (patch based and patch independent) • Quad and tri shell elements • Beam elements

Additionally controls are available to refine the mesh in regions of interest or ignore small geometric features that do not need to be represented in the simulation.


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Example mesh produced using Meshing

The meshing application also allows import of geometry from a wide range of sources

• ANSYS DesignModeler DesignModeler is a parametric feature-based solid modeler designed so that you can intuitively and quickly begin drawing 2D sketches, modeling 3D parts, or uploading 3D CAD models for engineering analysis pre-processing. If you have never used a parametric solid modeler, you will find DesignModeler easy to learn and use. If you are an experienced user in parametric modeling, DesignModeler offers you the functionality and power you need to convert 2D sketches of lines, arcs, and splines into 3D models. This is the recommended application for geometry generation and preparation for ANSYS AUTODYN simulations.

• 3D CAD models 3D CAD models can be loaded directly into the Meshing application. Providing the geometry is suitable and clean, the numerical mesh can be generated.

• FEModeler

FEModeler works with the standard finite element representation used inside ANSYS Workbench. FE Modeler supports robust data transfer from NASTRAN, ABAQUS, or ANSYS. FEModeler can be used to:

o Import an FE model from NASTRAN bulk data files, ABAQUS input files or ANSYS CDB Files. Alternatively FE information can be imported from Simulation.

Patch Independent Tet Mesh

Swept Hex Mesh


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o Navigate and visualize the data contained in the model. o Create named components based on element selections o Convert FE meshes into geometric bodies

FEModeler is available to all ANSYS AUTODYN-3D licensees Typical workflows for using ANSYS AUTODYN and the Meshing application inside Workbench are shown in the figure below.


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DesignModeler

FEModeler

Typical workflows using ANSYS AUTODYN and Meshing inside ANSYS Workbench The project page of ANSYS workbench is used to manage the above workflow and allows transparent communication of information from one application to another. Once you have created or opened an existing Workbench project from the Start Page, a Project Page replaces the Start Page as your project management tool, providing useful options as you move through the various Workbench modules.

CAD


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Example project page navigation for ANSYS AUTODYN and Meshing In the above example, a geometry has been generated in the DesignModeler application. This geometry has then been transferred to the Meshing application. Selecting the Meshing application on the project page exposes the ANSYS AUTODYN tasks:

• Start ANSYS AUTODYN Selecting this task will start ANSYS AUTODYN. No links to other applications will be made.

• Proceed to ANSYS AUTODYN1 ANSYS AUTODYN will start and automatically load the FE model from the selected meshing task on the project page. A persistent link between the ANSYS AUTODYN model and the model in the Meshing application is created. This allows changes to geometry and mesh to feed directly into the ANSYS AUTODYN model with minimal user intervention.

Using “Proceed to ANSYS AUTODYN” automatically transfers the following data to the ANSYS AUTODYN application

• Mesh o Nodes, elements, connectivity o Bodies defined in the Meshing application will be imported as

ANSYS AUTODYN Parts. Body Names will be transferred to the Part Names. Duplicate names will be appended with an identifying number

o An ANSYS AUTODYN component will also be generated for each Part defined in the Meshing application. If a multi-body Part, the component will include all associated bodies.

• Material assignments 1 Note this option is not currently available on Windows 64 bit installation. To transfer the mesh to ANSYS AUTODYN use New FE Model, Target System Nastran, Generate Data. From the AUTODYN applet use Import, MSC.Nastran.


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o A material will be created in ANSYS AUTODYN for each body defined in the Meshing application.

• Groups o Named selections defined in the Meshing application will be

translated into Groups in ANSYS AUTODYN. Point and line selections will be translated into node groups. Face selections will be translated into face groups and element selections into node groups.

• Shell thickness o Shell thickness defined in the Meshing application will be

translated into an initial condition in ANSYS AUTODYN and applied to the appropriate Parts.

• Beam cross-sections o Beam cross-sections will be translated into ANSYS AUTODYN

sections and applied to the appropriate Parts/Elements.

Typical model after proceed to ANSYS AUTODYN

After import, each ANSYS AUTODYN Part retains a persistent link2 back to the originating Body in the meshing application. Updates made to geometry (using DesignModeler), or Mesh (using Meshing) can be automatically transferred into the ANSYS AUTODYN model by using the Import, Update Model from Workbench option on the main ANSYS AUTODYN toolbar. The update process will

• Re-define the nodes and elements for each Part • Re-define groups (not available yet). Note that any previous operations

performed on groups (for example application of a boundary condition) 2 Note this option is not currently available for the Windows 64 bit installation.


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may become invalid. It is highly recommended that the application of boundary conditions etc is verified after the update process

• Retain material and initial condition assignments provided that only a single material and velocity is applied to a Part

• Update shell thickness • Update Beam cross section definitions • Retain existing settings defined on a Part by Part basis (eg interaction

and coupling) • Import any new Parts/Bodies which previously did not exist in the

ANSYS AUTODYN model

DesignModeler Meshing ANSYS AUTODYN

Update Geometry

Re-mesh retaining all previous mesh settings

Update Model retaining majority of previous

settings

Example demonstrating usage of persistent link between ANSYS AUTODYN and Meshing 2.3. ADVANCED MESHING AND ANSYS AUTODYN The Advanced Meshing application inside Workbench (ANSYS ICEM CFD/AI*Environment) provides additional meshing capabilities to the ANSYS AUTODYN user. The main distinguishing feature over the meshing application is the advanced blocking technology for hexahedral meshing on complex geometries. Other mesh manipulation and smoothing functions make this a very powerful tool for explicit transient dynamic mesh generation and the creation of high quality meshes for explicit solutions. The advanced meshing application is an option licensed separately to ANSYS AUTODYN. Typical workflows for using ANSYS AUTODYN and the Advanced Meshing application inside Workbench are shown in the figure below.


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DesignModeler

Typical workflow using ANSYS AUTODYN and Advanced Meshing inside ANSYS Workbench The transfer of data between Advanced Meshing and ANSYS AUTODYN is one way, in that there is no persistent link between the applications. To transfer the mesh from Advanced Meshing to ANSYS AUTODYN, in the Advanced meshing application use the File, Export mesh, To ANSYS AUTODYN option. This places a link on the project page to an explicit import file (.exp). Selecting this file on the project page, then selecting Proceed to ANSYS AUTODYN will start the ANSYS AUTODYN application and automatically import the generated mesh.

Typical project page navigation for ANSYS AUTODYN and Advanced Meshing

2.4. FEMODELER AND ANSYS AUTODYN ANSYS AUTODYN may also import meshes from FEModeler by selecting “Proceed to ANSYS AUTODYN” when an FEModeler file is selected in the Project Page. FEModeler works with the standard finite element representation used inside ANSYS Workbench and supports robust data transfer from NASTRAN, ABAQUS, or ANSYS.


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3. SOLVER ENHANCEMENTS 3.1. TRAJECTORY CONTACT (BETA Option) A new 3D contact algorithm is now available for all 3D Unstructured volume solvers (hex and tets), rigid bodies and SPH. This is a completely new algorithm/implementation of 3D contact and has three main benefits over the previous Gap based contact algorithm.

• There is no requirement to specify a contact detection zone or leave a physical gap between Parts at the start of a simulation. This makes model generation for complex 3D geometries, and the use of imported CAD geometries significantly easier.

• There is no constraint on the timestep due to contact. The algorithm detects node to face contact by tracking the trajectory of the nodes and faces over time. The removal of the timestep constraint on contact can give very significant performance improvements.

• The algorithm is energy conserving, in addition to momentum conserving for unconstrained nodes/faces.

This option is currently assigned Beta status and may not currently be as robust as other contact options available in ANSYS AUTODYN. Trajectory based contact is activated from the Lagrange/Lagrange interactions panel.


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The sub-options available for trajectory contact are: Activate Yes - activates contact

No - deactivates contact Shell node thickness (inactive) Selecting this option ensures that the

interaction distance of node belonging to a shell takes into account the corresponding shell thickness of the node. This option is currently under development.

Full SPH radius (inactive) Selecting this option ensures that the interaction distance of an SPH node takes into account the smoothing length of the node. This option is currently under development.

Check for initial penetrations On clicking this button, ANSYS AUTODYN will search the model for initial penetrations of nodes into surfaces. If any penetrating nodes/surfaces are found, a new Group will be created so that they can be identified/displayed using the


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Groups panel. Nodes that initially penetrate surfaces will be “missed” by the algorithm.

Plot Contact Positions The contact algorithm handles two major tasks, the first is contact detection and subsequent sliding and the second is contact response. The latter is calculated after all contact events have been treated and summed. The position of the nodes after sliding (Contact Positions) and the positions after contact response are usually slightly different, but in situations where the node velocities are small and internal element stresses are high, the difference can be significant. Using this option allows you to display the nodes at their Contact Positions.

Check now Press this option to immediately check for initial penetrations

Retain inertia of eroded nodes Select this toggle to retain inertia of nodes freed from elements during erosion

Interaction by Part Select interaction on Part by Part basis (as done with Gap contact)

Self-interaction of parts Set this toggle to activate self contact for volume elements

Self-interaction tolerance Percentage of the element characteristic dimension used as the trigger for element erosion. Values can range from very small (most accurate) to 0.5 (maximum allowed). Default value is 0.2. This is equivalent to defining a gap size, but is only used for self-interaction erosion purposes.

The performance improvement will depend on the application and speed-up’s in serial run time of between 2 and 4 have been observed during internal testing at Century Dynamics.


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Simulation runs 2.7 times faster using Trajectory contact

Example efficiency improvements using Trajectory contact

Note that the trajectory contact is an alternative to the Gap contact logic, not a replacement. The Gap contact algorithm may still be the best option for certain applications and remains the default option. Further, the trajectory contact option has been assigned Beta status pending further testing in the wider ANSYS AUTODYN user community. Current Limitations:

• Friction is not currently available with trajectory contact • The trajectory contact option cannot currently be used in parallel

simulations • Interaction of shell/SPH nodes and shell surfaces, accounting for their

full natural thickness/size is currently not available Please contact Century Dynamics for the latest status on the development of these items.


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3.2. GROUP CONTACT In many calculations, the contact region may be relatively small in comparison to the entire model, and as the interactions calculation is numerically intensive, it would be beneficial if the scope of its work were limited to this smaller area. The Group Contact enhancement allows the user to select a set of face groups to describe the extent of the interactions in unstructured models. In order to use contact by group, a set of face groups needs to be created for the regions that are to be included in the contact.

In the Interactions, Lagrange/Lagrange panel, Group Contact can then be activated by selecting the “Specify Group Contacts by Group” toggle. Press select, to open the “Select Groups to include in Contact” dialog, and use the Add/Remove button to specify which face groups are to be included in the contact calculations.

During execution, any faces eroded will be removed from the group, and any new faces uncovered will be added to a group named “Uncovered faces”. Unstructured Beams and SPH can also be included as a node group to participate in contact.


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Note that Group Contact is additive to Part contact. Selecting a Part for contact results in all external faces in that Part being checked for contact. Group contact should be used to add additional external faces from Parts that have been excluded from contact in the Part interaction matrix. Group contact is only applicable to faces of unstructured Parts.


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3.3. AUTOMATIC MASS SCALING Mass scaling is an artificial (numerical) mechanism for increasing the CFL (Courant–Friedrichs–Lewy) timestep of individual elements that govern the maximum allowed timestep of explicit transient dynamic solutions in ANSYS AUTODYN. Increasing the timestep has the obvious benefit of reducing the number of cycles required to run a simulation to a given point in time. Educated use of this option can therefore result in significant improvements in efficiency. The primary use of mass scaling is to increase the timestep of a small number of very small (or stiff) elements in the model, which otherwise would have controlled the timestep for all elements. Using this option, ANSYS AUTODYN will automatically add artificial mass to individual elements to ensure that their CFL timestep is at least equal to a value define by you. Mass scaling should only be used if the increased inertia of the scaled elements does not significantly affect the results of the simulation. Mass scaling can also be used to increase the timestep of elements that become highly distorted during the simulation. Extreme care should be taken to ensure that results obtained remain physical. Mass scaling is activated under Controls, Timestep and the input parameters are defined as follows: Automatic Mass Scaling - Activate automatic mass scaling Frequency (cycles) - Cycle frequency that ANSYS

AUTODYN will adjust the element mass scaling. Recommended default is only at start-up (cycle 0). Post cycle 0 adjustment will only take place for solid elements.

Min. timestep - Mass scaling is applied to all elements with a CFL timestep (multiplied by appropriate timestep safety factors) less than the specified value

Max. element scaling - Maximum mass scaling factor that can be applied to an element. Default is 100 (equating to 100 times original mass). If this limit is exceeded, no more mass is added to this element.

Max. part scaling - Maximum added mass that is allowed for an ANSYS AUTODYN Part, as a fraction of the original Part mass. Default is 0.05 (equating to 5% of the original mass. If this value is exceeded, the simulation will


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terminate with an error message. Two new element variables have been introduced with the development. These variables are automatically activated when mass scaling is selected: TIMESTEP: The CFL timestep for the element multiplied by the

timestep safety factor. Note for Beam elements there is a gobal and local Part safety factor

MASS.SCALE: The mass scale factor applied to the element. (1.0 indicates zero added mass, 2.0 indicates 100% added mass etc..)

A typical procedure to invoke mass scaling would be as follows

• Activate mass scaling retaining all the default parameters • Run the simulation for 1 cycle • Plot a contour of Timestep and review the element timesteps. Identify a

suitable timestep for mass scaling. The value chosen should exclude the majority of elements from mass scaling, and especially those in regions critical to the simulation results

• Re-load cycle zero • Enter the selected Min Timestep under Controls, Timestep • Run the simulation

Minimum CFL timestep = 2.0e-5 Mass Scale CFL timestep = 1.0e-4

=> Minimum CFL timestep = 1.0e-4

Small number of elements are mass scaled to maximum factor of 5.0

Timestep increased by factor of 5, for the addition of 0.02% of the Part mass

Example application of mass scaling

Important notes and limitations:

• Mass scaling will only be applied to Unstructured Elements/Parts • Mass scaling is only applied to elements filled with materials which use

a Linear or Hyperelastic equation of state • The actual timestep used in a simulation will generally be lower than

the Min timestep you define


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o The timestep used at cycle 1 of the simulation can be additionally reduced by a factor of 2. The timestep is then allowed to increase by a maximum of 10% per cycle.

o Large velocities can affect the timestep at cycle 0 o Other features of the code will influence the timestep, such as

artificial viscosity, blending, Gap contact. • For Tet ANP elements, the minimum timestep will be increased by

using mass scaling. However, due to nodal averaging of some quantities that influence the timestep, the actual user defined timestep may not be achieved.

• A summary of the contribution of mass scaling applied to the model can be obtained through

o Plotting a contour of variable Mass Scale. This is the ratio of current mass to original mass (without scaling).

o Review the .prt file output activated using Output, Print, Energy Summary


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3.4. NEW MULTI-MATERIAL PRESSURE EQUILIBRIUM OPTION A new multi-material “pressure equilibrium” option is now available to obtain a more accurate pressure computation for multi-material Euler elements that contain a mixture of two gases or explosives. The new pressure equilibrium calculation method is based on the assumption that the individual materials in the element have the same pressure, which needs to be found through an iteration on the different equations of state involved. The new option has been introduced to resolve mesh dependency problems that might occur when the “pressure averaging” method is used in multi-material analysis involving strong shocks, like explosions in air. Note that if the equilibrium option is selected, and a cell contains non gaseous materials, pressure averaging will be used locally in that cell. This problem is shown in the simple shock tube example below. The example simulates the expansion of a high pressurized region of hot gas into the ambient atmosphere and has been modeled as a multi-material Euler problem as well as a single material Euler problem.

In the picture below the multi-material solution is compared to the single material solution and it is clear that for the multi-material case the shockwave is moving slower into the air at rest and that the shock front exhibits an oscillatory behavior. This behavior is more prominent when using coarse meshes. For very fine meshes the multi-material “average” pressure solution will converge to the single material solution.


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When the “Equilibrium” option is used in the shock tube analysis above, the mesh dependency will not occur and the multi-material solution will compare very well with the single material solution, independent of the mesh size used.

The “pressure equilibrium option can be selected using the Solver options under Setup, Controls.

0.00E+00

5.00E+04

1.00E+05

1.50E+05

2.00E+05

0.00E+00 5.00E-01 1.00E+00 1.50E+00Distance along shock tube

Pre

ssur

e

Pressure - Single Material

Pressure - Multi-material

0.00E+00

5.00E+04

1.00E+05

1.50E+05

2.00E+05

0.00E+00 5.00E-01 1.00E+00 1.50E+00Distance along shock tube

Pre

ssur

e

Pressure - Single Material

Pressure - Equilibrium


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The “Averaged” option is selected by default for all models created in versions prior to Version 11. All models setup from scratch in Version 11 will use the “Equilibrium” option by default.


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3.5. ENHANCEMENTS TO THE ANP TETRAHEDRAL ELEMENT The ANP tetrahedral element first included in version 6.0 of the ANSYS AUTODYN software. The element is an extension of the advanced tetrahedral element (Burton 19963,4) and can be used as a majority element in the mesh. The ANP tetrahedral overcomes problems of volumetric locking, which occur with the SCP tetrahedral element. Note the ANP tetrahedral element is still susceptible to shear locking in bending dominated problems. The user should therefore be careful to verify their results in such cases. The tetrahedral element type can be selected under the Solver option for each Part. For meshes containing a majority of tetrahedral elements, the ANP option is recommended, and will be selected by default for Parts containing tetrahedral elements only. In version 11 of the ANSYS AUTODYN software the capability of the element has been extended to include:

• Porous, Compaction, P-Alpha and Hyperelastic equations of state • RHT-Concrete, Johnson Holmquist and Hyperelastic strength models • RHT-Concrete, Johnson Holmquist, Grady Spall and Johnson Cook

failure models • Crack softening with the Principal Stress/Strain failure models.

The full list of material models applicable to the ANP tetrahedral element in version 11 of ANSYS AUTODYN are shown in the table below.

Equations of State Strength Models Failure Models

Linear Elastic Hydro (Pmin) Polynomial Viscoelastic Plastic Strain Shock Von Mises Principal Stress Porous Johnson Cook Principal Strain Compaction Piecewise JC Principal Stress/ P alpha Zerilli Armstrong Johnson-Holmquist Rigid Steinberg Guinan RHT Concrete Hyperelastic Drucker-Prager Grady Spall Model Johnson-Holmquist Johnson Cook RHT Concrete Crack Softening MO Granular Hyperelastic

Valid Material Modeling Options for the ANP Tet Element

3 Burton A.J., “Explicit, Large Strain, Dynamic Finite Element Analysis with Applications to Human Body Impact Problems”, PhD Thesis, University of Wales, December 1996. 4 Bonet J, Burton A.J. “A simple averaged nodal pressure tetrahedral element for incompressible and nearly incompressible dynamic explicit applications”. Communications in Numerical Methods in Engineering 1998; 14, 437-449.


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Note that a hexahedral mesh will generally provide more efficient results than a tetrahedral mesh hence we only recommend the use of predominantly tetrahedral mesh models for convenience of mesh generation.

Example Simulation of an impact of a steel ball onto a ceramic tile taking

advantage of ANSYS Workbench unstructured meshing capabilities and the enhancements to the ANP tetrahedral element formulation in ANSYS

AUTODYN


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3.6. HP-MPI FOR PARALLEL PROCESSING ON LINUX ANSYS AUTODYN version 11 will utilise the HP-MPI message passing library on Linux. HP-MPI is a message passing interface which allows ANSYS AUTODYN to decompose a model and run the calculation over multiple processors whether as a distributed or as a share memory configuration or as a combination of the two. HP-MPI comes free to all ANSYS users, is easy to install and supports a wide range of interconnects. The motivation for the migration from PVM to HP-MPI message passing on Linux are:

• HP-MPI is fully tested and supported • Very widely used and trusted message passing library • Proven low latencies and high bandwidths, allowing very efficient

parallel calculations. • Ease of installation; HP-MPI will be installed along with the ANSYS

AUTODYN distribution. • HP-MPI supports all commonly used interconnects including TCP/IP,

Myrinet, InfiniBand and Quadrics. • The libraries for the various interconnects are provided by HP and the

user simply has to run an rpm to install the applicable libraries. • HP-MPI takes advantage of the most applicable protocol, utilising the

Shared Memory Protocol (SMP) for intra-node communication. • HP-MPI has advanced security features including ssh as the default

remote shell.


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4. MATERIAL MODELLING ENHANCEMENTS 4.1. HYPERELASTICITY A number of hyperelastic material models are now available for use in 2D and 3D Lagrangian volume elements. These models are typically used to model elastomers such as rubber type materials that can undergo large elastic strains. 4.1.1. Introduction to Hyperelastic Material Models A material is said to be hyperelastic if there exists an elastic potential function Ψ (or strain energy function) that is a scalar function of one of the strain or deformation tensors, whose derivative with respect to a strain component determines the corresponding stress component. This can be expressed by:

CS

∂∂

=ψ2

where: S = Second Piola-Kirchhoff stress tensor Ψ = strain energy function C = components of the right Cauchy-Green deformation tensor

The deformation tensor C is comprised of the products of the deformation gradient F:

FFC T= The Cauchy stress is obtained by:

TJ FSF1−=σ where,

Fdet=J and is also the ratio of the current deformed volume over the initial (undeformed) volume. The eigen values of C are the principal stretch ratios,

21λ , 2

2λ and, 23λ .

Particular forms of strain energy potential can be written as either a direct function of the principal stretch ratios or as a function of the invariants of the strain tensor C, I1, I2, and I3. In terms of the principal stretch ratios the invariants are commonly written as:

23

22

213

23

21

23

22

22

212

23

22

211

λλλ

λλλλλλ

λλλ

=

++=

++=

I

I

I

Hyperelastic materials generally have very small compressibility. For truly incompressible materials the volume of an element will always remain constant, and consequently J will be equal to 1. The hyperelastic material models implemented in ANSYS AUTODYN assume the material response to be ‘nearly incompressible’, and as such a small amount of volumetric deformation is allowed. The strain energy function is therefore split into a deviatoric component ψ̂ and a volumetric component ( )JU . Thus:


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( )JU+=ψψ ˆ The volume preserving part of the deformation gradient F is defined as:

1det;3/1 === − FFF JJ and consequently the deviatoric component of C, the right Cauchy-Green deformation tensor is:

FFC T=ˆ The modified distortional stretches and invariants are then:

3,2,1,3/1 == − pwhereJ pp λλ and:

23/4

2

13/2

1

IJIIJI

−

−

=

=

The strain energy potential can then be defined as either a function of the modified invariants or distortional stretches, and J. Hyperelastic Material Models Following are several forms of strain energy potential (ψ ) provided for the simulation of nearly incompressible hyperelastic materials. 4.1.2. Neo-Hookean The strain energy function for the Neo-Hookean hyperelastic model is,

( ) ( )21 1132

−+−= Jd

Iµψ

where the required input parameters are defined as: µ = initial shear modulus of the material d = incompressibility parameter.

and the initial bulk modulus is defined as:

K = 2/d 4.1.3. Mooney-Rivlin The strain energy function of a hyperelastic material can be expanded as an infinite series in terms of I1 and I2, as follows,

( ) ( ) ( )2210,

1133 −+−−= ∑∞

=

Jd

IIC nm

nmmnψ

The 2,3,5 and 9 parameter Mooney-Rivlin hyperelastic material models have been implemented and are described in turn below. 4.1.3.1. 2-Parameter Mooney-Rivlin Model The strain energy function for the 2-parameter model is,

( ) ( ) ( )2201110 1133 −+−+−= Jd

ICICψ

where: J = determinant of the elastic deformation gradient F. C10, C01 = material constants characterizing the deviatoric deformation

of the material. d = material incompressibility parameter.


31

The initial shear modulus is defined as: µ = 2(c10 + c01)

and the initial bulk modulus is defined as: K = 2/d

4.1.3.2. 3-Parameter Mooney-Rivlin Model The strain energy function for the 3-parameter model is,

( ) ( ) ( )( ) ( )22111201110 113333 −+−−+−+−= Jd

IICICICψ

where the required input parameters are defined as: C10, C01, C11 = material constants characterizing the deviatoric

deformation of the material. d = material incompressibility parameter

Other parameters are as defined for the two-parameter model above. 4.1.3.3. 5-Parameter Mooney-Rivlin Model The strain energy function for the 5-parameter model is,

( ) ( ) ( )( )( ) ( ) ( )22

2022

120

2111201110

1133

3333

−+−+−

−−+−+−=

Jd

ICIC

IICICICψ

where the required input parameters are defined as: C10, C01, C20, C11, C02 = material constants characterizing the deviatoric

deformation of the material. d = material incompressibility parameter.

See 2-Parameter Mooney-Rivlin model for definitions of remaining terms. 4.1.3.4. 9-Parameter Mooney-Rivlin Model The strain energy function for the 9-parameter hyperelastic model is,

( ) ( ) ( )( )( ) ( ) ( ) ( )( )( ) ( ) ( ) ( )23

2033

1302

2112

22

1212

2022

120

2111201110

113333

3333

3333

−+−+−+−−+

−−+−+−+

−−+−+−=

Jd

ICICIIC

IICICIC

IICICICψ

where the required input parameters are defined as: C10, C01, C20, C11, C02, C30, C21, C12, C03 = material constants characterizing the deviatoric deformation of the material. d = material incompressibility parameter.

See 2-Parameter Mooney-Rivlin model for definitions of remaining terms. 4.1.4. Yeoh The Yeoh hyperelastic strain energy function is similar the Mooney-Rivlin models described above except that it is only based on the first deviatoric strain invariant. It has the general form,

( ) ( )∑∑==

−+−=N

i

i

i

iN

ii J

dIC

1

21

10 113ψ


32

4.1.4.1. Yeoh 1st order The strain energy function for the first order Yeoh model is,

( ) ( )21

110 113 −+−= Jd

ICψ

where: N = 1. J = determinant of the elastic deformation gradient F C10 = material constant d1 =incompressibility parameter

The initial shear modulus is defined as:

µ = 2c10 and the initial bulk modulus is defined as:

K = 2/d1 4.1.4.2. Yeoh 2nd order The strain energy function for the second order Yeoh hyperelastic model is,

( ) ( ) ( ) ( )42

2

1

2120110 111133 −+−+−+−= J

dJ

dICICψ

where the required input parameters are defined as: N = 2. C10, C20 = material constants d1, d2 = incompressibility parameters

See 1st order Yeoh model for definitions of remaining terms. 4.1.4.3. Yeoh 3rd order The strain energy function for the second order Yeoh hyperelastic model is,

( ) ( ) ( )( ) ( ) ( )6

3

4

2

2

1

3130

2120110

111111333

−+−+−+

−+−+−=

Jd

Jd

Jd

ICICICψ

where the required input parameters are defined as: N = 3.

C10, C20, C30, = material constants d1, d2, d3 = incompressibility parameters

See 1st order Yeoh model for definitions of remaining terms. 4.1.5. Ogden The Ogden form of strain energy function is based on the deviatoric principal stretches of left-Cauchy strain tensor, which has the form,

( ) ( )∑∑==

−+−++=N

i

i

i

N

i i

i Jd

iii

1

2221

1113ααα λλλ

αµψ

4.1.5.1. Ogden 1st Order The strain energy function for the first order Ogden hyperelastic model is,


33

( ) ( )21

2211

1 113111 −+−++= Jd

ααα λλλαµψ

where:

λp = deviatoric principal stretches of the left Cauchy-Green tensor J = determinant of the elastic deformation gradient µp, αp and dp = material constants

The initial shear modulus, µ, is given as:

211

0αµµ =

and the initial bulk modulus is:

10

2d

K =

4.1.5.2. Ogden 2nd Order The strain energy function for the first order Ogden hyperelastic model is,

( ) ( )

( ) ( )42

2

1

2212

2221

1

1

1111

33 222111

−+−+

−+++−++=

Jd

Jd

αααααα λλλαµλλλ

αµψ

where: λp = deviatoric principal stretches of the left Cauchy-Green tensor J = determinant of the elastic deformation gradient µp, αp and dp = material constants

The initial shear modulus, µ, is given as:

( )22110 21 αµαµµ +=


10

2d

K =

4.1.5.3. Ogden 3rd Order The strain energy function for the first order Ogden hyperelastic model is,

( ) ( )

( ) ( ) ( )

( )63

4

2

2

1221

3

3

2212

2221

1

1

11

11113

33

333

222111

−+

−+−+−+++

−+++−++=

Jd

Jd

Jd

ααα

αααααα

λλλαµ

λλλαµλλλ

αµψ

where: λp = deviatoric principal stretches of the left Cauchy-Green tensor J = determinant of the elastic deformation gradient


34

µp, αp and dp = material constants The initial shear modulus, µ, is given as:

( )3322110 21 αµαµαµµ ++=


10

2d

K =

4.1.6. Arruda-Boyce This is a statistical mechanics-based model, also commonly referred to as the 8-chain model. The Arruda-Boyce strain energy potential is similar in form to a Yeoh model of order N=5 and is as follows,

( ) ⎟⎟⎠

⎞⎜⎜⎝

⎛−

−+−= ∑

=− JJ

dIC ii

ii

L

i ln2

1132

1

5

122λ

µψ

where the constants Ci have the following values,

673750519,

705019,

105011,

201,

21

54321 ===== CCCCC

and the following parameters are material variables,

λL = limiting network stretch d = incompressibility parameter

4.1.7. Material Data and Examples To use a hyperelastic material model in ANSYS AUTODYN the user must first select Hyperelastic for both the equation of state and strength model. The user can then choose the required strain energy function from the Model option as shown in the picture below:

With the release of v11, three sets of material data for rubber have been added to the standard ANSYS AUTODYN material library. The various coefficients for these materials have been fitted to give agreement with experimental5 data as shown in the figure below. The results shown here are from uniaxial tension experiments and simulations of a vulcanised rubber.


35

0

1

2

3

4

5

0 1 2 3 4 5 6 7 8

Engineering Strain

Engi

neer

ing

Stre

ss (M

Pa)`

2 parameter Mooney Rivlin

Arruda-Boyce

3rd Order Ogden

Experimental Data

The different models are generally applicable over different ranges of strain as illustrated in the table below, however these numbers are not definitive and users should verify the applicability of the model chosen prior to use.

Model Applied strain range

Neo-Hookean 30% Mooney-Rivlin 30%-200% depending on order Arruda Boyce Up to 300 % Ogden Up to 700%

The figure below shows the result of a 2mm diameter rubber ball bouncing off a rigid surface.

5

5 Treloar L.R.G., ‘Stress-Strain Data for Vulcanised Rubber Under Various Types of defomation’, Trans. Faraday Soc., Vol 40, pp. 59-70, 1940.


36


37

4.2. COMPACTION MODEL ENHANCEMENTS The compaction model has been updated to provide a more accurate representation of non-linearity when unloading a material. Therefore, the unloading method can now either be linear or non-linear. By default for previous versions of the compaction EOS linear unloading would be chosen and the user would be asked for soundspeed versus density information. If nonlinear is chosen then the variation of bulk modulus with density should be entered. The pressure will then be evaluated according to the bulk modulus at the present density. The algorithm logic to evaluate the pressure is shown below:

ρρρ

ddPK =)(

)()1()())(()1()(

iiiipKiPiPk ρ

ρρ −−⋅+−=

if ( )()( iPiP ck <= )

)()( iPiP k= else

)()( iPiP c= This produces a nonlinear unloading pattern, an example of which is shown below:

0

0.2

0.4

0.6

0.8

1

1.2

1.5 1.6 1.7 1.8 1.9 2 2.1 2.3 2.5

Density

Pre

ssur

e

cP

kP


38

4.3. NEW POWDER BURN MODEL The previous “Slow Burn” equation of state has been more appropriately renamed to “Powder Burn”. In addition, a completely new formulation for the powder burn model has been included6. Finally, the powder burn model is now available in all solver types, including multi-material Euler. Details of this significant enhancement are given below. There is a need to numerically simulate the combustion of materials where the dominant physical characteristic of the burning is deflagration rather than detonation of the combustible material. The complicated chemical reactions that dictate the burning of the energetic material are extremely difficult to model from first principles. Therefore a mathematical model based on the averaged quantities of the governing properties has been proposed6. The model was developed using detailed studies of a variety of experiments involving energetic materials where the convective burning front moves behind the pressure front of a shockwave. This type of burning occurs in many incendiary devices and munitions. 4.3.1. Theory The powder burn model is a multi-phase model where gas and solid can be present in one cell at the same time step. The total mass within each cell is found by added together the mass of the gas and of the solid. The volume taken by the gas and solid are both known and therefore the density, compression etc of the material within the cell can be calculated. The burning of the material is dependent on the burn fraction F(t) where,

)()()(

)(0

0

tMtMtM

tFs

ss −=

and

)()(

)(0

''

tMtM

tFs

s−=

The burning velocity, c(t), is given by a user supplied function, H, dependent on the pressure of the gas,

)()( gPHtc = .

It has been shown (4) that the burn fraction can be represented as a function of H and a function, G(F(t)), which expresses the size and shape of the burning surface, such that: 6 A Atwood, EK Friis and JF Moxnes, A Mathematical Model for Combustion of Energetic Powder Materials, 34th International Annual Conference of ICT, June 24-27, 2003, Karlsruhe Federal Republic of Germany.


39

)())(()(' gPHtFGtF = . The functions G and H are user supplied and are entered in the material data menu and a typical burn fraction variation in time is shown below:

The burn fraction should only be calculated on the amount of solid material within each cell which has been ignited. Therefore the total burn fraction within each cell, )(tFt , is found by multiplying the burn fraction, )(tF , multiplied by the ignition fraction, I(t), such that

)()()( tItFtFt ⋅= . The ignition fraction is dependent on the velocity of the burn front, V, where,

))(1))((()( 21 sgPHCCtV ργ++= and 1C , 2C and γ are user defined functions and sρ is the solid density averaged over the cell volume. The total burn fraction then dictates the amount of solid which is burnt and has changed into a gaseous state at each time step. The pressure of the solid can then be evaluated using a separate equation of state (EOS) which is user defined and can be either a linear or a compaction EOS. As the solid material burns it changes state such that when the cell is fully burned only gas is present within the cell. A typical density variation in time is shown below,

0

0 .2

0 .4

0 .6

0 .8

1

1 .2

0 .0 E + 0 0 3 .0 E -0 5 6 .0 E -0 5 9 .0 E -0 5 1 .2 E -0 4T im e [s ]

F(t)


40

4.3.2. Material Data Input The new powder model is currently present as an option within the old slow burn model. This name will be changed to Powder Burn model to better represent the physical processes occurring and also to be consistent with the presentation of such models in the available literature. ANSYS AUTODYN requires the user to input the values of the burn fraction growth parameters, G and c . These growth parameters are used to evaluate the change in the burn fraction where,

)()1( gc PHFGF −=∆ .

In order to evaluate the burn front velocity the relationship between H and

gP must also be entered in addition to the variation between density and γ in the relationship below:

))(1))((()( 21 sgPHCCtV ργ++= The unreacted solid can be represented using a compaction or linear EOS. 4.3.3. Example

0 .0 0 E +0 0

2 .0 0 E -0 1

4 .0 0 E -0 1

6 .0 0 E -0 1

8 .0 0 E -0 1

1 .0 0 E +0 0

1 .2 0 E +0 0

1 .4 0 E +0 0

1 .6 0 E +0 0

1 .8 0 E +0 0

0.00

E+0

0

1.97

E-0

2

4.80

E-0

2

8.31

E-0

2

1.23

E-0

1

1.67

E-0

1

2.14

E-0

1

2.63

E-0

1

3.12

E-0

1

3.63

E-0

1

4.14

E-0

1

4.65

E-0

1

5.17

E-0

1

5.69

E-0

1

6.21

E-0

1

6.73

E-0

1

7.25

E-0

1

7.77

E-0

1

8.30

E-0

1

T im e (m s )

Den

sity A ve ra g e S o lid D e ns ity

A ve ra g e G a s D e ns i ty


41

Example application of Powder Burn model used in the Multi-material solver to propel a sabot

and projectile inside an experimental gun chamber 4.4. JWL, MILLER EXTENSION Non-ideal explosives, such as explosives containing significant amount of Aluminum (Al) and ammonium perchlorate (AP), can release a substantial amount of energy from burning of Al and AP particles after the explosives are detonated. This energy release introduces a time-dependency into the traditional JWL equation of state. To take this additional energy and time-dependency into account, the traditional JWL EOS has been extended using the approach proposed by Miller 7 .

The new option, Miller extension, is included in the standard ANSYS AUTODYN JWL-EOS. This is activated by setting the additional parameter option to Miller extension.

The JWL EOS with Miller extension is

VQEe

VRBe

VRAP VRVR )()1()1( 21

21

λωωω ++−+−= −− ,

where nm Padtd )1( λλ

−= ,

Q additional specific energy, a energy release constant, m energy release exponent, n pressure exponent.

7 P.J. Miller, A Reactive Flow Model with Coupled reaction Kinetics for Detontation and Combustion of non-ideal explosives. MRS Symp.Proc., Volume 418, p. 413, 1996, MRS Society Pub.


42

A new variable LAMDA, which is the burn fraction of the additional energy term in the Miller extension of the JWL EOS, has been introduced. This variable can be contoured or recorded as a time history variable at specified gauge points.


43

4.5. TIME DEPENDANT ENERGY DEPOSITION EXTENSION TO JWL EQUATION OF STATE

Thermobaric explosives produce more explosive energy for a given size than conventional explosives and are generally designed to provide enhanced pressure and heat effects. This is typically achieved by the inclusion of specific additives, such as aluminum, that undergo combustion with atmospheric oxygen after the detonation reaction. This process is sometimes called ‘after-burning’. The standard JWL model takes no account of this ‘after-burning’ energy due to additional combustion processes. In order to model such additional energy a new feature is available in ANSYS AUTODYN that allows the user to deposit additional energy into the explosive over a specified time. The required inputs are shown in the figure below; energy per unit mass is specified along with a start and end time.

The example below demonstrates the effect of adding 2.15MJ/Kg of energy between 0.12 and 0.55ms to a 10Kg spherical charge of TNT modeled using standard JWL data. The pressure time history of a gauge shows that the additional energy results in a longer pulse duration and an increased impulse.

0

2000

4000

6000

8000

10000

12000

14000

0.0 0.1 0.2 0.3 0.4 0.5 0.6

Time (ms)

Pres

sure

(KPa

) TNT + additional Energy

TNT

0

100

200

300

400

500

600

700

0.0 0.1 0.2 0.3 0.4 0.5 0.6

Time (ms)

Impu

lse

(Pa

S)

TNT + additional energy

TNT


44


45

4.6. LEE-TARVER ENHANCEMENT The Lee-Tarver ignition, growth and burn model has been enhanced in two areas:

• Improved stability for multi-material Euler • Enhanced post-burn behavior for all solvers

4.6.1. Improved Stability for Multi-material Euler Applications The use of the Lee-Tarver model in multi-material Euler applications often lead to the occurrence of spurious large velocities that could lead to “time step too small” problems or Lee-Tarver Equation of State errors. The Lee-Tarver material model has been enhanced in such a way that multi-material Euler applications using the Lee-Tarver material model now run more robustly. A typical full multi-material Euler example is shown below where an aluminum pipe is filled with two explosives with a disk of polycarbonate in between. The donor explosive is detonated and the shockwave that propagates through the polycarbonate disk will cause the acceptor explosive to detonate sympathetically.


46

4.6.2. Improved Post-burn behavior for all Solvers The Lee-Tarver material model has been enhanced to obtain a more physical post-burn behavior for medium and large expansions. The strength of the material has been made dependent on the burn fraction, F, according:

0)1( σσ ∗−= F , where σ is the current yield strength and 0σ is the original yield strength of the unburned material. The example below shows the effect of this enhancement. The model shown in the previous section is now fully modeled in Lagrange. The analysis has been run further after full detonation of the Lee-Tarver acceptor explosive and the pipe and explosives will expand. It can clearly be seen that the Lee-Tarver explosive doesn’t expand correctly with the containment. With the Version 11 post-burn enhancement the Lee-Tarver explosive material expands correctly with the containment for medium and large expansions.


47

Version 6.1 Version 6.1

Version 11 Version 11


48

5. PRE- AND POST- PROCESSING 5.1. IMPROVED MEMORY MANAGEMENT DURING PRE-PROCESSING Increasing the complexity of simulations performed in ANSYS AUTODYN can mean that more elements are required to provide sufficient accuracy in the solution. In previous versions, pre-processing of models with large numbers of elements required significant amounts of memory to be made available to ANSYS AUTODYN, even though this memory was only required at the solution stage of the simulation. This new functionality allows for the generation of models that, due to their size, could not previously be setup on 32bit systems. The solution of these models can be achieved by running ANSYS AUTODYN remotely on 64bit Linux platforms. To remove the requirement for large amounts of memory during pre-processing, storage for solution variables is now only allocated at execution, rather than at the part definition stage as implemented previously. This memory saving allows for larger models (in terms of number of elements) to be created on (in particular) 32bit systems. Limitations Any pre-processing functions that manipulate the solution variables are limited by the memory management improvements. For example, if remapping is to be performed, then the variable arrays are allocated at the moment of remapping. It is important in this case to ensure that the system performing the pre-processing has enough memory available to hold the variable arrays. User subroutine considerations If your user subroutine accesses solution (grid) variables at cycle zero, then you should ensure that the following Fortran code is added and called once before any operations: CALL ALLOCATE_STR_VARS3(IERROR) This subroutine ensures that the solution variable storage is allocated in the correct manner. The data modified by your user subroutine will then be stored in the restart file as in previous versions of ANSYS AUTODYN. Examples As an indication of the memory savings achievable, the following tables show typical model sizes and corresponding memory usage comparisons between the new and the previous versions of ANSYS AUTODYN.


49

Structured Lagrange Sizing Comparison

No. elements ANSYS AUTODYN version

Memory Used

v6.1 1.25GB 2x106 Cells v11.0 733MB v6.1 1.54GB 2.5x106 Cells v11.0 888MB v6.1 Not Possible 3x106 Cells v11.0 1.05GB v6.1 Not Possible 4x106 Cells v11.0 1.36GB

Maximum Euler-FCT Sizing Comparison

No. elements ANSYS AUTODYN Version

Memory Used

2.5x106 Previous Version 1.5GB 4.72x106 Latest Version 1.32GB


50

5.2. RESULTS FILES The capability to output results files, which contain a reduced amount of information, has been implemented (currently only in ANSYS AUTODYN-3D). This allows the post-processing of large simulations on computers with limited resources. Result Files cannot be used for restarting a problem. The frequency of the result files is independent of the SAVE files. The control for results file output is located in the Output panel, under Results Files:

From here, the frequency of results file output and the variables to save into the file are selected. Note that only a limited set of results variables are selected by default.


51

When a simulation is performed with the results file option switched on, a new directory will be created in the directory where the simulation file is located. This directory will have the name <ident>_adres. For example, the results files from a simulation with model name ben3d1_0.ad will be stored in a sub-directory with name ben3d1_adres.

Results files have extension adres, and the model name is appended with two numbers:

• the first number is the cycle from which the simulation began, • the second number being the current cycle number.

For example, a results file ben3d1_10_25.adres indicates that the results file contains data at cycle 25 from the simulation ben3d1 that began at cycle 10. Note that the start cycle for each sequence of results files is stored in a file <ident>_<cycle>.ad_base. For example ben3d1_10.ad_base. This base file is essential for post processing using results files and must not be deleted. The base file contains data required for producing graphic output that for efficiency is not repeated in each of the Results Files. To use the results files for post-processing of a simulation, the option under the File menu option should be used.


52

Once a results file has been selected, various options within ANSYS AUTODYN will be inactive, since no model alteration is possible. The cycle drop-down menu from the Plots panel is automatically updated to represent the cycles of results files that can be loaded. In order to switch back to full restart files, simply load in a restart (cycle) file. The adres directory is designed to be independent of any other files, in order to share the results with colleagues simply transfer the directory. Post- processing using results files is significantly more memory efficient than from a restart file. Using results files, ANSYS AUTODYN only loads the data required to generate the requested Plots. The efficiency improvement will be problem dependant however a 2 to 3 times increase in the size of model that can be post-processed on a 32-bit Windows system can be expected. To use the results files to create an animation of the simulation, select the option “Scan for results files from this ident” from the Generate Multiple Slides panel.


53


54

5.3. IMPROVED COMPRESSION FOR SAVE FILES A new compression algorithm is now applied when saving cycle files to disk. The example below highlights the significant savings on disk space that can be achieved with the new algorithm. The saving will depend on the model size.

Cycle zero file size

Version 6.1 => 12.2 Mbytes

Version 11.0 => 2.5 Mbytes

Example demonstrating reduced size of Save files in v11.0 Note also that the new compression algorithm should also improve robustness when re-loading models containing erroneous results data. Also note that because of the change in file format, files saved in version 11.0 will not load back into previous versions. The Save As Version option can however be used to transfer models into previous versions if required.


55

5.4. UNSTRUCTURED PARTS TO INITIALIZE 3D MULTI-MATERIAL

EULER Unstructured Parts containing any type of volume element can now be used to initialize a 3D Multi-material Euler simulation. Using the Parts, Fill, Additional Fill Option, Part Fill option. Select the Unstructured Parts and the material to replace.

Mesh of Projectile and Target Multi-material mesh filled with Unstructured Part 5.5. UNSTRUCTURED PARTS TO INITIALIZE SPH Unstructured Parts containing any type of volume element can now be used to generate SPH Objects, which in-turn can be used to create SPH regions. Using the Parts, Geometry, Import Objects, Part option. Select the Unstructured Parts to convert from the displayed list. In addition to this extension, the efficiency of Packing all imported objects has been significantly increased.

Mesh of Projectile and Target SPH object created from Target Mesh and Packed with SPH


56

5.6. INTERACTIVE SELECTION OF PARTS Using <alt> + Left Mouse button you may select a part in the model view window and make it the current part. The part selected with the mouse will be selected in either the part list in the plots panel or parts panel. This is useful to identify parts and to make a particular part the current part active for zoning, filling or other part operations.

5.7. HIGHLIGHT PARTS

A new Additional component has been added to the Plots panel “Part Highlight”. When this option is selected, Parts selected in the plots panel will be highlighted on the displayed model. The default highlight color is golden yellow, you may alter the color and opacity of the highlight color that is applied to selected parts using the associated options panel. Selecting multiple parts in the parts list will highlight all the selected Parts.

<Alt>+LMB


57


58

5.8. INTERACTIVE SELECTION OF GAUGES Use the mouse to interactively select Elements or Nodes where you wish to place your gauge points by switching on Interactive Gauge points in the Gauges Panel.

The IJK indices or XYZ position of the selected element/node will be displayed, as they are selected. Gauges added via this method will also be cached until cleared by selecting the Undo button, or the Gauges Panel is closed. When adding Gauges via this method the part containing the Element or Node selected becomes the selected Part in the Parts panel. 5.9. GROUP OPERATIONS Two new operations are available for element groups. 5.9.1. Delete Elements Use this option to delete all elements with a selected Group. Select the Group containing the elements to delete and select OK. The elements will be deleted from the model.

<Alt>+LMB


59

Define Element Group Delete Elements in Group

Example use of Delete Elements Group Operation 5.9.2. Split Nodes Use this option to split nodes across material boundaries within a selected group. ANSYS AUTODYN will search through all elements in the selected group and identify nodes that are connected to elements (through the connectivity table) with different materials. Each node connected to more than one material will be replicated by the number of connected materials, while retaining the same physical location. The connectivity of each associated element will be updated. The option is useful for generating a sliding interface between two materials and enforcing a conforming mesh (coincident nodes) between the material interface at the start of the simulation.

Form Multi-body Part in DesignModeler Generate Conformal Mesh in Meshing

(with single node at material interface)

Create Element Group in ANSYS AUTODYN.

Split nodes across material interface. Nodes are duplicated at material interface to allow

sliding contact Example use of Split nodes to create conformal sliding interface


60

5.10. AUTOMATIC PARALLEL DECOMPOSITION OF EULER-FCT PARTS The automatic parallel decomposition algorithm has been extended to incorporate Euler-FCT parts, in addition to its present ability to handle unstructured Parts. This facilitates the decomposing of complicated Euler-FCT/Lagrange coupled models; the user need only stipulate the number of tasks over which the model should be assigned and ANSYS AUTODYN will automatically produce a decomposition configuration with good load balancing qualities and minimal inter-processor communication. To further enhance the efficiency of coupled calculations the sub-domains of the FE structure will be placed on the same processor as the FCT sub-domains located in the same geometric space. This decreases the necessary inter-processor communication for the coupling calculations. To automatically decompose an Euler-FCT model, press the Set Decomposition button from the Parallel menu. All Euler-FCT and/or unstructured Parts will be shown in the Automatic Decomposition dialog window:

The example below contains a brick structure in which an explosion is occurring. The brick structure is modelled using unstructured Lagrangian Parts, whilst the explosion in air is modelled using an Euler-FCT part. Here, only part of the Euler-FCT part is shown for illustration purposes, the Euler-FCT part extends above the brick structure.


61

Example decomposition of coupled Euler-FCT and Unstructured Parts If the user wishes to override this decomposition then the Euler-FCT part can still be manually assigned as before.


62

6. EXTENDED UNIT SYSTEMS 6.1. US CUSTOMARY UNITS US customary units have been added to units options when creating a new model. These are

• Length unit (inch or foot) • Mass unit (pound).

These units can be written in short as “in”, “ft”, and “lb”. One of the three time units can be used in conjunction with the US customary units: microsecond, millisecond, or second. Note they cannot be used together with Metric Units. For example, you cannot use inch for the length unit and kilogram for the mass unit.

The following table shows the unit for each type of physical variables in the US customary system: in, lb, s in, lb, ms in, lb, µs ft, lb, s ft, lb, ms ft, lb, µs Length in in in ft ft ft Mass lb lb lb lb lb lb Time s ms µs s ms µs Temperature K K K K K K Density lb.s2/in4 lb.ms2/in4 lb.µs2/in4 lb.s2/ft4 lb.ms2/ft4 lb.µs2/ft4


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in, lb, s in, lb, ms in, lb, µs ft, lb, s ft, lb, ms ft, lb, µs Inertia lb.s2.in lb.ms2.in lb.µs2.in lb.s2.ft lb.ms2.ft lb.µs2.ft Volume in3 in3 in3 ft3 ft3 ft3

Force lb lb lb lb lb lb Pressure psi psi psi psf psf psf Impulse lb.s lb.ms lb.µs lb.s lb.ms lb.µs Velocity in/s in/ms in/µs ft/s ft/ms ft/µs Work lb.in lb.in lb.in lb.ft lb.ft lb.ft Strain Rate 1/s 1/ms 1/µs 1/s 1/ms 1/µs Energy lb.in lb.in lb.in lb.ft lb.ft lb.ft Energy/Unit Mass in2/s2 in2/ms2 in2/µs2 ft2/s2 ft2/ms2 ft2/µs2 Energy/Unit Volume lb/in2 lb/in2 lb/in2 lb/ft2 lb/ft2 lb/ft2 Fracture Energy lb/in lb/in lb/in lb/ft lb/ft lb/ft Fracture Toughness Squared

lb2/in2 lb2/in2 lb2/in2 lb2/ft2 lb2/ft2 lb2/ft2

Specific Heat Capacity

in2/s2.K in2/ms2.K in2/µs2.K ft2/s2.K ft2/ms2.K ft2/µs2.K

Thermal Conductivity lb.s/K lb.ms/K lb.µs/K lb.s/K lb.ms/K lb.µs/K 6.2. MICRON UNIT SYSTEM A new micron (µm) length system has been introduced. This can be used in conjunction with a mass unit of picogram (pg) and time unit of microsecond or millisecond.

7. SUPPORTED OPERATING SYSTEMS AND COMPILERS


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The following operating systems are supported at release 11.0 of ANSYS ANSYS AUTODYN.

System C++ Fortran Windows XP Pro, 32 bit Microsoft Visual

Studio .NET 2003 including C++

Intel Fortran 9.0

RedHat WS 3 Intel Fortran 8.0 SUSE 9.1 Intel Fortran 8.0 RedHat AW 3 Intel Fortran 8.1 32 Bit Linux RedHat WS Release 3 (Kernel 2.4.21-4) Glibc version 2.3.2 64 Bit Linux (x86-64) SUSE Professional 9.1 (Kernel 2.6.4-52) 64 Bit Linux (Itanium II) RedHat Advanced Workstation 3 (Kernel 2.4.21-15-e.3smp) Glibc version 2.3.2 8. INSTALLATION 8.1. WINDOWS 32-BIT ANSYS AUTODYN version 11.0 for Windows 32-bit is now installed as part of the ANSYS product installation process. Note that the Windows 64-bit installation of ANSYS AUTODYN version 11.0 is still under development. Contact Century Dynamics if this is required.


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Select ANSYS AUTODYN from the product selection page and the ANSYS AUTODYN related files will be installed to the directory: {drive}:\Program Files\Ansys Inc\v110\AISOL\AUTODYN This directory contains the following sub-directories

The main ANSYS AUTODYN installation, including executables, .dll’s etc is contained in the intel folder. The recommended method of running ANSYS AUTODYN is via Start, All Programs, ANSYS 11.0, ANSYS Workbench. Then select ANSYS AUTODYN icon from the start page of ANSYS Workbench. Note that by default, the single precision version of ANSYS AUTODYN will be used. To run in double precision, from the start page of ANSYS Workbench, Select Tools, Options.


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8.2. WINDOWS 64-BIT (LIMITATIONS) The procedure for installation of ANSYS AUTODYN onto a Windows 64 bit operating system is the same as for Windows 32-bit. The installed software currently will however have the following limitations

• The ANSYS AUTODYN application is 32-bit. Problem size limits will be identical to those of a 32-bit Windows installation

• The interaction between the ANSYS AUTODYN applet and the

Meshing applet is not available. To transfer a mesh from the meshing application to ANSYS AUTODYN;

a. Proceed to FEModeller b. Export a Nastran File c. In the ANSYS AUTODYN applet, use the Import, MSC.Nastran

option to load the file generated from FEModeler d. The link between ANSYS AUTODYN and Meshing is not

persistant in this case hence the Update Model from Workbench option is not available on Windows 64 bit operating system

8.3. LINUX INSTALLATION The ANSYS AUTODYN version 11.0 Linux server will be installed alongside the other products installed from the ANSYS product family. By default, the base installation is:

\usr\ansys_inc\ A symbolic link is created to the installation directory and is located at:


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\ansys_inc Licensing programs files will be installed in: \ansys_inc\shared_files\licensing ANSYS AUTODYN specific files will be installed in: \ansys_inc\v110\autodyn With further sub-directories: \bin\<platform> - executables for each supported platform \lib\<platform> - runtime libraries for each supported platform \usrsub\<platform> - user subroutine files for each supported platform 9. LICENSING ANSYS AUTODYN version 11.0 will be licensed using the ANSYS FLEXlm license manager. Dongles and adin files will no longer be required. At the general release of ANSYS AUTODYN version 11.0, new FLEXlm license keys will be issued in exchange for the return of your existing dongles. The exact capabilities that the FLEXlm license keys will provide will be communicated to users prior to the release.

Autodyn New Features

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