CUBIT 11.1 Release Notes

Product Description

Product Highlights

Meshing: CUBIT is a solid-modeler based preprocessor that meshes volumes and surfaces for finite element analysis. Mesh generation algorithms include quadrilateral and triangular paving, 2D and 3D mapping, hex sweeping and multi-sweeping, tet meshing, and various special purpose primitives. CUBIT contains many algorithms for controlling and automating much of the meshing process, such as automatic scheme selection, interval matching, sweep grouping and sweep verification, and also includes state-of-the-art smoothing algorithms.

Geometry Preparation: One of CUBIT's strengths is its ability to import and mesh geometry from a variety of CAD packages. CUBIT currently integrates the ACIS geometry kernel directly within its code base, allowing direct manipulation of the ACIS native CAD geometry format within CUBIT. This reduces the errors and anomalies so often associated with geometry translation. CGM also boasts a facet-based geometry kernel developed at Sandia that can be used for remeshing or editing old mesh files or models defined by triangle facets. In addition, CUBIT has developed a comprehensive virtual geometry capability that permits local composites and partitions to geometry without modifying the underlying native geometry representation. The user can choose to ignore, clean-up or add features to the model allowing greater flexibility to meshing algorithms to generate better quality elements.

CUBIT Environment: CUBIT has developed both a convenient command line interface with an extensive command language as well as a polished graphical user interface environment. The GUI is based upon the cross-platform standard QT, which allows the same look and feel on all supported platforms. Also included is a graphical environment based upon the VTK graphics standard which has been optimized for display and manipulation of finite element data and geometry. Fast, interactive manipulation of the model is a tremendous advantage for models with thousands of parts or millions of elements.

For more information on CUBIT, including licensing arrangements and terms see the CUBIT website http://cubit.sandia.gov

New Features CUBIT 11.1

Meshing	Geometry	Properties and Support
Free Meshes Auto Deletion Exodus-II based Sizing Function Tet Cleanup Smooth Scheme Definition Smooth to Target	ITEM Enhancements Small Feature Detection Assembly Misalignment Detection Command Line Proximity Detection Enhanced Tolerant Imprinting Enhanced ITEM Decomposition Suggestions Improved Surface Overlap Detection Doubler Surfaces Extending Surfaces Enhancement Improved Surface Offset Separate Surfaces Stitch Surfaces Simplify Improvement Tweak with Limit Plane Tweak with Multiple Offsets Real Skew Control Webcut with General Plane	Graphics Performance NASTRAN and ABAQUS Boundary Conditions Automatic Sideset Enclosures Measure Void Display Curve Valence Selection Icons Draw Zoom Option Improved Webcut Preview Interactive Clipping Plane Improved Sideset Patch Common_To Grouping Seeded Mesh Groups

Meshing

Free Meshes
In previous versions of Cubit, in order for a mesh to exist, it had to be associated with an owning geometry. Cubit 11.1 introduces the concept of a free mesh, where elements can exist without the need for any associated geometry. Various operations can be performed with a free mesh and are outlined here:

Auto Deletion
Mesh can now be automatically deleted when a parent geometry is modified. Previously, modifying a geometric entity that contained mesh would not be permitted until the user removed the mesh from the entity. The auto deletion status can be controlled from a check box in the options dialog or from the command line. Default for this option is ON (mesh is automatically deleted).

Exodus II-based Sizing Function
Cubit 11.1 introduces the ability to use a field function for triangle and tetrahedral mesh generation for defining local element size. This new feature allows the user to import an exodus II mesh with scalar values defined at the nodal locations that represent target local element size information. The triangle and tet meshing algorithms will now take this sizing information in to account when generating the mesh. In previous versions of Cubit the ability to drive the size of elements used in the mesh through an exodus II-based scalar field function was available only for paving. This new capability is ideal for adaptivity studies where the local mesh size must change based on physical parameters obtained from a previous solution.

Tet Cleanup
The ability to improve the quality of an existing set of tetrahedra has been introduced in Cubit 11.1. Different than the traditional smooth operation that will maintain the original element connectivity, local operations such as swaps and collapses are performed on the specified set of tetrahedra to improve element quality. A volume already meshed with tetrahedra can be specified or a group of free tets can also be used in this command. In addition to the command panel, this capability is also available from the Mesh Quality Power Tool. Selecting a poor quality tet will provide an additional context menu option to cleanup the tets. This will attempt to improve the quality of the tets in the immediate vicinity of the selected tet.

Smooth Scheme Definition
A smoothing scheme can now be specified as part of the smooth command. In addition to the standard smooth scheme definition (ie. smooth scheme laplacian), this will set the scheme for the current smooth operation, (ie. smooth tet all scheme laplacian)

Smooth to Target
For free meshes, the ability to smooth a mesh to a specified geometry has been added. This is useful for cases where a coarse free mesh must be smoothed and snapped to a surface.

Back to New Features

Geometry

Assembly Misalignment Detection
Determining the appropriate merge tolerance for a model can be essential for creating conformal meshes on some models. The merge tolerance is a value that identifies at which distance different entities can be considered the same entity. Many entities will fail to merge because of widespread geometry tolerance or alignment problems that are either too difficult, time-consuming or even impossible to resolve. The ITEM workflow provides a diagnostic tool designed to guide the user to find and visualize the small misalignments that may lead to merge problems. It then presents possible solutions to fix these problems, or the ability to change the merge tolerance to ignore them during tolerant imprinting.

Command Line Proximity Detection
Nearly coincident entities can also be located from the command line without using the ITEM workflow by using a series of new commands to find vertex-vertex, vertex-curve and vertex-surface proximities.

Enhanced Tolerant Imprinting
Coupled with the improved ability to determine merge tolerance, the tolerant imprint operation has also been improved in version 11.1. This operation can now better detect misalignments within the given merge tolerance and modify the local geometry appropriately so that unwanted sliver features are not generated. This can be a tremendous time-savings particularly when dealing with complex assemblies.

Enhanced ITEM Decomposition Suggestions
ITEM provides the capability to list suggestions for webcutting that may help in defining sweepable or mappable volumes. This feature has been enhanced to include additional suggestions. In particular, it will now suggest symmetry webcuts as well as webcuts normal to a curve at a vertex.

Improved Surface Overlap Detection
A new filter_sliver option on the find surface overlap command will enable better detection of surface overlas. This command is most often used for filtering false positives where the surface overlap may detect overlaps following the merge operation.

Doubler Surfaces Used primarily for mid-surface shell modeling, the tweak doubler surface command takes a specified surface and creates drop-down surfaces either normal to the doubler surface or by a user specified vector to a target surface.

Extending Surfaces Enhancement Where previously only a single surface could be extended, using the command create surface extended from surface, the new "sheet" version of the command allows a set of multiple surfaces to be extended at the same time.

Improved Surface Offset Previous versions of Cubit provided the capability to offset individual surfaces to create separate new surfaces. The new "sheet" version of the command allows for simultaneous offset of multiple surfaces from a single volume. The result is a continuous set of surfaces offset from the volume. The images at right show the difference between the old and new capabilities.

Separate Surfaces
Surfaces can now be separated from a parent volume or sheet body. This provides the ability to manipulate surfaces independent of a parent volume or sheet body.

Stitch Surfaces
A new command to join sheet bodies together to create a larger surface has been added. A join tolerance can be provided so that less-than-perfect interfaces can be stitched together. It can also be used to create a closed volume from sheets.

Simplify Improvement
The ability to automatically create composite surfaces based upon neighboring surface normals has been improved. Where previously, strict C1 continuity was required between adjacent surfaces in order to define a composite surface, a relaxed criteria based upon local surface normals, (local_normals) can now optionally be used. The result is generally more surfaces meeting criteria for composite.

Tweak with Limit Plane
The ability to tweak a curve or surface to a target surface has been enhanced so that the extent of the tweak will not go beyond a specified limiting plane.

Tweak with Multiple Surface Offsets
The ability to tweak multiple surfaces simultaneously has been added with the ability to specify different offset values for each surface.

Real Skew Control Skew Control is an option in Cubit to attempt to maintain near 90 degree angles in a sub-mapped mesh by splitting curves using virtual geometry. A new command has been added to Cubit that provides an alternative to the virtual skew control operation, by explicitly splitting a surface into multiple real surfaces in order to maintain 90 degree angle criteria. This command is useful when a sub-mapped mesh is required and virtual operations cannot be used.

Webcut with General Plane
A new webcut option that allows specification of a plane from a variety of plane definitions has been added to this release of Cubit. Included with this command is a general plane definition panel that permits expanded options for defining a plane. This significantly increases the options for webcutting with a plane. In addition a plane can now be defined based on a nonlinear curve.

Back to New Features

Properties and Support

Graphics Performance
Cubit uses the open source library Visual Toolkit (VTK) as the basis for its visualization and graphics. By taking advantage of recent improvements to this toolkit as well as custom internal development, the graphics performance in Cubit has been tremendously enhanced. For example, where geometry models containing hundreds or thousands of entities may have taken considerable time to update or interactively transform and rotate in previous versions of Cubit, it can now perform these operations up to an order of magnitude faster. This now facilitates the interactive modeling of larger and more complex models where previously batch processing may have been required.

NASTRAN and ABAQUS Boundary Conditions
CUBIT has traditionally supported Exodus II as its principal format for assigning and exporting boundary conditions. Cubit 11.1 has expanded this capability by introducing a wide range of new tools to assign, visualize and export boundary conditions for alternate commercial FEA formats.

Assignment: The Cubit command panel now includes a complete set of tools for assigning specific boundary conditions. Some of these include the ability to graphically assign loads, restraints, contact sets, displacements, temperatures, heat flux, convection and coordinate systems. Geometry entities can be interactively selected and physical values assigned for each of these conditions

Visualization: Once boundary conditions are assigned, special graphical symbols can be displayed and highlighted with the model representing the different boundary conditions and their locations. Export: On export, the boundary conditions and their associated values will be transferred to the nodes and elements and written to the selected file. Cubit 11.1 currently supports ABAQUS and NASTRAN formats for these new boundary conditions.

Automatic Sideset Enclosures
Cubit has been enhanced to automatically generate sidesets on the "skin" of a finite element or solid model. This new capability will generate one sideset for every continuous set of element faces or surfaces it discovers. This feature is useful for defining boundary conditions that require a completely enclosed set of faces on the surface of the analysis model such as radiation enclosures. The command to measure voids works well with this new feature.

Measure Void
The volume of a closed set of mesh faces can now be computed. This is useful for computing enclosure volumes where elements do not exist.

Display Curve Valence A new tool has been included that will display all curves in the model color-coded according to the number of surfaces that are attached. Located in the Display Toolbar, it is useful for quickly discovering where surfaces may not be watertight, where curves displayed in red may indicate a non-closed volume. Also added is a new property "num_parents", which is used for extended parsing. The num_parents property has been added that will return the number of parents a given geometry entity has. For example a curve with num_parents=1, might indicate a non-watertight volume.

Selection Icons A new set of icons have been added to for different modes of graphical selection. These include inclusive and exclusive selection as well as xray and polygon selection. These new tools are included in the Display Toolbar

Draw Zoom Option
The draw command is frequently used in Cubit as a way to temporarily display geometry or mesh entities on the screen. The zoom option, appended to this command will now automatically change the viewpoint to zoom and center the specified geometry or mesh entities without the need for an additional separate zoom operation.

Improved Webcut Preview
The ability to preview a webcut operation is provided in various places throughout the Cubit GUI. This operation has been improved to extend the preview plane only to the extents of the target volume to be cut rather than the entire model.

Interactive Clipping Plane A new tool for interactively exploring elements and geometry has been added to Cubit 11.1. This tool, available from the Display Toolbar, will clip the current solid elements and geometry at a given clipping plane. The plane can be interactively manipulated to expose the interior elements or features of the model. This is ideal for exploring mesh quality of solid elements on the interior of a model. This option can be activated from the icons in the Display Toolbar or from the command line so that precise clipping options can be defined.

Improved Sideset Patch
The ability to specify a collection of quads or triangles as a sideset has been enhanced. The ability to define a set of co-centric circles as criteria for selecting faces in a sideset as well as the ability to include multiple surfaces in the definition has been added.

Common_To Grouping
The common_to operator has been as an additional option for grouping entities. This allows the user to create groups of entities that are common to two or more existing groups or entities.

Seeded Mesh Groups
It is often useful to specify a group of faces or triangles on the surface based upon the local features of the model. This new capability provides the option to specify a seed triangle or quad and it will collect all of the neighboring tris and quads until a specified local feature angle is exceeded. Alternatively, a divergence angle can be specified where all faces will be gathered until the normals differ from the seed face by a specified value. This capability is most useful for creating sidesets on a free mesh.

Beta Features

Cubit remains an active development platform for cutting-edge methods in geometry preparation and mesh generation. Some features that are still under development may not be quite ready for release, but may be valuable in some settings. The following is a list of new beta features that have been made available in Cubit version 11.1. Their functionality is not yet complete, has not been fully tested, however in many settings the new capability may be very valuable. Your help in reporting defects and offering suggestions on these features in appreciated. To turn on or off any of the features listed below, issue the following command from the command line:

set developer [on|off]

Wedge elements: The ability to import, export, display and create a wedge shaped element has been added.

Geometry Tolerant Mesh Generation: The ability to automatically suppress features in a model has been added. Given a size tolerance, features smaller than the tolerance will be omitted from the model and the finite element mesh will ignore the features. This capability will create free mesh elements unassociated with the original geometry. It is currently available for tet, tri and quad meshing.

Back to New Features

Limitations CUBIT 11.1

• IGES and STEP import functionality is not currently available for the Linux 64-bit platform.
• The Granite Geometry Kernel is currently not supported on Mac OS. As of this release, PTC has not announced plans to support a Mac OS version of Granite.
• The Granite Kernel supports most of the commands and options used with the standard ACIS implementation in CUBIT. See the Granite document in the users manual for a description of differences between the CUBIT's supported options between Granite and ACIS.
• The Mac OS X port does not support the changing mouse cursors on pre-selection It is recommended that a 3-button mouse be used for the Mac OS X version since interactive transformation utilize all three buttons.
• Smoothing the interior nodes of a free mesh only works with the (default) equipotential smoothing algorithm. The Mesquite smoothing algorithms do not currently function with free mesh.
• Nodesets and sidesets are not necessarily maintained after a refinement operation on a free mesh.

Defects Fixed in CUBIT 11.1

The following items are the user-reported bugs fixed since last release of CUBIT (November 2007). For more information contact Kevin Pendley (kpendle@sandia.gov)

*The defects listed above are only those user-reported issues deemed "critical" or "blocker". For information on other resolved defects contact Kevin Pendley.

Known Defects CUBIT 11.1

The following items are bugs or limitations that may be encountered in the current release of CUBIT. For more information on these defects or to report additional defects contact Kevin Pendley (kpendle@sandia.gov).

*The defects listed above are only those user-reported issues deemed "critical" or "blocker". For information on other known defects contact Kevin Pendley.

Documentation Updates

CUBIT 11.1 How To

New ITEM Tutorial

CUBIT 11.1 Contents of Release

Cubit Program: The installation package includes executables and libraries, packaged in tar.gz files for Unix machines. For Windows, the package is in a self-installing executable, and for Mac OS X a .dmg file is provided. Both a command line and GUI version of CUBIT are included with the installation package for all platforms.

Documentation: UNIX, Windows and Mac versions include full online documentation. Windows also includes .chm (Windows Help File), of the complete documentation that can be run separately from CUBIT.

Platforms Supported

CUBIT 11.1 supports the following Platforms

• Linux RedHat Enterprise 4, 32- and 64-bit
• Windows 2000, XP, Vista, 32- and 64-bit
• Mac OS X, Power PC and Intel based (universal)

Non-Sandia Users

CUBIT is available to for government and academic use. For information on licensing CUBIT go to the follow URL: http://cubit.sandia.gov/licensing.html. For current CUBIT users, CUBIT 11.1 may be downloaded from the website at the following URL: http://cubit.sandia.gov/downloads.html. If you obtained a password since the release of CUBIT 10.0, your password should work for 11.1 also.

Sandia Personnel Only

Windows

Download a Windows installation file from the dropzone. Go to the following directory \\dropzone\public\cubit\Windows. Copy the file Cubit.WindowsGUI.11.1.exe to your windows hard drive. Double click on the file and follow the installation instructions.

MAC OS X

Download a Mac OS X disk image file from the dropzone. Go to the following directory \\dropzone\public\cubit\MAC_OS_X. Copy the file Cubit_GUI_11.1.dmg.gz to your Mac harddrive. Use gunzip to unpack the disk image file.

UNIX/LINUX LANS

Check with your local LAN administrator for instructions on how to access CUBIT on your local LAN. In most cases typing one of the following commands at the UNIX prompt should allow you to execute CUBIT:

Contact Information

CUBIT Help

For general technical questions including download, installation and CUBIT technical assistance.

cubit-help@sandia.gov

CUBIT Licensing and Passwords

Jacqueline (Finley) Hunter
Cubit Licensing
Phone: 505-284-6969
Email: jafinle@sandia.gov

CUBIT Support Lead

Kevin Pendley
CUBIT Support Lead
Phone: 505-284-1957
Email: kpendle@sandia.gov

CUBIT Project Lead

Steven J. Owen
Sandia National Laboratories
Computational Modeling Sciences Department (org. 1421)
Phone: 505-284-6599
Email: sjowen@sandia.gov