| ADAMS/Flex Release Notes |
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| What's New |
Flexible Body Swap Replacing a rigid part with a flexible part is much easier in the 2005 release because of the Rigid->Flex swap functionality. Rigid-only MNFs are also available. Switching from one flexible body definition to another is also improved through the analogous Flex->Flex swap functionality. The rigid->flex swapping functionality in ADAMS/View lets you replace a rigid body with a flexible body. You access it by selecting:
The process starts by selecting a rigid body to replace and providing an MNF (or flexible body). If an MNF is not available, you will have to generate one using a finite-element package or ADAMS/AutoFlex. Once the MNF has been provided, the Rigid->Flex dialog box provides three easy-to-use positioning techniques to align the flexible body with the rigid body:
While positioning the flexible body, you can quickly switch to a two-part view consisting of only the rigid body and new flexible body. After the flexible body has been positioned, the Rigid->Flex dialog box displays a table of markers and connections that are to be migrated from the rigid body to the flexible body. The closest attachment nodes are automatically detected and the table can be easily sorted. If the proposed attachment node for a marker is not the desired one, you can select a different one, or launch a Node Finder to search for a different node. If the attachment nodes are offset from the marker locations, you have three options:
After reviewing the table and making any modifications, select OK, and all the markers and connections will be migrated to the flexible body as you requested. The rigid body will be deleted, or optionally kept and deactivated. In addition to Rigid->Flex swapping, ADAMS/View offers Flex->Flex swapping, which is similar to the Rigid->Flex swapping. It may be accessed with the menu picks:
For an example of this feature, see Knowledge Base Article
1-KB12258. |
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The 2005 release of MSC.Nastran will have a "Rigid" option, or what you can consider a geometry-only option for MNF generation. This allows you to quickly generate an MNF from the BDF without laboring over connection points, normal modes, or superelements. The MNF simply contains the element discretization and is rapidly generated. A rigid-only MNF like this allows you to build a flexible body in MSC.ADAMS, connect it to a model, and run a "rigidized" flexible body simulation. That is, the flexible body is treated as a rigid body. The value of this is that during model creation, you can quickly generate an MNF, bring it into MSC.ADAMS and examine where you want the connections to be made and at which nodes. You can even use the Rigid-to-Flex swapping dialog box to incorporate it into your model. Once the attachment nodes have been identified (using the Rigid->Flex swapping tool), you can return to MSC.Nastran and define your ASET degrees-of-freedom and compute an MNF with modes. The ADAMS/Flex Toolkit also allows you to a convert a flexible MNF to a "Rigid-Only MNF" through the MNF optimizer. Generating an 'Rigid-Only MNF' from an MNF containing modes is probably not something that you would routinely do, but it reduced the size of the MNF, making the file easier to share, and fostering collaboration during the early stages of flexible model development. For an example of this feature, see Knowledge Base Article
1-KB12413. |
Shortened Stress and Strain Modes Many customers have been looking for ways of reducing the size of their MNF files while improving performance. In ADAMS/Flex 2005, there is the option of keeping a reduced or shortened set of stress and strain modes. This gives you a compact MNF as well as faster hotspots retrieval. If stress (strain) recovery was requested from the finite element program when generating the MNF, the MNF contains grid point stresses (strains) for every mode. The collection of grid point stresses (strains) for a given mode is referred to as a stress (strain) mode. Typically, stress (strain) values are only requested from the finite element program for a subset of nodes in the MNF. A new text box, Stress & Strain Modes, has been added to the MSC->MNF Translator panel in the ADAMS/Flex toolkit. This option specifies how the MNF stores stress (strain) modes, particularly for nodes where stress (strain) was not requested from the finite element program. When set to SPARSE, modal stress information is only stored for those nodes that MSC.Nastran had computed stress and stored in the OUTPUT2 file. When set to FULL, the translator behaves as before, storing modal stress information at every node. This results in zero stress for those nodes that were not computed by MSC.Nastran. It is important to note that stress (strain) modes stored in a sparse format creates an MNF that is not compatible with previous versions of MSC.ADAMS. When set to Remove zero entries, the resulting MNF will be as equivalent as the Sparse option. This option, however, can be computationally more expensive than Sparse because the null stresses are removed after the fact, instead of up-front. This text box is also available in the MNF->MNF Optimizer. Here you would use the Remove zero entries option to condense an MNF with zero stress states, down to one with shortened stress and strain modes. The Sparse option allows you to maintain a reduced MNF during MNF optimization. It does not reduce an MNF that is already full. The Full option provides backward compatibility. It allows you to expand a sparse MNF so it can be processed in an earlier version of MSC.ADAMS. MSC.Nastran 2005 will support the direct generation of a sparse MNF. This capability is not yet available directly from other finite element (FE) programs; you will need to optimize your MNF using the ADAMS/Flex Toolkit. See the online help for ADAMS/Flex for more information. For an example, see Knowledge Base Article 1-KB12412. |
Documentation Improvements ADAMS/Flex Documentation Improvements The ADAMS/Flex documentation includes information on swapping rigid and flexible bodies. It also contains an updated tutorial that lets you step through replacing a rigid body for a flexible one. In the online help, select the Examples tab and then Getting Started Using ADAMS/Flex. Overall Documentation Improvements For MSC.ADAMS 2005, we've made improvements to the MSC.ADAMS help:
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| Changes |
Flexible Body Automatic Damping (Experimental Feature) The 2005 release introduces an experimental, step-size based adaptive damping for flexible bodies, which will allow simulations to run more robustly. It is envisioned that this will be useful in durability simulations and other applications where high-frequency modes are not of concern. We are interested in how the new damping model affects performance (CPU time), robustness, and quality of results for your models. Please note that this feature in not intended for production use, and may be removed in a future release without prior notice. Use: Set the environment variable for auto_damping and it overrides the traditional flex-body default damping. variable: MDI_FLEX_BODY_TESTING_OPTIONS
DOS Shell set MDI_FLEX_BODY_TESTING_OPTIONS=auto_damping(1.0, 0.01, 1.0) debug Korn Shell export MDI_FLEX_BODY_TESTING_OPTIONS="auto_damping(1.0, 0.01, 1.0)" UNIX setenv MDI_FLEX_BODY_TESTING_OPTIONS "auto_damping(1.0, 0.01, 1.0)" When using auto_damping with the F77 Solver the .msg file will contain an informational message listing your damping settings: Auto-Damping Parameters for Flex Bodies Gamma = 1.0 When using the ADAMS/Solver (C++) with the debug option, you can see a confirmation that auto_damping is being used by noting this information underneath the .msg file header... Flexible Body Testing Debug Information Max. increase per step = 1.000000e-02 Starting value for CRATIO = 1.000000e+00 For an example, see Knowledge Base Article 1-KB12259. |
License checking of MSC.Nastran ADMOUT=ONLY feature MSC.Nastran 2004 had introduced a new interface for generating MNFs. This interface allowed the direct creation of MNFs without translating an OUTPUT2 file to an MNF. This ADAMS Interface in MSC.Nastran is a licensed feature, and offers several advanced features. However, to allow time for users to transition to the new interface it was still possible to generate an OUTPUT2 in MSC.Nastran 2004 and later translate it to an MNF without additional licensing. This was accomplished with the following Case Control command:
For MSC.Nastran 2005, the release transition period has ended, so the ADMOUT=ONLY option has been deprecated, and obtaining an MNF from MSC.Nastran will always require the MSC.Nastran/MSC.ADAMS Integration license. |
Additional Changes 42795 Flexible bodies have full support of I3 and I4 inertia invariants when using in ADAMS/Solver (C++). Often these invariants are not needed, so a warning message will be issued letting you know when they may be disabled, for example:
11067 The location and orientation of a flexible body may now be directly desginated from the Create a Flexible Body dialog box. 42564 Messaging has been improved to help you identify the source of the problem when MNF file(s) referenced in a binary file cannot be found when a database is opened. Suggestions are made to use the aview.pth file, as shown in the sample message below:
45063 The MNF optimizer now keeps the nodal masses in the MNF file. This is especially advantageous for subsequent usage of the flexible body in ADAMS/Vibration as it will enable the visualization of modal energy distribution. See What's New for ADAMS/Vibration for more information about modal energy distribution. 46020 With the introduction of automatic dummy parts in ADAMS/Solver (FORTRAN), the flex-swap dialog boxes, and flexible body support in ADAMS/Solver (C++), ADAMS/View no longer needs to create dummy parts for various constraints/forces attached to flex bodies. Some undocumented functionality that created those dummy parts has been removed since it is now obsolete. |