Translating I-DEAS Data
In general, you build flexible bodies in Adams Flex by importing an Adams modal neutral file (MNF) representation of the flexible component. You can obtain an MNF of a flexible component in I-DEAS by performing a Superelement Creation analysis of the component's finite element (FE) model.
The steps are listed below. Click a link in a step to learn more.
■Mesh the model in the Meshing task.
Note: You can choose to mesh the model first, particularly if you want to create DOFs on nodes.
For more information also see the I-DEAS guide, Finite Element Modeling User's Guide.
Creating a Connection DOF Set
To create a connection degree-of-freedom (DOF) set:
1. Create a finite element (FE) model of the flexible component. Make sure the task is the Boundary Conditions task.
2. Set the analysis type to Superelement Creation.
3. Define DOFs at each joint or applied force marker location of the flexible component. You can define DOFs on geometry, or, if the model is already meshed, on nodes.
4. In general, specify all six (translational and rotational) DOFs at interface locations with beam or shell elements, but only three (translational) DOFs for solid-element meshes.
5. Create a boundary conditions set using the Boundary Conditions Management form. Select Connection Dof Set to use the DOF set you've created to define connection DOFs.
At this stage, you can also specify additional sets, such as restraint, constraint, or temperature sets. Use constraint sets to introduce constraint equations in your FE model. Use temperature sets to specify the temperature of the analysis for temperature-dependent materials. In general, a restraint set isn't recommended for superelement creation because it permanently grounds the component at each specified restraint location, possibly providing insufficient flexibility information for your component.
Meshing the Model
Mesh the model in the Meshing task. After you generate a mesh of your FE model, it's a good idea to obtain a list of the solid properties of your mesh. While this isn't necessary for modal neutral file (MNF) transfer, you can use this data to check the results of the MNF transfer. See
Checking the Results.
Solving the Model
To solve the model:
1. In the Model Solution task, create a Superelement Creation solution set using the boundary conditions set you created earlier.
2. On the Create Solution Set form, select Options, and then select Solution Control. Specify the number of normal modes and the optional frequency range that you want to capture for your component in the modal neutral file (MNF) for Adams simulation.
3. Request stress modes in the MNF by selecting Output Selection... in the Solution Set form, and then specifying Stress... Store in the Output Selection form.
For shell element models, specify in which shell surface to output stresses via the MDI_MNFWRITE_OPTIONS environment variable. For example, one of the following keywords needs to appear somewhere in the MDI_MNFWRITE_OPTIONS environment variable depending on the desired surface:
Surface KEYWORD options
Top TOP / top
Middle MIDDLE / middle
Bottom BOTTOM / bottom
Membrane MEMBRANE / membrane
Bending BENDING / bending
4. Select Manage Solve. Specify the name of the MNF to be created, with the .mnf extension.
5. Select Solve. If errors or warnings occur, select Report Errors/Warnings. Resolve any significant errors before you proceed.
Checking the Results
The following steps are not necessary for superelement creation but they provide simple checks and measures of a successful modal neutral file (MNF) transfer.
After you solve, compare the total mass and inertia properties of the MNF listed either in the analysis log file or list region with those obtained when you meshed the model. Check that they are in close agreement. Note that the values listed for the MNF are given in SI units, and you may need to convert them to model units for comparison.
Switch to the Post Processing task to perform the following checks:
■Select Select Results. On the Results Selection form, check that the number of normal modes solved equals the number of normal modes requested on the Solution Control form plus the number of degrees of freedom specified in the Connection DOF set.
■Animate some of these modes to ensure that there are no problems (such as breaks or cracks) in your FEA. The first few modes (up to six) should be rigid body modes (with a frequency close to zero), and the next few modes should closely resemble the natural free vibration modes of the component. The higher frequency modes should represent local flexible effects of the component at the connection DOF.