Run Analysis and Export a FEM File

Define and run a linear static, normal modes, or buckling modes analysis, then export a FEM file.

The analysis includes materials, concentrated masses, and loads and supports, but ignores constraints.

Location: Structure ribbon, Run tools, Analyze icon.

Run a Structural Analysis

Select a solver, run options, and run settings to run an analysis.

Before running a structural analysis, you must first define one or more load cases containing both loads and supports.

  1. Select whether to use the SimSolid or OptiStruct solver in the Preferences under Run Options.
  2. On the Structures ribbon, click the Run group label, then select whether to run the analysis locally or in the cloud on Altair One. You can also run analysis on a remote server, either manually or by setting up and using an Altair PBS server. (These options are only available for OptiStruct analysis.)


  3. Select the Run Analysis tool on the Analyze icon to define settings for the analysis.
    The options will vary based on whether you are running a SimSolid or OptiStruct analysis. Linear static analysis is run automatically, and you can choose whether to run a normal modes analysis.
    Run SimSolid Analysis Run OptiStruct Analysis
  4. If you have created multiple load cases, click the button next to Load cases and then select the checkbox next to each load case you want to analyze. Each load case will produce a different result.
  5. Click the Run button to start the analysis.
  6. Use the Run Status tool to monitor the progress of the run.


  7. When the run completes, click the green flag on the Analyze icon or double-click the name of the run in the Run Status window to view the results.
Tip:
  • Once the analysis is complete, you can interactively view the results using the Analysis Explorer.
  • You can save or delete runs using the right-click context menu in the Analysis Explorer or Model Browser.
  • If you don't want to wait for the run to finish, you can close the Run Status window and continue working in Altair Inspire. You can check on the status of a run at any time by clicking the Run Status tool on the Analyze icon.
  • There is no design space for an analysis, so there is no requirement to break up your model into design and non-design spaces and apply loads only to the latter. Any part can be analyzed. However, if you intend to optimize the part later, it is beneficial to split your part into design and non-design spaces and apply appropriate loads and supports prior to running a baseline analysis.

Run Options: SimSolid vs OptiStruct

Use the options on the Run Analysis window to define your analysis. Options vary based on whether the SimSolid or OptiStruct solver has been selected.

Run SimSolid Analysis Run OptiStruct Analysis

Name

When you run an analysis, the name of the run defaults to the name of the model. However, you can assign your own name to the run in the Run Analysis window.

Element Size (OptiStruct)

The element size dictates the quality of your optimization results. In general, the smaller the element size, the more accurate the result, but the slower it will run.
Note: To improve overall performance, when a CAD file is imported the mesh sizes are not calculated and are shown as Auto. Click the icon to display the Element Size.

The element size is calculated from the smallest features in the CAD. Cleaning up the CAD so there are fewer features will help jobs to run faster.

Normal Modes

You can choose whether or not to include normal modes, and how many, in your analysis. The results show the shape of the vibration at that frequency. You may also select whether to include supports from a particular load case in the drop-down menu.

Buckling Modes (Linear Buckling or Eingenvalue Buckling)

Buckling modes are used to predict when a part will bend or collapse under load. You may select the number of modes and which buckling load cases to include. The resulting buckling load factors help you determine the load required to cause your part to buckle. If the value is in-between -1 and 1 buckling is expected for the given load.

Solution Adaption (SimSolid)

SimSolid provides three solution adaption objectives to control solution accuracy.

  • Select For Stiffness (Faster) for general load path prediction and modes. This uses three adaptive solution passes and is typically the fastest solution method.
  • Select For Stress for more detailed stress calculation. This uses four adaptive passes and activates additional logic to more accurately refine the solution in areas of high stress.
  • Select Custom to choose your own custom settings in the Preferences.

Modal Prestress

Prestressed loadcases are linear.

Depending on preloading conditions, the resulting effect could be a weakened or stiffened structure.
  • If the preloading is compressive, it typically has a weakening effect on the structure (for example, column or pillar under compressive preloading).
  • If the preloading is tensile, it typically has a stiffening effect (for example, rotorcraft blade under centrifugal preloading).

Speed/Accuracy (OptiStruct)

Select Faster when stresses are not a major concern and testing your model to ensure that the kinematics of your loads and supports are correct. If you need more accurate results, select More accurate and rerun the analysis to achieve more precise stress and displacement results. This will also increase the run time. More accurate generates second-order elements.

Gravity

If the weight of a structure is a significant portion of the load it is bearing, then you should include gravity when running an analysis. Gravity pulls toward the negative z direction by default, but you can change the direction using the pull-down menu.

Load Cases

A load case is a set of loads and supports that act on a model at one time. You can assign loads and supports to specific load cases using the Model Browser or context menu. Then when you run an analysis, you choose which load cases to include in the Run Analysis window.

Inertia Relief

Inertia relief allows the simulation of unsupported structures. Typical applications are an airplane in flight, suspension parts of a car, or a satellite in space. With inertia relief, the applied loads are balanced by a set of translational and rotational accelerations. These accelerations provide body forces, distributed over the structure in such a way that the sum total of the applied forces on the structure is zero

Export a FEM File

Export a .fem or .ssp file using the Export button on the Run Analysis window.

  1. On the Structures ribbon, select the Run Analysis on the Analyze icon.
  2. Click the Export button on the Run Analysis window. For OptiStruct analysis, you will need to select a unit system for export.
  3. Choose a directory and a name for your file, then click Save. SimSolid results will be saved .ssp files, and OptiStruct results will be saved as .fem files.
  4. When the export is complete, double-click the name of the run to open the directory where the results file is located.
Note: Deleting an exported fem will not delete the fem file or folder. It will just remove the item from the list in the Run Status window.

Run Status

View the status of the current run, as well runs for the current model that have not yet been viewed. To see all past runs, you need to view the run history.

  1. Hover over the Analyze icon, then select the Run Status tool.

    The run status window is displayed.

  2. When the run is complete, review its status.
    Status Description Note
    The run completed successfully. This is also indicated by a green flag above the Analyze icon. You can click the green flag to display the results.
    The run was incomplete.

    If running an analysis, the run was incomplete. Some but not all of the result types may be available. You should run a new analysis to generate complete results.

    If running an optimization, the run was completed but with warnings or violations. Double-click the name of the run in the Run Status dialog, and then click the Design Violations button in the Shape Explorer for more information.
    The run failed and no meaningful results are available. This is also indicated by a red flag above the Analyze icon.
  3. View one or more runs.
    • To view a run, double-click the row.
    • To view multiple runs, hold down Ctrl or Shift while clicking the rows, and then click the View Now button.
      Note: If several runs are associated with the same part, the result from the most recently completed run for that part will be activated in the modeling window.
Tip:
  • To open the directory where a run is stored, right-click the run name and select Open Run Folder.
  • To view deleted or previously viewed runs, click the History button.
  • To delete a run, select the run and press Delete. You can also delete runs using the right-click context menu in the Analysis Explorer and the Model Browser.

Run History

View, sort, open, and delete past runs for the current and previous models.

Once you have viewed an analysis run, it is removed from the Run Status window but can be viewed using the Run History table.
  1. Hover over the Analyze or Analyze Fluids icon, then select the Run Status tool.

    The run history is displayed.

  2. Review the status of the run.
    Status Description Note
    The run completed successfully.  
    The run was incomplete.

    If running an analysis, the run was incomplete. Some but not all of the result types may be available. You should run a new analysis to generate complete results.

    If running an optimization, the run was completed but with warnings or violations. Double-click the name of the run in the Run Status dialog, and then click the Design Violations button in the Shape Explorer for more information.
    The run failed and no meaningful results are available.  
  3. To view a run, double-click the row.
Tip:
  • To open the directory where a run is stored, right-click the run name and select Open Run Folder. The default directory where the run history is stored can be changed in the Preferences under Run Options.
  • By default, you will receive a notification when the run history exceeds a certain size. You can change the size limit or turn off the notification in the Preferences under Run Options.
  • To delete a run, select the run and press Delete.