During our test drive with Autodesk Nastran In-CAD, we prepared a simple linear static analysis, the setup of which went smoothly. The biggest benefit was at the very least learning how Autodesk expects Inventor users to behave around a more robust simulation model and Inventor acting as a pre-processor for Nastran. In this article I will take a look at those results using Inventor now as the post-processor, how they were configured, and then some closing comments regarding the entire experience.


The results were consistent with what you’d expect.  Each results plot can be configured with the typical smoothed and contoured visualization. A well simplified configuration dialog allows users to configure the results plots with a basic set of options. I know that the company is looking at how users feel about this particular part of the UI; I feel that it is pretty easy to pick up on and use.

Autodesk Nastran In-CAD Stress Results Plot

Tip: You can turn off your mesh view for specific components using the Mesh Table

Each 3D results plot is stored in the overall template, and can then be employed in any of the case studies as desired. The standard array of plot types are available including displacement, Von Mises stress, principle stress, and more. Cross sectioning is configurable within the plot setting, permitting the particular plot to always section the model. Additionally, models can be sectioned through the Inventor interface, and then view the results.

Autodesk Nastran In-CAD Display Options

Tip: Configuring cross section in the saved results plot template permits additional information such as the element results along the cross section to be reviewed graphically. This is not the case when simply reviewing plots with Inventor’s section views enabled.

 Nodal information per plot style can be reviewed by turning on the nodal display, and passing the cursor over the nodes.

Autodesk Nastran In-CAD Results Plot

 Tip: Nodal label displays can be turned on by right clicking the Mesh categories Node header, and picking Query Display.

XY plots can be made by nodal results (such as displacement) and by element (stress, etc.). These need to be added by picking the respective node(s) or element(s), by a defined group of these, or by picking a model entity, such as an edge.

Autodesk Nastran In-CAD Simple XY PLOT

The user interaction in this process was a bit awkward, and definitely not on par with the foregoing UI experience. Moreover, the configuration of the plots was limited, and once a plot was created, there seemed to be no manner in which to change it. If you wanted something different, you have to discard the unwanted plot, and start over with a new one (multiple plots can be saved).

Note: It occurred to me that it might be possible to establish the plot by group, and then alter the group, thereby altering the plot criteria. I have not confirmed this possibility.

Reporting was similar to other reports I have experienced with Autodesk analysis software. The basic model information is provided, along with basic narratives that contain maximum type results data. These narratives can be configured during the report generation, which is then saved to the hard drive in an HTML format, with associated 3D colored plot images.

Autodesk Nastran In-CAD Report clip

The plots images are cut from the current model state, which may or may not be sufficient to deliver a respectable report. This is also typical of most Autodesk analysis software. I have never developed reports from a stock report plot (from any post-processor), but instead use them as a starting point to create a final report. I believe that most analysts do this, as it is impossible to predict exactly what aspect is important in any particular study, and that Autodesk understands this. As such we often see little enhancement of the results engines. This could be enhanced by an option to designate pre-formatted plots for reporting (see my mote in the comments below).

I do like that the report system previews each narrative in an editable window before it is finalized, which can allow users to develop a more substantiate report to start from. While some reporting options are configurable (in the overall options of the In-CAD software), this is limited.

Tip: Remember to create a new Analysis subset! (Like a new Inventor ‘Scenario’) Subsequent runs of the same analysis will overwrite the previous results. If you (like I just experienced) get a failure and overwrite your previous good results, you will feel quite foolish.

Closing Thoughts

Nastran is a fabulous analysis solution, no doubt. Having the ability to reach out to Nastran directly from Inventor is also a welcomed reality now. In-CAD is easy to learn and you can be up and running in less than an hour.

You will need some hardware to run In-CAD. Meshing can rapidly become quite complex without having to beg for it. While you may be used to running Inventor comfortably on a machine, In-CAD will suck up resources quickly, depending on how carefully you limit your model DOF and mesh complexity. Without trying it, I feel safe in predicting that you won’t be doing anything substantiation on a standard CAD station while solving studies with plasticity in non-linear analyses. (Cloud solving anyone?)

In-CAD model setups will increase your assembly and model file size. This is something that should be considered and a reasonable strategy imposed from the start. It stores the results separately, but the Inventor files still take on a large amount of data compared to the original file size, but not outrageous.

I did find some areas that I either expect to see adjusted soon, or desire to have available. These include (but not limited to):

  • Nodal results labels color can’t be read through results color plots, nor can it be altered; contrasting colors should be more dynamic
  • Need tools to pick all nodes from component, entity, or element selection, including a concext menu option
  • Need component groups
  • Need Results Properties Sets – Users should be able to create a ‘results property set’ that is characterized by a result plot style, which will act as a container for components. You simply identify your desired components in the set. Results only show up for those components. Very handy for studies that involve numerous components, but where the results are focused on select areas
  • Make it easier to exclude specific components from the results; meshes can be turned off, but the results continue to consider those bodies
  • More comprehensive and editable XY plot results
  • Ability to save 3D results plots in state (e.g. components, view angle, cross sectioned, criteria, etc.) and designate these as well as XY plots for reporting, thereby automating the process a bit more.

While this UI is not tuned for diehard analysts, I think In-CAD is a good tool to allow Inventor users (that don’t want to leave Inventor and learn a very complex interface) to have access to the power that Nastran offers, as well as analysts that need a CAD platform for their studies. There are limitations using In-CAD, in that some features in the Autodesk Nastran solver are not accessible without another pre-processor.  In-CAD will not easily replace a full-featured pre-post-processor that analysts may be relying on currently.

Companies purchasing Nastran should consider the type of pre and post processor that they require. As I understand it, the Inventor In-CAD Nastran deck is compatible with any Nastran pre-processor. In areas where both CAD users and analysts will be using Nastran, a strategic purchase of both Nastran and Nastran In-CAD licenses would be a wise choice. While the cost is the same, companies would still need a processor for the Nastran only license.

Note: The Autodesk Nastran Editor is not available for the Nastran In-CAD license.

I feel it is important to mention here that Autodesk included the Nastran solver as an option to their subscribers of Autodesk Simulation Mechanical, their full featured Pre-Post processor and solving package. The last information I was given indicated that the company was doing so free of charge. If users need Nastran and more pre-post capabilities, they might be wise to consider Simulation Mechanical as a viable alternative.