Preparing any of the analysis in Autodesk Simulation Multiphysics 2012 (formerly Algor) requires basic groundwork, such as meshing, to be complete before the analysis can actually begin. This is the same for all analysis types, be it linear, non-linear, fluid, etc. The following are some notes from my initial work in Simulation Multiphysics.
Meshing is a topic unto itself, and could contain volumes of information including algorithms and options used within this software. I can do more justice with it in another article, at a later time.
All simulations are meshed first, using the common processes. Mesh types include bricks, tetrahedrons, wedges, etc.. Keep in mind, however that certain options might be preferred over others, depending on the analysis type desired.
Simulation meshes the surfaces first. It has a similar interface to that of Inventor, in that element sizes can be tuned by ratios to that of the overall component size in a very simplified interface. Actual unit sizing can be used instead. The simplification comes from the model settings (below) which are currently set to automatically derive the surface mesh geometries from those of the overall model. Should this ‘automatic geometry-based mesh size function’ be turned off, substantially more detailed mesh settings are turned on in the surface options tab.
Once the surface mesh is satisfied, the interior solid meshes will be formed from the surface mesh, and must be completed before the actual analysis can begin. Once meshed, the process need not be repeated.
One cool point to mention about meshing is the reporting. If an error occurs during the meshing process, the specific face(s) are noted in a log, along with a link that enable you to zoom in to the specific area where the problem exists. A really sweet feature when dealing with tight radii and the like. I used this a great deal until I was able to simplify the model sufficiently.
Another thing I should mention is James Herzing from the SimSquad at Autodesk has developed a basic meshing guide that should be available in one of the AU2011 classes, and likely at the Simulation events. Bug the SimSquad guys until they give you a copy. I had the privilege of reviewing the document, and I must say it’s pretty nice. If you are new to meshing in Simulation, this is a must read.
Simplification is King
If you do not want a half gig mesh to run through EVERY PASS of the analysis, then you’ll need to shed some weight prior to meshing. The larger, more complex the mesh, the exponentially greater the time involved in the analysis. Complex analyses can easily take all night to run. I used Inventor on one design which was laid out with simulation in mind. However I use Autodesk Fusion to take care of the remainder of my model simplifications.
Nodes and Elements
Once the meshing process is completed, Simulation catalogues each node, element, and face with an identification number, which can be then be tracked through the entire analysis. Simulation is completely oriented towards nodes and elements. Coming from Inventor where surfaces are the normal method of interaction, dealing with nodes when I wanted surfaces felt quite awkward. Two weeks later, however, the process of selecting specific nodes became quite routine.
Forces are not usually applied to the entire length of a surface, and being able to narrow that application to a more finite region can make a difference in the analysis. I returning to Inventor stress analysis once, and felt out of place when I couldn’t pick specific nodes. It was then that I remembered all the times that I had to split a face just to apply a load to a region of a planar surface. I started to miss Simulation immediately.
Leveraging Inventor Start Simulation Export
I learned that using the Inventor Stress Analysis Environment can speed some preparations. Simulation Multiphysics will open any Inventor part or assembly file with no problems. However, it does not pull over the material properties in all cases until a simulation scenario is present in the Inventor design. Additionally, other settings can be pulled over from the scenario as well.
The tool that pulls all this together is the ‘Start Simulation’ export on the Inventor Add-Ins tab. This allows the model to be exported directly to Simulation Multiphysics 2012, and with it the options to pull in Simulation data as well. This is by far the fastest method, and when updates occur, these can be introduced into the Simulation environment automatically.
Using this tool, the export process opens Simulation, drops the Inventor assembly in, and with it the simulation data, material properties and surface contacts in one shot.
One other notable point that is by no means the least important is the only method of employing the Inventor Level of Detail in Simulation Multiphysics is to use the ‘Start Simulation’ export process.
Similar to Inventor, Simulation can save your setups and design information as separate scenarios that can be configured in any way you desire. I’ll skip the basics and say that these were extremely helpful when passing the analysis off to the Autodesk SimSquad, who then made a copy of my scenario and tweaked it as they needed. I was then able to compare the two without having to open separate files.
Element Types are numerous in Simulation Multiphysics, and are dependent on which type of simulation is desired. This list is related to the non-linear group. What I want to stress is the need to study these and determine which is best for your needs, and to keep in mind that some options are no available in all analysis types. I found a help page that was a great reference.
This is where we break off from basic preparation, and start getting into specifics of non-linear analysis features. The next article will include notes from using the non-linear Mechanical Event Simulation, where the focus is on humanistic responses to inertia in Autodesk Simulation Multiphysics 2012.