Submodeling Capability

[Anonymous]

Submodeling is a powerful tool available in many analysis tools. Even if the model sizes can be increased with currently technology, there is still a need for submodeling capability to analyze certain areas of a design. Development team can start with extending the interpolation tool for temperature results to displacement results and such.

[PipePakPat]

Hello Can,

Submodeling can be accomplished by several methods while using the Simulation Mechanical software, but this process is not automated or supported through the existing software interface.

Submodeling is accomplished by transferring the displacement (and perhaps rotations) from completed finite element analysis results from one model, and applying those displacements as input loads on a different finite element model which will then be analyzed to determine the overall states of deflection and stress.

The most basic example of this process would utilize an initial beam element model of a frame structure to determine the deflections and rotations of the model due to loading.  One would determine the portion of the model which demonstrated the most significant stress, then create a brick element "Sub-model" of that  portion of the geometry.  Once this sub-model is meshed, one would then generate beam elements on the cut faces of this sub-model where this geometry would have extended to create the full model.  The generate beam elements would be drawn from each node of the cut face to the centroid of that cut face.  These beam elements would be defined so that they are relatively stiff in comparison to the original geometry, then the full model's deflections and rotations are collected and applied to these centroid locations as "Displacement Boundary Elements".

Once all of the cut faces are constrained, any additional loads such as gravity and local forces are applied and the model is analyzed. 

The transfer of resulting deflections from one geometry to another is the the most painstaking phase of this process.  It is in this phase that automations is advantageous.  I have created such automations using Visual Basic run through an Excel Macro environment.

A more complex example would be the transfer of deflections from one 2D or Brick model to another.  Because the mesh or nodal locations are not shared between the two geometries, the deflection results must be interpolated from one mesh to the other.  Once these results have been interpolated to the new mesh, then these deflection results can be selectively added as displacement boundary conditions on the new geometry.  Autodesk Simulation already provides this functionality from an executable located in the software installation directory.

"ndxmap.exe" is the executable responsible for interpolation of results from one mesh to another.  It was originally created for the interface so that heat transfer results could be applied to ever changing mesh refinement for the purpose of thermal stress calculations.  This utility also can transfer displacement results from one mesh to another.  This utility requires that the original model's finite element database and results exist, as well as the new model's finite element database.  A new results file will be created for the new geometry, which can then be queried using the Excel macro above to automate the application of this displacements to pre-specified locations on the new model's geometry.

This is all pretty complicated and when one utilizes the existing utility run from the command prompt, running the Excel Macro and maintaining the finite element geometry within different models or design scenarios, we can acknowledge that even this level of automation is still cumbersome.... yet, this is what presently exists, and I would be glad to share this automation with you if you choose.  Unless there is an overwhelming need for this functionality, then I would not expect this type of automation to be incorporated into the software interface.

Pat

[nmt]

Hi all,

I also would like to see a method for submodelling inside Sim mech.

For advanced fatigue analysis of welds in a large structure this is a powerful metod in competing softwares.

Anyway I would be glad to get more info about Pat's existing methodes and macro.

Best regards / H. Nilsson

[PierreMalouf8976]

Hello to the group, I also would like to see an easy method that would permit sub-modelling to be done inside Autodesk Simulation Mechanical. I have done some research and noticed there is a school of thought based on the fact that computers/software is more powerful today, therefore simply refining the mesh eliminates the need to do sub-modeling. That is the way I understood it. The reality is quite different. A few years back I worked on a project where this approach was used (i.e. refine the mesh) to be able to model the area of interest. In this specific case, a high stress area around a 1/16-inch radius fillet located on an inside corner. This area had to be included in the model because it was a known crack initiation region. The analysis was fairly involved because it required doing a non-linear analysis with MES. In addition the run-time were fairly long because of the need to have a fine mesh. It is my opinion the analysis would have been quicker to run and less complicated if Sim Mech had the sub-modeling capability. The analysis would have been run with a coarse mesh and the results from that run used as boundary conditions for a second run with a finer mesh on the sub-model. Suffice it to say I sincerely believe being capable of running a sub-model within Sim Mech would be a very useful tool. In the meantime I would like to know more about Pat's existing methods and macros. Regards, Pierre Malouf