Simcenter 3D Solutions How to assign new FEM models to existing simulations with "ReplaceFEM"?

Simcenter 3D


During the design process it's not uncommon that small changes occur for a component, when the evaluation of the design by running simulations has already begun. These changes in the design lead to changes in the meshing and changes in the structural FE results which are the input for simulations like e.g. the Fatigue Life Prediction via Specialist Durability. Normally, the simulation would have to be redone from scratch, but there is an alternative. Simcenter 3D offers the option to use the command "Replace FEM" to change the FEM document to which a SIM document is linked. This means that the user can replace the FEM document of the old variant of the component in question with the FEM document of the new variant. Since all steps of the Specialist Solution for the Fatigue Life Prediction are in the SIM document, they don't have to be recreated to analyze the new variant. It is necessary though to adapt the reference to the structural FE results in the Load Events used.


Here is a description how to attach a new FEM document to an existing SIM document to made use of the already defined simulation items existing in the SIM document that otherwise would have to be recreated in a new SIM document. 

In our example, the component is formed by two intersecting tubes.
One variant is meshed with a smaller element size than the other one.

Our example uses the following files:
- "tubes_quad_f.fem"
This FEM document contains the mesh of Variant_1 of the component. This variant contains the coarser mesh. 
- "tubes_quad_s.sim"
This SIM document was built on the FEM document above. It contains the Load Event and the Specialist Solution that we want to reuse with the newer variant.
- "tubes_quad.op2"
This file contains the structural FE results from which the two files above were created via "Import Simulation".
- "tubes_quad_s-Specialist_Solution_-_Tubes.VLDResult"
The results file of the fatigue life prediction of Variant_1.

- "tubes_quad_fine_f.fem"
This FEM document contains the more refined mesh of Variant_2 of the component. 
- "tubes_quad_fine_s.sim"
This is the SIM document created along with the FEM document when importing the simulation. There is no element of the Fatigue Life Prediction with Specialist Durability in the document.
- "tubes_quad_fine.op2"
This file contains the structural FE results for Variant_2  from which the two files above were created via "Import Simulation".

Steps required to Replace the FEM:

Variant_1 is opened in Sincenter 3D.

In the Simulation File View, we see that "tubes_quad_s.sim" is depending on "tubes_quad_f.fem".

Same in the Simulation Navigator. The SIM document "tubes_quad_s.sim" is linked to the FEM document "tubes_quad_f.fem".

Furthermore, we can see that in this SIM document, we already have the items of the Specialist Durability Solution in the Simulation Navigator. The Fatigue Life Prediction is fully prepared with Load Event and Solution.

The maximum of the Max. Stress result is shown as result.

Next, we open Variant_2.

In the Simulation File View, we find the dependencies between the documents of the two variants.
SIM and FEM of Variant_1 (name root "tubes_quad") are linked and SIM and FEM of Variant_2 (name_root "tubes_quad_fine") are linked.
There is no connection between any document of the two variants.

The SIM document of Variant_2 doesn't contain any element of a Specialist Durability Solution as opposed to the SIM document of Variant_1.

We can use now "Replace FEM" on the SIM document of Variant_1.

There are two ways to select the new FEM document:
- selecting it from a pull-down menu with all open FEM documents,
- loading it from disk.
Replace FEM_window.jpg
We select the FEM document of Variant_2 and click "OK" to perform the change.

Looking at the Simulation File View after Replace FEM was used, we see the new dependencies between documents
The FEM document of Variant_2 ("tubes_quad_fine_f") is now linked to both SIM documents open.
The FEM document of Variant_1 ("tubes_quad_f") not connected to any SIM document open at this moment.

In the Simulation Navigator, we have now the FEM document with the new mesh connected to the SIM document with the already prepared Fatigue Life Prediction.

Note that the definition of the Load Event is unaffected by "Replace FEM"!
The reference to the data source of the structural FE results must be changed manually.
It needs to point to the OP2 file of Variant_2 instead of Variant_1.

Here we used a data source from external file, pointing to "tubes_quad_fine.op2" (from Variant_2).
(Hint: Do not forget to define the unit system as well!)

With the preparation done, we can now solve the Specialist Solution.

When the calculation has finished, we can move on to post-processing the results (Max. Stress including an annotation for the maximum result).
The value has changed significantly when using the more refined mesh of Variant_2.


KB Article ID# KB000065444_EN_US



Associated Components

Acoustics Additive Manufacturing Assembly FEM Correlation and Updating Durability Electromagnetics (High Frequency) Electromagnetics (Low Frequency) Flexible Pipe Laminate Composites Margin of Safety Motion Multiphysics NX Open Nonlinear Optimization Pre/Post Response Dynamics Rotor Dynamics Samcef Environment Simulation Process Management Thermal / Flow