SubModel in OptiStruct - Global/Local Zooming

Adriano A. Koga

Submodel technique is a powerful tool that can be used in many cases for structural models.

Submodel (or Local model) is based on using the displacements from a Global model, and map these to a small part of the original model, acting as boundary conditions for this new model.

The advantages of this approach are:

- after running the global model (with a coarse mesh), one can find out where the structure is more stressed, and then run only that region again with a finer mesh for a better representation;

- using submodel you can reuse a previous result (H3D file) and it is not necessary to re-run the whole model;

- multiple loadcases are supported;

- this can be used for later fatigue assessment, having a better representation on welds or other more detailed connections, that usually are not detailed in the global model;

The attached PDF file shows what are the steps for running a global-local model.

Also an example model is attached in the .zip file.

 

It used basically 3 main cards:

ASSIGN >> to load the initial global model H3D file

IMPORT(SUB = X) >> import the subcases from  global to local

SPC (M) >> special SPC card to map the displacements (and optionally rotations) from the global model to the new local model.

 

An example with a 3 point bending plate.

Running first the global model (left), with the whole model, and then, later on, using the global H3D file as an input for the Local analysis (right).

Gabriel Justo_22431

Really cool example, thanks for sharing!

 

Just a tip for anyone that will explore this feature (it's on your pdf file but I've had trouble in the past). If you have more than one Load Step you need to create one SPC load collector for each load step that will be analyzed with this approach.

Adriano Koga_20259

Updating:

In HM/HW 2020.1 the SPC(M) option is already available and it is mcuh easier to create the submodel setup, with no need of editing the solver deck outside of HyperMesh. (see the updated attachment)

Rogerio Nakano_21179

Thanks you for sharing this.

Example and illustrations are very helpful to understand the solution.

 

fujita

Thank you for this example.

Artur Czura_20412

I don't understand what I supposed to do at the beginning. The part of the model should be remeshed and rest of the model should be deleted? Or what exactly?

Adriano A. Koga

Artur Czura_20412 said:

I don't understand what I supposed to do at the beginning. The part of the model should be remeshed and rest of the model should be deleted? Or what exactly?

1) run your global model, and generate your H3D file

2) create the mesh only of the part that you want to study in detail (delete all the rest)

3) create the appropriate SPCM and IMPORT cards

4) run your submodel

 

Hope this clarifies.