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Errors in the analysis of Optistruct due to the modeling

Hi everyone.

I'm working on my final thesis on the optimization of a steel spatial node, I used Hypermesh to define a larger volume to use Optistruct to do topological optimization. In the modeling, I have defined separate rigid hubs that will define the arrival bolts of the reticular rods, so that they will not have to be optimized but which have the function of applying the forces, to which I have set RBE2 constraints. I have not defined any contact surface between the hubs and the hollow sphere (probably an error). In the upper hub, I set a fixed constraint, the only one in the whole model with all 6 dof.
I set axial forces to the axes of the hubs (at the point of definition of the RBE2) to check if the model was correct with a linear static analysis with optistruct. Unfortunately, it gives me error. I do not know where I'm wrong.

Can someone tell me where I'm wrong?

Thank you.

<?xml version="1.0" encoding="UTF-8"?>

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Altair Forum User

Hi albertolazzeri,

Please can you show us what error you are getting.

If possible please share your model file.

Use below FT link

https://ftin.india.altair.com:8443/filedrop/~osKE8Q

Thank you

Altair Forum User

Sorry, I forget to share it.

I'm sending the model file just right now.

Thank you so much.

<?xml version="1.0" encoding="UTF-8"?>

Altair Forum User

Hi,

Did you delete the shell(Tria) elements after you created the tetra mesh?

if not, please delete Tria elements and run the analysis again and check.

Thank you

Altair Forum User

Hello Premanand Suryavanshi,

no, I didn't. Can you explain me how can I separate this two kinds of mesh in order to delete them?

Is correct to follow this path: delete Panel, element selector, choose by config and select config type TRIA 3?

Thank you

Altair Forum User

Hi albertolazzeri,

I received your file and i checked your model. I see many of the components are not meshed.

1. The inner sphere is not meshed.

2. I'm not able to understand what is the use of those extended cylinders.

3. the cylinders are passing through the Hubs, which is not appropriate.

I would advise you to prepare the model properly first and then proceed with the next steps.

Thank you

Altair Forum User

The inner sphere should be a hole, the extended cylinders were used to cut the hubs in the proper path, are them elements of disturbance for analysis? I thought it was not necessary to eliminate them to proceed with a model check.

Anyway, I tried to delete the surfaces in excess and run the analysis, but the same error appears.

Altair Forum User

The inner sphere should be a hole, the extended cylinders were used to cut the hubs in the proper path

i think what ever you have modeled is wrong. Please can you check your model and create a proper model.

If possible please can you share more information about your project and the component (With some images).

Thank you

Altair Forum User

My thesis deals with researching a new organic form optimized for additive manufacturing.

The initial spatial node has the geometry shown in the images. I started from a sphere to see how tensions spread.

Do you think that what I have adopted up to now is a wrong approach?

<?xml version="1.0" encoding="UTF-8"?>

Altair Forum User

Hi albertolazzeri,

By looking at these images, i think you don't need inner sphere and those extended cylinders. What ever you have meshed, only those components are enough.

and i also see that you have not assigned properties to the components. Make sure you assign proper properties to the components and then run the optimization.

Thank you

Altair Forum User

Thank you very much for your support.

I'll check it immediately.

Thanks