Constraints and FEA

[Michael86Mc]

Hi There,

I've been struggling with this for quite some time now and it's most likely a gap in my knowledge.

I build my assembly and use various constraints to assemble the model. I believe that I have captured all degrees of freedom and by rights the model should be stable.

However, when I go to conduct FEA, the model warns of separation.

I even tried bonded contacts as a last ditched effort to make something work.

I have undertaken FEA on the assembly prior to adding extra components and it works fine but as I assemble more I am missing something.

I have uploaded the export to google drive as the platform here has 70MB maximum and the file is too large: https://drive.google.com/file/d/1m_qXqLr86IPNj44LelZdMv6VUHzZDrT9/view?usp=sharing

Any advice would be very much appreciated.

Thanks.

[kacper.suchomski]

Hello, constraints are used to define the relationship of the model to the environment (for example, a floor or a rigid link to a part that is not in the model).

Contacts, on the other hand, define the relationships between the individual parts that are modeled.

Review the definitions and cases in the manual, then verify the preparation of your model to FEA.

[Michael86Mc]

Thanks for your response.

I'm referencing this page:

https://help.autodesk.com/view/INVNTOR/2023/ENU/?guid=GUID-2DFEAF48-DCBF-4781-9AC7-76D91DC2D896

I'm still confused though.

As an example,

1) For linear rail and block I should use what type of constraint(s)? Joint and constrain?

2) For two faces with fixed or 'bonded' connection? Constrain?

I'm not understanding which method (joint, assemble, constrain) should be used in which case or is it a combination of all?

Screenshot here shows I'm using joints instead but still one item (first part) is under constrained.

Thanks for your help.

[Michael86Mc]

Ok, so I solved my own problem with the lack of full constraint on the top item.

I had to 'ground' the first part by right clicking on it and selecting grounded.

Still seeking some feedback on the types of constraints and how FEA interacts with them.

I'll keep working with attention paid to making sure everything is fully constrained and see what happens.

[TheCADWhisperer · Accepted solution]

@Michael86Mc 

1. You should install the latest Update for your version of Inventor http://manage.autodesk.com

2. Much of the data (Templates and so forth) are not needed at this end...

3. Assembly constraints have no bearing on FEA (unless you are running Dynamic Simulation>Motion Loads Analysis where constraints are converted to DS Joints).

You need to define all Constraints and Contacts in the FEA environment.