Help Determining Reaction Forces at Independent Node for Cylinder Fixed at 1 Node using RBE2 Elements

Rahul_P1

'I am a graduate student at Queen’s University in Kingston, Ontario, Canada. I am using Hyperworks for a topology optimization of a lunar rover chassis and was wondering if I could have some assistance with an issue I am having. I am trying to perform an inertia relief analysis of the chassis which means that I need to determine the reaction forces at the wheel connections of the chassis. The model is only preliminary so determining the reaction force at each node (at this point there are ~850 nodes) is not practical. Instead what I have opted to do is constrain 1 node at the center of the cylinder (there are two cylinders so one is fixed in 6 directions and the other is fixed in 5 to ensure chassis is simply supported) and connect this node to all nodes inside the cylinder using RBE2 elements. Here is an image of the constraint:
I want to have the reaction forces of the constrained node so that I can apply one load to this node and connect it to the cylinder nodes using RBE3 elements for the inertia relief model. When I try to get reaction forces using the SPCF global output request control card I am only able to get the reaction forces at the dependent nodes. I would like to know how to obtain the reaction forces ONLY at the constrained nodes instead of getting reaction forces at all dependent nodes.

If what I am asking is not clear please let me know how I can better describe my issue. '

Rahul_P1

The reaction forces at constrained nodes can be extracted in two ways,

You can use the SPCFORCE card or the GPFORCE card, I strongly recommend the gpforce card.
In both these cards you can choose the nodes for which you want to see the output, this is done by creating an entity set consisting of just the nodes whose reaction force we are interested in and then selecting this set in the gpforce or the spcforce card.

here I show the card image of the output requests spcforce and gpforce,

here I show the result of gpforce and spcforce at the constrained node.

here I show the result of gpforce, you will notice how gpforce card will output the spcforce as well among severall other grid point forces and moments, and also exactly at the contrained nodes alone automatically.

Rahul_P1

Rahul,

This has resolved my issue. Thank you for your prompt assistance!

Regards,
Ryan Pitre

Altair Forum User

How  to list all the reaction forces in a table format ? what format has to be requested?

Even I have defined the separate entity sets, I was not able to see the loads? 

Altair Forum User

Hi Arun,

 

.spcf folder should be available in the working directory if you have requested for spcfs. 

 

Altair Forum User said:

Even I have defined the separate entity sets, I was not able to see the loads? 

Can you please explain?

Altair Forum User

For Optistruct, Static Analysis

I have defined the SPCF requests in the Global output requests and have chosen the entity sets.

But It is not generating any spcf file.

Altair Forum User

Hi,

 

does anybody  knows if it works equal by using RBE3 Elements who are constrained over CBUSH Elements?

 

Regards

Benjamin