Modeling of Spring with Friction in CAESAR II 1

[Vikoll]

Dear Pipers

Could you please help me to model the Spring Can with friction between load flange and bottom of shoe.
I have checked this with CAESAR Application Guide Chapter 4-19, but some people say it's not the bast way to follow.
There is an opinion that the only one +Y restrain with friction has to be modeled for Cnode which is connected to the spring. All other restrains have to be omitted.
The Application Guide recommends to rigidly connect all DOF's except for the vertical spring stiffness.
I tried these two options and got different results

Your imput and suggestions will be greatly appreciated

Thanks and have a nice day.

 

[richay]

If you don't restraint the other DOFs (like the Applications Guide says), then the rigid element 15-20 could be suseptible to "rigid body motion". When that happens the analysis aborts with Fatal Error 256 - Singular Matrix, and then you send the job in to COADE and ask "What's wrong".

Restrain the other DOFs like the manual says.

Richard Ay
COADE, Inc.

 

[Vikoll]

Thanks Richay for you comments, but I probably did not discribe my situation quite clearly.
I use X and Z restrains between the node 10 and CNode 15 and +Y with friction for CNode 15.
My spring is also at Node 10 with CNode 15. I do not have the element 15 to 20 which is fine with SAESAR Application Guide 4-19

The opinion which I mentioned is not to use X and Z restrains between node 10 and and Cnode 15 and put only +Y with friction for Cnode 15 and connect the spring at Node 10 to CNode 15.

In other words the spring at Node 10 is connected to Cnode 15 where only +Y restrain with friction is modeled.
In both cases CAESAR runs analyses without fatal error, but gives different results
Please advise
Thank you in advance

 

[richay]

You still need the “X” and “Z” restraints. If you omit these, then node 15 can slide around in the XZ plane freely – and it will never put a load on 10. This was the whole point of going to the trouble of modeling more than a simple hanger/can at node 5 – you wanted the friction effects due to sliding. So (a) you need these, and (b) yes I would expect different answers.

Richard Ay
COADE, Inc.