Lay Flat Sheet onto Round Metal Block using Contacts - What am I missing? [HyperMesh / OptiStruct]

Turbokraken

Hello Everyone,

I am currently trying to do a small exercise to get to know the contacts better in HyperMesh/OptiStruct. For this, I created a flat sheet as a ply laminate and a round metal block made from steel. Now, the flat sheet is supposed to be suspended in the middle by SPC and the rest of it shall "fall down" onto the metal block. I have set the GRAV card as required and the sheet is falling as expected... right through the metal block.

What I need next is contacts I believe, however I have not quite grasped how it works. I have created contactsurfs for the metal block surface and the laminate sheet and applied a Contact. However when I vary the parameters of the contact, sometimes it kind of works but most of the times it does most. More often than not, the flat sheet is falling through the metal block yet again, but not after sticking on the upper metal block side in weird ways.

I am also unsure whether to use FREEZE or SLIDE. I am tending to SLIDE because thats what the sheet is supposed to do, but it only ever worked kind of with a FREEZE.

I have uploaded the .HM-file. It would be fantastic, if someone could check in and tell me what I need to do differently to finally make it work! I am expecting that the laminate will lay onto the metal block on the upper part, but not fully enclose the metal block on the lower parts due to its stiffness. This has however never quite happened...

Any help would be great!

Best Regards,

Lennart

Gildas_GUILLY

Hello Lennart,

You are right : SLIDE will be what you need here as it is the way to define a frictionless contact.
FREEZE type contact is actually a bonding interface (glued) between the faces you are putting in contact, but only in the region where the search distance parameter (SRCHDIS) will find connection, reason why you have "ut not after sticking on the upper metal block side in weird ways".
And even then, your SRCHDIS is too small to solve this problem efficiently.

Actually your model is missing several things to be able to simulate this correctly.
The main one is that this model needs to be solved with LARGE DISPLACEMENT and CONTINUUM SLIDING hypothesis. Currently you are using none.

My advice is for you to start familiarize with large displacement non-linear analysis.
The Optistruct help manual contains 9 tutorials on this subject (OS-T: 1500 to OS-T 1580).
I suggest you start by looking at those.

Best regards,
Gildas