How to apply fixed joints ?

Alexandre CHANAS

Hello to all,

I'm currently using Hypermesh for my internship, I created a model which you can see below.

The model is constituted of one 2D Shell mesh constrained for all dof in its edges linked to the red parts with FREEZE contact, the red parts are linked to the green part which is an actuation mechanism made of beam elements, this later is actuated thanks to a force which you can see in light blue, I'd like to use the Optistruct solver.

What I'd like to do is to link with fixed joints the beam elements highlighted with a black arrow, otherwise, I get deformations I'm not supposed to get as you can see in this picture (the other beam elements are supposed free to move).

I already tried to follow the tutorials/information from these sources: 

https://altairuniversity.com/wp-content/uploads/2017/09/how_do_I_ver1.pdf

https://2021.help.altair.com/2021/hwdesktop/hwd/topics/reference/hm/data_names-elements-joint_r.htm

https://community.altair.com/community?id=community_question&sys_id=7886c83a1b2bd0908017dc61ec4bcb3d#comment-45978

https://2021.help.altair.com/2021/hwdesktop/hwx/topics/pre_processing/entities/elements_1d_r.htm

https://2021.help.altair.com/2021.1/hwdesktop/hm/topics/tutorials/hm/tut_hm_4635_exercise_1_t.htm

I tried to create several nodes between the edges of the concerned elements, then try to link them thanks to FE joints -> RBEAM as I saw in a YouTube video that it linked all dof.

I also tried to separate the concerned elements into several components distinct from the green one, then link them thanks to MPC -> fixed, I failed to create bodies from these elements as explained in one of the links, I got a message which stated something like "The chosen node does not have a valid configuration to create bodies", I still tried to run the simulation in linear static.

None of these approaches worked, in one case it simply does as before, and in the second case it's even worse it acts as if there was no connection between the components.

Now I'm currently out of resources and I'd like to know how to manage this problem.

Thanks for your time.

Jason_Craanen

(this question was answered in support, adding my responses for others)

You do not need to put a fixed joint at those beam connections, you need to make sure none of the beams at those ends have pin flags or degrees of freedom allowed how you don't want it

https://2022.help.altair.com/2022.1/hwsolvers/os/topics/solvers/os/cbeam_bulk_r.htm?zoom_highlight=cbeam

 

 

 

Be aware the CBEAMs are not rigid so that can still exhibit deformation depending on the section, material and loading. Try utilizing your same setup with rigid members and see if they behave as you intended.

 if you are having out of plane twisting you do not think is realistic, you will need to create additional constraints.