modelling a beam with large deflection and thermal load

Altair Forum User

good morning,

I am fairly new to the Hyper works world and I am struggling on the following topic:

A Bow (for Archery) ist modelled in its unstressed geometry (with 3D bricks).

The String which is attached to the tip of the bow is in real life shorter than the bow. Hence in reality you bend the bow , attach the string and let it spring back a bit.

In the model I attach the string directly to the tip but I try to model it as a beam section with execessive length.

In the first load step I wand to shorten (ie. contract ) it by applying a low temperature load. Once the bow has reached its brace hight which is with the string under tension but the arrow basically not pulled back I will then later apply a second load stept where the string is drawn back.  

I got as far as modelling a beam and a string and run it static but that does not give the large defomation which occur.

I activated the NLstat command but that again ist only useful for small deflections. Since the stiffness matrix has to be reassembeld continuously,

I activated the NLGeom command. This gives useful results for the bending shape but I seem to have lost the possibility to apply the thermal load because there is no more Temp option any more like it was with static or Quasi static calculation.

Has anyone any idea how to progress from here?

An alternative to shorten the string by freezing would be maybe by removing elements? Don't know wether this is possible

This is only the beginning of a list of topics because there will be the contact issue between string an Bow later on.

regards

 

Rainer

Altair Forum User

Since there are no replies it may not be so easy? I changed the calculation now in a way that I use the LGDISP 1 Paramter and run it non linear quasi static. This allows for the large deformations. Unfortunately in this kind of calculation there are no 1D elements allowed. I modelled the string with 3D elements but on the result output I want the reaction forces as I draw the bow and this is not implemented yet in the code.

I found the Deform parameter though which allowes to apply a strain  on 1D elements. So maybe I should go back to non linear geometric calculation with 1D elements but use this artificial shortening instead of the low temperature contraction. I reread the instructions how to use the bulk data entry but I am still not sure how to apply this paramter to the bar elements Does anyone know a tutorial that shows its usage?

 

thanks

 

Rainer

Altair Forum User

Hi Rainer,

 

Unfortunately 1D elements are not supported with LGDISP in NLSTAT..

 

You can enforce artificial deformation using DEFORM, but please mind this is a static deformation for 1D elements.

 

There are no examples or tutorials available as of now. I will share any documents or data with you if I come across.

 

Meanwhile please refer to help for more information.