optimization of the weight of a dome-shaped reticular structure

[honor]

Hello everyone, first of all I apologize early if I am writing this discussion in a wrong place of the forum but I am new and I still have to understand well how it is structured the same, I explain my problem. I have to make an optimization of the weight of a mechanical structure formed by reticolar beams with ansys apdl software. the type of element I chose is the link180 and I have constraints on the maximum shift of knots that should not be more than 10 cm and on the admissible voltage that must be less than 250 mpa. I wrote my program in batch mode and when loading on ansys gives me error on a commando. to be more accurate gives me the error in the list piece:

*set,strlime,250e6
*set,strmax,0
etable,normal,ls,2
esell,all
*do,iel,1,336,1

*get,streal,elem,iel,etable,normal
streal=abs (streal)
*if,streal,gt,strmax,then
strmax=streal
*endif
*end

more precisely it gives me error on the *get command, which told me not to be suitable for that kind of operation I want to do. Does anyone know which other command I can use, to take the planned efforts with the etable commando and save them in a variable so that you can compare it with the permissible stress? Thanks for the answer.

 

[honor]

However the previous doubt has been resolved. Now my problem is that I used the link 180 element that has 3 degrees of freedom, but it does not solve the structure as it tells me that it does not find the degrees of freedom. someone can tell me some solutions, I thought that in the reticular structure there is internal lability, but I can't understand where. If so, would anyone know how to tell me the procedure to find it and solve it? Thank you.

 

[lucadileta]

However the previous doubt has been resolved. Now my problem is that I used the link 180 element that has 3 degrees of freedom, but it does not solve the structure as it tells me that it does not find the degrees of freedom. someone can tell me some solutions, I thought that in the reticular structure there is internal lability, but I can't understand where. If so, would anyone know how to tell me the procedure to find it and solve it? Thank you.

hi honor, to find internal lability that do not allow you to solve a structure perform a modal analysis and solve the problem immediately.

Bye!

 

[honor]

hi lucadileta, thank you for responding to me, since they are at first arms with ansys and I am learning as soon as I use it you could indicate the commands to use to perform this modal analysis. then more precisely the error that gives me and this "the degree of freedom is not available". Thank you in advance.

 

[lucadileta]

hi honor, on this link you find everything you need
http://www.mece.ualberta.ca/tutorials/ansys/it/modal/modal.htmlAre you wearing a gust?

 

[honor]

I'm using apdl