catenary - bilinear stiffness

[davideakatorrent]

Good evening to all,
I'm in the grip with the paran modeling of high-voltage wires. I have to make sure that the component has no compression resistance.
suggestions?
I don't know how to move.

Thank you.

 

[Onda]

if it is a cable, you can use a non-linear material with very low stiffness if used in compression and normal if used in traction. Obviously it should be solved with non-linear analysis.

 

[davideakatorrent]

wave, thank you for your interest.
what you suggest is to be done by creating a suitable field for the material (by selecting the strain as an independent variable and effort as the dependent one) and then inserting it into the non-linear elastic constituent model of my isotropic material.
Is that correct?
How do I then rule with the linear elastic model? What elastic form do I put? what I considered for traction behavior?
Thanks again

 

[Onda]

you have to make a bilinear elastic material. in patran you do a table where you have to give three points, the negative strain module, which will be very low. that to 0 that is the form of the material and that for the positive strain, equal to that to zero and equal to the module of the material. obviously do not put a module of 0 for negative strains not to run into numerical errors.
in the linear elastic insert the material module.
It seems to me that you have the strain as an independent variable and the elastic module as an dependent variable, I do not have patran underhand and I do not remember exactly.

 

[davideakatorrent]

Thank you, first of all.
I did as you say, but I think that as an employee variable, stress should be put (also because in the form of the constitutive bond, the strees/strain curves ask me).
I have obtained the vibration modes of the cable but, apparently, do not suffer from a possible change in the value of the young compression module, but only of the traction module (which however is fixed as known).
that all the logic of the model is wrong?

 

[Onda]

as I told you I didn't remember, however it's fine, since it's equivalent to putting the elastic module less than a constant.
I thought you had to do a non-linear analysis, not a modal.
In this case you have to do a modal with prestress, but I wouldn't know how to drive without taking the thing back and losing time.
in a standard modal the structure is not resolved for forces, so the cables have all elastic module and work both in traction and compression.
you should first make a non-linear, then a modal with restart from the non-linear solution.
Now I don't know what your goal is, of course, if you want the frequency of vibration of a cable in the fuction of its voltage, you don't have any other roads.