Learning Forum

[Pouya Rahimi]

Hi Everyone,

As I checked for different solution to remove the artificial stress in my results, I found that it is better that I use NL material properties. Now if I have just a Plastic Strain in a very small area of my model, everything is fine? generally my question is that how should I realize that my structure will not fail after considering local plasticity in my results? below is my results about Equivalent Plastic Strain.

Thanks for yor time...

[Erik Kostson]

 

 

 

Hi

 

Look at this differently, and start with the correct and appropriate model approach.

The 3D approach is not reomended here as it will reguire a very fine mesh to capture the response of such a frame structure. 

Structural engineers would model this type of frame structure with beam elements, and in that way also stress singularities are avoided. See how to use beam and shell elements in Ansys below:

https://www.youtube.com/watch?v=hb7BUcug8wY&t=478s

All the best

Erik

 

 

 

[Pouya Rahimi]

Thanks for your reply.

That was an example. Waht about if I want to use it in another mechanical equipment?

[Armin]

Hi Pouya,

Just to add, mesh size dependency after plastic localization is an open question in solid mechanics. It is known that localized plastic response can be significantly affected by element size (generally, it is not surprising to see that plastic deformation in localized regions keeps increasing by reducing the element size with no apparent tendency for convergence to a solution).
There are some numerical techniques proposed in the literature such as regularization methods that may be of help to you. You can look up online for "mesh regularization for localized plastic deformation" and you should be able to find some articles in this area.

[Pouya Rahimi]

Hi Armin

Thanks for your reply. According to EN 1993-1-5 there is a recommendation of 5% for max proncipal strain in FEM analysis result. So I can not use that criteria in my results?

[Armin]

No problem Pouya.
As I mentioned, mesh size dependency in localized plastic deformation may not be fully resolved by decreasing element size; however, if you're utilizing a particular standard, you can adhere to it.