Stress based FE is not popular. Why?

Hi all,

I have a doubt as follows.

"Why stress based Finite Element Analysis / Method is not popular compared to displacement based FE?"

With regards,

- Ramdas

Stress based FE

In displacement based FE we assume a suitable displacement function to model the actual displacement. We shall have a prior understanding on the displacement as the displacement constraints help us to assume the displacement field. More over the displacement field should satisfy the compatibility similarly if stress based based FE is employed the stress field should satisfy the equilibrium which is not easy to assume. Hence Displacement based FE is more popular and widely used..

Displacement-based vs stress-based FEM

Hi Ramdas,

Displacement-based modesl:

- Dispalcement field is approximated.

- Compatibilty conditions are required on element interfaces: since nodal values such as displacements, rotations can be determined directly from displacement field, these conditions can be easily satisfied by the assembly scheme.

Stress-based models:

- Stress fields are approximated.

- Equilibrium conditions on element interfaces are needed. To do this, we must derive the general forces (nodal forces)  which must be equilibrium with the stress field. This is not easy, especially for high order approximations. This can be explained why stress-based elements are not popular compared with the displacement ones. However, in the field of plastic limit analysis both kind of models are well developed.

Regards,

Canh Le

Canh V. Le, PhD Student
Computational Mechanics and Design (CMD)
Department of Civil and Structural Engineering
The University of Sheffield
Mappin Street,
Sheffield, S1 3JD, UK.
Phone: GB +44 1142225724

Hi RYELLAVA and Canh V.

Hi RYELLAVA and Canh V. Le,

Thank you very much for your thoughtful posts.

It looks stress based method is extensively used in Matrix Strutural Analysis (Flexibility method) for analysing framed structures. When it comes to continuum based elements, it is not popular.

With reards,

- Ramdas

Hi ramdas

flexibility method is used in frames as you can get the moments and forces directly there is no need to calculate displacements which are often not of much use (except under serviciability) for civil engineers. I agree with your remark