Finite Element

[gimini75]

Hi

Can you please help me here?

I want to know:
1- the difference between nodal stresses and elemental stresses.
2-How the computer uses these stresses if it is to use strain energy as the convergence criteria?
3-How the sub-structuring technique can be used to model large structures such as aeroplanes and automobiles etc?
4-What is difference between a plate and a shell element?
5-How von Mises stress is calculated?



Thanks for your help

[CFDFEAGURU]

A plate element has no curvature to it. A shell element has curvature.

Von-Mises criteria is also known as the Maximum-Distortion-Energy-Criterion and it is based on the distortion energy determination in a given material. Basically, a given structural component is safe when the maximum value of the distortion energy per unit volume in the material is less than the distortion energy per unit volume required to cause the material to yield in a tensile test.

See Mechanics of Materials by Beer and Johnston for more indepth information.

Thanks

[CFDFEAGURU]

Nodal stress is the stress values at the nodes in the element. Elements can have many nodes depending on the element if it is a plate, a brick, a tetrahedron, a line, and so on.

Elemental stress is the average of these nodal stress values in thier respective element. In real life analysis nodal stress is what is used for determining if a component is over stressed.

Sub-structuring is nothing more than breaking up a large model into smaller models. This is done to save computing time and to use multiple analysts to gain efficiency and actually make money on the project.

Thanks

[CFDFEAGURU]

Lastly, I have never used nor have I seen strain energy used as a convergence criterion.