Peak stress in shell elements ASME VIII div.2 1

[victor6397]

Hello mates,I'm getting into pressure vessels calculation with ASME VIII div.2 and I have some doubts about stress linearization (I know only non linear analysis are suitable for inexperienced people like me )

Maybe the question is very silly, but I'm still learning and i haven't found a clear answer for me in this forum.

If we use a model with shell elements, I understand that stress linearization is not necessary, since we get directly the membrane plus bending components. But what about areas with stress concentrations like a bolt hole or an abrupt change of geometry? Would this stress be categorized as secondary? Then, would it not be appopiate to use shell models to evaluate failure modes such as fatigue which require taking into account the peak component?

I Hope you can help me. Thanks!

 

[TGS4]

Shell elements are really good for thin-shell analyses for demonstrating Protection Against Plastic Collapse, Protection Against Collapse From Buckling, and Protection Against Failure From Cyclic Loading: Ratcheting. They are not good for Protection Against Failure From Cyclic Loading: Fatigue or Protection Against Local Failure.

Regarding fatigue, you will typically need a peak stress, which a shell element cannot provide to you, directly. However, if your fatigue calculations include the Structural Stress Method for the Fatigue of Weldments, then shell elements are ideally-suited to provide you with the stresses needed for those calculations. Furthermore, there exist hand-calculations that can bridge the gap between shell elements and peak stresses.

Regarding your question about stress categorization, I will kindly direct you to paragraph 5.2.1.2.

 

[victor6397]

Thank you very much TGS4, I am learning a lot by reading your posts and replies