ASME VIII Design By Analysis with Ansys WB 15 4

[RobertoA73]

I have to do a stress analysis of a ball valve according to ASME VIII part 5 (Design By Analysis) but i have some doubts.
What kind of linearization should be used in Ansys WB 15? Von Mises linearization is correct to use to evaluate membrane and bending+membrane along SCLs?

Thanks

Roberto

 

[ASMS81]

What do you mean with "kind of linearization"?

Which stress to linearize?

 

[rickfischer51]

My advise is to sit down and read Part 5 completely, then read it again. It's all in there. For instance, at 5.2.2.1.a it says "A quantity known as the equivalent stress...", and at 5.2.2.1.b it says " The maximum distortion energy yield criterion shall be used to establish the equivalent stress." Then at 5.2.2.3 Linearization of Stress Results For Stress Classification it says "Results from an elastic stress analysis can be used to compute equivalent linearized membrane and bending stresses..."

Do yourself a favor and look at 5.2.3 Limit-load Analysis Method. In the long run it is a lot easier than the Elastic Stress Analysis Method. It is also less conservative.

Rick Fischer
Principal Engineer
Argonne National Laboratory

 

[TGS4]

In addition to Rick's excellent advice, I would also recommend reading all of Annex 5-A. When you are computing linearized membrane+ bending, pay special attention to 5-A.4.1.2 and bitter that Ansys does not comply with these requirements.

I would also note that for a complex geometry such as a valve, pay special attention to the caution that we provided in 5.2.1.2. Then read Rick's advice again. Although I would skip limit load and go straight to elastic-plastic, if for nothing else but satisfying protection against local failure.