PWHT allowable stress
PWHT allowable stress
(OP)
I'm doing a simulation of a PWHT and I'd like to know if ASME say something about allowable stress for the thermal stresses originating from the PWHT.
Thanks,
Francisco
Thanks,
Francisco
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RE: PWHT allowable stress
RE: PWHT allowable stress
RE: PWHT allowable stress
RE: PWHT allowable stress
RE: PWHT allowable stress
The criteria in the Code (ASME Section VIII, Division 2, Part 5) is NOT appropriate for this type of analysis.
You need to think about how this thing could "fail". Then, protect against it. Forget about using ANY of the criteria listed above, unless you know/appreciate/understand WHY it's being used.
RE: PWHT allowable stress
Yes, I understand that PWHT is for stresses relieve. But no, I don't include any residual stresses from forming/welding in my analysis since I don't know how much is stress is on it.
I think the "system" will fail if there are "excessive" stresses above the yielding stress. But how much above the yielding?
I'm doing a linear elastic analysis. Since I'm using shell element type, I want to evaluate stresses in the TOP, BOTTOM and MIDDLE surfaces of the shell.
RE: PWHT allowable stress
Please define failure in this case. I would recommend that you reference ASME Section VIII, Division 2, Part 5 when answering this. Excessive stresses above yield mean nothing, for example in a system where the resultant displacements are constrained. Are you really worried about plastic collapse? Or ratcheting? Or buckling?
Let me understand this correctly, you understand that there a phenomenon going on, yet are ignoring it, solely because you are ignorant of the magnitude? I understand that you are new here to eng-tips (welcome and enjoy the ride), but this is starting to sound really odd/dangerous. Why are you even looking at this using FEA in the first place? Are you trying to quantify the stresses resulting from a local PWHT?
I will also note that in addition to this being a highly plastic operation, you are also well into the creep regime. Short term creep can be a significant component. The resulting redistribution of stresses from creep deformation can dramatically alter the state of local stresses.
RE: PWHT allowable stress
Actually I'm performing the FEA to quantify the stresses from the PWHT procedure. I first place I don't want residual stress near the welding (it's a nozzle's welding). So I'm looking in the ASME code to see if there is something about a allowable stress for the PWHT or for there stress.