Ratcheting Assessment per ASME VIII Div. 2

[RoNas09]

Hi guys,

I'm willing to understand better about a ratcheting assessment analysis of a pressure vessel. I'm assuming that ratcheting assessment is a cyclic analysis, and if there are thermal and/or mechanical transient loads, then the analysis becomes necessarily time-dependent.

After reading the Annex 5.B of ASME VIII Div. 2, I have some doubts about the procedures described in item 5.B.5.2:

1-) STEP 3 says:

Scan the interior points of each event and delete the time points at which none of the stress components indicate reversals (peaks or valleys).

So, I understood that in order to find the time points at which peaks and valleys occur, I should use the 6 stress components histograms (not the loading history) and look for all reversal points. These reversal points, then, become relevant to a ratcheting assessment analysis. Is that interpretation correct?

2-) If the above interpretation is correct, then how am I supposed to answer STEP 4 and determine the time point with "the highest peak or lowest valley", considering that I have 6 stress components histograms, and the peaks and valleys of each one of these histograms not necessarily occur at the same time?

3-) There may be a lot of peaks and valleys depending on the number of existing transients, which can turn the post processing of a cyclic analysis impracticable. Is there any design strategy or thumb of rule that reduces the number of points of interest conservatively?

Thanks in advance.

 

[Kora1503]

There's a relationship between loading and stress. I believe that you can use the loading history. This answers all your questions.

 

[RoNas09]

Thanks for your answer! Although, I believe Annex 5.B is clear when it says that one should use the stress component histograms, and not the loading history. Thus, all the other doubts are still valid. Could someone please help me with them?!