Fatigue analysis screening criteria - Method B (ASME VIII-II $ 5.5.2.4) 1

Cathie16 · Sep 6, 2024

Hello all,

In ASME fatigue screening methods, could someone please explain how to find the N[(KfbHc(3S))/2] in the eq. 5.19 ? Does it corresponds to N at [(KfbHc(3S))/2 ] in SN curve of the selected material?

Similarly for eq.5.20, whether ΔPN = 2PSas/[KfbHc(3S) ? or if ΔPN is the maximum range of pressure fluctuation during normal operation, excluding startups and shutdowns (input to be given by client) then NΔP is the corresponding number of significant cycles ?

This part is bit confusing and will appreciate really any suggestions on this?

Thanks in advance

TGS4 · Sep 6, 2024

As said in the last sentence of Step 1.:

ASME Section VIII said:
Note, in eqs. (5.19) through (5.24), the number of cycles from the applicable design fatigue curve (see Annex 3-F) evaluated at a stress amplitude of s[sub]e[/sub] is defined as N(S[sub]e[/sub]).

Regarding your second question - the answer is yes.

Is that clear now?

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Fatigue analysis screening criteria - Method B (ASME VIII-II $ 5.5.2.4) 1

Cathie16

Materials

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TGS4

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