Fatigue screening - Method B - ASME VIII Div.2 Ed. 2023

[pvros]

Dear All,
as per ASME VIII div.2 ed.23, fatigue screening method B has changed.
I am not sure on how to understand certain calculation of the screening.

Let check for instance eq. (5.19).
The damage associated with the full range pressure cycle is the ratio between the number of full pressure cycle by N[Kfb*Hc*(3S)/2].

What is N[Kfb*Hc*(3S)/2]?

Is [Kfb*Hc*(3S)/2] the Se (computed equivalent stress)?
Thus N[Kfb*Hc*3S)/2] = N[Se]?

Moreover, at step 2 of 5.5.2.4, code is writing to calculate factors C1 and C2 based on table 5.10 and determine Kfb and Hc. I suppose it is a refuse and C1/2 do not exist anymore. With table 5.10 i can directly evaluate Kfb and Hc.

 

[TGS4]

What is N[Kfb*Hc*(3S)/2]?

Is [Kfb*Hc*(3S)/2] the Se (computed equivalent stress)?
Thus N[Kfb*Hc*3S)/2] = N[Se]?

Yes

Moreover, at step 2 of 5.5.2.4, code is writing to calculate factors C1 and C2 based on table 5.10 and determine Kfb and Hc. I suppose it is a refuse and C1/2 do not exist anymore. With table 5.10 i can directly evaluate Kfb and Hc.

Correct - there is no more C₁ and C₂. That is an unfortunate remanent from the editorial process. That will be corrected in the 2025 Edition.

 

[GD2]

My interpretation:
1. Equation 5.19 is to calculate 'Damage'. Damage is unitless and a fraction.
2. What is N[Kfb*Hc*(3S)/2]?
Answer: This part is to determine the alternating equivalent stress amplitude (Se/2, equivalent stress (Se) divided by 2), which is equal to[Kfb*Hc*(3S)/2] Use this amplitude to determine total number of allowable cycles (N) from the 'Design Curves'.
3. The equation could have been simplified for better understanding.

GDD
Canada