API579/ASM FFS Table F.12 - Fatigue Crack Growth Data for Use With the Bilinear Equation 1

[jkampman]

Figure F.8 shows the growth rate curve at Regime C to be steeper than at Regime B.
However, the parameters in Table F.12(M) result in a less steep curve for the Upper stage compared to the lower stage.
Does anyone understand this?

 

[danb3]

Hi jkampman,
The lower and upper stage crack growth curves for a bilinear fatigue crack growth model both still relate to the 'Regime B' striation growth behavior. In that Figure it shows a linear growth for simplicity.
P.S, it seems that you are using an older version of API 579-1/ASME FFS-1 (2007?), I would recommend using the latest version which is API 579-1/ASME FFS-1 2021.

 

[jkampman]

Hi danb3,
Thanks for the clarification (and the version tip)! Do you know if there is a way to determine where regime B ends and regime C starts?