Good morning fellow stressers (it's morning in my place anyways),

This might be a silly question, but hey its morning...most of my brain haven't woken up yet.

I was just wondering, for Carbon, low alloy, series 4xx, high alloy steels and High tensile steels, ASME VII Div.II (and Caesar of course) provides fatigue curves for UTS ≤ 80 ksi & UTS 115–130 ksi. So, how do you interpolate for UTS 80–115 ksi as mentioned is ASME? Does anybody have ever done this before?

Thanks for reading & comments (if any) .

While not an exact answer to your question, I have been in this position before, and I opted to use the more conservative curve, rather than assume linear interpolation is indicative of the lifetime reduction effect from cycling the piping.

I observed less allowable stress for no. of cycles in PD5500 curves compared to ASME VIII curves. Roghly 35 to 40% difference. How's that for same material? Which one is more reliable ! This is sligly off track to main question but has relavance.