ASME BPVC VIII-2 2010 fatigue screening
ASME BPVC VIII-2 2010 fatigue screening
(OP)
I have a pv made from 17-4ph ss subject to 2000 cycles design life.
Equation 5.18 (p5-16) says I can skip the fatigue analysis if my number if cycles is less than "N(C1*S)".
S is the allowable stress (58ksi) from Sec II. C1 is 4 from a table. So I am checking to see the number of allowed cycles at 4x the allowable stress. Turns out I am limited to ~15 cycles, regardless of the actual stress or pressure I put in my vessel.
What am I missing? Thanks!
Equation 5.18 (p5-16) says I can skip the fatigue analysis if my number if cycles is less than "N(C1*S)".
S is the allowable stress (58ksi) from Sec II. C1 is 4 from a table. So I am checking to see the number of allowed cycles at 4x the allowable stress. Turns out I am limited to ~15 cycles, regardless of the actual stress or pressure I put in my vessel.
What am I missing? Thanks!





RE: ASME BPVC VIII-2 2010 fatigue screening
RE: ASME BPVC VIII-2 2010 fatigue screening
RE: ASME BPVC VIII-2 2010 fatigue screening
Also, Div 2 is NOT set up for FEA for ALL designs - the design-by-rules of Part 4 is set up to not have to do advanced analysis. If you have fatigue - and most failures that I have investigated fail do to cracking from cyclic loading - then there is no "end-run" around the rules. Do the fatigue calcs. You use a high strength material like 17-4PH to take advantage of the high allowable stress. However, 17-4PH is not similarly invincible to fatigue - and by having the vessel in a highly stressed state, and then cycling that, you are practically begging for a fatigue failure. DO THE FATIGUE CALC!
RE: ASME BPVC VIII-2 2010 fatigue screening