I required one information regarding the extraction of stiffness coefficient value from fig of appendix P API650.
My question is that if we have the vale of a/R other than define in fig i-e a/R=0.005, a/R=0.02, & a/R= 0.04 then is there any method to locate the a/R line(e.g as per calculation it becomes 0.0025) in that figure? Defiantly these three lines must have some basis for their locations in the fig., but what are that basis?