Flex Fatigue of PFA Tubing - Relating MIT Tester Results to Reality

[wdornfeld]

I have an application where one end of a ~12" length of 8x6mm Perfluoralkoxy PFA ultra high purity tubing is continuously cycled about 3/4" sideways (+/- 3/8"). I can find "MIT Flexural Life" (ASTM D2176) properties of PFA that report 200,000 cycles of life. I believe that the MIT tester is flexing samples that are between 10 and 30 mils thick around a 15 mil radius nose. I calculate this as putting between 25 and 50% alternating strain on the material, respectively - pretty darned big. I am used to S-N diagrams for ductile metals, and am looking for how to relate my application strain to the MIT tester results to estimate life for my case. Thanks for any guidance.