Roughness vs fracture toughness

[inventeer]

I'm looking for a correlation between surface roughness and fracture toughness of superelastic nitinol.

I know fracture mechanics states that smoother surfaces will be stronger than rougher ones because there are less imperfections for cracks to nucleate from. It is also common practice to polish nitinol in high-stress applications like stents.

Is anyone familiar with a graph of surface roughness measured in Ra vs fracture toughness in nitinol alloys? I would also be very interested in a graph of Ra vs fatigue life for various loading scenarios.

Thanks!
Mark