Hi Abhinav,

SMART crack growth for fatigue uses Paris’ Law to compute crack growth for a single cycle. SMART then tracks the growth and the number of cycles through the simulation.

If you set the **Crack Growth Option** property to **Fatigue**, your structure is subject to constant amplitude cyclic load.

A Stress Ratio of 0 means the load goes from 0 to 100%, which in your case is 600 N/mm. Your load graph shows a peak of 36000 N so I hope your tooth width is 60 mm wide.

SMART tells you how many cycles have occurred to get to a specific crack extension. Your load graph shows 2.5 cycles/sec or 2.5 Hz. That is not an input to SMART. If you want to know how much time has elapsed for a specific number of cycles, divide the cycles by 2.5 to get the number of seconds.

For example, if the SMART probe on number of cycles shows 1e6 cycles, your load profile gets there in 1e6/(2.5*3600) = 111 hours.