For the given material, if the stress concentration factor is 2 and Notch sensitivity is 0.1, then the fatigue stress concentration factor is:

Concept:

Theoretical Stress Concentration Factor (K_t):

It is the ratio of actual stress near discontinuity to the nominal stress from the elementary equation.

Fatigue Stress Concentration Factor (K_f):

It is the ratio of the fatigue strength of an unnotched member to the fatigue strength of the same member with a notch.

Notch Sensitivity (q):

Calculation:

Given:

K_t = 2, q = 0.1

∵ 

⇒ K_f – 1 = 0.1

⇒ K_f = 1.1

Theoretical stress factor (K_t) can also be calculated from the figure if irregularities dimension is given-

where a = Semi-major axis perpendicular to the direction of load and b = semi-minor axis parallel to the direction of load.

For sharp crack

B → 0 ∴ K_t = ∞

For circle

A = B

∴ K_t = 3