Notch Sensitivity and Defect Sensitivity under Fatigue Loading: Two Sides of the Same Medal

Notch sensitivity and defect sensitivity are two different aspects of the fatigue behavior of materials. The paper extends the Kitagawa diagram to blunt cracks (U-shaped notches) and presents the simple expression (a*/a0)0.5 = Kt. In such an expression a0 is the El-Haddad's length parameter and a* is a particular blunt crack depth corresponding to the intersection between the ΔKth and δσ0/Kt curves. The new expression provides an explicit bridging between the notch sensitivity and the sensitivity to defects.