Influence of the notch radius on changes of the $ {\Delta}J$ parameter under fatigue crack growth rate

In the paper, the influence of the notch radius on changes of the $ {\Delta}J$ parameter under low and high-cycle fatigue is discussed. The tests were carried out on plates made of FeP04-UNI 8092 deep-drawing steel. The specimens were characterised by double symmetric lateral notches with the notch root radius ranging from 0.2 mm to 10 mm. The MTS 809 servo-hydraulic device was used for tests performed at the Department of Management and Engineering in Vicenza (Padova University). All fatigue tests were performed under force control, by imposing a constant value of the nominal load ratio, $ R=0$, and a load amplitude $ P_a=6$ and 7 kN (which corresponded to the nominal amplitude of normal stresses $ \sigma_a=100$, 117 MPa before the crack initiation). The test frequency ranged from 13 and 15 Hz.