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F. Iacoviello et alii, Frattura ed Integrità Strutturale, 34 (2015) 406-414; DOI: 10.3221/IGF-ESIS.34.45 409 Figure 7 : Pearlitic DCI before long annealing heat treatment. Figure 8 : Pearlitic DCI after long annealing heat treatment (ferritic matrix and degenerated graphite elements). C Si Mn S P Cu Cr Mg Sn 3.66 2.72 0.18 0.013 0.021 0.022 0.028 0.043 0.010 Table 2 : Ferritic DCI chemical composition (100%F). In addition, a 3D fracture surface reconstruction procedure was performed. Corresponding to the same specimen position, a stereoscopic image was obtained performing an eucentric tilting around the vertical axis and capturing two different images, with a tilting angle equal to 6° (tilting results in a static center point in the image), Fig. 9. 3D surface reconstruction was performed using the Alicona MeX software and profile evolution was analysed corresponding to graphite nodules. Finally, static overloads were applied according to the following step-by-step procedure: 1) Applied K I increase was obtained by means of a servohydraulic machine under load control conditions. Corresponding to each overload, COD was measured. Applied K I values were: 10, 20, 30, 40 MPa  m, respectively. 2) The load was decreased to zero and the specimen was removed from the grips. Using the “screw loading machine” in Fig. 10, the specimen was loaded again up to the same COD value obtained in step 1. This “screw loading machine” allowed to observe the specimen lateral surface by means of a SEM under overloading conditions. Figure 9 : Eucentric tilting. Figure 10 : “Screw loading machine”. R ESULTS AND DISCUSSION Fatigue crack propagation he result of the long annealing heat treatment of the pearlitic DCI is a ferritic matrix with degenerated graphite nodules. These are characterized by a larger radius and by a higher surface roughness, if compared to the “starting” pearlitic DCI (Fig. 7 and 8, respectively): the outer shield obtained during the long annealing treatment T