Issue 49

G. Meneghetti et alii, Frattura ed Integrità Strutturale, 49 (2019) 82-96; DOI: 10.3221/IGF-ESIS.49.09 90 Once evaluated the (2 , ') p k n  constant, the experimental procedure for the J-integral evaluation can begin. In this paper, it will be described with the reference to a specimen of those tested during the crack propagation tests and highlighted in Fig. 8, by means of a red circle [28]. The selected sample has r n =0.1 and 2  =45°, and the total crack length is a=11.66 mm, while the applied gross-section stress amplitude is 81 MPa with a test frequency of 35 Hz, translating into a  K I,FE evaluated by linear elastic finite element analysis equal to 35.4 MPa·m 0.5 . Fig. 9 shows the temperature map averaged over 1000 frames, after the motion-compensation process. Figure 8 : Crack propagation curves (red circle the specimen considered in this paper to describe the experimental procedure to evaluate the J-integral). Figure 9 : Average temperature field for a specimen having 11.66-mm-long crack, loaded at  K I,FE =35.4 MPa·m 0.5 , f L =35 Hz. The cross sign indicates the crack tip position as estimated by the optical microscope. 8 13 18 23 28 33 38 a [mm] N, number of cycles V_45_R01_14 V_45_R01_16 V_45_R01_17 V_45_R01_18 V_90_R015_3 V_90_R015_4 V_90_R015_5 V_90_R015_6 V_90_R015_7 V_90_R015_8 AISI 304L R=-1 10 2 10 3 10 4 10 5 10 6 Crack tip