Issue 41

G. Meneghetti et alii, Frattura ed Integrità Strutturale, 41 (2017) 299-306; DOI: 10.3221/IGF-ESIS.41.40 304 (SIF) range,  K=K max -K min , for different crack lengths. In view of this, linear elastic, two-dimensional, finite element analyses were performed by using the 4-node SOLID182 element of ANSYS ® commercial code. To account for the machine grip effect, displacements were applied in the numerical model to the appropriate lines shown in Fig. 2a. Figure 6 : a fatigue crack observed during the tension-compression fatigue tests, (a=25.60 mm,  K=61.77 MPa·m 0.5 , f L =30 Hz) (a) and crack propagation data (b) . Figure 7 : Crack growth rates vs  K (a) and Q* evaluated by using R c =0.52 mm (b) . Fig. 7a shows the Paris curve of AISI 304L stainless steel, along with the 10%-90% scatter band and the crack growth rate scatter index T da/dN (T da/dN =4.00), calculated under the hypothesis of log-normal distribution of da/dN. In the same figure, a vertical band defined by two dashed vertical lines is reported, on the left hand side of which all data points satisfy the conditions of applicability of the LEFM according to Eq.4 [17], while on the right hand side of the band they do not:                2 ' ,02 4 ,( ), 2 p K a w a L (4) where a is the crack length, w the specimen width (w=46 mm, see Fig. 2a), 2L the specimen length (2L=90 mm, see Fig. 2a) and  ' p,02 the cyclic engineering proof stress equal to 265 MPa [9]. The data that did not satisfy the condition of applicability of the LEFM were not included in the statistical analysis reported in Fig. 7a. One can note that on the right 8 10.5 13 15.5 18 20.5 23 25.5 28 30.5 33 35.5 38 1.E+02 1.E+03 1.E+04 1.E+05 1.E+06 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 (b) 10 100 da/dN [m/cycle]  K [MPa ·m 0.5 ] Comply with LEFM, Eq. 4 Do not comply with LEFM, Eq. 4 10 -8 10 -7 10 -6 10 -5 10 -4 500 T da/dN =4.00 (a) 0.1 1 10 100 1000 da/dN [m/cycle] Q* [MJ/(m 3 ·cycle)] Comply with LEFM, Eq. 4 Do not comply with LEFM, Eq. 4 10 -8 10 -7 10 -6 10 -5 10 -4 T da/dN =3.34 (b) R c =0.52 mm (a) 2 mm