Issue 50

A. Salmi et alii, Frattura ed Integrità Strutturale, 50 (2019) 231-241; DOI: 10.3221/IGF-ESIS.50.19 234 Tab. 3 provides the 2024T3 aluminum alloy chemical compositions [ 4]. Table 3: Chemical composition by mass in percentage. R ESULTS AND DISCUSSION aris and Erdogan have constructed a quantitative framework of fatigue fracture mechanics, which correlates the fatigue crack growth rate to the range of stress intensity factor as follows [16]: m da C K dN   (1) where C and m are empirical material constants, ∆K = K max - K min is the stress intensity factor range in fatigue loading, N is number of cycles, and da is crack extension length. The following correlation gives the relation between C and m parameters: Log C = a + bm (2) a and b 0  where: a is the ordinate at the origin and b is the slope of the regression line. Or C = m A B (3) with A =10 = a p da dN       B =10 = k b p   ( ); ( ) p p da mm k MPa m dN cycle                Coordinates of the pivot point [17]. The material constants in Paris equation depicted in Tab. 4 [18]: Plate thickness 2.29 mm Plate thickness 6.35 (mm) m = 3.2828 m = 4.224 C = 3.63 E-13 C = 1.51 E-15 Table 4: Material constants in Paris law for aluminum panel. The total number of stress cycles N required for a short crack to propagate from the initial crack length a 0 to any crack length a can then be determined as 1 z i i N N    (4) N i stress cycles required for the appearance of the initial crack i = 1; 2; 3; . . . ; z z number of grains transverse by the crack Material Cu Fe Si Cr Mg Mn Zn Ti 2024-T3 4.82 0.18 0.07 0.02 1.67 0.58 0.06 0.15 P