Issue 35

S. Boljanović et alii, Frattura ed Integrità Strutturale, 35 (2016) 313-321; DOI: 10.3221/IGF-ESIS.35.36 319 2 w =85.725 mm, 2 t = 18 mm and 2 r = 57.15 mm [23]. The initial crack lengths are: a 0 = 5.303 mm and b 0 = 3.573 mm, for depth and surface directions, respectively. The lug, made of PMMA, is subjected to an external force with constant amplitude (a far field maximum force P max = 2300 N), and the following material parameters are assumed: C A =2.294114032  10 -6 , m A =5.598311. 0 2 4 6 8 10 0 2 4 6 8 10 N [cycles] (x10 3 ) b [m] (x10 -3 ) Calculated curve Experiment 0 2 4 6 8 10 0 2 4 6 8 10 N [cycles] (x10 3 ) a [m] (x10 -3 ) Calculated curve Experiment (a) (b) Figure 4 : Crack length versus number of loading cycles for the pin-loaded lug with semi-elliptical crack emanating from a hole: (a) a versus N , (b) b versus N . Initial crack length: a 0 = 5.303 mm, b 0 = 3.573 mm. Experimental results from Ref. [23] . 0 4 8 12 16 0 2 4 6 8 10 b [m] (x10 -3 ) a [m] (x10 -3 ) a=5.553 mm a=5.803 mm a=6.053 mm a=6.303 mm a=6.553 mm Initial crack 0 4 8 12 16 20 0 2 4 6 8 10 b [m] (x10 -3 ) a [m] (x10 -3 ) a=6.803 mm a=7.053 mm a=7.303 mm a=7.553 mm a=7.803 mm Initial crack (a) (b) Figure 5 : The crack path modeling of semi-elliptical crack emanating from a hole. Initial crack length: a 0 = 5.303 mm, b 0 = 3.573 mm. The strength of the lug configuration with semi-elliptical crack emanating from a hole is here investigated through the stress intensity factor calculation and fatigue life estimation. In order to calculate the stress intensity factor, Eqs. (3)-(12) together with Eq. (13) are employed, then by applying Eqs. (2a) and (2b), the crack length is computed as a function of the number of loading cycles. Fatigue life calculations for depth direction and surface direction are shown in Fig.4a and