Issue 35
S. Boljanović et alii, Frattura ed Integrità Strutturale, 35 (2016) 313-321; DOI: 10.3221/IGF-ESIS.35.36
2 w =85.725 mm, 2 t = 18 mm and 2 r = 57.15 mm [23]. The initial crack lengths are: a 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. = 5.303 mm and b 0
10
10
8
8
6
6
4 a [m] (x10 -3 )
4 b [m] (x10 -3 )
2
2
Calculated curve Experiment
Calculated curve Experiment
0
0
0
2
4
6
8
10
0
2
4
6
8
10
N [cycles] (x10 3 )
N [cycles] (x10 3 )
(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] .
20
16
16
12
12
8 a [m] (x10 -3 )
8 a [m] (x10 -3 )
4
4
a=5.553 mm a=5.803 mm a=6.053 mm a=6.303 mm a=6.553 mm Initial crack
a=6.803 mm a=7.053 mm a=7.303 mm a=7.553 mm a=7.803 mm Initial crack
0
0
0
2
4
6
8
10
0
2
4
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8
10
b [m] (x10 -3 )
b [m] (x10 -3 )
(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
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