Issue 35

S. Boljanović et alii, Frattura ed Integrità Strutturale, 35 (2016) 313-321; DOI: 10.3221/IGF-ESIS.35.36 315 S TRESS INTENSITY FACTOR CALCULATION n order to estimate the fracture strength and fatigue lives of engineering components, significantly important parameter is the stress intensity factor due to the fact that it includes the geometry, material and loading conditions. As the pin-loaded lug with semi-elliptical crack emanating from a hole [Fig.1, case 1] is investigated, the relationship for stress intensity can be expressed as follows [16]: 2 2 , , , , , I sh a a a r r b K S G F Q b t t w w           (3) where 2 I K  represents the stress intensity factor range for two-symmetric cracks initiated at a hole and S  is the applied stress range. The function Q, as the shape factor for an ellipse, can be written on the following way: 1.65 1 1.464 b Q a         ; 1 a b       (4) where a and b are the crack length in depth direction and surface direction, respectively. The influence of various boundaries can be expressed by the boundary correction factor, as follows: 2 4 1 2 3 1 2 3 2 sh w a a F M M M g g g f f t t                         (5) where M 1 , M 2 , M 3 , g 1 , g 2 , g 3 represent functions related to crack configuration and loading, and they are given by: 1 b M a  (6) 2 3 2 0.05 0.11 M a b         (7) 3 3 2 0.29 0.23 M a b         (8) 1 4 2 1 2.6 2 1 cos 1 4 a a t t g a b                        (9) 2 3 4 2 2 1 0.358 1.425 1.578 2.156 1 0.08 g            (10) I