Issue 35

S. Boljanović et alii, Frattura ed Integrità Strutturale, 35 (2016) 313-321; DOI: 10.3221/IGF-ESIS.35.36 313 Focussed on Crack Paths Fatigue failure analysis of pin-loaded lugs Slobodanka Boljanović Mathematical Institute-The Serbian Academy of Sciences and Arts, Kneza Mihaila 36, Belgrade, Serbia slobodanka.boljanovic@gmail.com Stevan Maksimović VTI-Aeronautical Department, Ratka Resanovića 1, Belgrade, Serbia s.maksimovic@open.telekom.com A BSTRACT . In the present paper, mathematical models are proposed in order to analyze the strength of pin- loaded lugs with semi-elliptical crack and through-the-thickness crack. The crack growth investigation of considered crack configurations tackles the fatigue life evaluation and the crack path simulation of semi-elliptical crack. The residual strength is estimated by applying the two-parameter driving force model. The numerical and analytical approaches are employed for the stress intensity factor calculation. Experimental fatigue crack growth data are used in order to verify efficiency of the developed models. A good correlation between fatigue crack growth estimations and experimental observations is obtained. K EYWORDS . Cyclic loading; Strength estimation; Crack path; Semi-elliptical crack at a hole; FEM. I NTRODUCTION erospace systems can realize their stationary and moving operational duties through the load transfer assembly known as lug-type joint. In such linkage under cyclic loading, the high stress concentration, contact pressure and fretting can lead to the crack initiation, crack growth and even catastrophic failure. Consequently, for safety design and exploitation of the fracture critical pin-loaded lug is significantly important the development of reliable computational models. Fatigue and fracture strength estimations related to the damaged lug demand accurate evaluation of both, the stress state field around the crack tip and the stress intensity factor. In the literature, a variety of methods have been employed to calculate the stress intensity factor either of planar crack or through-the-thickness crack configurations. Thus, the propagation process of such crack situations can be theoretically investigated by applying the following approaches: approximate analytical methods [1, 2], weight function [3, 4], finite element method [5, 6], finite element alternating method [7, 8]. Within the context of fracture mechanics, the failure analysis under cyclic loading can be realized through appropriate crack growth laws. Paris and Erdogan [9] experimentally investigated the propagation process, and found that the crack growth is depended on the applied stress intensity range. Then, Forman [10] suggested that the stress ratio and the fracture toughness together with the stress intensity factor range can be used to describe the crack propagation under cyclic loading. Weertman [11] recognized that the crack growth can be consider if the maximum stress intensity factor are include together with the facture toughness and the stress intensity factor range. Further, Elber [12] suggested that the A