Issue 47

Yu. G. Matvienko et alii, Frattura ed Integrità Strutturale, 47 (2019) 303-320; DOI: 10.3221/IGF-ESIS.47.23 310 respectively. Maximum circumferential strain at the hole edge equals to max   = 0.01 for max  = 250 MPa. This loading range for this aluminium alloy leads to arising high-level plastic strains at the hole vicinity during several first cycles and further material hardening for specimens with small plain hole due to stress concentration influence [37]. The value of theoretical stress concentration factor for central open hole of diameter 2 0 r = 4.0 mm in rectangular plate of width w = 30 mm is equal to t K = 3.06 [38]. This fact might lead to a considerable residual stress and, in turn, fracture mechanics parameters redistribution for specimens of T5-H1 group due to low-cycle fatigue. The cycle with parameters   = 350 MPa and R = –1.0 represents the lower limit of stress ratio values, which might take place during operations of airplane structures with pin or/and rivet joints. a b c d Figure 4 : Specimen T5_25H. Interference fringe patterns obtained in terms of in-plane displacement component u (a, b) and v (c, d); a, c – initial crack length 0 a = 0 with the increment 1 a   = 2.62 mm (left) and 1 a   = 2.48 mm (right); b, d – initial crack length 1 a  =2.62 mm with the increment 2 a   = 1.82 mm (left) and initial crack length 1 a  = 2.48 mm with the increment 2 a   = 2.10 mm (right).