Issue 47

Yu. G. Matvienko et alii, Frattura ed Integrità Strutturale, 47 (2019) 303-320; DOI: 10.3221/IGF-ESIS.47.23 309 a b c d Figure 3 : Specimen T5_21H. 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   = 2.36 mm (left) and 1 a   = 2.35 mm (right); b, d – initial crack length 1 a  =2.36 mm with the increment 2 a   = 1.82 mm (left) and initial crack length 1 a  = 2.35 mm with the increment 2 a   = 1.96 mm (right). Interference fringe patterns of the type shown in Figs. 1–4 are obtained for all specimens accordingly to both loading programs for three notch length increments. Thus, a total number of interferograms is equal to 2×3×14 = 84 for specimens of both groups. Symmetrical configuration of fringe patterns in Figs. 1, 2 and 3, 4 with respect to the crack line clearly demonstrates the validity of mode I conditions. The same configuration takes place for all crack length increments for all specimens. This means that SIF and T-stress values can be reliably determined from the relationships developed for modified version of the crack compliance method [36]. R ESULTS AND DISCUSSION choice of loading programs is based on the following. The cycle with parameters   = 350 MPa and R = –0.4 gives maximum tensile and minimum compressive remote stress max  = 250 MPa and min  = –100 MPa, A