PSI - Issue 39

N.A. Makhytov et al. / Procedia Structural Integrity 39 (2022) 266–272 Makhutov N.A./ Structural Integrity Procedia 00 (2019) 000–000

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In Fig. 1c the effect of decreasing crack growth rates with decreasing initial angle of inclination ∗ β , and rate speeding in the direction of the b axis depending on the growth rate in the direction of the calculated axis ∗ a are clearly illustrated. For engineering calculations, a complex configuration of the crack surface development, with sufficient accuracy, can be modeled by a design semi-elliptical plane with an inclination angle ∗ β . A crack is modeled by its projection onto a plane perpendicular to the axial force (the first main to stress).

(a)

(b)

(c) Fig. 1 . (a) Scheme of a tubular welded specimen with initial cuts; (b) the isometric image of a crack developing from initial semi-elliptic notch: A is the calculated surface of the crack, B is the contour of the real surface of the crack, C are the points of the real surface of the crack; (c) photograph of the crack surfaces development with an initial angle in the cross section of the specimen after the final rupture at a nominal relative load 1.00; 1.04; 1.40; 1.90 / ⋅ ± ± = ± ⋅ ± = m m T σ σ σ on specimens made of 08Kh18N10T steel. For measurement of the opening and local strain top cut on polished surface sample inflicted the square net with at a walk 0.05 – 0.10 mm on special device (Fig. 2a) increase cracks in depth sample valued the method of the paints, carried in half of the cycle of the sprain in cavity of the rift through determined number of the cycles loading. Accuracy of the fixing of the net of the high-hat by means of scale of the microscope (0.005 mm). In process of the test measured length of increase crack and local strain, as from 0.01 mm by means of optical system (Fig. 2b). Kinetics of the change the form whole surfaces of the developed rift defined on picture of the bands of the paint. Accuracy of the measurement strain by method of the nets increases on measure of the increase deformation. Local strain measured by means of optical system, collected on base of the horizontal microscope of the type MG, accurate to 0.0001 mm.