PSI - Issue 36

Ivan Pidgurskyi et al. / Procedia Structural Integrity 36 (2022) 171–176 Ivan Pidgurskyi, Mykola Pidgurskyi, Petro Yasniy et al. / Structural Integrity Procedia 00 (2021) 000 – 000

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approximated values of the coalescence factor γ coal . Moreover, the influence of these two input factors is ambiguous: at larger values of a/ 4 c and small a coal / a , the coalescence factors γ coal are maximal ( γ coal ≥ 3 at a coal / a < 0.2), gradually decreasing with the increase of a coal / a . The minimum values of the coalescence factor γ coal are within range γ coal.min = 1.48… 1.51 with the changes in the values of the factors: 0.14 ≤ a/ 4 c ≤ 0.22 and 0.7 ≤ a coal / a ≤ 0.95. The maximum values of the coalescence factor γ coal at a coal / a < 0.2 can be explained by the large values of SIF K 1 in the conjugation zone at the initial stage of crack coalescence. As a coal / a increases further, the SIF values and the coalescence factors γ coal in the saddle-shaped contour decrease, approaching the SIF value at the deepest point of the surface crack formed as a result of the coalescence. Another reason for the increase in the values of γ coal is the increase in the input factor a/ 4 c , which characterizes the geometric parameters of the merging cracks. Thus, increasing of a/ 4 c to 0.125; 0.175; 0.25 leads to the increase in γ coal by 1.11; 1.26; 1.57 times, respectively, compared with γ coal = 3.04 for a/ 4 c = 0.075. The values of the coalescence factors γ coal during the coalescence of surface cracks obtained from the regression equation (2) allow to determine the maximum SIF in the coalescence zone depending on (1). According to the obtained values of SIF and known values of the cyclic crack resistance of the material, we can proceed directly to the study of the kinetics of fatigue failure and survivability of the structural element. 4. Conclusions A simulation model of coalescence of two semi-elliptical surface cracks during their gradual coalescence under cyclic loading has been developed. The model is based on substantiation of geometrical parameters of a series of fixed configurations contours simulating development of saddle-shaped front of the united crack and on an estimation of SIF of characteristic points of these contours. A regression equation, which estimates the coalescence factors of two identical surface cracks during their coalescence, which depend on the geometric dimensions of the crack and the parameter of their relative coalescence, Anderson, Ted L., 2017. Fracture Mechanics Fundamentals and Applications, Fourth ed., Boca Raton, CRC Press. Andreikiv, О.E., Babii, А.V., Dolinska, І.Yа., 2020. Influence of the Working Media and Maneuvering Loading Mode on the Servi ce Life of Spraying Booms of Field Sprinklers. Materials Science, Vol. 56, 166 – 173. Banks, Jerry, Carson, John, Nelson, Barry, Nicol, David, 2009. Discrete-Event System Simulation. 5th Edition – Pearson, 648 p. Bezensek, B., Hancock, J.W., 2004. The re-characterisation of complex defects: Part I: Fatigue and ductile tearing, Eng. Fract. Mech. V.71, I. 7 8, 981-1000. Brighenti, R., Carpinteri, A., 2013. Surface cracks in fatigued structural components: a review / Fatigue Fract Engng Mater Struct, 36, 1209 – 1222. Coules, H.E., 2016. Stress intensity interaction between dissimilar semi-elliptical surface cracks International Journal of Pressure Vessels and Piping, V.146, 55-64. Kikuchi, M. 2016. Study on multiple surface crack growth and coalescence behaviors AIMS Mat. Sci., 3(4), 1623-1631. Law, Averill M., (2014). Simulation Modeling and Analysis. McGraw-Hill Series in Industrial Engineering and Management, 5th Edition, 800 p. Patel, S. K., Dattaguru, B., Ramachandra, K., 2010. Multiple Interacting and Coalescing Semi-Elliptical Surface Cracks in Fatigue P. 1: FEA, SL, V.3, N.1, 37-57. Pidgurskyi, I., Stashkiv, M., Pidgurskyi, M., 2021. Investigation of the coalescence of twin coplanar semi-elliptical fatigue cracks in structural steel elements under cyclic loading. Machines. Technologies. Materials ., Vol. 15, Issue 8, 316-318. Pidgurskyi, M., Stashkiv, M., Pidgurskyi, І., Makar, A., 2020. Numerical investigation of stress intensity factors for surfac e cracks under coalescence. Procesy zmęczenia i mechanika pękania. Opole, Vol. 536, 231-246. ISSN 1429-6063, ISBN 978-83-66033-76-4. Santorico, Stephanie, Shin, Mark, 2010. Tutorial for the R Statistical Package. University of Colorado Denver, 30 p. is obtained. References