Issue 32

I. Telichev, Frattura ed Integrità Strutturale, 32 (2015) 24-34; DOI: 10.3221/IGF-ESIS.32.03 33 The Tab. 1 presents a comparison with the computational results obtained by the finite element method [1] to quantify the critical crack length in the cylindrical pressurized module experiencing 68.6 MPa hoop and 34.3 MPa longitudinal stresses respectively. The numerical analysis was performed for 2219-T87 aluminum alloy shell with the following parameters: σ u =430 MPa, σ y =343 MPa, E =73800 MPa, ν=0.33, wall thickness t s =3.17 mm, toughness at the crack initiation K ic = 68 MPa m 1/2 and toughness at the maximum load K c max = 92 MPa m 1/2 [1]. The comparisons shows that the computational results obtained by the finite element and singular integral equations methods are in a good agreement. The numerical experiments on the reinforced habitable modules of the International Space Station showed the “unzipping” of the pressure wall is unlikely. Method Critical crack length, mm Crack initiation Crack unstable growth Elasto-Plastic FEM [1] <599 1041 Present approach 590 1082 Deviation,% N/A 3.4 Table 1 : Critical crack length (specimen: 2219-T87, t s =3.17 mm) C ONCLUSIONS he present paper is focused on the engineering methodology which is viewed as a key element in the spacecraft design procedure providing that under no circumstances will the “unzipping” occur. A model of crack propagation in impact-damaged pressurized aerospace structure is presented. The non-linear fracture analysis is performed by the method of singular integral equations. Comparisons of the calculated results with the test data and numerical results obtained by finite element method showed good agreement. The suggested SIE-based approach is concluded to be effective way of assessing the fracture behavior of the impact damaged aerospace pressurized structures. A CKNOWLEDGEMENTS his work was supported by a Discovery Grant No. 402115-2012 from the Natural Sciences and Engineering Research Council of Canada. R EFERENCES [1] Couque, H. et al. SwRI-NASA CR 64-00133 (1993). [2] Lutz, B.E. & Goodwin, C. J.. NASA CR 4720, (1996). [3] Elfer, N. C. NASA CR 4706, (1996). [4] Telichev, I., Unstable crack propagation in spacecraft pressurized structure subjected to orbital debris impact, Canadian Aeronautics and Space Journal, 57(1) (2011) 106-111. [5] Patsyuk, V. I., Rimskii, V. K., Instantaneous formation of a round hole in a stretched plate, Int. Applied Mechanics, 27 (1991) 1117-1123. [6] Muskhelishvili, N.I., Some basic problems of the mathematical theory of elasticity, Leyden: Noordhoff Int. Publ. (1975). [7] Savruk, M. P., Method of singular integral equations in linear and elastoplastic problems of fracture mechanics, Mat. Sci., 40(3) (2004) 337-351. [8] Ladopoulos, E.G., Singular Integral Equations: Linear and Non-Linear Theory and Its Applications in Science and Engineering, Springer Verlag Gmbh, (2000). [9] Chernyakov, Y.A., Grychanyuk V., Tsukrov, V.I., Stress–strain relations in elastoplastic solids with Dugdale-type T T