PSI - Issue 42

Vera Petrova et al. / Procedia Structural Integrity 42 (2022) 1145–1152 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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5. Conclusions Based on classical but rather effective analytical and numerical methods, such as the method of analytical functions of complex variables and singular integral equations, the problem is studied for FGC/H structures containing a pre existing system of multiple cracks. Formulas with application of the RoM model were used to evaluate the properties of FGCs. At first, the stress intensity factors are calculated, then, using the fracture criterion of maximum hoop stresses, the fracture angles and critical stresses are obtained. Illustrative examples are presented to show the influence of material and geometrical parameters of the problem on the fracture characteristics of interacting cracks. The weakest cracks in the considered system of three edge cracks are the outer edge cracks (1 and 3) in the FGC/H structure, (ceramic/metal/)metal. The shielding effect is observed for the middle crack 2. The presence of an internal crack with the center on the line of crack 2 suppresses the propagation of the middle crack 2 and enhances the propagation of the outer edge cracks 1 and 3. That is, an additional internal crack influences on the edge crack interaction, but the shielding effect is generally not disturbed. The structural variation of fracture toughness for the FGM was taken into account in the calculations. For the grading parameter λ in the RoM model, it was obtained: variation of λ leads to a significant change in the fracture parameters, in particular, critical loads. On the basis of the developed theoretical model, which allows to correlate the material parameters, geometrical parameters and the main fracture characteristics, an optimization problem can be solved, e.g. to find a gradation parameter and crack arrangements that maximize the thermal critical stresses, i.e. increasing the fracture toughness for FGC. 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