PSI - Issue 68

Elena Fedorova et al. / Procedia Structural Integrity 68 (2025) 908–914 Elena Fedorova et al./ Structural Integrity Procedia 00 (2025) 000–000

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Fig. 3. Loading fixture in Tinius Olsen H25KT testing machine (a); typical loading curve (b).

The coating delamination zone was further studied using SEM micrographs to estimate the surface area of spallation occurred (Fig.4).

Fig. 4. SEM micrographs of representative TBC delamination zone.

The mode II energy release rate determined with the peak load for initial delamination and estimated surface area of delaminated zone according to Hutchinson (1991) approach are varied from 90 to 120 J/m 2 . The advantages and disadvantages of considered configurations (Fig. 2b) were evaluated during the tests. It was observed that increased contact area in the case of configuration with round punch makes it difficult to position it along the substrate/TBC interface. Therefore, the configuration with flat punch is recommended to be tested. 4. Influence of TGO thickness on residual stress state and interface cracking behavior A two-dimensional finite element model of a periodic segment of TBC system was created using the ANSYS software (ANSYS, 2016). The TGO/BC and TGO/TC interfaces were modeled by a sinusoid with wavelength of 50 μm and amplitude of 10 μm, thus forming the TGO layer. Different thicknesses of TGO – 10, 5, 2.5 and 1 μm were considered. The model includes more than 30000 second-order elements with the generalized plane strain option. Mesh refinement to a linear element size of 0.05 μm was used in the areas adjacent to the interface boundaries. Contact cohesive elements were generated at the nodes located at TGO/BC and TGO/TC interfaces. The boundary conditions of symmetry and periodicity are applied on the opposite lateral edges of the segment, the nodes at the boundary of the metal substrate are fixed along the y direction (Fig. 5).