Issue 35

K. Slámečka et alii, Frattura ed Integrità Strutturale, 35 (2016) 322-329; DOI: 10.3221/IGF-ESIS.35.37 327 Figure 7 : The stress state (  1 ,   2 ) in the top coat for t TGO = 0 µm (left) and t TGO = 3 µm (right) in all nodes of the YSZ top coat. The third principal stress,  3 , is compressive in the whole YSZ layer. Incorporating Microstructure and Damage evolution – FEMME The damage, which affects the thermal conductivity, has an influence on the temperature of the TC and substrate. To evaluate this, the temperature in each of the finite elements is computed as the average of the temperature in its nodes; this is illustrated in Fig. 8, which shows the variation of the average temperature at two points, on either side of the TGO layer, that are the same distance (5 mm) from the center of the tube. With this we evaluate points under and above the TGO layer. The damage is calculated as an average, from the point analyzed to the surface, of the ratios between the current Young modulus of each element (this reflects erosion of CA cells) and its original values. Figure 8 : The relationship of the element temperature and damage to the external temperature, at a two points on either side of the TGO layer that are both a distance of 5 mm from the tube center. The element temperatures are lower than the external temperature due to the low thermal conductivity of the top coat. This is clearly affected by the damage evolution, as the relationship exhibits two regions of different slope; the region at lower external temperature is associated with fractures propagating through the TGO layer, while the region at higher temperature is associated with fracture propagating from the TGO layer to the external surface. Up to 820 ºC the