4.3 Mesoscopic composite model of the simulation of creep cavity damage and fracture

The flow diagram structure is shown in Figure 10; the FE model of the polycrystalline case is shown in Figure 11 [31].

At the time of 78.9 hours, there were seven grain boundary elements that failed. If that is deemed as creep fracture time, then it agrees with the majority of all

#### Figure 9.

Inverse U<sup>0</sup> and stress level for P91 at 625°C.


#### Table 4.

The values of nucleation coefficient and growth coefficient and lifetime prediction.

Modeling of Creep Deformation and Creep Fracture DOI: http://dx.doi.org/10.5772/intechopen.89009

Figure 10. The flow diagram structure [31].

Figure 11. The FE model of the polycrystalline case study [31].

#### Figure 12.

The location of the first seven failed grain boundary elements [31].


#### Table 5.

The sequence and time of fracture [31].

#### Figure 13.

The damage evolution with time of the seven failed grain boundary elements [31].

uni-axial creep tests conducted [9]: In uniaxial test, one specimen is fractured at 16.6, 17.9, and 58.3 hours, respectively. It is worthy to mention that the simulation was conducted for plane strain case; hence a longer lifetime at the same applied stress is expected.

The location, the sequence of fracture, and the time of fracture of grain boundary element are shown in Figure 12 and Table 5, respectively. The creep cavity damage evolution with time of the first seven failed grain boundary elements is

#### Modeling of Creep Deformation and Creep Fracture DOI: http://dx.doi.org/10.5772/intechopen.89009

#### Figure 14. The evolution of normal stress with time [31].

shown in Figure 13. The whole all normal stress evolution and the creep cavity damage evolution are shown in Figures 14 and 15, respectively.
