PSI - Issue 28

Mingyang Li et al. / Procedia Structural Integrity 28 (2020) 472–481 Author name / Structural Integrity Procedia 00 (2019) 000–000

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is not obvious. However, when it comes to 50 grains, only the characteristics of the major crack is dominant. Next, the grain number is constrained as 150, but the porosity ratio is increased from 2% to 5%, by rising 1% for each case (Fig. 9). Although the change is not obvious initially, with the rise of the porosity ratio, the severity of the fracture especially the main crack becomes increasingly significant.

(a)

(b)

(c)

Fig. 8. Porosity distribution (left), crack distribution with grains (middle) and damage at 2 μs (right), (a) 150 grains, (b) 100 grains, (c) 50 grains

Finally, the GBC value is increased from 0.5 to 1. The remaining variables are kept the same. By doing so, the behaviour at the microscale becomes more identical to the macroscopic material. It is obvious that the behaviour of the main cracks is converted from intergranular pattern to transgranular pattern (Fig. 10). In conclusion, the severity of the crack especially the newly created cracks are influenced by the number of grains and porosity. Concerning the influence of grain boundary strength, with the increase of GBC, the effect of porosity dramatically decreases and the fracture pattern in microscale becomes identical to the macroscale crack pattern.