PSI - Issue 37

Evangelia Nektaria Palkanoglou et al. / Procedia Structural Integrity 37 (2022) 209–216 E. N. Palkanoglou et al. / Structural Integrity Procedia 00 (2019) 000 – 000

214 6

10

5

min distance max distance

Fraction of debonded areas (%)

320 340 360 380 400 420 440 460 480 500 0

Temperature (  C)

Fig. 3: Evolution of thermal decohesion of vermicular inclusion due to interaction with particle of equal size and shape.

3.2. Interaction between vermicular and nodular inclusions

The influence of a nodular inclusion on the fracture of a vermicular one and vice versa is presented in this section. The initiation and evolution of graphite debonding for a nodular inclusion when interacting with a vermicular one is depicted in Fig. 4. Debonding of a nodular particle when interacting with a vermicular one started later compared to the previous combination of particles (see Section 3.1), regardless of the distance between them. Interaction between the two vermicular particles caused development of stresses in microstructure due to their complex shape that accelerated the appearance of debonding. In addition, the phenomenon was affected by the distance between the two particles. This might be attributed to the lower symmetry of the problem. As already discussed, decohesion is generally caused by the different response each constituent of microstructure has to thermal load; however, secondary stresses developed due to this particular combination of particles might have triggered the appearance of decohesion at different temperature levels. Further, the evolution of debonding was highly influenced by the interaction between the two particles. As the distance between them became smaller, the fraction of the areas of the nodular particle that lost their contact with the matrix increased, due to the secondary stresses induced by the interaction.