PSI - Issue 68

Minghua Cao et al. / Procedia Structural Integrity 68 (2025) 828–834 M. Cao et al. / Structural Integrity Procedia 00 (2025) 000–000

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The damage distribution in graphite inclusions at 20 °C at the end of the thermal cycle was summarized for comparison (Fig. 5). Graphite with T-CTE (Figs. 5(d)-(f)) exhibited higher damage values than those with C-CTE (Figs. 5(a)-(c)) due to greater interaction between the graphite particle and the matrix in the former case. The maximum thermal mismatch between the graphite and matrix domains occurred near the top surface of the unit cells resulting in higher damage at this location. Spherical graphite and vermicular graphite VV particles showed higher damage values compared to vermicular graphite VH particles, which can be attributed to the larger volume of the former two in the Z direction.

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Fig. 5. Graphite damage distribution at 20 °C after cooling down for graphite particles with different graphite CTEs: C-CTE for Ver_VV (a); Nod (b) and Ver_VH (c); T-CTE for Ver_VV (d); Nod (e) and Ver_VH (f).

3.2. Effect of graphite on matrix behaviours Analysis of distribution of shear strains and stress in the metallic matrix for all cases showed concentration along the 45° and 135° direction in the XY planes (Fig. 6), with the strains approaching the absolute value of 8.5× 10 !1 . The strong shearing observed in the matrix is thought to significantly contribute to the damage in the graphite inclusions (Schmauder et al. (2003)). Consequently, the areas of high shearing in the metallic matrix correspond to the locations with the highest levels of graphite damage, maintaining a consistent relationship between the shear stress and the damage occurrence. When the vermicular graphite with sharper, more angular edges (Ver_VV) comes into contact with the matrix, both the affected area and the maximum shear stress and shear strain levels in the matrix are greater than when the graphite has more rounded edges (Ver_VH).

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