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

212

4

effect of this parameter on the overall response. Specifically, an interfacial layer covering 1% of the overall volume of the unit cell does not affect the quality of numerical results (Palkanoglou et al., 2020).

(a)

(b)

(c)

(d)

Fig. 2: Geometrical parameters of unit cells in μ m: (a) and (b) minimum distance; (c) and (d) maximum distance.

Assuming the effective thermomechanical behaviour for the metallic matrix, it was considered as an isotropic and ductile material. Therefore, an elastoplastic J 2 flow theory of plasticity was selected to describe its constitutive behaviour. In addition, the yield point and yield strain were assumed to be temperature-dependent. Although graphite is brittle and soft, there is some evidence in the literature that it has a limited ability to deform plastically; hence, the classical plasticity theory can be used for it ( Seldin, 1966; Greenstreet et al., 1973; Andriollo et al., 2015). The values of all constitutive parameters for both graphite and matrix are given in Table 2. It is noted that the effective properties assumed for the metallic matrix were derived from in-house mechanical tests of CGI specimens.

Table 2: Constitutive parameters for matrix and graphite inclusions. Ferritic matrix

Coefficient of thermal expansion

Young’s modulus (GPa)

Poisson’s ratio

Yield point (MPa)

Temperature (°C)

Yield strain

50

324.0 316.8 301.2 265.9 257.7

0.209% 0.195% 0.225% 0.178% 0.179%

150 300 400 500

150

0.25

1.2×10 -5

Graphite

50

15.85

0.2

2.9×10 -6

27.56

0.184%