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dissertation global and local fracture properties of metal matrix ...

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σ p<br />

max [MPa]<br />

σ p<br />

max [MPa]<br />

1200<br />

800<br />

400<br />

1200<br />

800<br />

400<br />

0<br />

0<br />

Section 4<br />

0 100 200 300 400 500<br />

r [µm]<br />

a)<br />

0 20 40 60 80<br />

θ [°]<br />

60<br />

15 min<br />

200h<br />

15 min<br />

200h<br />

b)<br />

Fig. 4.25. The σ p max-values vs. (1) the distance between crack tip <strong>and</strong> particle, r, (2) the angle<br />

between the crack tip <strong>and</strong> the particle for different aging conditions <strong>of</strong> the PM-MMC.<br />

For the present model, i.e., spherical particles <strong>and</strong> isotropic material behavior, the maximum<br />

normal interface tractions are identical to the maximum principal stresses in the particle [88].<br />

However, the interfacial stresses for the Al2O3 <strong>and</strong> SiC particles in the MMCs can be<br />

estimated according to Argon et al (Eq. 2.3), as well. These values are also listed in Tables<br />

9.1-9.17. It is seen that they are slightly less in comparison with the σ p max-values. The<br />

dependence <strong>of</strong> these interfacial stress values on the r <strong>and</strong> θ is similar to dependence <strong>of</strong> the<br />

σ<br />

p max-values (Figs. 4.25 - 4.27).

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