PSI - Issue 10

V.N. Kytopoulos et al. / Procedia Structural Integrity 10 (2018) 272–279 V. N. Kytopoulos e al. / Structural Integrity Procedia 00 (2018) 000 – 000

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3. Results and discussion

In Fig.3 the master-curve of the measurements concerning the evolution of the fracture damage with different types of initial damage is shown. At first, one may observe the expected decreasing behavior of fracture damage with in creasing initial damage. In respect to this fact, edge crack initial damage causes linear decrease whereas the hole initial damage a lower rate-coupled non linear decrease in the fracture damage. This could be explained by the fact that upon stressing high stress concentration fields formed around “sharp” edge crack, as dominant energy sink, may lead to an early crack initiation and propagation, coupled with a high rate of strain energy inflow into the crack region. This high rate, in turn, reduces the needed time and energy for formation of other kinds of damages within the material. In contrast to this, in the case of initial hole damage, the low stress concentration fields around hole sites permit enough time for energy dissipation needed for development of other “surplus” microdamage sites within the material of crack region taking place up to final fracture. In Fig.4 the evolution of damage process in intensity number k with initial damage is presented. One can observe the similar behavior of this number with that of fracture damage. It seems that the process intensity of damage forma-

1.2

0.8

D f

0.4

Initia l hole-damage Initia l common edge-crack damage Slanted edge-crack damage

0

0

0.2

0.4

0.6

D 0

Fig. 3. Master curve: Evolution of fracture damage D f with initial damage D 0 .

1.2

0.8

k

0.4

Initia l hole-damage Initia l common edge-crack damage Slanted edge-crack damage

0

0

0.2

0.4

0.6

D 0

Fig. 4. Evolution of damage process intensity number k with initial damage D 0 .