PSI - Issue 28

Carlos D.S. Souto et al. / Procedia Structural Integrity 28 (2020) 146–154 Carlos D.S. Souto et al. / Structural Integrity Procedia 00 (2020) 000–000

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4.1. Modified virtual crack closure technique

In Omicron, two finite element models were developed: one where the crack belongs to a plane of symmetry (1 / 4 plate model) and another where the crack does not belong to a plane of symmetry (1 / 2 plate model). Using the mVCCT, the value of a increased from 0 to w and the stress intensity factor was determined for each value of a .

(a) 1 / 4 plate model (crack with symmetry).

(b) 1 / 2 plate model (crack without symmetry).

Fig. 5: Node path definition in Omicron to increase the length of the crack, a .

To simulate the uniaxial tensile test, the following boundary and load conditions were used for the 1 / 4 plate model:

x = 0 ⇒ u = 0

y = 0 ∧ x > a ⇒ v = 0

y = h ⇒ σ y = 500 MPa

(12)

And for the 1 / 2 plate model:

x = 0 ⇒ u = 0

y = − h ⇒ v = 0

y = h ⇒ σ y = 500 MPa

(13)

As seen in Figure 6 and Figure 7, Omicron automatically updates the crack’s length to determine the stress intensity factor. Figure 8 shows the obtained results for K ( a ). For future comparisons is considered a = 5 mm, K = 1980 . 5 MPa · mm 1 / 2 .

(a) 1 / 4 plate model (crack with symmetry).

(b) 1 / 2 plate model (crack without symmetry).

Fig. 6: Deformed state (deformation scale: × 10) and von Mises stress for a = 5 mm.