Issue 30

C. Barile et alii, Frattura ed Integrità Strutturale, 30 (2014) 211-219; DOI: 10.3221/IGF-ESIS.30.27

Figure 5 : Screenshot of the area of analysis included between the outer circle (dashed line) and the inner circle (dotted line). The solid line identifies the drilled hole.

Depth [mm]

σ xx

[MPa]

σ xx

[MPa]

|Δσ xx (Δr ext

%|

σ xx

[MPa] =3.5)

|Δσ xx

% |

σ xx (r ext

[MPa] =4.36)

|Δσ xx

%|

(r ext

=4)

(r ext

=3)

=-1)

(r ext

(Δr ext

=-0.5)

(Δr ext

=+0.358)

0.04 0.12 0.20 0.28 0.36

148 126 103 103

131 118 101

11.5

142 124 102

4.0 1.6 0.9 3.4 2.9

150 128 103 107

1.3 1.6 0.0 3.9 5.5

6.3 1.9

96 72

7

99 70

68

5.8

68

Table 2 : Summary of the calculated stress for the default radius of r ext

=4 and the percentage change of stresses Δσ xx

using different r ext .

Figure 6 : Plot of the difference in terms of measured stress at different depths. The difference are calculated for three different values of the external radius with respect to the reference value r ext =4 It can be observed that increasing the external radius of analysis to the maximum value R ext =3.48 mm (r ext =4.36), which means an 8.95% of variation with respect to the default value, calculated stress at 0.36 mm depth changes about 5.5 %. Analogously, decreasing the external radius of analysis to the value R ext =2.4 mm (r ext =3), which means a 25% of variation with respect to the default value, the calculated stress at 0.36 mm depth changes about 5.8 %. From Fig. 5 it can also infer that the maximum difference (17 MPa) is obtained by using the smallest value of external radius in correspondence of the smallest depth, that is to say at about 11.5 % of variation. This attitude could be connected to the fact that reducing the

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