Issue 50

I. G. F. Silva et alii, Frattura ed Integrità Strutturale, 50 (2019) 46-53; DOI: 10.3221/IGF-ESIS.50.06

Figure 2 : Safety margin M 1 .

Figure 3 : Safety margin M 2 .

Limit load analysis The limit load analysis must also be applied to check for failure by plastic collapse. This application was performed with the help of PICEP software [12] to calculate the critical crack size (L cr ). Two applications of the limit load analysis were performed for each of the evaluated materials, called Case 3 and Case 4, defined according to the LBB methodology. In Case 3, the verification considered the normal operation loading plus SSE. In Case 4, the verification considered the excessive loading. Tab. 7 presents the calculated values for Case 3 and 4, respectively.

Critical crack size for Case 3 - L cr3 [mm]

Critical crack size for Case 4 - L cr4 [mm]

Material

SA-508 Cl. 3 SA-106 Gr. B SA-376-TP304

452.29 421.73 415.62

415.62 378.94 378.94

Table 7 : Critical crack size for Cases 3 and 4.

The safety margin was defined as the ratio between L cr and L Q

, where M 3

corresponds to the safety margin for Case 3, and

M 4 corresponds to the safety margin for Case 4. The performance evaluation of materials for limit load analysis was based on the values of these safety margins. Figs. 4 and 5 present the safety margin M 3 and M 4 , respectively, for each of the evaluated materials.

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