PSI - Issue 17

V. Chmelko et al. / Procedia Structural Integrity 17 (2019) 520–525 Chmelko, V., Bíro, D./ Structural Integrity Procedia 00 (2019) 000 – 000

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During vessel is loaded by internal pressure, the triaxial state of stress acts in the shell. Because of that, a criterion of destruction was defined: a state, in which equivalent stress reached the value of the true tensile strength of the material tensile diagram (Fig. 5) was considered as a burst pressure.

Fig. 5. FEM-model of pipe with corrosion defect .

Table 2 shows the burst pressure values for the samples of pipeline (D = 151mm, t = 4 mm) with a corrosion defect of wall thickness obtained experimentally (p experiment ), FEM simulation (p FEM ) and calculated by criteria ASME B31G resp. DNV-RP-F101.

Table.2 Comparison of the burst pressures

Specimen

p experiment (MPa)

P FEM (MPa)

ASME B31G (MPa) DNV-RP-F101 (MPa)

No. 1 No. 2 No. 3

32.1 30.0 18.5

30 27

21.5 19.8 12.2

23.9 21.8 13.7

16.5

4. Conclusions

The highest values of burst pressures are the true pressures obtained by experiment (p experiment ). Results from numerical simulations are the closest to these true values. Difference between them is 6.5% for specimen No. 1, 10% for No. 2 and 11% for No. 3 (used criterion is H-M-H; using of Tresca criterion resulted in significantly greater difference in destructive pressure values compared to experimental values – it is in accordance with Zhu and Leis 2007). Values of burst pressure calculated by DNV-RP-F101 are different about 20% and ASME B31G about 30%. These results represent the pure conservativeness of the relationship from standards because no other non quantifiable effects existed in these cases (ideal geometry, true material diagram obtained by experiment). When the calculated burst pressure values are compared between ASME B31G (the most conservative case) and experimental value (for specimen 2), the safety factor is: = 1.51 ⇒ = 1.51 ∗ (6)