PSI - Issue 18

Vladimír Chmelko et al. / Procedia Structural Integrity 18 (2019) 600–607 Chmelko, V., Berta, I / Structural Integrity Procedia 00 (2019) 000 – 000

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Fig. 5 Experimental measurement of burst pressure: 1 - frame of electrohydraulic pulsator, 2 - straight-line hydraulic motor, 3-tested specimens

Results in Tab. 1 show a very good agreement of analytical and numerical solution for a very long defect-free cylindrical vessel, and also a very good agreement of analytical solution with numerical for a closed cylindrical vessel corresponding to the experimental model - these results are practically identical for the binary model of material used. Values of experimentally determined burst pressures are almost 4% higher than analytical and numerical solutions for bilinear material model. The results of relatively demanding experiments have shown that the choice of the Huber Mises-Hencky criterion is in better agreement with reality (for a given type of task and material) than under the Tresca criterion. 5. The burst of pipes with corrosion defect The same specimens of pressure pipe was also used to determine the burst pressure when a 41mm (25mm wide), 24, 35 and 75% wall thickness reduction in the direction of the vessel axis was simulated (Fig.6). Used material model, the FEM simulation procedure and the experimental measurement of the burst pressures were the same as in the previous chapter. Tab. 2 shows the burst pressure values for a sample of a corrosion defect pipeline obtained experimentally (p experimental ), obtained by numerical calculation in ANSYS (p FEM ) with the criterion of destruction according to the criterion H-M-H (eq. 16) and obtained by calculation according to ASME B31G resp. DNV-RP F101. The highest burst pressures are the true pressures obtained experimentally. Numerical computations using the criterion H-M-H - 6.5%, 10% and 11% were the closest to these real values (use of Tresca criterion resulted in significantly greater difference in destructive pressure values compared to experimental values). The burst pressure values calculated using the relationship from standards differ by more than 20% (standard DNV-RP-F101) and by more than 30% (ASME B31G standard). The relatively high conservative results of the burst pressures obtained by the standards (ASME, DNV) is understandable. However, in numerical models, all factors can be taken into account to determine destructive pressures closer to their true values. They are therefore a tool that could legitimately help to prolong the serviceability of damaged pipe sections and thus establish more realistic safety values against the destruction of such pipe sections.