Prevention of catastrophic failure of pressure vessels and piping: Comparison of experimental and computational results of the pressure vessel test HC2

The structural integrity assessment of pressure boundary components requires reliable knowledge of the relevant material parameters and valid, reliable analysis methods. To improve the accuracy and validity of the experimental and computational fracture assessment methods, a four year research programme on elastic-plastic fracture mechanics was performed during the years 1985-1989 under auspices of the Nordic Liaison Committee of Atomic Energy. The scope of the programme included the testing of small fracture mechanics specimens and full-scale pressure vessels in order to provide experimental data for the validation of stress and fracture mechanics analyses. The two main tests were conducted on a decommissioned reactor pressure vessel from an oil refinery plant. Before testing, axial flaws were produced along the inner surface of the vessel. After the first test, the vessel was repaired by welding using the temper-bead technique without postweld heat treatment. Residual stresses, which were measured during and after welding, influenced the fracture behaviour of the vessel causing a discrepancy between the actual rupture pressure and the estimated rupture pressure. The effect of welding residual stresses and material property variation on the fracture assessment of the second pressure vessel test has been studied. The results of the analysis are presented and compared to the experimental findings.