Finite-element pre-analyses for pressurized thermoshock tests: Vessel I: Tests 4, 5 and 6

The behaviour of a model pressure vessel is studied in a pressurized thermal shock loading. The tests were performed at the Prometey Institute in St. Petersburg. The calculations were performed at the Technical Research Centre of Finland. This report describes the preliminary finite- element analyses for the fourth, fifth and sixth thermoshock tests with the first model pressure vessel. Seven pressurized thermoshock tests were made with the same model pressure vessel using five different flaw geometries. In the first three tests the flaw was actually a blunt notch. In the two following tests (tests 4 and 5) a sharp pre-crack was produced before the test. In the last two tests (tests 6 and 7) the old crack was used. According to the measurements and a post-test ultrasonic examination of the crack front, the sixth test led to significant crack extension. Both temperatures and stresses were calculated using the finite- element method. The calculations were made using the idealized initial flaw geometry and preliminary material data. Both two- and three-dimensional models were used in the calculations. J-integral values were calculated from the elastic-plastic finite-element results. The stress intensity factor values were evaluated on the basis of the calculated J-integrals and compared with the preliminary material fracture toughness data obtained from the Prometey Institute. When the calculated temperatures, strains and crack opening displacements are compared to measured values, a sufficient agreement is observed. The calculated stress intensity factor exceeds the preliminary material fracture toughness value and thus crack initiation is predicted.