Validation of a Concept for Burst Pressure Prediction by Damage Mechanics

Abstract

In ASME and EN pressure vessel standards the stress-based dimensioning is currently performed by either applying experience-based safety factors directly on the material’s yield or tensile strength (EN) or incorporating them in the allowable stress derivation (ASME). The current concept is penalizing modern high strength pressure vessel steels due to their yield-to-tensile ratio. The application of these steel grades is hindered despite their excellent mechanical properties. Possible benefits cannot be exploited. Probabilistic safety concepts are a suitable approach to derive adequate safety factors for high strength steels. But their application requires a large number of expensive full scale burst tests. Therefore, it is proposed to replace these by numerical simulations using damage mechanics. This paper aims at validating such a concept for the numerical prediction of burst pressures. The presented procedure uses a Gurson model to represent ductile failure behavior on the specimen scale and correlates it to an efficient strain-based failure criterion, which is more suitable for simulations on full component scale. The validation is performed on a demonstrator pressure vessel of the high strength steel P690Q. The strain-based failure criterion is derived on small scale tests and applied in simulations of the pressure vessel. The numerically predicted burst pressure only exceeds the actual burst pressure by 6% and the critical locations are correctly predicted. The approach is validated successfully. Suggestions for further improvements are made.