Application of new constraint based Master Curve in fracture assessment of pressure vessels

摘要

This paper represents the ability of the recently developed methodology for evaluating fracture probability of the ferritic steel components based on the Master Curve methodology. Due to crack-tip constraint, a cracked component may experience a significant change in its effective fracture toughness under a given load and temperature, whereas the Standard Master Curve (SMC) method cannot take into account this change. In this study the conservatisms associated with SMC method for low constraint geometries is investigated for a pressurized cylindrical vessel containing an internal semi-elliptical axial crack. A modification of SMC is developed based on the Q parameter as the crack-tip constraint. The usability of the Modified Master Curve (MMC) approach for structure integrity assessment of the pressure vessel is demonstrated. Three different assessment methodologies including, classical fracture mechanics, SMC, and MMC are compared for failure assessment of a cracked pressure vessel in ductile-to-brittle transition (DBT) region. It is shown that the developed MMC approach has appropriate capability to reduce the overly conservatism in failure assessment results obtained from the other two methods.