Fatigue crack growth calculations for a vessel internal corner crack under repeated thermal transients

Abstract

A problem of current fundamental and industrial interest is the structural integrity of pressure vessels containing defects when subjected to repeated thermal shock at constant internal pressure. The component considered is a nozzle to a hemispherical pressure vessel intersection containing a defect at the internal corner. A range of 12 cases of thermal shock loads characterised in severity by two dimensionless parameters, the Biot ( B) and Fourier ( F) numbers, were applied. Estimation of remaining life for each case was carried out based on the PD6493 procedure. Numerical modelling of the crack growth from the quadrant shaped crack showed that more severe shocks accelerate crack growth while less severe shock leads to slow growth or eventual crack arrest. The effect of the Biot and Fourier parameters on the remaining life of the component was quantified. A methodology that comprises of heat transfer, thermal stress and fracture mechanics of defect assessment is applied to a problem of industrial interest.