Material constraint parameters for the assessment of shallow defects in structural components. Part II: Constraint-based assessment of shallow defects

Abstract

This Part II paper describes a series of constraint-based R6 assessments of shallow-cracked specimens under equibiaxial loading using material constraint parameters obtained from lookup tables presented in the companion Part I paper. Parameters are derived for an A533B-1 steel forging from a knowledge of the yield and flow behaviour of the material and a calibration of the Beremin model parameter m. Resulting assessments, which use both T- and Q-stress to quantify constraint, are found to be conservative with respect to the available experimental data. The results are also used to predict the influence of T-stress on the Master Curve reference temperature. Available data are broadly in agreement with the predicted trend curve. Finally, the results demonstrate that out-of-plane biaxial loading increases constraint to the extent that the inherent conservatism of the elastic T-stress at high L r is eroded. Out-of-plane constraint effects are only properly accounted for by the hydrostatic Q-stress and for this reason, the use of T to assess biaxial loading situations should be undertaken with a degree of caution.