Analysis of Residual Stresses and Assessment of Postulated Cracks in a Core Shroud Weld

Abstract

In order to assess postulated cracks in weldments of a BWR core shroud residual stresses are calculated by simulating the welding process. In the numerical analysis, weld metal deposition and the sequence of weld passes follow the manufacture protocol. The calculations are performed using the finite element program ABAQUS and a material model with kinematic nonlinear hardening. Calculations of the crack driving parameter, the stress intensity factor, are carried out for postulated circumferential cracks using a numerical procedure, as well as by applying a weight function solution specially developed for cracks in a thin-walled cylinder. The results give rise to a discussion on the validity of linear elastic fracture mechanics for assessing defects in weldments. Additionally, for a complete circumferential crack the trend in the stress intensity factor is studied when the crack depth approaches the full wall thickness.

Welding mechanics for advanced component safety assessment

“…Therefore the knowledge about distribution and magnitude of the residual stresses from measurement or calculation is of utmost importance for the residual life of the shroud. In the study reported here the welding process has been simulated to calculate residual stresses in the component and to use such loading as input to a fracture mechanics analysis [4]. Figure 14 shows the finite element model of the relevant section of the core shroud geometry with the two thin shells surrounding the reactor core made of steel 1.4550 (X10CrNiNb18 9) connected to a flange ring by two circumferential welds.…”

Simulation of Welding Residual Stress to the Fracture Strength of Steel Moment-Resist Frame Connection

“…Zhang and Dong [4] presented their efforts on welding procedure simulation by finite element method, and fracture mechanics is also incorporated with residual stress results to present the impact on structure safety. Applications of this technique in other engineering fields like Varfolomeyev and Siegele [5] used ABAQUS to simulate welding process of core shroud welding in reactor of nuclear power plants. Stress intensity factor is calculated for postulated crack to evaluate the effect upon integrity of reactor structure.…”