FINITE ELEMENT ANALYSIS OF THE EFFECT OF MECHANICAL STRESS IMPROVEMENT PROCESS ON WELD RESIDUAL STRESS AND FLAW GROWTH IN A THICK-WALLED PRESSURIZER SAFETY NOZZLE

摘要

The Mechanical Stress Improvement Process (MSIP) is generally accepted as an effective method to modify the residual stress field in a given component to mitigate subcritical crack growth in susceptible components [1] [2] [3]. In order to properly utilize MSIP, residual stress prediction is needed to determine the parameters of the MSIP application and the expected final residual stress field in the component afterwards. This paper presents the results of a 2D axisymmetric finite element study to predict weld residual stresses (WRS), and associated flaw growth scenarios, in a thick-walled pressurizer safety nozzle that underwent mitigation by application of MSIP. The authors have developed a finite-element analysis methodology to examine the effect of MSIP application on WRS and flaw growth for various hypothetical welding histories and boundary conditions in a thick-walled pressurizer safety nozzle. In doing so, a wide range of repair scenarios was considered, with the understanding that some bounding scenarios may be impractical for this geometry.