Residual Stresses in Clad Nuclear Reactor Pressure Vessel Steels: Prediction, Measurement and Reconstruction

Abstract

Most residual stress measurement methods are limited in terms of their stress and spatial resolution, number of stress tensor components measured and measurement uncertainty. In contrast, finite element simulations of welding processes provide full field distributions of residual stresses, with results dependent on the quality of the input conditions. Measurements and predictions are often not the same, and the true residual stress state is difficult to determine. In this paper both measurements and predictions of residual stresses, created in clad nuclear reactor pressure vessel steels, are made. The measurements are then used as input to a residual stress mapping technique provided within a finite element analysis. The technique is applied iteratively to converge to a balanced solution which is not necessarily unique. However, the technique aids the identification of locations for additional measurements. This is illustrated in the paper. The outcomes from the additional measurements permit more realistic and reliable estimates of the true residual state to be made. The outcomes are compared with the finite element simulations of the welding process and used to determine whether there is a need for additional input to the simulations.

Redistribution of residual stress by thermal shock in reactor pressure vessel steel clad with nickel alloy

“…However, the residual stress is not completely erased [2][3][4] because additional stresses are generated upon cooling due to the difference in thermal expansion coefficient between the cladding and parent materials. The residual stress in pressure vessel steel clad with stainless steel has been well characterised in previous work using modelling techniques [2,4] and experimental measurements [2][3][4][5][6][7][8][9][10]. In general, material which has been post-weld heat-treated contains high tensile residual stress in the cladding of around 200 -400 MPa, and lower-magnitude tensile or compressive stress in the parent [3,7,11].…”

A Combined Experimental and Modelling Approach to Elastic–Plastic Crack Driving Force Calculation in the Presence of Residual Stresses

“…3). An estimate of the complete residual stress state in the un-notched specimens was reconstructed from measured residual elastic strain data using the iterative technique described previously by Coules et al [24] and others [25,26]. First, three Fig.…”