Residual stresses in condition monitoring and repair of thermal power generation components

Residual stresses have a significant impact on fatigue and fracture of engineering components and structures, with an effect that is largely dependent on the sign of the residual stress relative to that of the applied stress, i.e. on whether they add to, or subtract from, the applied stress. The present paper will emphasise the importance of detailed knowledge of residual stresses to applications in thermal power generation. The context of the examples is condition monitoring and repair procedures where assessment of the influence of residual stress fields is important to both fatigue and fracture performance, and to certification of the repair procedure itself. The main conclusion in the paper is that the innovative use of solid-state friction taper hydro-pillar processes can offer additional capability in condition monitoring of through-thickness creep damage in thermal power plant, as well as provide cost-effective local repair of creep or fatigue damage in, for example, thick-walled steam pipe and blade-disc attachment holes.