Inverse estimation of the transient-state stress distribution in the power boiler pressure components

• An original algorithm for stress monitoring in the power boiler pressure components.
• A numerical model based on two problems with exact analytical solutions.
• Numerical and experimental verification of the proposed method.
• Comparing the reconstructed strain distribution with measured strain transients.

The aim of this work is to present an inverse method of stress estimation in pressure components of power boilers. The proposed algorithm reconstructs the time- and space-dependent temperature, strain and stress distribution in some cross sections of thick-walled cylindrical elements without information concerning the thermal boundary condition on the inner surface. The solution is possible thanks to “measured” temperature histories in easily accessible points located on the component outer surface. In order to stabilize the solution, the data are smoothed out using digital filters based on local polynomial approximation. The material properties of the power boiler elements are assumed as temperature-dependent and the inverse problem is solved iteratively.The proposed method is verified numerically and experimentally in a steam header located on a laboratory stand in the Cracow University of Technology. The presented method may be used in monitoring systems of both conventional and nuclear power plants.