Various State-Of-the-Art Methods for Creep Evaluation of Power Plant Components in a Wide Load and Temperature Range

Abstract

Many power plant components are exposed to high temperature environments and complex loading conditions over long period of operation. An important part in the life-time assessment is the reliable prediction of strain/stress state using robust creep modeling to avoid possible integrity or functionality issues and failures in such components. The goal of this work is to apply different state-of-art creep models including the empirical Norton-Bailey, modified Garofalo equations and the advanced constitutive visco-plastic model KORA to the analysis of typical high-temperature power plant components in a wide range of loads and temperatures. Among other things, an advantage of each model and its robustness is discussed, which should reflect both inelastic deformation and stress relaxation. The material parameters were identified from experimental data for 10%CrMoV heat resistant steels in the creep range. The results of non-linear Finite Element Analysis (FEA) were used for the subsequent integrity assessment of benchmark examples as well of the practical example of the steam turbine component. The material laws were implemented in the commercial software NX CAE. The results for long-term assessment of real steam turbine component are presented and discussed. In addition, an outlook on further developments of the material modeling and assessment procedure is also provided.