Measurement of creep damage by the natural frequency method

The natural frequency method (NFM), a novel approach for the measurement of creep damage, is proposed in this paper. The technique, with instrument configuration and experimental procedure, is described in detail. The application of the approach has been made on 25Cr20Ni steel, widely used for furnace tubes. The measured results of creep damage show good agreement with theoretical predictions. The critical damage value ω_cr of 25Cr20Ni also has been obtained by the proposed approach. Compared with the current density method and the loading and unloading method, NFM has many advantages, such as higher accuracy, simpler apparatus, and better repeatability. On the basis of NFM, an efficient approach can be given for life prediction and extension of high temperature components.