The Forefronts and Issues of the Assessment of Strength of Materials at High Temperature III: Interaction between Low-Cycle and High-Cycle Thermo-Mechanical Fatigue Loadings.

Structural reliability of thermal barrier coatings (TBCs) used in advanced land-based gas turbine power generation systems, has recently been increased year by year. This energy system has a potential ability that it is flexible to absorb fluctuation in power supply from current renewable energy systems. However, the TBCs are frequently subjected to thermo-mechanical fatigue damages, where understandings not only on the traditional steady state thermo-mechanical fatigue (SS-TMF) failure but also on a new type of failure; i.e., non-stationary TMF (NS-TMF) failure, have been essential. In the latter a special consideration should be taken to non-steady or transient thermal response of TBCs. In this work some characteristic features of the NS-TMF failure were introduced, in comparison with those of the SS-TMF. A simple mechanical model by which the transient thermal is passively taken into consideration has been presented to analyze the NS-TMF failure life, those were sensitively influenced by the physical properties of TBCs system and the Biot-number. A method to predict the TMF life superimposed by the NS-TMF was also discussed to avoid this type of new subject. ©2024 The Society of Materials Science, Japan.