Abstract
Low cycle fatigue (LCF) and creep fatigue interaction (CFI) loadings are the main factors resulting in the failure of many critical components in the infrastructure of power plants and aeronautics. Accurate prediction of life spans under specified loading conditions is significant for the design and maintenance of components. In the present study, various LCF and CFI tests are conducted to investigate the effects of temperature, strain amplitude, hold time and hold direction on the fatigue life of P92 steel. To predict fatigue life under different experimental conditions, various conventional life prediction models are evaluated and discussed. Moreover, a new empirical life prediction model is proposed based on the conventional Manson-Coffin-Basquin (MCB) model. The newly proposed model is able to simultaneously consider the effects of temperature, strain amplitude, hold time and hold direction on predicted life. The main advantage is that only the known input experimental parameters are required to perform the prediction. In addition to the validation made through the experimental data of P92 steel conducted in the present paper, the model is also verified through numerous experimental data reported in the literature for various 9–12% Cr steels.
Highlights
Many critical engineering components used in aeronautics, power generation plants and the petrochemical industry inevitably suffer from high temperature low cycle fatigue (LCF) and creep fatigue interaction (CFI) damage due to the complicated temperature transients and increasing requirements of operational flexibility [1,2]
The first is prediction models based on fracture mechanics, while the second is models based on cumulative damage theories
The life reduction is dramatic at low strain amplitudes, while it becomes saturated as the strain amplitude exceeds 0.6%
Summary
Many critical engineering components used in aeronautics, power generation plants and the petrochemical industry inevitably suffer from high temperature low cycle fatigue (LCF) and creep fatigue interaction (CFI) damage due to the complicated temperature transients and increasing requirements of operational flexibility [1,2]. Concerning high Cr martensitic steels, an increase in martensitic lath width, growth of subgrain size, reduction of dislocation density and coarsening of numerous precipitates are typical factors affecting the life span [3,11,12]. These complicated damage mechanisms make it difficult to accurately predict the life spans for LCF and CFI loadings. In the experimental part, a series of LCF and CFI tests at various test conditions are conducted to investigate the effects of strain amplitude, temperature and hold condition on the life span of P92 steel. Based on the experimental results and the conventional Manson-Coffin-Basquin (MCB) model, a new empirical life prediction model is proposed and validated by the obtained experimental data in the present paper and by the extensive experimental data reported in the literature
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