# Fatigue Damage Assessment of Turbine Runner Blades Considering Sediment Wear
## 1 Introduction
[PERSON] [11] studied fatigue life prediction methods and crack growth mechanism models for mechanical structural components, based on a multi-factorial modified fatigue theory. Bayesian theory was introduced for data fusion during experimental data processing, aiming to achieve high-precision predictions of structural fatigue life and reliability assessments. [PERSON] et al. [12,13,14,15] took a high-head Francis turbine as the research subject, analyzing and calculating the pressure pulsations and equivalent stresses on the surface flow fields of both long and short blades under various operating conditions using numerical simulation. They also studied the primary factors influencing the fatigue life of the turbine runner. Applying the theory of fatigue cumulative damage, the fatigue life of runner blades under different working conditions was determined. [PERSON] et al. [16] took the runner of a hydropower station as an example and considered factors affecting the runner, including the average stress, stress concentration, surface state, and size factor. They used MSC Fatigue software to calculate the runner's life, providing valuable data for the subsequent operation and maintenance of the power station. To ensure the safe operation of the Zhang pumped storage power station, [PERSON] et al. [17] conducted unsteady numerical analysis of the full flow field and predicted the fatigue life of the runner under various operating conditions based on the dynamic stress characteristics of the runner. [PERSON] et al. [18] used fluid-structure coupling calculations to analyze the characteristics of the internal flow field in a specific type of hydraulic turbine, studied the causes of the runner's vibration, and predicted the fatigue life of the runner under fluctuating water pressure. [PERSON] et al. [19] aimed to explore the impact of vibration under complex operating conditions on the fatigue reliability life of turbine blades in a hydraulic turbine. They established different reliability models for various operating conditions and developed an integrated reliability assessment model based on these models. The correctness and feasibility of the integrated reliability assessment model were also verified. In summary, numerical analysis and calculation of the internal flow field and fluid-structure coupling of the runner are relatively mature at present. Most studies on the fatigue life of runner blades focus on analyzing the surface dynamic stress of the blades under specific operating conditions to directly predict the life of the blades, without considering the impact of structural changes caused by wear on the blades during operation on their service life. However, blade wear occurs in practice, altering the structure of the affected areas and resulting in increased dynamic stress, which significantly impacts the blade's fatigue life. Therefore, it is essential to consider blade wear in actual operation when predicting the life of runner blades. This paper analyzes the stress changes in the critical areas of the hydraulic turbine runner blade before and after wear occurs, and determines the progression of fatigue damage in these areas under continuous wear. Ultimately, it is concluded that considering the wear of the blades is essential for estimating the service life of the turbine runner, which more accurately reflects the actual operational lifespan. It provides insights for the safe and stable operation and maintenance of the turbine unit in the future.