Life Prediction And Dynamic Reliability Analysis Of Aircraft Turbine Disc

As the critical part of aircraft, aero engine provides power for aircraft. It plays a very important role during the flight of aircraft, which is taken as the "heart" of the aircraft. Due to the vast number of the components, bad working conditions, and complicated structure, the aero engine is easy to fail, which will affect the structural strength and security of aero engine significantly.The main factors which restrict aero engine’s life and reliability are the life and reliability of the main components. As the key-critical and key-durable components of engine, turbine disc’s failure will affect the costs to operate and maintain directly, as well as the reliability of aero engine. And turbine disc’s main failure mode is low cycle fatigue. With the development of aviation industry, the requests of aero engine’s performances, such as higher thrust weight ratio and lower fuel consumption, are increasing day by day, which lead to higher security and increasingly grim stress and temperature load. Own to the cumulative effects of stochastic loads, and time-dependent relative sizes for stress and strength, reliability of disc therefore is influenced by the useful life and the number of loads. Furthermore, the stochastic loads are connected to the length and initial time of working time, so dynamic reliability analysis for turbine disc is required. For aforementioned reasons, the researches for low cycle fatigue life prediction and dynamic reliability of turbine disc are very important to practical engineering.The centrifugal force(disc and blade) and thermal stress are considered, and the strains as well as stress of disc are analyzed. Furthermore, the low cycle fatigue life for disc based on the elastic-plastic analysis results is predicted. Dynamic reliability of the disc is analyzed in final chapter.The dissertation is divided into three parts under considering aforementioned problems:(1) The 3D model and finite element calculation model of disc are established according to the geometric data, and then the centrifugal force and thermal stress can be calculated. Afterwards, the elastic-plastic stress and strain of the turbine disc are analyzed by combining the above calculation for the material parameters, and the corresponding dangerous position of turbine disc and its spectrum of stress as well as strain can be determined.(2) Theoretical stress concentration coefficient of turbine disc is determined based on the results of stress calculation and strength analysis. Then asymmetrical cyclic load is translated into symmetrical cyclic load. The S-N curve method of nominal stress is used to analyze the turbine disc’s fatigue life. The local stress and strain as well as fatigue performance parameters of the turbine disc are determined, the methods for local stress and strain, morrow correction model and Mason-Coffin correction model, are employed to predict the low cycle fatigue life. Finally, the comparisons with the nominal stress method are also given.(3) Considering the influence of number of cyclic loading to reliability, fit fatigue life distribution function of the turbine disc is fitted according to the results of the turbine disk life prediction and the material fatigue properties of GH4133 B. The reliability models of turbine disc under deterministic load, single random load as well as various random loads are established to assess reliability for turbine disk based on the traditional stress-strength interference model, conditional fatigue reliability and total probability formula. Furthermore, the time-varying fatigue reliability model under multiple stochastic loads is established for dynamic reliability analysis based on the aforementioned results and probability characteristics of Poisson distribution.