Research On Fatigue Reliability Optimization Design Methodology Of Turbine Shaft

Aeroengine is a key tool for mankind to soar into the sky.It is an aerodynamic device that integrates a variety of cutting-edge technologies.Without advanced aeroengines,there would be no qualitative leap in the manufacture of aircraft.As the core of the engine,the turbine shaft is regarded as a paramount part of the main shaft transmission system of an aeroengine.As long as the turbine shaft is not replaced,the service life of the engine will not be deemed to be over.Nevertheless,the long-term high temperature and high pressure environment,as well as the random and variable loads,pose challenges to the reliability and optimal design of the turbine shaft.How to develop an efficient and practical optimization design strategy under the premise of high reliability is a principal issue for improving the performance of turbine shafts and then aeroengines.The research on the turbine shaft is confronted with three problems including the complexity of the geometry of the turbine shaft,the difficulty of the data acquisition,and the verification of the theoretical analysis results.Consequently,the implementation of the research requires a large amount of practical experience summaries and the support of advanced technology.Reliability has always been the theme of turbine shafts because reliability analysis and optimization can promote the manufacture of aeroengine.In this work,concentrating on the fatigue failure mode of the turbine shaft,a new design scheme of a turbine shaft is proposed;firstly,a parameterized model and a finite element(FE)analysis model are established;then the analysis of fatigue life and structural reliability is conducted;combined with assembly conditions,the reliability optimization design plan of the turbine shaft is proposed and the results are verified.The specific content of this article principally includes the following parts:(1)Parametric modeling and fatigue life analysis of the turbine shaft.In this part,based on the data in the project,the parametric modeling of the turbine shaft is completed using software UG NX 8.0.Considering the influence of temperature on material performance parameters,the turbine shaft is segmented into three parts,and the individual model of their own is established,simultaneously.According to the stress distribution,the fatigue dangerous area of each part is found out.The effective fatigue life model is used to calculate the high-cycle fatigue life and low-cycle fatigue life of the turbine shaft,and an improved method is proposed as a reference.The calculation results provide a data support for the subsequent structural reliability analysis of the turbine shaft.Only if the accurate basic data is figured out can the satisfactory results of analysis and optimization be obtained.(2)Reliability analysis of turbine shaft based on Kriging model.Under the influence of multiple random variables,it is not likely to give an explicit expression of the limit state function of the turbine shaft,so the Kriging model is resorted,combined with an improved learning function,to establish an efficient and effective model that meets the requirements.The advantages and disadvantages of the proposed method and the regular method are compared and analyzed through two numerical examples.Furthermore,the structural reliability of the turbine shaft is obtained which is used as the constraint of the subsequent optimization design.(3)The fatigue reliability optimization of the turbine shaft.Based on the previous analysis,optimization variables that affect the fatigue reliability of the turbine shaft are decided,then the mathematical model is established with the minimum weight of the turbine shaft as the optimization objective.Combining the infilling sample criterion,the Kriging model is used to establish the approximate relationship between the objective and the variables.An improved particle swarm optimization(PSO) algorithm is proposed so as to enhance the global searching ability.Afterwards,the reliability optimization of the turbine shaft is conducted and the results are substituted into the FE analysis for comparison,with the error is 0.028%.Under the premise of reliability,the total weight of the turbine shaft is reduced by 0.0274 kg.