| Aeroengine plays an important role in aircraft structure,which is called the"heart" of an aircraft.It is the power source of an aircraft and has a great influence on the overall performance and reliability of the aircraft.Despite the high reliability of modern aeroengine components due to strict standards and practices,turbine blade failures in normal working environments are still a common condition endangering flight safety.Turbine blade is one of the key components of aeroengine fracture.It is subjected to a variety of complex loads during long-term operation under abnormal and harsh conditions,and the probability of failure is relatively high.In the failure analysis of turbine blade failure parts,it is found that the fatigue fracture failure accounts for the highest proportion of the total failure and is the main failure mode.Therefore,it is necessary to adopt scientific means to correctly analyze and evaluate the reliability of turbine blades of aeroengines so as to maximize their functions under the premise of avoiding accidents and disasters.In this paper,the main failure modes of a turbine blade of an aeroengine are analyzed.The main research work is as follows:(1)The physical analysis of turbine blade failure is carried out,and the stress of turbine blade under maximum operating conditions is calculated by finite element software ANSYS Workbench.Based on the results of finite element analysis,the maximum stress sample data of turbine blade under low cycle fatigue fracture failure mode are obtained by combining finite element numerical simulation,response surface method and Monte Carlo method.The process of material strength degradation is studied.Hidden strength degradation information is extracted from material P-S-N curve.Based on non-stationary Gamma random process,a stochastic model of structural strength degradation is established.The dynamic reliability of turbine blades under low cycle fatigue fracture failure mode is solved by stress-strength interference model.(2)Based on the low cycle fatigue life model of turbine blades and considering the randomness of the correlation coefficients in the life model,Monte Carlo sampling of the life model is carried out.The life sample data are analyzed and the reliability model of low cycle fatigue life of turbine blades is established by using the method of probability weighted moment parameter estimation.(3)The vibration characteristics of turbine blades are studied,and random variables affecting the natural frequencies and exciting force frequencies of turbine blades are analyzed.Considering the fuzziness of resonance criterion,the normal distribution membership function is introduced to define the failure area and corresponding membership function of the turbine blade,and the fuzzy reliability analysis model of the turbine blade anti-resonance is established to provide reference for avoiding resonance and frequency modulation modification of the turbine blade.(4)Study on high and low cycle composite fatigue failure modes of turbine blades.The maximum stress of turbine blades under combined failure mode was analyzed.The dynamic reliability of turbine blades under combined failure mode was solved based on the established structural strength degradation model and stress-strength interference model. |
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