Research On Vibration Fatigue Characteristics Of Hard Coating Damping Blade

Blades is one of the key bearing components of aeroengine,which is of great significance to the stable operation,safety and reliability of aeroengine.Blades usually work at high rotational speed,high pressure and big thrust-weight ratio conditions,and are subjected to centrifugal load,pneumatic load,mechanical vibration excitation,noise excitation and other loads.Due to the thin structure of the blade,fatigue damage is easy to occur,especially the fatigue damage caused by vibration is currently the main failure form of the blades,causing serious harm.The hard coating damping with special mechanical structural characteristics has vibration reduction properties,which can reduce the resonant amplitude and vibration stress of the structure.The development of hard coating damping provides new ideas and approaches to improve the vibration fatigue of blades.However,the research on hard coating damping mostly focuses on the mechanical properties and vibration damping properties,and lacks specific research on the vibration fatigue properties of hard coating structures.Therefore,studying the vibration fatigue characteristics of hard coating damping blades has important engineering value for improving the vibration fatigue performance of blades,prolonging the vibration fatigue life and promoting the application of hard coating.In this study,aiming at the vibration fatigue problem of hard coating damping blades,combined with test,numerical calculation and simulation analysis,the vibration fatigue S-N curve,vibration fatigue life and estimation methods of random vibration fatigue life of hard coating damping blades are studied.The main research contents and results are as follows:(1)The blade test pieces with NiCrAlY hard coating are prepared by atmospheric plasma spraying technology,and resonant fatigue tests of hard coating blades are carried out.Based on the crack images of the test pieces obtained by scanning electron microscopy,the variation law of natural frequency and propagation behavior of fatigue crack,the vibration fatigue failure criterion of the blade test pieces based on natural frequency is proposed.The vibration fatigue S-N curves of uncoating and hard coating blade specimens were obtained,and their vibration fatigue life and crack propagation characteristics were studied.(2)The natural and damping characteristics of uncoating and hard coating blades were studied through modal tests.The power spectral density of random load is determined by 1/3 octave method and accelerated fatigue test method.The random vibration fatigue life and crack propagation characteristics of uncoating and hard coating blades are studied.The results show that under the same excitation of straight random power spectral density,hard coating damping can improve the random vibration fatigue life of blades and slow down the rate of fatigue crack growth.(3)The dynamic analytical model of hard coating blade is established by using the complex modulus method and the solution method of equivalent parameter of hard coating blade is obtained.The frequency domain method for estimating the random vibration fatigue life of hard coating blade is proposed.The natural frequency,vibration displacement at tip,power spectral density of vibration stress response at dangerous point and vibration fatigue life of hard coating blade are studied.(4)Based on the finite element method,the natural characteristics,response characteristics and random vibration fatigue life of uncoaling and hard coating blade are analyzed,.and the corresponding fatigue life nephogram and damage nephogram are obtained.The results show that compared with uncoating blade,the random vibration fatigue damage of hard coating blade is reduced and the fatigue lift is prolonged.For hard coating blade;the damage of coating surface is less than that of uncoating surface.In this study,the S-N curve of vibration fatigue of hard coating blade is obtained,the influence rule of hard coating damping on vibration fatigue life and fatigue crack growth rate of blade under the same excitation level,the same stress level and random vibration state is studied,and the estimation method of random vibration fatigue life of hard coating damping blade is proposed.The research results show that hard coating damping has broad application prospects in improving vibration fatigue performance of blades,and provide basic data and theoretical support for the research of vibration fatigue life of hard coating damping structures.