Vibration Analyses Of The Blisk And Hard Coating Damping Design For Its Vibration Reduction

Blisk is a new-type structure component in aeroengine which incorporate the blade and disc integrally.The use of blisks not only increases aerodynamic efficiency,it also significantly reduces the number of components in a single stage and reduce s blade drag and weight.Ironically,this new design created a very similar structural concern.Firstly,stiffness of blade and disc in blisk are close because of the thinner disc than the traditional disc with tenon,which results in more prominent coupled vibration problem.Moreover,as single pieces of material,blisks have very little instrinsic damping without the frictional interface created by attachment mechanism in traditional tenon structure.So the blisks experience much higher vibratory stresses associated with resonance excitation due to the perodic aero-dynamic loading,leaving them much more susceptible to high-cycle fatigue than individually manufactured blades.From the above,novel damping technologies for blisk are necessary.Aiming at the vibration reduction for blisk,this paper presents a novel damping strategy by means of hard coating.Based the the model,dynamic characteristics and vibration response under typical load conditions of blisk with hard coating will be studied further.Then,damping mechanism and vibration damping design method of blisk with hard coating can be presented,which can reveal the influence mechanism of damping parameters on vibration characteristics of blisk.The results of this project will provide theoretical guidance for the design and application of blisk in aero-engine,and help to improve the design level and running stability of aero-engine.In this dissertation,with the support of Natural Science Foundation of China(NSFC)"Dynamic characteristics of blisk and its damping design method by hard coating " and"Multi-scale simulation and active design of damping vibration attenuation of thin-walled components with hard coating",the dynamic modeling method and coupling vibration analysis of blisk,vibration and damping analysis of the blisk with hard coating on blades and disc,multiobjective optimization of the coating parameters and layout for vibration reduction,intentional mistuning design for mistuned blisk,and the anti-fatigue properties of hard coating are deeply investigated via the combination of analytical study,numerical analysis and experimental research.The main achievements are as follows:Considering the structure features of blisk and material properties of hard coating,an analytical approach is developed to calculate the free vibration characteristics and damping effect for the blisk with damping hard coating,based on the constitutive model of complex modulus and Rayleigh-Ritz method.NiCrAlY coating is deposited on single side of the blades to investigate its effect on the natural frequencies,modal loss factors and frequencyresponses.Influences of the coating thickness on the variation of natural frequencies and damping capacity are discussed.Damping capacity and the structural influence of the hard coating on the given bladed disk are optimized by the non-dominated sorting genetic algorithm(NSGA-II)coupled with the Kriging surrogate model.Material and geometric parameters of the hard coating are taken as the design variables,and the loss factors,frequency variations and weight increment are considered as the objective functions.Results of the biobjective optimization are obtained as curved line of Pareto front,and results of the triple-objective optimization are obtained as Pareto front surface with an obvious frontier.For sake of meliorating the localization extent and increasing the robustness of the random mistuning blisk,intentional mistuning design by hard coating is presented creatively,based on the research of the effect of hard coating on the mode localization and amplitude amplification.Results reveals that,under the condition of intentional mistuning design by hard coating,response of the blisk is in a low vibration level,and has a strong robustness to random mistuning.Reduced order model of the blisk with cracked blade is established based on the vibration fatigue crack form.Mode localization and vibration response characteristics are investigated.By combining the Paris model and Raju-Newman's formula of the plate with oval crack,crack extension curve of the blisk under aerodynamic load.Then the crack extension characteristic of the blisk with hard coating is investigated,which reveals the sound suppression effect of hard coating.Through the research of present dissertation,modeling method considering the structure features of blisk is grasped,coupling vibration mechanism is confirmed.Hard coating damping technique is proposed for vibration reduction and antifatigue of the blisk,and the influence of hard coating damping to vibration response and fatigue failure of the blisk are obtained.Multiobjective optimization of the coating paraneters and layout are conducted to obtain more superior damping effect.The research results can help to improve the design capabilities and operational stability of the blisk in aeroengine,which have significant values in both academic and practical aspects.