Modeling And Analysis Of Vibration Characteristics Of The Hard-coating Blisk Based On Lumped-parametric Model

Compared with the traditional dovetail joint blade disk,the blisk is thinner and less damped,and more likely to experience extreme vibration even fatigue failure under broadband excitation.So it is important to control the extreme vibration response levels in the design and use of blisks.The hard coating technology is a new mode of vibration reduction,and it can be used in some extreme environments such as high temperature and high corrosion,so it can be considered to apply to vibration reduction in blisks.In order to better apply hard coating damping to blisks,a lumped parameter model was established,and the vibration characteristics of the hard-coating blisk composite structure were analyzed.The influence of the change of different parameters on vibration characteristics of the blisk also was considered,and the mistuning of the blisk was researched.The main research contents and conclusions of the paper are as following:(1)The lumped-parametric model with two-degree-of-freedom per blade disk sector of the hard-coating blisk was created,and the identification of the mass,stiffness and damping of the model were realized by the result of the finite element technique.Then,the blisk deposited with NiCrAlCoY+YSZ hard coating was taken as an example to carry out a case study,and the change of the vibration characteristics of the uncoated and coated blisk was analyzed.The results were compared with the finite element method results,which proved the good effect of vibration reduction of the hard coating,and the rationality of the developed lumped-parametric model.(2)The vibration test system of the hard-coating blisk was constructed,and the identification of the parameters of the lumped-parametric model was realized systematically by the obtained test data such as natural frequency,modal shape and vibration response of the uncoated blisk.Meanwhile,a case study was implemented,and the results calculated by the model were compared with the test results.It was found that the natural frequency of the blisk decreases when the blisk was coated,and the response amplitude also decreases.And the variation of the vibration characteristics of the blisk before and after the coating of two methods is consistent,which further proves the rationality of the model.(3)The coating thickness,elastic modulus and loss factor were selected as variables,and the vibration characteristics were calculated using the developed lumped-parametric model.And the change law of vibration characteristics of the coated blisk after the variation of the above-mentioned coating parameters was studied.The results showed that the natural frequency of the blisk decreases with increasing coating thickness,and increases with increasing elastic modulus,while the loss factor has rarely effect on its natural frequency;at the same time,with the increasing coating thickness,increasing elastic modulus,or increasing loss factor,the vibration response of the coated blisk was reduced.(4)The lumped parameter model with mistuned coating parameters was provided,and four common types of intentional mistuning such as harmonic,alternating,linear,and pseudoharmonic were introduced by the coating.The equation of motion of the mistuned hard-coating blisk was established,and the method of solving the natural frequency and vibration response of the blisk was determined.Meanwhile,the quantitative parameters for evaluating the strength of mistuning were given.Finally,the effect of the intentional mistuning of the mistuned coating on the vibration characteristics was analyzed by an example.The results show that after the intentional mistuning caused by the coating of the blisk,the maximum response of the system rapidly increases with increasing mistuning up to a certain value,but the response decrease with a further increase in mistuning,which called "threshold" phenomenon.(5)A lumped parameter model with randomly mistuned parameters of the blisk substrate was created,and Monte Carlo method was performed to study the statistical characteristics of natural frequency and vibration response of the randomly mistuned coated blisks.Then,four common types of intentional mistuning such as harmonic,alternating,linear,and pseudoharmonic were introduced.With considering the intentional mistuning of coatings or blades and random mistuning of the substrate,the robustness of intentional mistuning was analyzed.It is shown that the robustness of the intentional mistuning of the blade stiffness in randomly mistuned blisks was good,but the intentional mistuning of the coating stiffness was not obvious.The lumped parameter model of the hard-coating blisk developed in this paper can be used to analyze the vibration characteristics of real blisk qualitatively.And the related research results can provide a reference for the design of the vibration reduction of the coating damping.