Vibration Characteristics Test And Theoretical Analysis Of Hard-Coating Cylindrical Shell

Due to high strength-to-weight ratio and other superior performance,the cylindrical shells have been a commonly used component in a variety of engineering applications.Especially in the field of aircraft and aerospace,the cylindrical shells that serve as supporting and bearing parts are widely used.In the service process,however,the cylindrical shells are most likely subjected to combined interaction of many dynamic loads,such as mechanical load,inertia force,flow field,thermal field,etc.which will easily lead to fatigue failure of cylindrical shell.Therefore,it is of great importance to develop the corresponding measures of vibration reduction to suppress above destructive vibration.Notably,recent studies have found that hard coating also have damping effect and become a kind of vibration reduction technology with considerable application prospect.The greatest technology advantage is that hard coating can maintain its original damping capacities in high temperature and high corrosion environment.To apply this technology scientifically,the vibration test and dynamic modeling should be investigated for effectively predicting the vibration characteristics of the hard-coating cylindrical shell.This study is mainly classified to four chapters.(1)The vibration characteristics of the cylindrical shell with and without hard coating(NiCoCrAlY+YSZ)were obtained by experiment,which were shown as follows:the natural frequencies of the cylindrical shell with and without hard coating were obtained by impact test,and also the sweep range and rate were determined;the natural frequencies of the cylindrical shell with and without hard coating were accurately obtained by sweep test of vibration table under different excitation level,and the modal damping radio were calculated by half-power bandwidth method;dwell test was carried out under a certain excitation level,then the resonant response corresponding to the natural frequency was measured.The experiment shows that the natural frequency of the cylindrical shell with hard coating will change,the modal damping radio will increase and the response will reduce.In other words,the hard coating has the effect of damping vibration reduction.(2)The finite element model corresponding to test object was created,and the influence of mesh quantity,simulation pattern of substrate and hard coating,and boundary conditions on the vibration characteristics of hard-coating cylindrical shell were discussed.Then,the mesh quantity,simulation pattern of substrate and hard coating,and boundary conditions were determined reasonably.And the modal analysis and harmonic response analysis were also carried out.Finally,the influence of coating position on the vibration characteristics and resonant response of hard-coating cylindrical shell was analyzed by coating hard coating on the top,middle and bottom surface of the shell,respectively.(3)Base on Love's shell theory and energy method,the solution process for vibration characteristics of the hard-coating cylindrical shell was derived by beam function method and orthonormal polynomial method.Then,the hard-coating cylindrical shell in the test was taken as research object to solve the vibration characteristics of the shell,and the results obtained by test,FEM and theoretical analysis,respectively,were compared.Finally,the influence of hard-coating parameters(thickness,Young's modulus and loss factor)on the vibration characteristics of the shell was analyzed by self-developed MATLAB code.(4)Taking both the material damping of hard coating and proportional damping into consideration,the resonant response of hard-coating cylindrical shell under base excitation was calculated by theoretical analysis.Then,the influence of hard-coating parameters on the resonant response of the shell was studied.This paper can provide reference for the selection and preparation of hard-coating material or further study on the damping mechanism of coating material.And it can also provide the support for the application of hard-coating damping technology in aviation.