Vibration Characteristics Testing And Mistuning Identification For Composite Structure Of Blisk With Viscoelastic Damping

In order to meet the development requirements of integration and lightweight in aeroengine parts,the blisk has been widely used in the compressors,fans and turbines.Different from classic bladed disks,the blisk has better mechanical properties,less weight and less components,therefore,other forms of damping have to be introduced in the use of blisks,for lacking of the friction contact devices to neutralize the dynamic stresses generated by random vibration.Viscoelastic damping material has good capability of vibration damping and some materials can work at high temperatures,so we can consider coating it on the blades of blisk to construct viscoelastic damping coating for vibration reduction.In order to better apply viscoelastic damping to blisks,vibration performance testing and mistuning identification for blisks with viscoelastic damping treatment should be carried out.The paper is based on this issue and the main research contents are as following:(1)Modal parameters testing for blisks with and without damping treatment was carried out.First of all,the natural frequencies of blisks were roughly measured by using pulse hammer excitation method.Then,modal testing for blisks was carried out in the manner of moving excitation points and fixing pickup points.Finally,the natural frequencies,modal damping ratios and mode shapes were obtained by LMS software analysis.Experiments demonstrates that the natural frequencies of blisks with damping treatment change,modal damping ratios increase and vibration damping effect is obviously.(2)Vibration characteristics testing for blisks with and without damping treatment was carried out under base excitation.First of all,the natural frequencies of blisks were roughly measured by using pulse hammer excitation method.Then,sweeping testing for blisks was carried out by using electromagnetic vibration generator system in the manner of base excitation,picked up the response signals with lightweight acceleration sensor and accurately measured the natural frequencies of the blisk.Finally,fixed frequency excitation for blisks was carried out in the manner of base excitation,measured the resonant response and calculated the modal damping ratios of each order by using the semi-power bandwidth method.Experiments demonstrates that the modal damping ratios of blisks with damping treatment increase,resonant responses decrease and vibration damping effect is obviously.(3)The degree of vibration localization of blisk with damping treatment was identified based on modal assurance criterion local factor.First of all,the identification principles for vibration localization was introduced.Then,the identification principles for vibration localization was validated by using the finite element models of coupling beams and blisks.Finally,modal testing for blisks with and without damping treatment was carried out and the degree of vibration localization of blisk was identified based on experimental datas.Results demonstrates that the method can accurately identificate the degree of vibration localization of blisk with damping treatment,and can provide technical support for the application of viscoelastic damping in blisks.(4)The mistuning identification for blisk with damping treatment was carried out based on component mode mistuning model and fundamental mistuning model respectively.First of all,the mistuning identification principles were derived in detail.Then,the identification principles were validated based on the finite element models of mistuned blisk with damping treatment.Finally,modal testing for blisks with three damping treatment schemes were carried out respectively and the mistuning were identified based on experimental datas.Results demonstrates that the methods can accurately identificate the mistuning of blisks with damping treatment.In the study of vibration reduction for blisk by using viscoelastic damping,the vibration characteristics of blisks with and without damping treatment should be obtained accurately,and testing methods and processes for the vibration characteristics of blisks were presented in this paper.In addition,the identification methods for vibration localization and mistuning developed in this paper are effective,so they can provide technical support for the promotion and application of viscoelastic damping in blisks,and they are important for promoting the application of viscoelastic damping technology in engineering.