Online Vibration Monitoring And Crack Detection For Rotated Blades Of Aeroengine

Cracks are common failures of aeroengine rotated blades.Online monitoring of rotated blades through their vibration to identify cracks early in various working conditions is significant for operational safety.Open-closed crack is a practical form of early cracks and results in nonlinear vibration response.While some common structures of rotated blades can also lead them to vibrate nonlinearly and seriously interfere online identification of early cracks.Thus,it has high theoretical and application value to extract vibration features due to crack considering common structures.In this paper,the impact of tenon connection and shroud contact is considered.The influence mechanism of crack on blade trunk is analyzed and its features from blade vibration response are extracted by numerical simulation,based on features of two common techniques in online vibration monitoring.Experiment is carried out on test ring for online vibration monitoring of rotated blades,to verify the correctness of theory proposed in this paper.1.Resistance strain gauge measurement and Blade Tip Timing,common techniques in contact and non-contact method respectively,are introduced in detail.Their operating principles and subsequent data processing methods are stated.Conclusions about their characteristics and blade vibration information they can get are made to point out some directions which should be focused on in vibration feature extraction of crack.2.Tenon connection and shroud contact,two common structures are considered in simplification of real blades.Dry friction and coupling force due to these structures are analyzed.A lumped parameter model of bladed disk is built and blades vibration response is obtained by solving dynamics equation of the model through numerical simulation.The result can be a reference for analysis on blades vibration response when crack occurs.Besides,it proves that tenon connection and shroud contact can cause nonlinear vibration on blades.3.The influence mechanism of crack on blade trunk’s stiffness is analyzed and a nonlinear model of changing stiffness of cracked trunk is built.Regularity of impact by crack’s parameter on trunk’s stiffness is explored.In time and frequency domain respectively,some notable features are extracted from blades vibration response with crack occurring.These findings can provide significant technique instruction and theoretical basis for online identification on rotated blades in aeroengine.4.An experiment is carried out utilizing the test ring for online vibration monitoring and the excitation system.Blades are chosen and cracks are premade on specified ones artificially.The vibration signals of blades are obtained by Resistance Strain Gauge Measurement.The vibration response signal of one blade occurred was obtained on the excitation system.The amplitude and peak of 1 times excitation frequency of spectrum are extracted and compared before and after crack.Effect regularity of crack on the above two parameters was explored.The experiment result proves that,theoretical findings proposed in this paper are reasonable and the vibration feature extracted is good guidance to support online identification of crack technically.