| The turbine blade with high temperature,high speed,complex aerodynamic force and large centrifugal load is easy to break fault,which leads to serious accident of engine and aircraft.With the improvement of the technical level of the low cyclic fatigue Basic test,the main failure mode of the engine turbine blade has been converted from the traditional static strength failure to the vibration fatigue failure.In order to determine the vibration stress level of the turbine blade under the working state,the vibration stress measurement of the turbine blade must be carried out on the basis of the numerical calculation..In this paper,the theory and technology of aeroengine turbine blade dynamic stress measurement are studied and applied to a certain type of engine.The main research contents of:1.The principle of strain testing for dynamic stress signal acquisition,the basic structure,type and working characteristics of the high temperature resistance strain gauge,and the adjustment circuit which converts the strain signal to the voltage signal are studied.The installation process and location determination principle of the dynamic stress measurement of turbine blades are studied in combination with the characteristics of the turbine blade.2.A type of USB brush ring is designed and developed.It is verified by experiments that the technical indicators of 10 channels,32 k Hz dynamic strain measurement,80 degrees Celsius working temperature and 6000 rpm rotor speed are achieved.The external interface only needs to use the 4 channels of the brush ring,which is not limited to the limit of 2 times the number of strain sheets used in the traditional channel,which effectively reduces the number of channel use.The device has been tested on the test-bed and has not been applied to the whole engine test.3.Three kinds of vibration signal processing methods for dynamic stress measurement of turbine blades are studied,which are amplitude domain analysis,Fourier analysis and order analysis.Combined with resonance theory and the working characteristics of turbine blades,the natural frequencies,mode shapes,exciting force and resonance of turbine blades are analyzed.It is pointed out that the ultimate goal of dynamic stress measurement of turbine blades is to avoid the resonance frequency and resonance speed region of blades and prevent the resonance from causing fatigue damage.The analysis steps of dynamic stress measurement for turbine blades are also presented.According to the working characteristics of the high temperature strain gauge and the measurement of the dynamic stress of the turbine,the error processing of the measured data is studied and analyzed,and the error estimation formula is given.4.For a certain type of cracking failure aeroengine turbine blade,according to the results of finite element calculations,the vibration modes and stress distribution of the blade are analyzed,and the possible resonance risk points leading to cracks in the turbine blade are obtained.On this basis,a set of mature dynamic stress measurement system is used to test the dynamic stress of the turbine blade for six times.Through the feedback of the dynamic stress measurement results to the blade design,the dynamic stress of the turbine blade's normal working speed range is gradually reduced and the crack is eliminated. |
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