An Efficient Approach For Identification Of Damage In Aero Engine Blades Using Acoustic Emission

Compressor blades are one of the key components of aero-engines and operate in a very harsh environment.Blade failures occur frequently and the consequences are serious.Therefore,it is urgent to improve the fault monitoring and predicting capability of the aero-engine blades to ensure the safety and economy of the aircraft.In view of the fact that this paper proposes the application of acoustic emission(AE)technology to the monitoring and prediction of aero-engine blade damage,and carried out some basic research works:(1)The research on the identification of deformation damage stage of TC11 titanium alloy based on acoustic emission was carried out.In this work,the tensile test of TC11 titanium alloy specimens based on AE monitoring were conducted.The obtained AE signals were decomposed and denoised by the variational mode decomposition(VMD)method,they were decomposed into two different frequency ranges,and a new AE parameter is defined as ratio of AE signal energy.It was used as an indicator to identify the degree of deformation,and its effect is significantly better than the traditional AE parameters.A phase identification control model based on the ratio of AE signal energy was established,which can be updated and improved with the increase of experimental accumulated data.(2)The method of crack initiation identification of TC11 titanium alloy based on acoustic emission was studied.Based on the AE signals generated by TC11 titanium alloy during deformation damage,two new AE parameters were defined as partial energy ratio(PE)and weight peak frequency(WPF),and they were combined to establish a method for judging crack occurrence.Tensile tests of TC11 titanium alloy flat specimens with triangular and circular notches based on AE monitoring were carried out to verify the effectiveness and applicability of the above method.The detected crack occurrence time were earlier than the time when the macro crack can be observed,which proved the superiority of the AE technology applied to the early crack detection of materials/components.(3)The research on blade fatigue crack propagation life prediction method based on AE is carried out.In this study,the AE technique was utilized to monitor the fatigue crack growth of the gas turbine engine low-pressure compressor rotor blades and TC11 titanium alloy plates.The relationship between the cumulative AE hits and the fatigue crack length was established,before a method of using the AE parameters to determine the crack propagation stage was proposed.The t-SNE method was used to classify and reduce the AE parameter set,and realize the identification of the critical point of the test piece entering the unstable stage.A mathematical relationship between the AE energy rate and crack growth rate was developed to predict the crack extension rate of the blade material and the residual fatigue life of the blades.