Research On In-Situ Ultrasonic Testing For Cracks On High-Pressure Compressor Disc Based On Longitudinal-Wave Reflection Method

The compressor disc is one of the most critical rotating parts in an aero-engine.Its quality is directly related to the safety of the engine and the aircraft during the flight.Cracks had been found repeatedly on the chamfer of the mating teeth in the third-stage disc rim of the highpressure compressor,when the aero-engines were returned to the factory for overhaul.Cracks are the most dangerous defect,their existence can cause the entire high-pressure compressor disc to burst,resulting in catastrophic consequences.Therefore,how to detect the damage area of the high-pressure compressor disc as soon as possible when cracks occur in the disc during the operation process is of realistic significance to prevent the rupture of the high-pressure compressor disc.Usually,for the detection of compressor disc,it is decomposed into a singlepiece state for ex-situ testing.However,inspection after disassembling may cause secondary damage due to improper disassembly and assembly.In addition,the cycle of the inspection after disassembling is long,and the engine attendance rate is not guaranteed,which affects the normal flight training.In this paper,an ultrasonic testing technique based on longitudinal-wave reflection method is proposed to realize the in-situ detection of cracks on the chamfer of the mating teeth in the rim of the high-pressure compressor.In this paper,combined with the basic theory of ultrasonic testing,the ultrasonic longitudinal-wave reflection method was determined to be the research direction based on the morphological characteristics of cracks in high-pressure compressor disc and the fit construction of the high-pressure compressor disc in the components.The related equipment and instruments were also introduced.In order to carry out the subsequent experiment smoothly,a simulation sample of the highpressure compressor disc with cracks was designed and manufactured.The longitudinal-wave reflection method with straight probe was used to test the simulation sample.It was determined that the method could not detect the cracks on the chamfer of the mating teeth in the rim of the high-pressure compressor because the flaw echo signal could not be recognized effectively affected by the air interface on both sides of the defect.The water distance of the focus detection for the high-pressure compressor disc using the point focusing probe(working frequency: 10MHz;focal distance: 3in;wafer diameter: 0.375in)was analyzed and calculated.And it was verified by the water immersion method of ultrasonic.On the basic of this work,a probe auxiliary frock was designed and manufactured,so that the detection of cracks on the chamfer of the mating teeth in the rim of the high-pressure compressor by the longitudinal-wave contact method with focusing probe could be realized.The simulation sample with cracks was tested by the longitudinal-wave contact method with focusing probe.The detection ability and blind area of the detection of cracks on the chamfer of the mating teeth in the rim of the high-pressure compressor by this method were determined.Finally,the invalid part was tested by the longitudinal-wave contact method with focusing probe.The result shows that the method can detect the natural defects in the invalid part,and the component status is consistent with the single-part status.The longitudinal-wave contact method with focusing probe can realize the in-situ detection of cracks on the chamfer of the mating teeth in the rim of the high-pressure compressor.