Study On Ultrasonic Testing Method Of High-temperature Alloy Turbine Disc

With the high-performance and large thrust-to-weight ratio aero-engine ofdevelopment, production and use,the capacity and quality of the turbine disk materialshave become increasingly demanding.Currently,the high temperature alloy material ismainly used,which is characterized by coarse grains, prone to crack and segregationdefects.Therefore, non-destructive testing is required from the raw materials, thevarious stages of the blank to the finished product.Superalloy turbine disk acceptancecriteria level is very high, a few hundred microns, or even tens of microns in sizedefects is not allowed usually,such characteristics to non-destructive testing proposedchallenge.Ultrasonic method is the main method for detecting focusing probescanning detection of flooding C, but the depth of focus is limited and difficult todetect large and thick component, combined with coarse grain materials, seriousscattering, low signal-to-noise ratio, so the detection results are unsatisfied.Studyingnew methods for ultrasonic testing is imperative to improve the detection results. Thisthesis focuses on the problems of superalloy materials ultrasonic testing, using phasedarray dynamic focusing method and time proof by contradiction to solve the problemof low signal-to-noise ratio, the limited detector thickness and a small defectrecognition difficulties.The contents of the study are as follows:Firstly, the high temperature alloy samples of different sizes and different apertureflat bottom hole are designed and manufactured, the thickness of samples is80mm,the smallest aperture is0.5mm.Secondly, the low-frequency broadband plane probe and signal processingmethods is used to improve the signal-to-noise ratio.The wavelet threshold is used toprocess ultrasonic signals,analyzing the principles and processes of denoising.Theresults showed that: the wavelet threshold signal had higher signal-to-noise ratio thanthe original,can identify the defect signal, reaches the purpose of noise reduction.Thirdly, the method focusing probe and feature extraction was proposed to solvethe identification of small defects.Feature scan imaging detection using a focusedprobe formed a variety of features.The results showed that:the result of test wasintuitive without noise reduction, feature scanning the bottom hole artificial defectsdetected of depth10mmΦ0.8mm.Fourthly, the ultrasonic dynamic focusing and time reversal adaptive focusingtechniques is used to solve the large, thick superalloys tiny defects detection.This paper researched the principle and method of the annular phase controlled bursts ofcolumns dynamic focusing, analyzed the characteristics of the annular phase controlarray of focusing point to sexual and delay from the sound field distribution, etc., andstudied the impact of the focal length, frequency, element spacing and other factors onthe sound field,used Labview preparation of the analysis software and Field II tosimulate focusing on the annular phased array, provided a theoretical basis for thedesign of the transducer.The experimental results showed that: the use of a variety of measures or themethods could effectively improve the turbine disk detection signal-to-noise ratio ofthe high-temperature alloys, successfully detected1.0flat bottom hole equivalentincreased the signal-to-noise ratio of up to6dB or more, which used focus modecould significantly increase the signal-to-noise ratio, wavelet signal processingmethod could only improve the signal-to-noise ratio.The future direction ofdevelopment still need to work on to improve the detection performance of thesystem.