| With the rapid development of power industry in China, various types of largecapacity thermal power unit continue to spring up, power structure and the operationcondition is more complicated. It is easy to form structure micro cracks and corrosiondefects for the structure under the action of alternating stress and corrosion mediumfor a long time, and these micro defects easily without being noticed under thecondition of rapid expansion, caused huge losses to the production. Therefore, urgentneed to develop micro defects nondestructive testing methods. In view of thecorrosion of high temperature and high pressure under the complex environment, suchas industrial structure safety assessment needs, in this paper, study on nonlinearultrasonic modulation nondestructive testing methods, And applied to two typicalindustrial component defects (fatigue crack and damage of the heat test), concreteresearch content including:(1) In view of the fatigue crack detection problem, developed a different side ofincentive ultrasonic modulation defect detection and location method. Using thebispectrum technology analyzes the detection signal, and frequency of excitationsignal is studied on the result of double spectrum detection.(2) Nonlinear wave characteristics in the solid analysis combined with thebispectrum analysis of ultrasonic signal, extract the defects for a quantitativeevaluation of nonlinear ultrasonic modulation characteristic parameters of ultrasonicmodulation factor. Along with the phase difference frequency is studied in doublespectrum value of distribution, select the best phase threshold, and the optimizedultrasonic modulation factor applied to the quantitative characterization of microcracks.(3) Aimed at pipe thermal damage detection problem, use of ipsilateral incentivemode ultrasonic modulation testing pipe thermal damage detection experiment, usingthe proposed nonlinear ultrasonic modulation factor, studies the quantitativeassessment of thermal damage to the pipes. |
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