Frequency mixing nonlinear ultrasonic detection method for structure microcracks based on bispectrum analysis

Abstract

The invention provides a frequency mixing nonlinear ultrasonic detection method for structure microcracks based on bispectrum analysis, and belongs to the detection field of nondestructive examination. The method comprises the steps of firstly, obtaining an amplitude-versus-frequency curve of an excited probe and an excited receiving probe through frequency sweep experiments, and determining probe excitation frequency or range according to the amplitude-versus-frequency curve; then, carrying out different lateral excitation frequency mixing mode experiments, tracking difference frequency and sum frequency signals, and determining an optimal frequency of the excitation signals according to amplitude-versus-frequency response characteristics of the difference frequency and sum frequency signals; performing bispectrum analysis on the time domain signals at the optimal frequency, and determining whether structure microcracks exist in a test piece or not according to whether mixing components appear in the bispectra or not; and scanning the length direction of a test piece and tracking the difference frequency and sum frequency signals by changing time delay of the excitation signals, and determining the positions of the structure microcracks according to the amplitude-versus-frequency response characteristics of the difference frequency and sum frequency signals. Influences on experimental results caused by nonlinearity of an experiment apparatus can be prevented by employing two probes to excite the signals; and the positions of the structure microcracks can be identified by making the two signals encountered through controlling the delay time of the excited signals.

Description

technical field [0001] The invention relates to an ultrasonic detection method for structural microcracks, in particular to a nonlinear ultrasonic detection method based on bispectrum analysis for mixing effect. The method is suitable for early diagnosis of micro-defects due to metal fatigue, deformation and damage, and belongs to the field of non-destructive testing. Background technique [0002] During the manufacture, processing and use of metal components, micro-defects will inevitably be formed inside or on the surface. Under the action of load, temperature change and corrosive medium, microcracks continue to expand and form macrocracks, which eventually lead to fatigue failure of components. Microcracks have become a major hidden danger affecting the normal operation of industrial components. Therefore, the detection of microcracks in components has important engineering practical value. [0003] Conventional ultrasonic testing technology is based on the reflection, ...

AI Technical Summary

Problems solved by technology

Through the bispectral analysis of the received signal, the judgment of whether there is a crack defect in the test piece is realized, but the mixed frequency detection under the

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