Method of frequency-doubling modulation nonlinear ultrasonic guided wave time-reversal detection of pipeline microcracks

Abstract

The invention discloses a method for detecting pipeline microcracks by frequency multiplication modulation nonlinear ultrasonic guided wave time reversal, which belongs to the field of non-destructive testing. The steps are as follows: 1) Signal excitation: two sets of transmitting ultrasonic transducers, the first set excites single low frequency; the second set excites double high frequency; 3) nonlinear analysis: according to the sound field modulation side lobe frequency is ω 1 +ω 2 =3ω 1 Signal selection time reversal window function; 4) Signal time reversal: reverse the intercepted time reversal signal, and then send the time reversal signal by the excitation signal transducer; 5) Energy focusing: the signal is realized at the microcrack focus. The invention utilizes the advantages of long propagation distance of ultrasonic guided wave and high sensitivity of nonlinear ultrasound to microcracks, and at the same time utilizes the characteristics of time reversal algorithm self-adaptive focusing to realize identification of microcracks; uses nonlinear ultrasonic parameters to discriminate the size of cracks.

Description

technical field [0001] The invention belongs to the field of non-destructive testing, and relates to a method for detecting pipeline microcracks by frequency-multiplying modulated nonlinear ultrasonic guided wave time-reversal. Background technique [0002] After the material is subjected to high temperature, high pressure and long-term cyclic load, micro-cracks and micro-damages of different degrees will appear in the stress concentration area. When the area and density of micro-cracks gradually increase, macro-cracks will be formed, resulting in structural failure, potential safety hazards, and serious production accidents. [0003] Ultrasonic non-destructive testing is a widely used crack detection method. The existing linear ultrasonic testing method is based on sound velocity and acoustic impedance to detect cracks. The size of the microcrack is generally much smaller than the wavelength of the linear detection ultrasound, and the local material property change caused ...

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Problems solved by technology

When the area and density of micro-cracks gradually increase, macro-cracks will be formed, causing structural failure and potential safety hazards, and serious cases will lead to production accidents

[0003] Ultrasonic non-destructive testing is a widely used crack detection method. The existing linear ultrasonic testing method is based on sound velocity and acoustic impedance to detect cracks. The size of the microcrack is generally much smaller than the wavelength of the linear detection ultrasound, and the local material property change caused by the microcrack is very small, and the detection effect of the microcrack by linear ultrasound is very poor.

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