Method for detecting microcracks of pipeline through frequency multiplication modulation and time reversal of nonlinear ultrasonic guided wave

Abstract

The invention discloses a method for detecting micro-cracks of a pipeline through a frequency multiplication modulation and time reversals of a nonlinear ultrasonic guided wave, and belongs to the field of nondestructive detection. The method comprises the following steps: 1) signal excitation: using two groups of emission ultrasonic transducers, wherein a first group of emission ultrasonic transducer excitating a single low-frequency, and a second group of emission ultrasonic transducer excitating a double high-frequency; 2) signal reception: the second group of emission transducer simultaneously receiving signals as a reception transducer; 3) nonlinear analysis: selecting a time reversal window function according to a sound field modulation side lobe frequency of omega1+omega2=3omega1; 4) signal time reversal: reversing intercepted time reversal signals, and sending the intercepted time reversal signals by the excitation signal transducers; and 5) energy focusing: focusing the signals at the micro-cracks. According to the method for detecting micro-cracks of the pipeline through the frequency multiplication modulation and time reversals of the nonlinear ultrasonic guided wave, the identification of micro-cracks is realized by utilizing the advantages that the propagation distance of the ultrasonic guided wave is long and the nonlinear ultrasound is highly sensitive to micro-cracks, meanwhile utilizing the characteristic of adaptive focusing of the time reversal algorithm; and the crack size is determined by utilizing a nonlinear ultrasonic parameter.

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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