Method for identifying microcrack direction in plate based on nonlinear frequency mixing technology of Lamb waves

A direction identification, nonlinear technology, applied in the processing of the detected response signal, the use of sonic/ultrasonic/infrasonic waves to analyze solids, and the use of sonic/ultrasonic/infrasonic waves for material analysis, etc. It can solve the problem of small amplitude, sum frequency and difference frequency The signal is not easy to extract and identify, the signal is weak, etc.
CN111157629AActive Publication Date: 2020-05-15NANJING UNIV OF TECH
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Patent Information

Authority / Receiving Office
CN · China
Patent Type
Applications(China)
Current Assignee / Owner
NANJING UNIV OF TECH
Publication Date
2020-05-15

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Abstract

The invention discloses a method for identifying a microcrack direction in a plate based on a nonlinear frequency mixing technology of Lamb waves. The method includes, firstly, extracting a sum frequency signal and a difference frequency signal in a damage response signal by adopting a pulse inversion method; obtaining a directional mode pattern of a nonlinear scattering coefficient beta through the extracted sum frequency signal and difference frequency signal; and determining the maximum forward scattering point and the minimum backward scattering point of the Lamb wave, and taking the direction vertical to the connecting line of the maximum forward scattering point and the minimum backward scattering point of the Lamb wave as the direction of the micro-crack, thereby realizing the identification of the direction of the micro-crack. According to the invention, the Lamb wave excited by frequency mixing interacts with the nonlinear medium to generate a new frequency component; the sumfrequency and difference frequency effective frequency components in the damage response signal are effectively extracted through a pulse inversion method, the microcrack direction is recognized by researching the nonlinear scattering degree of Lamb waves in different directions of the microcrack, and the technical problems that the amplitude is too small, and the sum frequency and difference frequency signals with weak signals are not easy to extract and recognize are effectively solved.
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Description

technical field

[0001] The invention relates to the field of non-destructive testing, and more specifically, relates to a method for identifying the direction of microcracks in a plate based on the nonlinear frequency mixing technology of Lamb waves. The method is suitable for identifying the direction of microcracks in plate structures. Background technique

[0002] Plate structures are widely used in various equipment, and fatigue cracks are one of the main forms of damage. Fatigue cracks will lead to stress concentration in the structure. If no treatment measures are taken in time, the cracks will accelerate the expansion under load and eventually lead to structural fracture. Therefore, the detection of cracks at an early stage using non-destructive testing (NDE) is crucial to maintain the integrity and safety of structures.

[0003] Lamb wave has the characteristics of long propagation distance and slow energy attenuation, and is considered to be one of the most potenti...

Claims

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