Crack Defect Size Quantification Method Based on Laser Ultrasonic Surface Wave Time-Distance Curve

Abstract

The invention discloses a crack defect size quantification method based on the time-distance curve of the laser ultrasonic surface wave. The displacement table is operated to make the excitation laser perform one-dimensional scanning at a distance that does not pass through the crack and is parallel to the detection direction of the surface wave probe; the excited The surface waves are scattered at the four corners of the crack; four time-distance curves are fitted according to the time changes of the four scattered waves, and the crack size information is calculated by carrying the distance information from the excitation point to the edge of the crack; Extraction; predict the position of the next point by fitting the known points to reduce the search range and increase the accuracy; then window the waveform at the next point as the new reference waveform, and finally iterate to obtain the time-distance curve of each waveform. The time-distance curve is fitted by a polynomial, which increases the resolution and functions as a filter. The invention uses the waveform information generated by laser ultrasound to quantitatively characterize the length and width of the crack defect, has low equipment requirements and high efficiency, and can better quantify the size of the crack.

Description

technical field [0001] The invention belongs to the technical field of material defect detection, and in particular relates to a crack defect size quantification method based on laser ultrasonic surface wave time-distance curves. Background technique [0002] Cracks are common defects in materials that propagate under external loads and eventually cause serious damage. Non-destructive testing methods commonly used in crack detection include ray testing, ultrasonic testing, magnetic particle testing and eddy current testing techniques, penetration testing, thermodynamic methods and chemical analysis methods. Among them, laser ultrasonic detection has the advantages of flexible sound source and non-contact. [0003] At present, crack detection based on laser ultrasound can be divided into one-dimensional detection and two-dimensional detection. The former usually detects one dimension of the defect, such as the measurement of defect position, depth and other parameters, while...

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Problems solved by technology

[0003] At present, crack detection based on laser ultrasound can be divided into one-dimensional detection and two-dimensional detection. The former usually detects one dimension of the defect, such as the measurement of defect position, depth and other parameters, while the measurement of crack length and width is rarely involved. ; Two-dimensional detection requires complex scanning to describe cracks, and often focuses on the performance of two-dimensional images while ignoring the rich information on one-dimensional. At this time, its efficiency and accuracy mostly depend on the scanning mechanism, so the requirements for equipment are high.

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