Material near-surface macro-micro defect integrated ultrasonic detection method based on spatial modulation laser ultrasonic sound spectrum

Abstract

The invention discloses a material near-surface macro-micro defect integrated ultrasonic detection method based on a spatial modulation laser ultrasonic sound spectrum. Firstly, a double-spacing optical mask plate is used for enabling a high-energy pulse laser beam irradiated to the surface of a measured material to form two kinds of periodically distributed grid-shaped laser spots; two columns ofultrasonic surface waves with different frequencies are excited at the same time in a measured area. Linear or non-linear interaction occurs in a measured area; the laser ultrasonic detection unit receives a surface wave signal on one side of the surface; fourier transform is carried out on the rear half section of the received surface wave signal pulse sequence to obtain a spatial modulation laser ultrasonic frequency spectrum curve, and finally integrated detection of linear ultrasonic and nonlinear ultrasonic is achieved according to the two fundamental frequencies in the frequency spectrum and the components of the nonlinear frequency mixing components of the fundamental frequencies.

Description

technical field [0001] The invention relates to a nondestructive detection method for macroscopic and microscopic defects on the surface of materials and near the surface, in particular to an integrated ultrasonic detection method for macroscopic and microscopic defects near the surface of materials based on spatially modulated laser ultrasonic sound spectrum. Background technique [0002] Some important structures in the mechanical system are prone to damage or defects on the surface and near surface of the structure due to corrosion and fatigue loads during operation. Usually, the damage is gradually expanded from the initial micro-nano-scale micro-defects to millimeter-scale macro-defects, and further expanded until the final destructive fracture failure of the structure. Existing nondestructive testing technologies for mechanical structures are mainly aimed at the detection of millimeter-scale macroscopic defects, but there is a lack of effective nondestructive testing m...

AI Technical Summary

Problems solved by technology

Conventional ultrasonic testing methods are mainly aimed at the detection of macroscopic defects, while the detection sensitivity for microscopic defects is very low. In recent years, the emergence of new nonlinear ultrasonic testing methods has greatly improved the detection ability and sensitivity of microscopic defects.

However, the existing ultrasonic testing methods are mainly based on conventional contact piezoelectric probes, which require good contact between the probe and the component under test and the support of liquid couplant, which can be used for sensitive parts of the mechanical structure that are prone to damage (such as sudden changes in geometric shape). Poor accessibility and low spatial resolution

Moreover, conventional linear ultrasound used for macroscopic defects and nonlinear ultrasonic used for microscopic defects are very different in measurement methods, signal processing and analysis. The two technologies are not universal, and there is a lack of integrated detection for macroscopic and microscopic defects. methods and techniques

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