An all-optical laser ultrasonic measurement method for internal defects of materials

Abstract

The invention discloses a full-optical laser ultrasonic measuring method for internal defects of a material. The method comprises the following steps: firstly, measuring the two-dimensional position and the size of the internal defect of a measured object on an x-y plane, and subsequently measuring the depth of the internal defect of the measured object in the z direction. By adopting the method, the three-dimensional position and the size information of the internal defect can be obtained by scanning, and the method is high in precision and efficiency, and is applicable to non-destructive detection on various materials.

Description

technical field [0001] The invention belongs to the technical field of laser ultrasonic non-destructive testing, in particular to an all-optical laser ultrasonic measurement method for internal defects of materials. Background technique [0002] Internal defect is a kind of defect that exists widely in various workpiece materials. If it is not detected and confirmed in time, it may lead to the fracture and damage of the workpiece, which will seriously affect the production safety. However, due to the concealment of internal defects and their extensive existence in various materials, as well as the requirements of high-precision, high-speed online inspection, harsh environment and safety inspection, it is still very difficult to carry out non-destructive inspection of internal defects. The existing conventional non-destructive testing methods mainly fall into four categories: eddy current testing, magnetic particle testing, radiographic testing and ultrasonic testing. The us...

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Problems solved by technology

The electromagnetic ultrasonic testing method can only detect large conductive materials and is greatly affected by the surface quality, such as document 2 (patent application number: 201210290309.X, "Metal defect detection method for laser-electromagnetic ultrasonic nondestructive testing system") and document 3 (Optics & Laser Technology, Vol.44, 860-865 (2012), "Inspection of cracks using laser-induced ultrasound with shadow method: Modeling and validation"); the air-coupled ultrasonic detection method is limited by its principle, the probe and the detection object should keep a suitable distance, and the ultrasonic wave will pass through two severe Attenuation, detection accuracy is poor, and it is difficult to detect tiny internal defects, such as document 4 (Journal of Mechanical Engineering, Vol.44, 10-14 (2008) "Development of Air-Coupled Ultrasonic Nondestructive Testing Technology"); Laser ultrasonic testing has the advantages of non-contact, broadband, remote control, high penetration, and the ability to simultaneously excite multiple modes of ultrasonic waves. Reception and other issues, such as in Document 5 (Japanese Journal of Applied Physics, Vol.40, 1477-1481 (2001), "Nondestructive detection of small internal defects in carbon steel by laser ultrasonics"), in order to change the directionality and excitation efficiency of ultrasonic bulk waves, the laser energy is increased to cause damage to the material surface

[0004] The above method also has a major disadvantage for detecting internal defects of materials, that is, it can only detect the existence and size of defects, and cannot accurately locate the three-dimensional position of internal defects.

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