Multimodal ultrasonic Lamb wave complex defect tomography method

Abstract

The invention provides a multimodal ultrasonic Lamb wave complex defect tomography method. The method comprises the following steps: presetting a sensitivity threshold THs and a sensitivity dead zone dz, and calculating to obtain the appropriate working frequencies of Lamb waves with A0 and S0 modals; carrying out A0 wave cross-hole tomography and S0 wave cross-hole tomography under respective working frequency conditions by respectively using A0 wave EMAT array and S0 wave EMAT array; and carrying out image fusion, and organically combining two results to obtain a final defect image reconstruction result. The method fully uses different sensitive areas of the Lamb waves with different modals to carry out complementation of the sensitive areas, so the method has the advantages of enlargement of the integral sensitive area of tomography, reduction of influences of noises, effective reduction of the difficulty of extraction of defect characteristic information from a slowness distribution map, improvement of the identification efficiency and imaging precision of complex defects, and wide application prospect.

Description

technical field [0001] The invention relates to a multi-mode ultrasonic Lamb wave complex defect tomography method, which belongs to the technical field of non-destructive testing. Background technique [0002] The specific information such as the outline and size of the defect can be obtained quickly and effectively by using the ultrasonic Lamb wave defect tomography technology. This technology inherits many advantages of traditional ultrasonic Lamb wave detection. Lamb wave travel time (Time-of-flight, TOF, refers to the propagation time of Lamb wave between the transmitting and receiving transducer pairs) cross-aperture tomography technology, using linear transducer array for fan beam projection and imaging, is a kind of An efficient and fast tomography method based on an iterative method. The direct output of this imaging method is the distribution of Lamb wave slowness (reciprocal of velocity), which reflects the distribution of defects through the variation of slowne...

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Problems solved by technology

However, when encountering complex defects with gradual depth changes, more noise will be superimposed on the obtained slowness distribution, and the slowness changes caused by defects will be covered by noise to a certain extent, which will make the slowness distribution from The difficulty and error in extracting defect feature information from the slowness distribution map will increase, which will affect the imaging results

The Chinese patent document discloses a "ray-tracing ultrasonic Lamb wave defect tomography method". This technology involves an ultrasonic Lamb wave online detection method for aluminum plate defects, using an EMAT (Electromagnetic Acoustic Transducer) array to send and receive a single Lamb wave , by combining the iterative reconstruction algorithm and the ray tracing correction algorithm to reconstruct the tomographic image, the comprehensive detection and defect analysis of single round hole defects in aluminum plates can be realized more accurately, but this technology is limited to regular defects with uniform depth, and the depth change The specific size and outline of complex defects cannot be estimated very accurately, and there are certain limitations

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