Efficient ultrasonic phased array phase shift migration imaging method for defects in multi-layer structure

A method for detecting a defect in a multi-layer structure based on efficient ultrasonic phased array phase shift migration imaging, comprising the following steps:

• (1) acquiring, by an ultrasonic phased-array sensor, full matrix capture data D (xr, xs, t) of a multi-layer structure, wherein xs represents a position of an sth transmitting element;
• xr represents a position of an rth receiving element, D (xr, xs, t) represents a signal transmitted from the sth transmitting element and received by the rth receiving element at a time t;
• (2) transforming, by a processor, the full matrix capture data D (xr, xs, t) to a frequency-wavenumber domain wavefield data D (krx, ksx, ω) by means of three-dimensional fast Fourier transform, wherein krx represents a horizontal wavenumber of a receiving element, ksx represents a horizontal wavenumber of a transmitting element, and ω represents a frequency;
• (3) for a non-traversed layer in the multi-layer structure, extrapolating, by the processor, a surface wave field of the multi-layer structure to an upper interface of the non-traversed layer, to obtain wave field information of the non-traversed layer;
• (4) according to the obtained wave field information, performing, by the processor, focus imaging on the non-traversed layer in the frequency-wavenumber domain;
• (5) repeating, by the processor, the steps (3) and (4), until all layers are traversed, to obtain an imaging result of the multi-layer structure;
• and
• (6) determining a defect in a multi-layer structure based on the imaging result.