High-precision ultrasonic imaging method for internal defect of complex-shaped component based on search-vector imaging condition

A high-precision ultrasonic imaging method for an internal defect of a complex-shaped component based on a search-vector imaging condition, comprising:

• (1) inputting an excitation signal, a sound velocity model, and full matrix capture (FMC) data;
• wherein the FMC data is measured from an ultrasonic phased array;
• (2) preprocessing the excitation signal and the FMC data to obtain a sound source matrix and a residual matrix within a frequency domain, respectively;
• discretizing the sound velocity model to obtain a sound velocity vector, and obtaining an impedance matrix by calculation;
• (3) for any discrete frequency not traversed in a predetermined frequency range selected according to a center frequency band of the FMC data, solving the sound source matrix and the residual matrix by LU decomposition of the impedance matrix to obtain a forward wave field and a residual wave field of the discrete frequency, respectively;
• (4) multiplying the impedance matrix by the forward wave field after obtaining a partial derivative of the sound velocity vector to obtain a total virtual source matrix, and normalizing the forward wave field by an amplitude of an excitation value of the excitation signal to obtain a unit forward wave field;
• (5) multiplying the total virtual source matrix by the unit forward wave field and the residual wave field to obtain a partial derivative matrix and a gradient matrix corresponding to the discrete frequency, respectively;
• and
• (6) repeating steps (3) to (5) until all the discrete frequencies in the predetermined frequency range are traversed completely to obtain partial derivative matrices and gradient matrices of all the discrete frequencies in the predetermined frequency range, and obtaining an imaging result of an internal defect of a complex-shaped component by using a search-vector imaging condition.