Deconvolution processing for improved acoustic wavefield imaging

The invention relates to a frequency domain sparse inversion-based quantitative detection method for defects in a TOFD (time of flight diffraction) blind area and belongs to the field of non-destructive testing technologies. According to the method, a test system composed of a TOFD ultrasonic detector, a TOFD probe, a wedge and a scanning device is adopted; a near surface area in TOFD detection isscanned, and collected aliased time-domain signals are processed, so that a sparse inversion model is established; with the sparseness and decomposable characteristics of a reflection sequence considered, an objective function for TOFD blind area detection is established in a frequency domain; high-signal-to-noise ratio portion spectral data are selected, and inversion is performed on the high-signal-to-noise ratio portion spectral data, and the separation of aliasing signals comprising straight-through waves, defect upper end point diffraction waves and defect lower end point diffraction waves is realized; and acoustic-path difference between the straight-through waves, the defect upper end point diffraction waves and the defect lower end point diffraction waves is read directly, the buried depth and height of defects in the near-surface blind area are determined. Compared with other near-surface defect detection methods, the method can separate a plurality of aliasing signals, can simultaneously measure the depth and height of the defects in the near-surface blind area, has no additional requirements for a hardware system, and has a high engineering application value.

Frequency domain sparse inversion-based quantitative detection method for defects in TOFD (time of flight diffraction) blind area

In ultrasonic nondestructive testing, the reflection sequence always overlapped or immersed in noisy. A sparse deconvolution was proposed to enhance significantly the resolution of the original time trace, making it possible to determine the amplitudes and the arrival times of the wave packets contained in the original time sequence. With the purpose of ensuring sparsity, Compressed sensing (CS) and Orthogonal matching pursuit (OMP) were used for pulse-echo signal reconstruction to obtain sparser distortion function for sparse deconvolution. Simulated results and experimental verification which performed on time of flight diffraction (TOFD) specimens demonstrated the proposed method.

Wang Rui

Papers

Compressed Sensing Based Ultrasonic Nondestructive Testing by the Use of Sparse Deconvolution