Synthetic aperture combination imaging of cracks in titanium alloy based on laser ultrasonics
In this paper,a multi-modal combination imaging method based on synthetic aperture focusing technique is proposed to address the laser ultrasonic imaging problem of internal fatigue cracks in titanium alloy.The scanning la-ser source method is employed to extract time-domain mode-echo signals from different detection positions.By analy-zing the amplitude distribution of reflected longitudinal waves and reflected shear waves in the B-scan image,the tem-poral characteristics of crack echo signals are partitioned and recombined.Furthermore,inversion focusing is applied to accomplish the recognition and image reconstruction of internal cracks.The feasibility of this approach is demon-strated by conducting numerical simulations of the internal crack imaging process in titanium alloy plates using COM-SOL Multiphysics,and its viability is further validated using MATLAB image algorithms.Compared to single-mode wave imaging,the imaging method that combines reflected longitudinal wave and reflected shear waves effectively re-duces artifacts,enabling accurate localization and image reconstruction of internal cracks.The relative errors of the re-constructed crack positions in the X-axis and Y-axis are both within 3％.
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