A defect positioning method based on
laser ultrasonic B scanning comprises the steps of carrying out B scanning on the surface of a
metal material, and acquiring a B scanning
signal; preprocessing theB scanning
signal, decomposing the B scanning
signal into different frequency bands, and extracting a
wave crest moment of a
longitudinal wave defect echo to obtain a propagation distance of the
longitudinal wave of each scanning point; drawing n ellipses by taking an excitation
laser point and a receiving
laser point as two focuses of the ellipses and taking a
longitudinal wave propagation pathas a
long axis of the ellipses; and solving the intersection points of the adjacent ellipses, and connecting the intersection points in sequence to obtain the contour of the defect and the position coordinates of the defect. A
metal material with internal defects is used as a target
verification object, internal defects in a certain longitudinal section are detected through longitudinal
waves in aB scanning mode by means of a laser
ultrasonic detection platform, reconstruction of B scanning signals is achieved by means of signal
noise reduction,
feature extraction and the like, and information such as a shape, a size and a position of the defects is detected. And a purpose of visual quantitative identification of defects is achieved.