Method for improving longitudinal resolution of TOFD (time of flight diffraction) detection with Burg algorithm based autoregressive spectrum extrapolation technology

Abstract

The invention discloses a method for improving longitudinal resolution of TOFD (time of flight diffraction) detection with a Burg algorithm based autoregressive spectrum extrapolation technology, and belongs to the technical field of ultrasonic non-destructive detection. The method adopts an ultrasonic detection system comprising a TOFD ultrasonic detection instrument, TOFD probes, a scanning device, software integrating TOFD conventional analysis functions and a computer. According to the method, TOFD scanning is performed on defects, collected time-domain aliasing signals containing upper-end and lower-end diffraction waves of the defects are subjected to autoregressive spectrum extrapolation processing; the -6dB frequency bandwidth is taken as the benchmark, defect signals in the frequency band range are selected, defect signals outside the frequency band range are estimated with the Burg algorithm, so that the frequency bandwidth is broadened, the longitudinal resolution of defect detection is improved, and the defect height quantification is realized. Compared with other methods for improving the longitudinal resolution of TOFD detection, the method does not have additional requirements for a hardware system, is not limited by exciting pulse time width of the detecting probes, and has higher engineering application value.

Description

technical field [0001] The invention relates to a method for improving the longitudinal resolution of TOFD detection based on an autoregressive spectrum extrapolation technology based on the Burg algorithm, which belongs to the field of ultrasonic nondestructive testing. Background technique [0002] In order to effectively evaluate the physical integrity of the inspected object, it is necessary to inspect all defects, as well as accurately locate and quantify them. At present, the Time of Flight Diffraction (TOFD) technology is one of the most accurate ultrasonic detection and quantification methods. Compared with the traditional pulse echo method, TOFD technology has more advantages in detecting vertical crack-like defects, and can achieve accurate quantification of defect height. [0003] The detection longitudinal resolution is one of the key factors affecting the quantitative accuracy of TOFD. In order to further improve the vertical resolution of TOFD detection, the ...

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Problems solved by technology

The TOFD detection resolution can be improved to a certain extent through parameter optimization, but limited by factors such as the frequency of the detection probe and the depth of the defect, the improvement of the longitudinal resolution is limited; the extraction effect of the defect signal in the image energy distribution method is greatly affected by the quality of the image to be processed , there is often the problem of difficult separation of defect signals; the spectrum analysis method is limited by the frequency bandwidth of the probe, when the propagation time difference between the upper and lower ends of the defect is less than (f is the probe frequency), this method is no longer applicable

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