Adaptive filtration of ultrasonic signals in car body adhesive bonds evaluation

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Adaptive filtration of ultrasonic signals in car body adhesive bonds evaluation

Severin, F.M. / Maev, R.G.

Growing incorporation of adhesive joints in automotive body production routine demands development of fast and reliable non-destructive testing methods. The structural geometry of 'metal sheet - structural adhesive - metal sheet' makes it complicated to use the convenient pulse-echo ultrasonic technique. A few algorithms of received signal processing were proposed for elimination of reverberation oscillations, detecting and interpretation of the informative signals. These methods based on adaptive filtration and correlation analysis were realized for scanning acoustical microscope data obtained in experiments with epoxy-based polymer adhesive samples. Their advantages and effectiveness were demonstrated and compared. Limitations of these techniques are also discussed. The problem of reliable analysis and interpretation of acoustical signals is still the key point in the ultrasonic evaluation technique. Noise and random factors like surface roughness limits the quality of information obtained, in particular, contrast of acoustical images. Sophisticated digital processing using whole waveform can improve performance of ultrasonic measurements. The cross-correlation method produces images with increased contrast and better detectability for several basic defects in metal-polymer-metal layered structures. Using this method for ultrasonic testing of thin sheets adhesive bonding gives a certain advantage over the convenient C-scan imaging technique.