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Ultrasonic imaging of steel-adhesive and aluminum-adhesive joints using two dimensional array Bita GHAFFARI 1 , Kimberly A. LAZARZ 1 , Jonathan DEKAM 1 , Sergey TITOV 2 , Elena MAEVA 2 , Mircea PANTEA 2 , Roman Gr. MAEV 2 1 Research and Advanced Engineering, Ford Motor Company, Dearborn, MI, USA Phone: 1 313 8455489; e-mail: [email protected], [email protected] 2 Institute for Diagnostic Imaging Research, University of Windsor, Windsor, Canada; e-mail: [email protected], [email protected], [email protected], [email protected] Abstract This work is devoted to development of techniques for detection of adhesive in joints and image construction of the adhesive spatial distribution. Based on numerical modeling, the specific behavior of the reverberating pulse- echo waveforms in steel adhesive and aluminum adhesive multi layered structures is analyzed. It is shown that the energy of the received waveform weighted within a certain time gate can be used as a metric for discriminating between no/adhesive areas. To generate the image of the adhesive distribution the waveforms received by the elements of the matrix ultrasonic array were independently processed and the outputs are spatially interpolated and compared with a certain threshold. The developed algorithms have been tested on steel-to-steel, aluminum-to- aluminum and aluminum-to-steel adhesive joints using 15 MHz, 52-element, 10 mm x 10 mm matrix array of ultrasonic transducers. Keywords: adhesive joint, matrix array, ultrasonic image, signal processing 1. Introduction Ultrasonic non destructive evaluation of steel adhesive and aluminum adhesive joints is an important process in aerospace and automotive industries. Imaging of adhesive coverage in joints is a challenging problem due to the large acoustic impedance mismatch between metal and adhesive, variability in the thickness of metal and adhesive layers, and possible deviation from perfect geometry in the joint’s layered structure. The reverberating strong ultrasonic echoes from the first metal sheet overlap the weak responses from the internal interfaces and defects in the adhesive joint. Though these challenges were recently overcome for steel- adhesive joints using an ultrasonic pulse-echo technique, the difference in acoustic impedances of steel and aluminum leads to a lack of robustness in utilizing the same algorithm for aluminum-adhesive joints. The thicknesses of the adhesive layer and metal sheets may vary within 0.1-1 mm and 7-10 mm, respectively. Typical widths of adhesive beads in automotive applications are 10-15 mm; it is therefore desired to be able to read the adhesive bead width with a spatial resolution of 1 mm or better. These requirements have proved very challenging to a large number of ultrasonic nondestructive techniques [1, 2]. It was shown that sufficient spatial resolution could be
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  • Spring '18
  • Prof Lilly
  • Adhesive, Impedance matching, aluminum-to-steel adhesive joints, Adhesively Bonded Joints

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