Accurate Location of Key Features in Ultrasonic-based Spot Weld Inspection

Abstract

Ultrasonic-based non-destructive spot weld inspection techniques heavily rely on advanced signal processing al-gorithms developed for this particular application. RSWA-F1® [1] and RSWA-F2® [2] are two portable ultrasonic devices from Tessoni® designed and manufactured for the use in automotive industry to evaluate the quality of resistance spot welds. Both the RSWA-F1® and RSWA-F2® employ the multi-channel matrix transducer technology to collect and analyze data from the surface and internal structures of the weld. The original signal processing algorithm used in the first generation of the RSWA was based on detecting the amplitude of internal reflection between welded metal plates. The second generation on the other hand incorporated the secondary echo detection analysis because the amplitudes of internal reflections were often small compared to noise. In this paper, we briefly introduce a new technique that a further developed version of it may be used in the third generation of the RSWAs to extract accurate location of key features more efficiently. High degree of accuracy is obtained for the correct location of the key characteristics, e.g., the delay line, surface pulse, first echo, backwall and potential defects inside the weld nugget.