Compression wave NDE of adhered metal lap joints: uncertainties and echo feature extraction

This paper deals with the use of compression wave pulse-echo ultrasound for the NDE of simple adhered metal lap joints in which both the bondline and the adherend thicknesses may be variable and unknown—a situation commonly found in automotive superstructures. Of specific interest are the detection of void disbonds at near and far adherend/adhesive boundaries, and the estimation of the characteristic acoustic impedance of the adhesive as an indicator of cure. Modelling of the wave system indicates how absorption in the adhesive, reverberations in the adherends, and the transducer response affect the signal detections and the robustness of signal calculations required for NDE.