Lawrence Berkeley National Laboratory

This paper describes models and methods for estimating the acoustic reflectivity of the welded interfaces between spot-welded sheets from normal-incidence pulse-echo ultrasound signals. The simple geometry of the problem allows an abstraction that does not resort to complex wave equations. Instead, a reflectivity model predicts the timing and amplitude of the echoes arriving at the probe. This reflectivity model is nested in a signal processing model; recovering reflectivity first requires deconvolution to recover discrete impulses from the probe signal, then processing these with the reflectivity model. Reflectivity maps of spot welds generated with this model show promise for predicting weld quality.