Model-based estimation of ultrasonic echoes. Part II:Nondestructive evaluation applications

摘要

For Part I see ibid., vol.48, no.3, pp.787-802 (2001). Accuratenestimation of the ultrasonic echo pattern leading to the physicalnproperty of the object is desirable for ultrasonic NDE (nondestructivenevaluation) applications. In Part I of this study, we have presented angeneralized parametric ultrasonic echo model, composed of a number ofnGaussian echoes corrupted by noise, and algorithms for accuratelynestimating the parameters. In Part II of this study, we explore thenmerits of this model-based estimation method in ultrasonic applications.nThis method produces high resolution and accurate estimates fornultrasonic echo parameters, i.e., time of flight (TOF) amplitude, centernfrequency, bandwidth, and phase. Furthermore, it offers a solution tonthe deconvolution problem for restoration of the target response, i.e.,nultrasonic reflection and transmission properties of materials, from thenbackscattered echoes. The model-based estimation method makesndeconvolution possible in the presence of significant noise. It can alsonrestore closely spaced overlapping echoes beyond the resolution of thenmeasuring system. These properties of the estimation method areninvestigated in various ultrasonic applications such as transducernpulse-echo wavelet estimation, subsample time delay estimation, andnthickness sizing of thin layers