Detection of Weak Interface Signals for Same Material Bond/Weld Inspection.

In same material joining processes, remnants of the original interface may be acoustically weak and difficult to detect ultrasonically in the presence of grain noise. For the nearly perfect (but potentially inadequate) bond or weld the remaining interface may be defined only by small voids, cracks, or by weak echo surfaces (grain boundaries) approximately aligned in the original interface plane. In this study, we investigate the utility of correlation-based techniques for revealing the presence of interface signals in the presence of grain noise as the signal-to-noise ratio is pushed below 1.0. These techniques are attractive since they are independent of absolute scale and since the grain noise near the bond/weld time window may be useful in establishing baseline results for a region without an interface (grain noise only). Experimental results from two different same material joining processes are included in the study along with supporting results from a simulation driven by experimental data. © 2003 American Institute of Physics [ABSTRACT FROM AUTHOR]