I would appreciate if someone can guide me in the following issue. I have been studying the possibility of measuring thicknesses and characteristic impedances/sound velocities of layered materials on a substrate by using ultrasonic waves. The main advantage of this analysis is the feasibility of detecting a large number of layers. It looks possible to diagnose materials thicker than 100-micron-thick (perhaps thinner too) and also non-uniform sound velocity patterns, this should work for materials having impedance differences lower than ~30%. Does anyone know any industrial need or application for this analysis?
17:45 Oct-27-2009 Rolf Director, Editor, Publisher, Internet, PHP MySQL NDT.net, Germany, Joined Nov 1998 602
Re: Ultrasonic NDT for layered materialsIn Reply to Gustavo at 11:14 Oct-25-2009 (Opening).
The plastic industries is using already ultrasonic for thickness measurement of layers, but still not in quantity. They are locking always for cheap solutions. Good chance you have in medical and automotive tubing and also the packaging industry has need for good quality control for some productions, e.g., fuel tanks, barrels for dangerous goods. In the databse we have some articles of this issue.
Thanks for your answer. Basically, I have worked on the development of a theory that can be applied for reflected acoustic waves. I am convinced that it is possible to measure in a relative easy way the thicknesses and sound velocities (or characteristic impedance) for media composed of many layers and also to characterize graded changes of velocity as a function of depth. I guess that this last case should be useful for certain industrial processes, such as temperature modification; I mean processes that could affect the velocity within the media. The analysis might be advantageous in regard of simplicity and calculation speed. However, it requires wideband ultrasonic measurements, what it is not much conventional. The thickness that could be resolved mainly depends on the freq. range; for the very beginning I assume that the highest freq. will not be higher than 20MHz.
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