Online Close Loop Control of Ultrasonic Consolidation Using Ultrasonic Nondestructive Testing

Layer by layer manufacturing offers a unique opportunity for online NDT since it is probable that defects formed in one layer might be corrected in subsequent layers by suitable selection of parameters. A high frequency ultrasonic NDT setup has been integrated into an existing Ultrasonic Consolidation (UC) machine along with the ability to change process parameters on the fly. Ultrasonic Consolidation is a layer based solid state process which bonds one layer of foil on top of another. This leads to a very fine grained subsurface microstructure which has good strength, and is free from common metal joining problems such as solidification cracking and gas entrapment. But the drawback is that it poses problems such as delaminations when the bonding parameters are not optimal. Solid state fusion processes hence have great potential if good bonding characteristics could be identified and ensured. To overcome this, we are implementing a high frequency ultrasonic NDT system and developing a control process based upon real-time measurements of part density, part quality (% well bonded area), grain size, and yield strength calculated from shear and longitudinal waves.

References
1. Gonzalez, R. and B. Stucker, (2012) “Experimental determination of optimum parameters for stainless steel 316L annealed ultrasonic consolidation,” Rapid Prototyping Journal, Vol. 18 Iss: 2, pp.172 - 183. 2. Papadakis E.P., (1967) “Ultrasonic Phase velocity by Pulse echo overlap method incorporating diffraction corrections,” J. Acoust. Soc. Amer., 42:1045-51.
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