Review by NDTnet The paper was presented by Daniel Barnard. The Dripless Bubbler technique successfully merges focused beam ultrasonics, a method of maintaing a captured water column, and portable robotic scanner. The scanner used in this phase of work is the PANDA II by Tektrend International, Inc. This scanner has a flexible scan frame that conforms to the curvature of the fuselage in order to allow the transducer within the DB to more closely maintain an incidence normal to the scan surface. This unit is also very light and simple to assemble in the field. The motion control, data acquisition and analysis software, ARIUS II, also by Tektrend, manages the scanning operations. The data acquisition system allows the acquisition of full waveform data capture and storage for post processing. In preparation for scanning, the transducers position in the transducer cylinder is adjusted to optimize focusing conditions. In operation, the Dripless Bubbler is scanned in a raster pattern over the area of interest, typically using the full waveform capture feature. The data can then be post processed with virtually any gating scheme, producing amplitude and time-of-flight C-scans and both horizontal and vertical B-scans and displaying any number of the images simultaneously. Daniel Barnard Dripless Bubbler A Tektrend Scanner and System was used

The Dripless Bubbler has been developed for the nondestructive inspection (NDI) of aircraft structures through the FAA's National Aging Aircraft Research Program. The intended purpose of the Dripless Bubbler (DB) is evaluating the extent of corrosion and adhesive disbond in aluminum fuselage. This method merges the high spatial resolution, consistent coupling and focusing gain advantages of focused-beam immersion ultrasonics with a portable scanner and data acquisition system. Immersion quality images are produced by this technique as a result of a these advantages. A bubble-free contained water pool allows scanning over surface irregularities such as button-head rivets, lap splices and doublers, in any orientation, with no loss of couplant.

The system has been tested in the laboratory and in field trials at several air carrier maintenance facilities and at the FAA - Airworthiness Assurance NDI Validation Center (AANC). The results of these tests and field trials have lead to improvements in the design and operation of the DB and scanner. Recent Beta-site tests at air carriers facilities have identified areas, such as the inspection of composite structures, where more work is needed. Recent tests have also demonstrated that the system can characterize exfoliation corrosion around ferrous fasteners on aluminum wing skins.

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