Tecnatom (San Sebastian de Los Reyes, Spain) has optimized the application of phased array technology to Through Transmission Ultrasonic (TTU) inspection by means of an innovative squirter and highlighted this development at the 2015 Paris Air Show (June 15-21, Le Bourget, France).
Most ultrasonic testing (UT) requires coupling the sound wave transducers with a gel or fluid, most typically water. Large automated nondestructive testing (NDT) machines use multiple transducers to scan a part coordinated with a squirter to enable targeted coupling of the transducers. Until now, it is commonly accepted that in order to detect a 6mm defect, three overlapping passses are required , each of 2 mm width, in order to assure a good laminar flow in the squirter, good coupling and, thus, good quality in the results.
In order to increase the productivity of TTU inspection, Tecnatom has developed a patented Array Probe TTU squirter that assures a 20 mm wide laminar flow, which allows an inspection pass of 14-16 mm in width. Validation has been successful, with excellent results in the UT acquisitions recorded in Tecnatom’s INSPECTVIEW advanced NDT suite.
The combination of this new element plus Tecnatom‘s data acquisition system (DAS) meets aerospace industry standards and manufacturers' procedures. This Phased Array TTU technique is now being integrated into the Tecnatom product line, and an industrial robot-based system is in final implementation at a customer site with a second project in process. Tecnatom, has thus provided a validated TTU Phased Array solution for composites NDT with dramatically increased productivity, necessary for meeting the industry's drive to reduce manufacturing time and cost and ability to meet high-volume production rates.
Background on TTU
UT inspection techniques detect internal damage in composite structures using the attenuation or reflection of ultrasonic waves. In TTU, a UT probe on one side of a component transmits (T) an ultrasonic pulse to a receptor (R) probe on the other side. The absence of a pulse coming to the receiver indicates a defect.
Pulse-echo is the other most common UT technique, in which the T and R transducers are positioned on the same face of the structure. Any reflections or disturbances in the echo received by the receptor could indicate an internal defect.
Which technique is used depends on the material to be inspected, the accessibility of the structure's surfaces and the requirements of the inspection itself.
TTU inspection is commonly used for inspection of honeycomb and other cored sandwich structures, while PE is typically used for the inspection of solid laminates. When portions of a sandwich structure — or other elements which attenuate sound waves (foams, etc.) — are included in a fully integrated part, TTU is also necessary for the inspection of these particular areas.