Automated Surface Microstructure Nondestructive Evaluation (NDE) Process for Aerospace Materials

ABSTRACT:Building upon its successful effort to identify grain structures in titanium alloys, in Phase II, TRI/Austin will use a combination of highly focused polyvinylidene floride (PVDF) ultrasonic (UT) transducers and high gain amplifiers to perform ultrasonic backscattering measurements to identify signals corresponding to the grain structure in commercially pure Ti and Ti-6Al-4V. TRI/Austin will partner with the Advanced Manufacturing Center at the University of Texas at Austin to fabricate highly characterized pure Ti and Ti-6Al-4V specimens containing specially designed and tailored microstructures. Additionally, Dr. Paul Panetta of Applied Research Associates, Inc. will leverage previous work on grain sizing in Ni superalloys to provide consulting on backscatter measurements in Ti. TRI will use its customized UT facilities to perform backscatter attenuation, fast Fourier transform, and phase-to-peak measurements and analyses to identify the microstructures and construct attenuation vs. grain size curves for the Ti alloys. Additionally, the TRI team will investigate the abilities of the UT system to identify different crystal orientations and structures, as identified in the specimens using scanning electron microscopy and electron backscatter diffraction. The effort will culminate in the fabrication of a prototype UT system that will demonstrate inspection capabilities on a component/part of the sponsors choice.BENEFIT:Ultrasonic systems, such as the one proposed in this work are non-contacting, safe, and are a widely adopted means to perform non-destructive inspections in many industries. The ability to be able to inspect a component and quantify the grains on the surface (including the size, shape, micro-texturing, etc.) is invaluable to the end user of the component. In the case of the Air Force, the proposed technology will assist in ensuring better part quality, tighter controls on the inspection intervals and life predictions, and better supplier and manufacturing controls. Additionally, quantified C-scan images and datasets will fit neatly into the Air Forces Digital Twin initiatives to digitize inspection records, CAD files, repairs, etc associated with each individual airframe. This technology is also capable of supporting Air Force sustainment efforts through the scanning of disassembled components that are periodically inspected in the depots. Other potential adopters of this technology would include any military branch operating jet engine aircraft.Industry has also expended effort in such a UT technology capability. Raw material manufacturers are pushing the boundaries of metallurgy by making materials containing larger and larger grain sizes to increase the structural properties of these materials. Relationships do not exist to provide a means of comparing the UT signal from the inspection of Ti parts to the grain size. This relationship is very important, because if the grains grow excessively large, the reflected UT signal will continue to increase and potentially reach the same level as that of a void, inclusion, or other defect, rendering the material un-inspect-able, meaning it cannot be quality certified for sale or use. This is important not only to the aerospace industry, but to others such as semiconductor manufacturers where the grain size and a lack of a presence of voids are key to the usability of the part.