SBIR-STTR Award

Resonant ultrasound inspection can rapidly find cracks flaws and tolerance errors in solid structures. In metallic bearings, we have measured sphericity to 50ppm (.0002 mm in .5 cm bearing) and, in addition, were able to determine the presence of flaws with the same sensitivity. Recent tests by LANL, using a joint LANL/Quatro patent disclosure, have increased this sensitivity several fold, however, these results have not been quantified. This concept utilizes the detection of harmonic comparisons in both the dry and solvent wetted conditions. Quatro will apply this technique to ceramic bearings by subjecting the substrate to a broad spectrum acoustic signal and examining the resultant harmonic resonances . Our instrumentation will then subtract the spectra to determine the presence of flaws. The objective of this proposal is to develop a process, including the software, hardware and procedures by which a ceramic bearing may have its spectrum taken within 1 second. This will then be developed into an acceptance test to select qualified bearings. To determine manufacturing tolerance limits and non destructive detection of stress or corrosion induced cracks and flaws. This technique should be less expensive, faster,Portable and more versatile than pulse echo, fluorescent dye penetrant, magnetic particle and eddy current techniques. Resonant ultrasound inspection detects flaws on inaccessible internal surfaces

In Phase I, Resonant Ultrasound (RUI) was applied to Si3N4 ceramic bearings to determine their quality. By calculating the spherical mode degenerate resonance of a homogeneous isotropic elastic sphere, we were able to predict all resonant frequencies . A coarse scan does not find all resonances, however subsequent examination of the predicted region yields a 100% correlation with the model. A cerbec laboratory process produced 1/4 inch SiN spheres which are essentially perfect (2 ppm total defects). An operationally superior process labeled NBD-200 produces spheres which contain 100 ppm total defects. These bearings show much higher wear capabilities that the earlier NBD-100 samples. The RUI measurement detects all flaws including asphercity, density variations, cracks and voids. It can be used to find batch to batch variations rapidly. Phase 1I will develop an automated process by which Si3N4 spheres, of various diameters may be cheaply, rapidly and reliably selected after meeting acceptance criteria. The laboratory process by which Si3N4 races may be evaluated will also be developed including the resonance model. Anticipated

Benefits:
This method will provide a cost effective monitoring technique for use in various stages of bearing production. If successful, dimensional tolerances and bulk integrity can be measured inexpensively, thus achieving a high level of reliability for a low cost of inspection.