SBIR-STTR Award

Ceramic machining generates subsurface cracks that can grow and lead to the fracture of machined parts. It is thus important to measure the damage due to machining. Such a measurement could be used to improve machining methods, and for the nondestructive evaluation of machined parts.The technique we propose is based on using scattered ultrasonic surface waves to measure the size and distraction of micro-cracks associated with machining damage of ceramic surfaces. Very simply, we will use surface wave transducers for operation in the25-50 Mhz frequency range and measure the average back scatteredsurface wave signal as a function of distance away from the transducer. The measurement is made in a broad band (pulsed)mode. The received signal is digitized and stored, the transduceris moved slightly and a new signal is captured and added to the previous signal. This process is repeated a number of times and an exponential decay of the surface wave is measured as a function of distribution of surface micro-cracks.Our overall goal is to develop a fast, simple, efficient and inexpensive commercial tool for the inspection of machining damage.Commercial Applications:This project will demonstrate the technical feasibility of a technique which can be developed into a commercial surface machining inspection system. An inexpensive and quantitative measurement system will not only be used to improve machining methods but also for the inspection of machined parts. Ceramic parts would no longer be limited by machining damage and have a longer lifetime. This enhanced performance will lead to wider use and acceptance of ceramic parts.