Evaluation of Machining Damage in Brittle Materials. Final Report

摘要

An acoustic surface wave measurement technique was developed to find and size machining damage induced and surface cracks. Hot pressed silicon nitride (Norton's NC-132) was used. The measurement technique consists of exciting a leaky surface wave on the sample while immersed in a water tank. The transducer is pulse excited and operates at a frequency of 50 MHz. The signal from surface cracks is digitized and stored in a minicomputer. A reference signal from a 90 exp 0 corner in the sample is also digitized and stored in the minicomputer. The scattering coefficient of the crack as a function of frequency is then calculated by dividing the crack signal by the reference signal via a Wiener filter. (ERA citation 10:001060)