Scanning Acoustic Microscopy of Partly Embedded Cracks in Polycrystalline Alumina
Reflection scanning acoustic microscopy (SAM) at 1 GHz has been used to examine artificially induced cracks in alumina samples. The results are compared with the corresponding optical micrographs and scanning electron microscope images. For a sample with a 0.08 μ m centre-line average (CLA) surface finish, the SAM working with a 400 μ m frame size, showed that a crack that appeared to be about 150 μ m in length in the corresponding optical image was, in fact, at least 200 μ m in length. For a sample with a good engineering finish of 0.15 μ m CLA, the SAM was able to reveal crack detail to a degree comparable with that revealed by an optical microscope working under optimum conditions. On a sample with a highly polished surface it was possible to distinguish between cracks and grain boundaries by using the V(z) response of the SAM, in agreement with theory.
Philosophical Transactions of the Royal Society of London Series A
- Pub Date:
- November 1986