An improved method, in which samples are covered with an adhesive tape, has been developed for the nondestructive evaluation (NDE) of green-state ceramics. The tape serves to protect the sample from contamination by ultrasonic couplant, and the adhesive serves to couple ultrasonic waves into the sample. This tape can be removed without any damage to the surface. If the sample is sealed by the tape, water-immersion C-scan imaging can be applied. Furthermore, if a water bag is placed onto a taped sample and a transducer is scanned in the water, complete sealing is not necessary; hence, practical industrial testing of large or curved samples may be achieved. This method has been applied to large and thick (70 mm dia and 19 mm thick) green-state alumina with 4 percent PVA binder. Subsurface features such as an inclusion (2 mm dia paper sheet at 8 mm depth) and large variations with time of the amplitude and time delay of the back-surface echo associated with variations in humidity were recorded by using a 0.5 MHz, 4 in. (10 cm) focal-length transducer. A detailed comparative study between acoustic images before and after sintering was also conducted.
|Number of pages||7|
|Specialist publication||Materials Evaluation|
|Publication status||Published - 1989 Jul 1|
ASJC Scopus subject areas
- Materials Science(all)
- Mechanics of Materials
- Mechanical Engineering