caa a22 4500 388021896 CHVBK 20180307124926.0 cr unu---uuuuu 161130e199807 xx s 000 0 eng 10.1557/JMR.1998.0269 doi S0884291400045052 pii (NATIONALLICENCE)cambridge-10.1557/JMR.1998.0269 Detection of contact damage in ceramics by an ultrasonic method [Elektronische Daten] A pulse-echo ultrasonic technique consisting of focused normal-incident compressional waves was used for the detection and evaluation of surface and subsurface damage in micaceous glass-ceramic and silicon nitride samples. The damage was produced by indentation with a tungsten carbide ball. The nature of the damage was found to be material-dependent and was classified into two types: Hertzian cone cracks in the silicon nitride, and distributed subsurface microcracks in the glass-ceramic. While the cone cracks were visible on the surface as circular ring cracks, the distributed subsurface microcracks were not associated with any visible surface cracks. Both the cone cracks and the distributed subsurface microcracks were easily detected by the ultrasonic technique. In addition, the ultrasonic beam was focused to different depths below the surface of the glass-ceramic sample to probe the subsurface region containing the microfracture damage. Copyright © Materials Research Society 1998 Ahn Hyo Sok Korea Institute of Science and Technology, Seoul, Korea Jahanmir Said National Institute of Standards and Technology, Gaithersburg, Maryland 20899 Slotwinski John A. National Institute of Standards and Technology, Gaithersburg, Maryland 20899 Blessing Gerald V. National Institute of Standards and Technology, Gaithersburg, Maryland 20899 Journal of Materials Research Cambridge University Press 13/7(1998-07), 1899-1904 0884-2914 13:7<1899 1998 13 JMR https://doi.org/10.1557/JMR.1998.0269 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1557/JMR.1998.0269 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Ahn Hyo Sok Korea Institute of Science and Technology, Seoul, Korea NATIONALLICENCE 700 1- Jahanmir Said National Institute of Standards and Technology, Gaithersburg, Maryland 20899 NATIONALLICENCE 700 1- Slotwinski John A. National Institute of Standards and Technology, Gaithersburg, Maryland 20899 NATIONALLICENCE 700 1- Blessing Gerald V. National Institute of Standards and Technology, Gaithersburg, Maryland 20899 NATIONALLICENCE 773 0- Journal of Materials Research Cambridge University Press 13/7(1998-07), 1899-1904 0884-2914 13:7<1899 1998 13 JMR CC0 http://creativecommons.org/publicdomain/zero/1.0 nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-cambridge