Elastic Wave Signal Characteristics of SiC Ceramics with Crack Healing Ability by Wavelet Analysis

Abstract

This paper reports for signal characteristics of before-and-after healing treatment SiC ceramics with crack healing ability. The elastic wave signals generated during the compress load by a Vickers indenter on the brittle materials were recorded in real time, and the waveforms of the individual signals were examined and classified based on their spectral characteristics. The compress loads were applied with the range from 9.8N to 294N. In a bulk SiC specimen, the AE signals occurred only when the load was compressive loading and unloading. But, in the after crack healing specimen of 294N only, even though the external compressive load was stopped and kept on holding constant load states, the AE signals occurred irregularly and continuously. The results of the WT and frequency analysis showed that these existed as the property of frequency in the limited range between 100kHz and about 200kHz. Three-point bending test was performed for the cracked and healed SiC specimens. Consequently the bending strength of the crack healed specimens was recovered completely, but most of the samples with the crack healed showed that the properties of the dominant frequency were comparatively lower than that of the bulk SiC samples. The classification of the wave signals can be used to develop algorithms for autonomous health monitoring systems of brittle material structures.

Bending Strength of Al₂O₃ Ceramics for Textiles Machinery and Elastic Wave Characteristics by Wavelet Analysis

“…The Fracture Wave Detector (FWD; Model FM-1, Digital Wave Corp., Englewood, Co.) was used to detect the elastic wave [10]. The test specimen was mounted on the flat base of Vickers.…”