Acoustic Emission Analysis of Flexural Damage

The acoustic emission (AE) technique was applied to detect the acoustic signals during flexural mechanical test arising from damage and cracking events. All the signals were collected by two piezoelectric sensors (Nano-30, frequency of 140 kHz with band-pass filtering of 150–400 kHz), and were analyzed using a digital signal processor with an AEwin v3.61 AE system (Physical Acoustic Corporation, USA). To improve the conduction of the signals between the specimens and detectors, Vaseline was smeared on the surface of sensors. To filter the noise acoustic signals from other environmental sources, an amplitude acquisition threshold of 40 dB was used in all experiments.