![]() Thus, distinguishing different source mechanisms and extracting signals from HIC is only the first step of analysis and a vital process for improving the accuracy of source location. Signals of H 2 evolution and corrosions are inevitably collected at the same time together with those from HIC. However, they often lack the sensitivity needed for practical use.įor energy pipelines, the generation and propagation of HIC is always accompanied by H 2 evolution and corrosion activities. In such cases, wideband or broadband AE sensors are more suitable. However, a large range of frequencies may exist, particularly in cases where multiple damage mechanisms are present, and the acquired signals are influenced heavily by the response of the sensors. Sensors are therefore typically selected based on the peak frequency of the wave. Most of the AE sensors used in practice have their own distinct acoustic resonance, thus the name resonant AE sensor, which means the measurement is significantly more effective at a particular frequency. This makes the selection of sensors vitally important. It is thus desirable to identify signals that can best characterize the source. Signal pattern recognition (i.e., identifying different fracture mechanisms) is needed in order to understand HIC occurrence or damage mechanisms. ![]() The acquired signals are influenced by not only the fracture mechanism, but also wave propagation through the structure and, significantly, the response of sensors. ![]() It can also acquire low-energy signals better, which is more suitable for monitoring over a long distance.Įlastic waves generated from local crack changes in structures such as HIC are captured by AE sensors and converted into electrical signals for further analysis. VS150-RIC can identify HIC signals better and provide source locations more accurately. Results show that signal characteristics from different mechanisms can be identified more clearly by Nano30, which is conducive to signal classification. A basic reference for the selection of sensors for HIC monitoring is provided according to different test purposes and monitoring environments. Obtained signals were analyzed and compared on three aspects, i.e., in signal acquisition, signal discrimination, and source location to demonstrate the influences of the two types of AE sensors. In this study, two commonly used AE sensors (Nano30 and VS150-RIC) were used for monitoring HIC processes using the electrochemical hydrogen-charging method under laboratory conditions. Most piezoelectric sensors have resonance and thus are effective for a certain frequency range, and they will fundamentally affect the monitoring results. AE uses piezoelectric sensors to convert the elastic waves generated from the growth of HIC into electric signals. ![]() Acoustic emission (AE) technology is a non-destructive testing (NDT) technique that is able to monitor the process of hydrogen-induced cracking (HIC). ![]()
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