The Research Of Metal Pitting Corrosion Acoustics Emission Inspecting And Signal Process

Metal corrosion is the most dangerous phenomenon attacking different construction materials, especially pitting corrosion. Pitting corrosion is a type of local corrosion attack as the result of which pits are formed, while the remaining metal surface practically remains untouched. This paper aims to research AE inspecting of metal pitting corrosion, and tries to identify AE signal of pitting corrosion by wavelets and ICA. The ultima intention of this research is serving for inspecting metal pitting corrosion by AE technology, which is important meaning in reducing the expense of checking and maintaining, in lessen environmental pollution, in increasing the security of equipment. By analysis for form and growing of metal pitting corrosion, film breaking arouses pitting corrosion with stress producing. Otherwise, small hydrogen air bubble will bring AE, which is the same theory with film breaking. Mechanism model of AE source was founded, and surface displacement quantity grade was estimated, so that amplitude was calculated. This amplitude is much more than value of noise. It is proved that pitting corrosion AE signal is inspected by AE technology. At that time, parameter characteristic and wave characteristic has been identified. This is instructed to inspect metal corrosion by AE technology. By establishing effective experiment plane, acoustic signal sample of pitting corrosion was distilled. Experiment indicates that AE can find material corrosion damage earlier than ordinary nondestructive testing. By studying change disciplinarian of corrosion degree and AE signal with corrosion time, change relation between corrosion degree and AE parameter has been achieved. This explains that AE technology can be used in detecting forepart corrosion, researching corrosion growing orderliness, inspecting and evaluating corrosion damage. Based on corrosion AE signal characteristic and the need of identifying AE sources, wavelet function which is fit for corrosion AE signal has been confirmed. By using wavelet Multi-Resolution Analysis, signal has been de-noised. De-noised arithmetic was given in detail, and the reliability of arithmetic was validated by imitated experiment. The result proved that de-noise effect was excellent. The way of separating AE mixed signal has been brought forward. This way is that ICA is combined with wavelet. Separating effect is excellent. ICA software makes ICA much more credibility.