Research On Acoustic Emission-Based Early Warning Technique For Offshore Structures

This paper is aimed mainly at the application of early warning technique with acoustic emission to large steel structures—offshore platforms, and is funded by'863'High Technology Research and Development Program of China(No.2006AA09Z355). Acoustic emission(AE) technique is a dynamic and passive non-destructive testing(NDT). The given relations are existent between changs of AE signals vs. time and damage processes of structures,and also the damage processes can be traced and refected, so the safety early warning can be done on structures based on AE. The paper suggests a new early warning method for offshore structures based on AE technique, which could be used to not only monitor the service status but also provide early warning effectively in time. Experimental research is performed on the application of AE based early warning technique, which includes:(1) The experimental investigation of damage process monitoring of metal components with AE: Serial AE monitoring testing projects are designed, the high toughness steel material specimens are factured, and the experiments of tensile fracture and fatigue crack of specimens are carried out under the existing experiment conditions.(2) Parameter analysis and wave analysis of AE signals: The results from the test using AE to monitor the process of fatigue crack and tensile fracture of rod-type specimens, and tensile fracture of A3 plate specimens are analysed and discussed, it is shown that the AE features can be used to describe the corresponding damage mechanical behavior and express specimen damage types. Some other important conculsions about AE features are also drawn. AE signals characteristics of some key damages are gained through wave analysis methods such as FFT, wavelets transform, bispectrum etc., which proved that the wave analysis methods above-mentioned is more effective for damage types recognition.(3) The research on elementary scheme of AE-based early warning technique for offshore platforms: With considering failure criterions based on AE parameters, early warning index for steel structures monitored by AE is proposed, and the primary scheme about the application of early warning technique with AE on the offshore structures is suggested.