Research On Fatigue Crack Identification Method Of Marine Engineering Pipeline Based On Acoustic Emission Technology

At present,considering that a large part of China's offshore oil and gas platforms have entered the later stage of their design life,fatigue cracks on key structures of offshore oil and gas pipeline systems in many offshore platforms in complex and harsh environments,and health monitoring is required for these significant offshore projects to ensure their safe and stable operation during service.In this paper,the two aspects of complex environmental noise interference and effective feature extraction of fatigue crack acoustic emission signals faced by acoustic emission technology for monitoring offshore oil and gas pipeline systems are studied.The main work contents are as followsIn order to solve the above problems,two kinds of fatigue crack recognition methods are proposed from different starting points.Probabilistic neural network combined with empirical modal decomposition as feature extraction for fatigue crack identification and probabilistic neural network combined with wavelet packet as feature extraction for fatigue crack identification.The former is to eliminate the interference of invalid noise information by optimizing the feature information,and the latter is based on the characteristic frequency of the fatigue crack acoustic emission signal to eliminate the interference of low frequency noise.And verify the above two methods by experiment respectively.Firstly,a small test piece with Q235 carbon steel as the base material is taken as the research object.The fatigue test is performed on the small test piece with Q235 carbon steel as the base material to obtain acoustic emission signals of fatigue cracks.The validity of the two fatigue crack identification methods is verified on the test piece.Secondly,after investigation,it is known that pipeline vibration fatigue exists widely in various offshore oil and gas platforms.Therefore,the structural model of the offshore oil and gas platform pipeline system is the research object,the purpose is to identify the fatigue cracks caused by the vibration of offshore oil and gas pipelines.Exploring the influence of the internal pressure of the pipeline system structure on the recognition results and verifying the recognition effect of the above two methods on the actual pipeline system structure.Finally,the experimental research is carried out with the small test piece of Q235 carbon steel as the base material and the structural model of offshore oil and gas pipeline systems The test results show that the above two methods of fatigue crack identification can achieve good recognition results and have a certain anti-interference ability,which provides an experimental and theoretical basis for acoustic emission technology to monitor fatigue cracks of oil and gas pipelines on offshore platforms.