Magnetic Memory Signal Extraction And Analysis Of Defects In Single-layer Submarine Pipeline

The safe operation of the submarine pipeline will be affected due to the processing factors,transportation medium and complicated load.At present,there are certain limitations on the common detection methods for submarine pipelines,that is,only the macroscopic damage can be detected,and the internal detection is prone to the problem of jamming.The magnetic memory detection technology does not require pipe magnetization in advance,early stress concentration and hidden damage can be found,which plays a very good role in the safety assessment of submarine pipelines.Based on the finite element multi-field coupling simulation calculation,the distribution of magnetic field characteristics of single defects with different sizes under load is studied firstly,and the peak trend of magnetic field strength when load and size changes are obtained.Secondly the different distributions of the double defects are studied,and the relationship between the different influencing factors and the peak value of the magnetic field strength is established.The results show that the influence factors have different influences on the peak value of the magnetic field strength,and the stress state and stress concentration coefficient at the defect have a great influence on the evaluation of the magnetic field strength signal.In order to verify the accuracy of the finite element simulation calculation,the non-contact magnetic memory test simulation experiment of the submarine pipeline was verified in the laboratory environment.The results showed that the relative error of the peaks was generally small.In view of the dispersibility,ambiguity and uncertainty of the experimental data,and the change of some influencing factors,this paper introduces four kinds of synthetic characteristic parameters to fully reflect the defect state characterized.The influence of position factors on the four characteristic parameters is determined,and the fitting relationship and variation law of the synthetic characteristic parameters applicable to the specific influencing factors are finally determined,which provides a theoretical basis for the subsequent safety evaluation of the submarine pipelines in service.