Detection And Evaluation On Jack-up Platform Structural Stress Concentration Zone Based On The MMM Technique

Jack-up platforms play a key role in offshore oil exploration and development because of its advantages of variable operating environment and changeable job status. However, due to the mobility and movement of its operating characteristics, as well as the complexity and randomness of marine environment and other factors, jack-up platforms will generate stress concentration of the structure in the process of running. As a result, the bearing capacity will decline, which will induce disasters and cause serious consequences petroleum economic losses and environmental pollution. Metal magnetic memory testing technology overcomes the shortcoming of the traditional nondestructive testing and can realize the rapid detection to stress concentration area of the ferromagnetic metal components. It has important significance and application value for early detection of security risks due to structural damage and sudden fatigue damage prevention.In order to provide guidance basis for jack-up platform bearing parts metal magnetic memory engineering detection, based on the analysis of jack-up platform structure stress concentration factors from two aspects of structural destructive and structural integrity, the experimental study of tensile specimen structure stress concentration detection on the basis of metal magnetic memory testing technology with the use of TSC-2M-8 metal magnetic memory testing equipment and tensile load test system. The tensile specimen magnetic memory signals of the different stress stages(elasticity, yield, plasticity and necking) was analyzed, and the MMM signals changing rule was summarized.With tensile specimen magnetic memory testing signals of different stress stages as the object, wavelet analysis was used for the original test data filtering noise. Through comparative analysis, db2 wavelet was selected as the wavelet function, and the wavelet decomposition scale was 4, and the threshold selection is Heursure threshold. The feature analysis was executed to the de-noised signals, and finally the difference between the minimum and maximum Tensile Specimen MMM signal value Deta, MMM signal average value H? p?, MMM tangential component signal pxH extreme value and MMM normal component signal pyH gradient value py?H were determined to be the characteristic criteria of structure stress concentration.Finally, based on the results of indoor jack-up platform model test, taking one jack-up platform structure bearing components legs, crane hook, deck and cantilever beam section as objects, the actual engineering test researches were conducted. Combined with the structure characteristics of different components, from the perspective of sensor selection, corresponding metal magnetic memory detection methods were put forward. Engineering test analysis was carried out based on the testing data of different components. The degree of structure stress concentration was confirmed and its safety and reliability were evaluated, which will provide the reference basis to the jack-up platform structural health inspection.