Design And Experiment Of A Novel Accurate System For Underwater Inspection Based ACFM

With the rapid development of offshore oil industry, more and more offshore oil equipment is used, regularly effective detecting is urgent. For this situation, this paper uses FEM, establishes the models for underwater inspection based ACFM, analyze the influences of seawater environment on the crack characteristic vectors, design the underwater inspection probe, Optimize the underwater intelligent recognition software, develops an experimental prototype of the underwater detection probe- signal processing systems- software, and test the experimental prototype. This paper discusses the research from the following aspects:(1) Study of the Theory and Numerical Model of ACFM in the seawater environmentBased on the Theory and Numerical Model of ACFM in air environment and FEM, the system for underwater inspection is established. According to electromagnetic field attenuation, interference of seawater environment and the evolution characteristics of the component defects underwater, this paper analyzes the influences of environmental factors such as temperature, salt on the distribution of Induced electromagnetic field; and explores its influence on the crack characteristic vectors, providing the basis of the defect size inversion underwater detecting for future.(2) Design of the underwater inspection probeBased on underwater inspection theory model, establishing the different parameters of the simulation model, analyzing the influences of the different inducing frequency on the crack characteristic vectors, eventually, 5 kHz frequency was determined to be the inducing frequency of the underwater ACFM system. Adopting the combination of simulation and data processing methods, this paper analyzes the variation tendency of induction electromagnetic field- B and the crack characteristic vectors-distortion of BX、BZ under the different 3-D size of inducing core, combining the basis with reality, it also optimizes the size of inducing core, and the best dimension of the inducing core was determined. Based on the result and conventional probe, a new underwater inspection probe was designed. Considering the influence of the umbilical cord transmission on detection signal, the probe increases the ability of signal processing to ensure the accuracy of the detection signal. So, the probe has the better ability of the signal processing and detection to adapt the underwater detection.(3) Experimental prototype for underwater inspection developmentThe overall scheme of the underwater inspection system was designed, and each hardware and software was optimization designed.Eventually, experimental prototype with the robe of underwater inspection and identification algorithms at the core was developed.(4) Experimental test based on experimental prototypeThe detection of experimental prototype for the ability of lift-off and defect size inversion was experimented. The results show that the experimental prototype of the underwater detection probe- signal processing systems – software can fast, accurately detect the crack of underwater metal structures, and be able to lift-off and defect size inversion.