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Butterfly diagram is an essential method for determine the presence of defects in alternating current field measurement. To study the mapping relationship between conventional crack butterfly diagrams and crack profiles, COMSOL Multiphysics was first used to numerically simulate cracks of different sizes, and reconstruction equations for length and depth feature quantities were established. Secondly, through comparative analysis, the corresponding relationship between the characteristic signal and the butterfly diagram was explored, and a mapping equation between the two was further established by combining image processing methods and conventional linear fitting methods. Finally, detection tests were conducted on groove shaped cracks of different sizes of Q235 steel. The experimental results show that the crack profile errors based on length and depth are 5. 46% and 6. 02%, respectively. The study achieved the reuse of butterfly diagrams, providing important references for defect risk assessment methods. [ABSTRACT FROM AUTHOR]

Alternating current field measurement (ACFM) technology is widely used in defect detection of metal structures in manufacturing and other industrial fields. The angle deflection and crack location problems of single sensor in the process of unpredictable defect detection were studied. Firstly, through the COMSOL Multiphysics simulation results, it can be seen that the X and Y direction components of the field strength have a law of signal complementarity during the angular deflection process, and then the data augmented grey neural network model (DA-GNNM) prediction was realized by establishing a scale factor. At the same time, simulation prediction and regression prediction showed that DA-GNNM model has better prediction effect. In addition, the deflection crack was reconstructed by multigradient deflection simulation. Secondly, the DA-GNNM prediction model was verified to be reasonable by building an experimental platform and signal feature extraction, with an average prediction error of 2. 56% . Finally, the deflection of the reconstructed image of the crack in the non-parallel detection process is further improved through the prediction angle. [ABSTRACT FROM AUTHOR]

Aiming at the ship risk focusing on calculating the occurrence probability, its control and intervention effect is difficult to assess and reasoning difficulties, the do operator-based ship risk intervention and reasoning method was proposed. Firstly, the causal network was established using a priori knowledge. Secondly, the Leaky Noisy-Or hypothesis and hidden variable nodes were introduced to establish a structural twin-based causal network model. Finally, counterfactual inference was performed based on do operator interventions, and the effectiveness of interventions was determined using sufficient and necessary causes that cause failures. The case analysis shows that the proposed method can effectively measure the effectiveness of risk control measures and determine the impact of the intervention's behavior on the hazard source ranking, with certain stability and superiority. [ABSTRACT FROM AUTHOR]

The traditional underwater alternating current filed measurement（ACFM） does not take into account the influence of shell material on the detection signal and each parameter of the equipment in the simulation design. In order to solve this problem, an ACFM simulation model was established, the size and shape of the magnetic core were optimized and the probe size was reduced. The effects of the conductivity and permeability of the nondestructive testing（NDT） probe housing material on the detection signal were simulated and analyzed. The most suitable shell material for deep water NDT is 304 stainless steel and the best current frequency, and the parameters of the NDT probe were optimized. The results show that when the conductivity of the shell material reaches 107 S/m, the characteristic signal detects by the magnetic sensor reverses and the frequency of the current more than 7 kHz leads to serious distortion of the detection signal. The permeability of shell material attenuates seriously to the amplitude of Magnetic induction intensity Bz in z direction and magnetic induction intensity Bx in x direction. The research results are beneficial to the development and design of NDT. Reset [ABSTRACT FROM AUTHOR]