Numerical Simulation and Experiment on Magnetic Flux Leakage Inspection of Cracks in Steels
The magnetic flux leakage inspection method is widely use d in the detection of pipelines, storage tanks and other steel materials. Especially in c orrosion pits detection, it has become a matured technology. As cracks may exist in the steels which may lead to big hazards, its detection becomes very important. Meanwhile, the cracks evaluation by MFL inspection can be determined by many parameters, it has much difficulty t o implement due to its weaker signals compared with pits. In this research, the finit e element model for cracks’ MFL is established and corresponding method are carried out. Furthe rmore, parameters such as depth, width, angle of cracks and scanning direction are analyzed. Also, the experiments are done which show great reliability comparing with numerical s imulations. The results show that the cracks can not be detected when the scanning direction para llels with it. So the cross-scanning method is recommended for MFL inspection on cracks.
Modelling and experimental investigation of ferromagnetic material for angular defect detection
Ferromagnetic materials were widely used in various applications, on which crack is one of the most common defects caused by stress and environment factors, especially angular defects. In this paper, angular defects were modelled in the finite element simulation software COMSOL. Based on pulsed magnetic flux leakage testing, the distribution of magnetic flux leakage signal of defects were simulated. Compared with rectangular defects, some features were extracted to recognize the oblique crack. Then the experiments validated the correctness of simulation.
Finite element calculations on the effects of permeability variation on magnetic flux leakage signals
Abstract Magnetic flux leakage anomaly signals from pipeline inspection tools can be obtained from hard spots or other regions of anomalous permeability. The signals obtained from corrosion pits are dependent on pressure and this is attributed to stress-induced permeability changes. The results of two-dimensional finite element calculations of the effects of permeability measurements on such signals suggest that permeability changes by as much as a factor of two may be required to produce these effects.