Science Direct Science  Direct Science   Direct Science    Direct

Science     Direct

Numerical simulation on magnetic flux leakage evaluation at high speed
 Homepage   page 1    page 2     page 3      page 4     page 5      page 6     page 7     page 8     page 9

Fig. 8. Proposed high-speed MFL inspection system with three sensor arrays.

5. Conclusion and further work
In this paper, based on numerical simulations carried out in ANSOFT Maxwell EM, eddy currents in steel specimen due to moving probe and their effect on MFL signals from a highspeed MFL inspection system are investigated. According to the numerical simulations on high-speed MFL inspection systems, it is concluded that:
† Despite that DC excitation current is also employed in highspeed MFL inspection systems, eddy currents are generated because of the probe that travels at high speed. The influence of eddy currents in specimen on MFL signal involves not only the shape but also the magnitude of the signal measured. With the probe speed rising, the signal magnitude drops, which results in low signal-to-noise ratio in practical inspection system. As a result, high-sensitivity sensor/sensor array is in demand. Moreover, in high-speed MFL inspection systems, it is necessary to apply the noise suppression techniques to cripple systematic noise and extraneous noise. Compared to static MFL inspection system, more sophisticated techniques, e.g. adaptive filter and algorithms, wavelet analysis [24] for signal processing might be employed in a high-speed MFL inspection systems.
† Since the inspection system runs at high velocity, the signal acquisition time should be shortened. Therefore, the instrumentation of signal acquisition should have high sampling frequency and comply with Nyquist law, and sensor/sensor array in high-speed MFL inspection systems are required to have high bandwidth in order to ensure fast response to an instantaneous magnetic field change.
† The features of MFL signals from high-speed MFL inspection systems used for defect characterization will be determined by the electromagnetic simulations for inverse models. The inverse models will rely on the probe moving speed. Therefore, the measurement and characterisation will integrate the speed of the probe for the defect identification and analysis.

 

                                                                                                        Get ready for KPSS exams