Design And Implementation Of U-shaped Electromagnetic Fusion Sensor For Detection Of Defects In Ferromagnetic

High-speed rail-the business card of China.Ferromagnetic materials are widely used in high-speed rail tracks,due to the harsh natural environment and workability collision,the track and hooks and other equipment will inevitably produce wear or cracks,regular flaw detection to ensure the safe operation of high-speed rail,has a very important strategic significance.At present,the use of leakage,magnetic particle and eddy current detection methods for pipe flaw detection more.Due to the high magnetic permeability of ferromagnetic materials lead to shallow defect detection depth,the surface induction current distribution is not uniform affect the detection accuracy.In addition,a single electromagnetic detection method can only obtain a physical field signal,resulting in easy detection of leakage,false detection and low efficiency problems.To address these issues,this thesis investigates the U-shaped electromagnetic fusion sensor for ferromagnetic component defect detection from several aspects,including theoretical analysis,simulation study and experimental verification.First,the detection mechanism of the leakage and eddy current effects is analyzed theoretically to lay the theoretical foundation for electromagnetic fusion detection.Based on the magnetic dipole and transformer models,combined with the magnetic field boundary conditions and the law of mutual inductance,the relationship between the leakage and eddy current signals and the defect size are analyzed and summarized,and the mechanism of electromagnetic fusion is elaborated.The distribution of the magnetic field in the spatial physical field of the specimen is studied around the pulsed eddy current convergence depth and the rectangular coil excitation magnetic field,which provides a theoretical basis for the design of the geometry of the U-type electromagnetic fusion sensor.Second,finite element simulation study of U-shaped electromagnetic fusion sensor.With the goal of achieving the maximum sensitivity and resolution of U-type probe defect detection,the U-type probe size（excitation coil size:45 mm long,45 mm wide,4.6 mm thick,30 mm high,and silicon steel sheet core size:15 mm long,30 mm high）and the array sensor center distance（5.4 mm）are studied and obtained.The values of the three directional components of the conduction current XYZ and the distribution of the eddy current detection current Z-direction in the leakage magnetic detection specimen are explored to obtain the array layout of the array sensor in the U-shaped probe.The relationship between defect width and depth and electromagnetic fusion signal is investigated,and a linear negative correlation between defect values and magnetic field eigenvalues are obtained.The influence of the material properties of the ferromagnetic components on the detection signal was analyzed,and the magnetic permeability was found to have a greater influence on the fusion signal.Finally,the U-shaped electromagnetic fusion sensor defect detection experiment and analysis.A robotic arm clamping sensor device and data processing platform were built to achieve high precision scanning and signal storage of defects 0.06 mm.A pre-processing platform for the signal was integrated using multi-cycle zero starting point rising edge waveform and eigenvalue extraction techniques.The excitation signal parameters were optimized to effectively improve the defect detection depth（12 mm）.The consistency of the array amplitude with the simulation results is verified,and the stability of the whole system and sensor is tested.The relationship between defect size and signal eigenvalues was analyzed in the time domain,frequency domain,and power spectrum,and the amplitude eigenvalues of the fused signals were linearly and negatively correlated with both defect depth and width.The sensor defect detection performance was evaluated using multiple quantitative defect detection data,and the results showed that the BX side of the leakage detection was more sensitive to width defects(K_GMR4=40.762),the BZ direction was more sensitive to depth defects(K_HALL8=0.431),and the eddy current detection was more sensitive to width defects(K_HALL5=70.943).