| As a new type of transportation mode,high-speed EMU brings a lot of convenience to people's travel.With the design requirements of high-speed and heavy-duty in China,the load-carrying components of high-speed EMUs are successively connected by welding.With the design requirements of high-speed and heavy-duty in China,the load-carrying components of high-speed EMUs are successively connected by welding.Aluminum alloy welded components are subject to defects due to many factors,such as welding process,stress concentration,welding residual stress,welding materials,etc.It will directly pose a threat to the safe use of components,and carry out research on the nondestructive testing and evaluation technology of key load-carrying components of high-speed EMUs,which can effectively guarantee the normal operation of high-speed EMUs and improve the reliability and safety of high-speed EMUs.It has extremely important engineering application significance.This paper takes the key load-carrying components of high-speed EMUs as research objects,carries out simulation and experimental research on weld eddy current testing,and verifies existing vehicles.The eddy current finite element model of welding probe for aluminum alloy plate and welded member is established.The simulation results show that: When the size of the inner wall of the excitation coil is 8 × 4mm(length × width)and the coil is placed at an angle of 45 °,the amplitude of the detection voltage is the largest.The thickness of the excitation coil decreases by about 7% for each 0.05 mm increase in the thickness of the excitation coil.The height of the excitation coil is in the range of0.5mm to 1.5mm.The height of the excitation coil is proportional to the amplitude of the detection voltage.The excitation frequency is in the range of 100 k to 1000 k Hz.The excitation frequency is inversely proportional to the amplitude of the detection voltage.The crack length determines the position of the voltage amplitude when it rises and falls and the length of the distance that remains stable at the peak.The crack depth determines the highest value of the voltage amplitude,and the voltage amplitude always peaks at the center of the defect.When the crack depth is 0.5,1,and1.5 mm,the voltage amplitude changes due to the uneven conductivity of the material are 28.9%,26.0%,and 22.3% when the conductivity is uniform.Taking the aluminum alloy T-shaped load-carrying component as the research object,the welding seam eddy current testing probe was developed,the optimal detection frequency was determined,and the defect detection test research was carried out.The effects of different lift-off heights on the amplitude and phase of the detection signal were tested.The linear relationship between the lift-off signal phase deflection angle and the lift-off height is: y=18.3x-1.3,and the linear relationship between the defect signal amplitude and the lift-off height is: y=-62.5x +144.8.When the lift-off height is 0.6mm and 1.2mm,the defect amplitude decreases by 27.6% and51.7%,respectively.The phase difference between the defect signal and the lift-off signal changes by only 5 °,which is 12.2% when compared with the original phase difference.Taking ferromagnetic load-carrying components as the research object,artificial comparison blocks of “V” slot with simulated undercut defects of 3×0.2×0.2mm and3×0.2×0.5mm were produced,and the detection parameters were developed.Optimized experimental research,developed a welding seam eddy current testing probe dedicated to ferromagnetic materials,carried out optimization research on defect detection test technology,and effectively found defects in comparative test blocks. |
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