| Railway transportation is one of the most important components in China’s transportation field,which has played a huge role in promoting the development of China’s national economy.In recent years,the mileage of railways operations in China has been increasing,and the speed of train operation has been greatly increased.At the same time,the safety of train operation has also attracted much attention.In order to ensure the safe operation of trains and minimize or avoid the occurrence of railway accidents,the relevant railway departments have put forward higher standards and stricter requirements for the maintenance of railways and trains.As a core component that carries the weight of the train and supports the operation of the train,the hollow shaft has problems in its production quality or damage during service,which will bring significant hidden dangers to the train’s operation safety.The current research on hollow shaft defect detection technology is diverse,most of which have shortcomings or deficiencies such as complicated operation,low efficiency,and unintuitive detection results.In this paper,Electromagnetic Tomography(EMT)is used to study the detection of hollow shaft defects.This technology is based on the principle of electromagnetic induction and has the advantages of non-contact,nonintervention,low cost and high efficiency.It can also achieve the visual inspection of hollow shaft defects.The main contents of this article are as follows:(1)The structure characteristics and defect types of the hollow shaft are introduced in detail.A variety of hollow shaft detection methods are analyzed and compared.A hollow shaft defect detection method based on electromagnetic tomography technology is proposed,and the basic principles and application value of EMT technology are analyzed.(2)Based on the structural characteristics of the hollow shaft of high-speed trains and the principle of EMT technology,a hollow shaft model and a new EMT sensor array for hollow shaft defect detection are designed.The structure of the sensor is designed according to the hollow shaft model,and the coil size is determined by analyzing the effect of the coil size on the excitation magnetic field.(3)Based on the designed hollow shaft model and sensor array,a hollow shaft defect detection simulation system was established in the electromagnetic simulation software,and the system was used to perform simulation calculations.The effect of excitation signal related parameters on the internal magnetic field of the hollow shaft model is studied,and the sensitivity of the hollow shaft detection is also analyzed.(4)The principles of three image reconstruction algorithms,LBP,Tikhonov and Landweber,are studied.The three algorithms are used to reconstruct the simulation data of the hollow shaft defect,and good image reconstruction results are obtained.In addition,the image reconstruction quality evaluation standard was used to analyze and compare each image reconstruction algorithm.The results show that the Landweber algorithm has the best detection effect.(5)Based on simulation analysis,a hollow shaft defect detection EMT experimental system was built,which improved the system integration to a certain extent,enhanced anti-interference ability,and completed the collection of experimental data by controlling the experimental system.The reconstructed images calculated from the experimental data combined with the three image reconstruction algorithms are basically consistent with the simulation results,which further verifies the effectiveness of the EMT technology in hollow shaft defect detection. |
