Abstract
A portable detecting device was developed for the magnetic detection of cracks existing in railway tracks. The device is equipped with permanent magnets, which produce a uniform magnetic field inside and near the surface of the magnetically soft steel of a railway track, and GMR sensors. Due to the high sensitivity of the GMR sensors (in variations of the tangential component of the magnetic field which is parallel to the direction of motion) the device is capable of producing voltage peaks or dips, for quite small deviations of the near-surface magnetic field from the uniform field of the magnets. Finite element numerical simulations showed that the tangential component of the magnetic field exhibits sharp peaks above cracks, due to the stray magnetic field produced by them. Laboratory measurements, made on pieces of railway tracks with cracks, reproduced qualitatively the results of simulations. They showed that the sensors (moving near cracks) produce sharp voltage peaks with magnitude that depends on the size of the cracks. Based on these measurements, we conclude that the developed device can successfully detect cracks and defects in railway tracks and give information on their size. The method can be generalised for detection of cracks in all magnetic steels.
Highlights
Railways are currently one of the prime modes of transportation and, as they are closely associated with intensive passenger and cargo conveyance, they own high risk in terms of potential loss of human life and destruction of assets [1*,2]
Despite the fact that improved safety standards are constantly being introduced, the forces acting on a rail track – due to wheel-rail contact stresses (WRCS) – are quite large and frequently repeated and – combined with the high speeds of modern trains – can result in the quick evolution of small defects and cracks into partial or complete rail track failure, which can cause catastrophic accidents such as train derailments [1,2]
GMR sensors are being used in hard disk drive (HDD) industry as the basic part of the reading heads of modern HDD, where the rotation frequency of the plates is of the order of 104
Summary
Railways are currently one of the prime modes of transportation and, as they are closely associated with intensive passenger and cargo conveyance, they own high risk in terms of potential loss of human life and destruction of assets [1*,2]. A different approach, for the detection of surface cracks in magnetized rail tracks (and generally in magnetic steels), is the use of magnetic field sensors. GMR sensors are being used in hard disk drive (HDD) industry as the basic part of the reading heads of modern HDD, where the rotation frequency of the plates is of the order of 104. Preliminary laboratory measurements, performed on rail tracks with known cracks, showed a correlation between the geometric characteristics of the cracks and the characteristics of the recorded signals
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