Rail Diagnostics Based on Ultrasonic Guided Waves: An Overview

Rail tracks undergo massive stresses that can affect their structural integrity and produce rail breakage. The last phenomenon represents a serious concern for railway management authorities, since it may cause derailments and, consequently, losses of rolling stock material and lives. Therefore, the activities of track maintenance and inspection are of paramount importance. In recent years, the use of various technologies for monitoring rails and the detection of their defects has been investigated; however, despite the important progresses in this field, substantial research efforts are still required to achieve higher scanning speeds and improve the reliability of diagnostic procedures. It is expected that, in the near future, an important role in track maintenance and inspection will be played by the ultrasonic guided wave technology. In this manuscript, its use in rail track monitoring is investigated in detail; moreover, both of the main strategies investigated in the technical literature are taken into consideration. The first strategy consists of the installation of the monitoring instrumentation on board a moving test vehicle that scans the track below while running. The second strategy, instead, is based on distributing the instrumentation throughout the entire rail network, so that continuous monitoring in quasi-real-time can be obtained. In our analysis of the proposed solutions, the prototypes and the employed methods are described

Railway Operation Risk Management at Belarusian Railway Enterprises

Railway transport in the Republic of Belarus is an important part of the infrastructure system that determines the development of the country's economy. The development of the management of track facilities is closely related to the increase in the operational reliability of the main elements of the superstructure of the track, and in particular, as the most expensive, railway rails. Their replacement and repair during operation causes delays in the movement of trains, creates significant organizational difficulties. Therefore, to improve reliability and ensure traffic safety, it is necessary to process the results of rail diagnostics with an assessment of the risks of their operation.Железнодорожный транспорт в Республике Беларусь является важной частью системы инфраструктуры, определяющей развитие экономики страны. Развитие управлением предприятий путевого хозяйства тесно связан с повышением эксплуатационной надежности основных элементов верхнего строения пути, и в частности, как самых дорогостоящих, железнодорожных рельсов. Их замена и ремонт при эксплуатации, вызывает задержки в движении поездов, создает значительные организационные трудности. Поэтому, для повышения надежности и обеспечения безопасности движения необходимы средства обработки результатов диагностики рельсов с оценкой рисков их эксплуатации

Integration of an Ultrasonic Sensor within a Robotic End Effector for Application within Railway Track Flaw Detection

The rail industry is constantly facing challenges related to safety with regard to the detection of surface cracks and internal defects within rail tracks. Significant focus has been placed on developing sensor technologies that would facilitate the detection of flaws that compromise rail safety. In parallel, robot automation has demonstrated significant advancements in the integration of sensor technologies within end effectors. This study investigates the novel integration of an ultrasonic sensor within a robotic platform specifically for the application of detecting surface cracks and internal defects within rail tracks. The performance of the robotic sensor system was assessed on a rail track specimen containing sacrificial surface cracks and internal defects and then compared against a manual detection system. The investigation concludes that the robotic sensor system successfully identified internal defects in the web region of the rail track when utilising a 60° and 70° wedged probe, with a frequency range between 4 MHz and 5 MHz. However, the surface crack investigation proved that the transducer was insensitive to the detection of cracks, possibly due to the inadequate angle of the wedged probe. The overall outcome of the study highlights the potential that robotic sensor systems have in the detection of internal defects and characterises the limitations of surface crack identification to assist in enhancing rail safety

Novel Approaches for Structural Health Monitoring

The thirty-plus years of progress in the field of structural health monitoring (SHM) have left a paramount impact on our everyday lives. Be it for the monitoring of fixed- and rotary-wing aircrafts, for the preservation of the cultural and architectural heritage, or for the predictive maintenance of long-span bridges or wind farms, SHM has shaped the framework of many engineering fields. Given the current state of quantitative and principled methodologies, it is nowadays possible to rapidly and consistently evaluate the structural safety of industrial machines, modern concrete buildings, historical masonry complexes, etc., to test their capability and to serve their intended purpose. However, old unsolved problematics as well as new challenges exist. Furthermore, unprecedented conditions, such as stricter safety requirements and ageing civil infrastructure, pose new challenges for confrontation. Therefore, this Special Issue gathers the main contributions of academics and practitioners in civil, aerospace, and mechanical engineering to provide a common ground for structural health monitoring in dealing with old and new aspects of this ever-growing research field

Скоростные погрешности инерциального метода выявления коротких неровностей рельсов

Introduction. Efficient operation of a system for measuring rail surface short-wavelength irregularities depends on evaluation of the signal length with respect to travelled distances, i.e., the standard maximum defect length and the distance between the wheels of a car bogie. When recording an accelerometer signal with respect to time due to the effect of velocity, the signal length corresponding to these spatially constant distances will vary.Aim. Development of an algorithm for determining rail running surface defects using the data obtained by accelerometers mounted on the axle boxes of a car bogie under their not equidistant spatial record.Materials and methods. The data obtained when passing a laboratory car equipped with a system for measuring short-wavelength irregularities was used. The search and determination of irregularity parameters was carried out by an inertial method. The methods of normalization and correlation analysis were used.Results. An algorithm for determining rail running surface defects based on an inertial method was developed, considering the spatial non-equidistance of the signal. The implemented correlation analysis allows compensation of high-velocity errors when determining the defects. In the considered example, the relative error equaled 0.4 %. Compensation of velocity errors reduces the probability of type I errors in defect determination.Conclusion. The developed algorithm considers velocity errors associated with the application of inertial methods for detecting short-wavelength irregularities. The implementation of correlation analysis reduces the probability of type I errors when determining rail running surface defects.Введение. Для работы системы измерения и расчета коротких и импульсных неровностей на поверхности катания рельсовых нитей необходимо определять длину сигнала, соответствующую прохождению расстояний (нормативная максимальная длина дефекта и расстояние между колесными парами тележки вагона). При записи сигнала от времени из-за влияния скорости длина сигнала, соответствующая этим неизменным в пространственном отношении расстояниям, будет разниться.Цель работы. Разработка алгоритма поиска дефектов поверхности катания рельса по показаниям акселерометров, установленных на буксовых узлах тележки вагона, при их неэквидистантной пространственной записи.Материалы и методы. Рассматриваются данные, полученные в результате проезда вагона-лаборатории с установленной на нем системой измерения и расчета коротких и импульсных неровностей на поверхности катания рельсовых нитей. Поиск и определение параметров неровности поверхности катания рельса осуществляются инерциальным методом. Для разработки алгоритма использовались методы нормировки, корреляционный анализ.Результаты. Разработан алгоритм поиска дефектов поверхности катания рельсовых нитей инерциальным методом с учетом пространственной неэквидистантности сигнала. Внедренный в алгоритм корреляционный анализ позволил скомпенсировать скоростную погрешность определения дефекта. В рассмотренном в статье примере относительная погрешность равна 0.4 %. Компенсация скоростной погрешности в разы снижает вероятность возникновения ошибки первого рода в определении дефекта.Заключение. Разработанный алгоритм позволяет учесть скоростные погрешности при инерциальном методе выявления коротких неровностей. Использование корреляционного анализа снижает вероятность ошибки первого рода при поиске дефектов поверхности катания рельса

Current state of the research on optoacoustic fiber-optic ultrasonic transducers based on thermoelastic effect and fiber-optic interferometric receivers

The work is devoted to an overview of the current state of optoacoustic fiber-optic ultrasonic transducers based on thermoelastic effect and fiber-optic interference receivers, its scope, technologies and materials used, the advantages and disadvantages of different methods and the prospects for the development of the industry.The work has been supported by the Russian Science Foundation 21-12-00304

Various modulated hybrid pulse compression for advanced ultrasound technology and its non-destructive testing application

This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University LondonUltrasound is a sound wave with a frequency greater than 20 kHz. It obeys the propagation laws of reflection, refraction, diffraction, and scattering. Because of its excellent physical properties, ultrasound has been used in a variety of fields, including industry and medicine. There are many techniques that use ultrasound as detection methods in the field of non-destructive testing (NDT) and medical treatment. In a typical ultrasound system, a sine wave or pulse signal with a fit window is considered as the transmitted signal. This results in low accuracy in some special situations, such as testing high attenuation material. The signal-to-noise ratio (SNR) is an important parameter for evaluating the performance of an echo signal or imaging. However, under high attenuation materials or noisy conditions, SNR will significantly decrease. Under these conditions, valid information in the received signal will be obscured by noise. This situation can cause errors in the detection system. In an ultrasound system, increasing the SNR of the echo signal can reduce detection errors and improve accuracy. First, in ultrasound systems, a noise reduction method based on pulse compression has been investigated and applied. Convolution and modulation were used in the proposed method to generate new hybrid emission signals. The hybrid codes can only be distinguished by a special matched filter that is related to the emission signals. The echo signals processed by a special matched filter have a high main lobe and a very low side lobe, implying that the side lobe level and SNR will increase. When compared to traditional denoising methods, the proposed method can significantly improve SNR while only requiring a change in the transmission code without requiring any hardware changes. Second, in a low voltage ultrasonic testing (UT) system, a hybrid phase modulated code excitation method based on the Barker and Golay code pairs was proposed and implemented. In a UT system, the lower the pulsing voltage, the lower the SNR of the signal. Attempting to reduce the pulsing voltage will result in noisy and unusable results. The proposed hybrid method can increase main lobe power in low average power transmitted and received signals. The proposed method has been theoretically examined and then tested in simulation studies. The experimental results showed that the main lobe level of the code produced by convolution of Barker code and Golay code pairs is around 30 dB higher than the simple pulse, and the main lobe of the combined code is around 15 dB higher than the traditional Barker code, with the sidelobe being the same as the Baker code that constitutes this combined code. As a result, the combined code’s peak sidelobe level (PSL) is approximately 5 dB lower than the traditional Barker code. Because of this, UT devices can be used in real-world applications, even in low-voltage situations. Third, the torsional wave mode T(0,1) hybrid phase modulated code excitation method has been proposed and applied in a long range guided wave testing (GWT) system. The proposed hybrid method combines the Barker and Golay code pair and is modulated by a fitted sine wave. This method combines the benefits of these two coding methods and increases code length flexibility. The SNR and PSL of the processed signal are used to assess the method’s performance. The proposed method has been tested in GWT using both finite element method (FEM) simulation and real-world testing. The results of pipeline laboratory testing revealed that the best increasing SNR of BCG is around 33.5 dB when compared to a simple pulse at 40 kHz, and the peak sidelobe level is around -24 dB. The proposed method, as well as other traditional methods, were used for pipeline defect detection testing. The results of the tests showed that the hybrid coded excitation method can detect notches that are difficult to detect with other methods and effectively improve the SNR. The applied method’s increasing SNR is around 6 dB, which agrees with the simulation and laboratory testing results. In UGW testing, the proposed coded excitation method was highly regarded. Finally, the non-linear frequency modulated (NLFM) hybrid pulse compression method has been proposed and implemented in an ultrasound imaging (UI) system. The proposed code combines the Barker and Golay codes and is modulated using a non-linear frequency method based on the Zak transform. Theoretical research on signal generation and decoding has been presented, as well as cyst phantom simulation. The simulation analysis shows that the novel code method can improve the contrast ratio by 15.96 dB and the SNR by 36.64 dB when compared to a simple pulse signal. Overall, this study demonstrated that the proposed novel method can be effectively used in ultrasound detection methods to improve performance

Rail Diagnostics Based on Ultrasonic Guided Waves: An Overview

Rail tracks undergo massive stresses that can affect their structural integrity and produce rail breakage. The last phenomenon represents a serious concern for railway management authorities, since it may cause derailments and, consequently, losses of rolling stock material and lives. Therefore, the activities of track maintenance and inspection are of paramount importance. In recent years, the use of various technologies for monitoring rails and the detection of their defects has been investigated; however, despite the important progresses in this field, substantial research efforts are still required to achieve higher scanning speeds and improve the reliability of diagnostic procedures. It is expected that, in the near future, an important role in track maintenance and inspection will be played by the ultrasonic guided wave technology. In this manuscript, its use in rail track monitoring is investigated in detail; moreover, both of the main strategies investigated in the technical literature are taken into consideration. The first strategy consists of the installation of the monitoring instrumentation on board a moving test vehicle that scans the track below while running. The second strategy, instead, is based on distributing the instrumentation throughout the entire rail network, so that continuous monitoring in quasi-real-time can be obtained. In our analysis of the proposed solutions, the prototypes and the employed methods are described