Track Damage Research Articles

Railway vibration – fast physics-based models for the prediction of ground vibration and the identification of track damage

The following applications of machine learning/AI for railway vibration will be discussed: 1. The prediction of the wave propagation from a railway line (completely physics based for surface lines, for tunnel lines (partially) physics-based ML for surface lines). 2. The track behaviour for the emission of train-induced ground vibration (physics based for homogeneous soil, ML for layered soil). 3. Track damage detection and quantification from FRF and moving load response. 4. Bridge damage detection and localisation from modal analysis and moving load response. 5. The use of axle-box acceleration for the identification of track/sub-soil condition and bridge resonances. Prediction calculation of railway vibration usually needs time-consuming finite element, boundary element and wavenumber domain calculations. For a user-friendly prediction software, fast calculations are needed. Several time-consuming detailed calculations should be used to develop simpler and fast models. The dynamic stiffness of isolated or un-isolated railway tracks from detailed calculations with a continuous soil is approximated with the simpler Winkler soil. The vehicle-track resonance (P2 resonance) rules the effect of the mitigation measures, and it can also be used for the on-board monitoring of the track and sub-soil condition. For the identification of track damage such as gaps between sleepers, track slabs and layers, detailed models with a continuous soil have been updated to get the best fit to the measured frequency response functions from hammer tests and the deformation pattern from the moving load response. Whereas the track damage can be locally identified, this is more difficult for bridges where the modal analysis gives mainly global information. The influence lines of the inclination for statically passing vehicles (locomotive, truck, compaction ) have been used to localise bridge damage (stiffness variations). The on-board monitoring of rail bridges needs special conditions (regular trains with special speeds) to excite and measure the bridge resonance.

The Soleymani and Collins Obstetric morbidity score (SaCOMS): A quantitative tool for measuring maternal morbidity from complex obstetric surgery such as placenta accreta spectrum (PAS)

It is currently very difficult to compare different management strategies for complex obstetric surgery, such as hysterectomy for severe Placenta Accreta Spectrum (PAS), as there is no widely accepted consensus for the classification of maternal surgical morbidity. Many studies focus on the amount of blood products transfused or admission to intensive care units (ICU). However, these are dependent on local policies and available resources. It also gives an incomplete representation of the entire ‘patient journey’ after they leave the operating room. Subsequent repeat procedures for lower urinary track damage is arguably worse from the woman’s perspective than a short stay on an intensive care unit (ICU) for observation.We suggest a version of the Clavien-Dindo morbidity classification specific to obstetrics. Then employ it to build a quantitative morbidity score which aims to reflect the whole ‘patient experience’ including the post-operative pathway. We then demonstrate the utility of this system in a cohort of women with Placenta Accreta Spectrum (PAS).The Clavien-Dindo classification was modified to reflect obstetric procedures and a quantitative morbidity measure, the Soleymani and Collins Obstetric Morbidity Score (SaCOMS), was developed based on this. Both were then validated using a survey-based consultation of a panel of experts in PAS and retrospectively applied to a cohort of 54 women who underwent caesarean hysterectomy for PAS.Clinicians with expertise in PAS believe that the Modified Obstetric Clavien-Dindo classification system and the novel SaCOMS tool can improve assessment of maternal morbidity, and better reflect the ‘patient experience’. Application of the classification system to a single-centre PAS cohort suggested that surgery by gynecologic-oncology surgeons may be associated with decreased incidence and cumulative morbidity outcomes for women with PAS, especially those with the most severe presentation.This study presents a clinically useful obstetric-specific classification system for surgical morbidity. SaCOMS also provides a quantitative reflection of the full patient- journey experienced as a result of surgical complications enabling a more patient-centered representation of morbidity.

Mechanical performance of CRTS II slab tracks in reinforced-unreinforced transition zone in extreme heat events

Anchors have been widely utilized to reinforce the CRTS II slab tracks. The mechanical performance of the tracks in the reinforced-unreinforced transition zone exposed to extreme heat waves can be very complex due to the difference in mechanical properties between the two kinds of track segments. This paper investigates the damage behavior of the tracks in the reinforced-unreinforced transition zone in extreme heat events. A finite element model of the CRTS II slab track in the transition zone has been established and validated, in which the nonlinear mechanical properties of track materials and interfaces are considered by applying the Concrete Damaged Plasticity model and the Cohesive Zone Model respectively. The nonlinear temperature field in the track structure in extreme heat events is applied to the model. Structural damage of the track, including slab-end arching and interfacial failure, in the transition zone under extreme heat is thoroughly investigated. In particular, the effects of joint use of post-installed reinforcement anchors and other track maintenance measures like interface adhesives and concrete joint restoration are studied. The following conclusions are drawn: (1) The more reinforced track-slabs in the transition zone, the milder the track diseases including slab-end arching and interfacial gapping. (2) Joint use of anchor installation and other maintenance measures such as interface adhesives and concrete joint restoration shows a better effect on mitigating track damage than using post-installed reinforcement anchors solely. (3) Concrete joint restoration overweighs interface adhesives in terms of reducing slab-end arching and interfacial damage when they are jointly used with post-installed reinforcement anchors. (4) In the transition zone, track damage surges when the air temperature increases from 42 ℃ to 47 ℃, which is the temperature range for an extreme heat wave. Monitoring of track state in the transition zones is necessary during extreme heat waves. The novel findings are expected to provide some insights into the mechanical performance of slab tracks and help to prevent potential damage to the tracks in the transition zone, which is a common and practical issue in railway engineering.

The parameter identification of metro rail corrugation based on effective signal extraction and inertial reference method

Rail corrugation is a severe track damage and failure problem in metro lines. So, the accurate assessment of rail corrugation is significant for the safety and comfort of vehicles. It is an efficient means to detect rail corrugation through the acceleration signal. However, the acceleration signal contains the mixed signal caused by vehicle component noise and wheel polygonal wear, resulting in poor rail corrugation detection accuracy. Therefore, a new method is presented to extract the effective signal components and accurately identify the rail corrugation. Firstly, the Cubic mapping, modified sine algorithm, and Lévy flight are introduced into the dung beetle optimizer algorithm. A new improved dung beetle optimizer (IDBO) algorithm is presented to optimize the hyperparameters of the VMD algorithm, which can increase the signal decomposition performance of the VMD. Secondly, the fast independent component analysis method separates the independent components (ICs) from the VMD modes and original acceleration signal. Based on the selection criteria of ICs, the dominant signal components related to rail corrugation are determined. The rail corrugation amplitude can be obtained through the inertial reference method. The experimental results demonstrate that the presented method has better rail corrugation recognition accuracy, the root mean square error is smaller than the comparison method, and the corrugation wavelength of the straight track is larger than the curve track.

Fracture behavior investigation of ballastless track of high-speed railway based on DIC technique

To investigate the issues of transverse through cracks and interlayer damage of the CRTS III slab ballastless track under train loading, the digital image correlation (DIC) technique was employed to reveal the damage mechanisms of the reduced-scale concrete of track slab structural concrete (TSSC) and track slab-filled laminated structural concrete (TSLSC). The results indicate that under train loading, the transverse through cracks of TSLSC exhibit a multi-stage, layer-by-layer cracking characteristic, and there is a risk of cracking in ballastless track when the bottom longitudinal strain exceeds 0.0004. The sudden increase in interlayer longitudinal shear strain difference in the third stage under train loading demonstrates that shear stress is the primary cause of interlayer damage in ballastless track. Tensile damage models based on ultimate stress–strain relationship and yield-fracture strain were established, and a non-contact testing method for the constitutive relationship and energy absorption effect of ballastless track was proposed using DIC technology, aiming to provide reference for the analysis and prediction of ballastless track damage under train loading.

Nonlinear autoregression-based non-destructive evaluation approach for railway tracks using an ultrasonic fiber bragg grating array

The safe operation of railway systems relies on rapid and accurate non-destructive damage detection and evaluation techniques to help rule out potential threats brought by rail track damages. In this paper, an innovative fiber Bragg grating (FBG) array-based sensing system is developed for rail defect inspection by integrating the ultrasonic testing technology, and a nonlinear autoregressive neural network with exogenous inputs (NARX) is proposed for rail damage detection based on measured ultrasonic signals. The developed sensing system can realize the high-speed and multiplexed ultrasonic signals demodulation. The NARX is proposed to process the ultrasonic signals obtained by the developed sensing system, and a specified probabilistic damage sensitive feature (DSF) is tailored to indicate rail health status, derived from the probability density function (PDF) of NARX prediction errors. To verify the proposed sensing system and damage identification algorithm, experimental studies considering four rail conditions (i.e., intact, cracked, bump, and welded conditions) are conducted in this study. First, baseline NARX models are priorly trained using ultrasonic signals acquired on an intact rail segment; then, DSFs corresponding to each condition are calculated enabling effective rail damage diagnosis. To optimize the training parameters of NARX models, three different training functions are utilized to select the most appropriate parameters that are sensitive to rail damages. Last, large-scale testing is conducted, further proving the applicability and reliability of the proposed rail damage evaluation approach. Through this study, it is suggested that integrating high-performance sensing technologies with effective data processing tools would maximumly enable efficient and robust non-destructive testing, especially on important infrastructures such as rails.

Indigo carmine dye for detecting urinary track damage during vaginal surgery

ObjectiveUnrecognized ureteral and bladder injury increase morbidity and mortality in gynecologic surgery. The primary objective of this study is to analyze the efficiency of a systematic intra-venous (IV) injection of carmine indigo to detect bladder injury in gynecologic vaginal surgery for benign disease. The secondary objective is to analyze the cost and use of carmine indigo. Study designA retrospective, monocentric study was conducted in a tertiary hospital between January 2018 and October 2021. All patients undergoing a vaginal surgery of hysterectomy for benign disease or anterior prolapse were systematically included. Patients can be systematically included by the automatic coding of surgery. After anesthesia, during the patient's installation, an intravenous injection of 5 mL of intravenous indigo carmine (Carmyne®) diluted in 100 mL of physiological serum was systematically administered by the anesthesia team. Intraoperative cystoscopy was performed only in cases of suspected associated ureteral injury. ResultsWe recorded 443 vaginal hysterectomies for benign disease and 95 vaginal anterior prolapse surgeries. There were 6 (1,4%) bladder injuries during vaginal hysterectomies and 1 (1,1%) bladder injury during vaginal prolapse surgery. All bladder injuries were diagnosed intraoperatively. No ureteral injury was diagnosed in this series of patients. No complication related to IV indigo carmine injection was found. In this tertiary hospital, 1085 ampoules of carmine indigo were ordered during the same period, approximatively 270 per year. The total cost to the gynecology and obstetrics department was 19,600 euros, or about 4,900 euros per year. Half of the carmine indigo was used in vaginal surgery and half in laparotomy, caesarean section and endometriosis surgery for suspected bladder or ureteral injury.

Enhancement of Track Damage Identification by Data Fusion of Vibration-Based Image Representation

Enhancement of Track Damage Identification by Data Fusion of Vibration-Based Image Representation

Application of improved genetic algorithm in the optimal design of seismic parameters of rail vehicle

Abstract This paper first considers the seismic parameter model of rail vehicles with rail constraints and investigates the mechanism of beam-rail interaction under earthquake action. The computational parameters of rails, main girders, and piers are optimized using analytical and finite element methods during earthquake action. Finally, the NSGA-II genetic algorithm is improved and applied to optimize the seismic parameters of rail vehicles, and seismic damage indexes evaluate the damage to rails and vehicles. The results show that by optimizing the seismic parameters of rail vehicles, the track damage is lower than the median value of μ [μ 1 = 1.03404, μ 2= 1.2013] under the same earthquake intensity, and the probability of lateral damage to vehicles is reduced by 0.15. Applying the improved genetic algorithm proposed in this paper can effectively improve the seismic performance of rail vehicles and provide some theoretical support for the design and safety of rail vehicles.

Nonlinear modelling for structural damage assessments of reinforced and coated longitudinally coupled slab tracks

Interface debonding and slab end arching of the anchor-reinforced and coated longitudinally continuous slab tracks have been unprecedentedly investigated in this study. A novel finite element model of the longitudinally continuous slab track has been established by incorporating a tailored cohesive zone model to mimic nonlinear constitutive relationships. The new model has been validated by over 100 field measurement data. This paper is the first to assess the influences of the dual applications of anchors and coatings on the damages of the longitudinally continuous slab tracks, and to identify the effectiveness of different track maintenance methods in mitigating track damages. This study exhibits new findings: (1) In comparison with traditional tracks, the tracks constructed with anchors, coatings, and the combined use of both can reduce the maximum vertical relative displacement between the concrete slab and the mortar layer by 75%, 40%, and 85% respectively. (2) In comparison with 4 anchors, 6 or more anchors in each slab can help to prevent inner interface defects. However, an increase in anchor quantity above 6 anchors does not have a significant impact on the interface damage mitigation. (3) For the anchor-reinforced tracks, the organic coating outweighs the inorganic coating to improve interface damage mitigation.

Temperature field test and prediction using a GA-BP neural network for CRTS II slab tracks

AbstractThe CRTS II slab track, which is connected in a longitudinal direction, is one of the main ballastless tracks in China, with approximately 7365 km of operational track. Temperature loading is a very vital factor leading to slab track damages such as warping and cracking. While existing research on temperature distribution rests on either site tests in special environments or theoretical analysis, the long-term temperature field characteristics are not clear. Therefore, a long-term temperature field test for the CRTS II slab track on bridge-subgrade transition section was conducted to analyze the temperature field. A GA-BP (genetic algorithm optimized back propagation) neural network was trained on the test data to predict the temperature field. The vertical and lateral temperature distributions in four typical days were carried out. We found that the temperature along the track was distributed in a nonlinear manner. This was particularly distinct in the vertical direction for depths of less than 300 mm. The highest and lowest daily temperatures and the daily range of the temperature were analyzed. With the increasing depth, the daily highest temperatures and range of the temperature were smaller, the daily lowest temperatures were higher, and the time corresponding to this peak value appeared later in the day. Both the highest and lowest daily temperature could be predicted using the GA-BP neural network, though the accuracy in predicting the highest temperature was higher than that in predicting the lowest temperature.

Dynamic performance of CRTS III ballastless track structure under the train load and temperature

Due to the thermal deformation of the track structure under natural temperature, it inevitably changes the initial condition of the track, and causes significant influence on the dynamic performance of the track under the moving vehicle. This work aims to reveal the interfacial damage and dynamic behaviors of the track structure subjected to the temperature and a moving vehicle. For this purpose, a thermomechanical coupling analysis method of CRTS III is developed by loading the temperature and train load. Among them, a three-dimensional vehicle-track interaction model is established to obtain the rail-supporting force. Besides, a transient heat transfer model of CRTS III is developed by introducing the complex thermal boundary where the solar radiation and heat convection are taken into account, and thus the temperature field of CRTS III under the natural environment is obtained in a space–time scale. The dynamic behaviors of the track and interfacial damage under different temperatures, interface strength and speeds of vehicle are investigated by the proposed methodology. The results indicate that the temperature significantly influences the acceleration and displacement of the track slab, especially in the frequency range of 25 Hz–75 Hz and the response amplitudes also increase 2–6 times. The temperature is the main factor inducing interface damage instead of the train load, therefore, we should pay more attention to the interface debonding in summer.

Annealing of swift heavy ion tracks in amorphous silicon dioxide

The annealing kinetics of the high energy ion damage in amorphous silicon dioxide (a-SiO2) are still not well understood, despite the material's widespread application in material science, physics, geology, and biology. This study investigates how annealing temperature, duration, and ambient environment affect the recovery of irradiation damage produced along the trajectory of swift heavy ions in a-SiO2. The track-annealing kinetics and the changing ion track morphology were investigated using synchrotron-based small-angle X-ray scattering (SAXS) and etching methods. We found that track annealing proceeds quicker near the sample surface demonstrated by a changing track etch rate as a function of depth. Measurements of ion tracks using SAXS show only small changes in the radial density distribution profile of the ion tracks. Activation energy of the annealing process at different sample depths was determined and the effect of the capping layer during the annealing process was also studied. Combination of oxygen diffusion and stress relaxation may contribute to the observed behaviour of preferential and anisotropic healing of the ion track. The results add to the fundamental understanding of ion track damage recovery and may have direct implications for materials for radioactive waste storage and solid state nanopores.

Running safety assessment of trains considering post-earthquake damage state of bridge–track system

A bridge–track system (BTS) is inevitably damaged during an earthquake; this is reflected in its stiffness deterioration and residual deformation, which affect the post-earthquake running safety of trains. The influence of the post-earthquake damage state of an actual BTS on train running safety remains unclear. Hence, this study mainly discussed the influence of post-earthquake bridge–track damage state and residual deformation on running safety and established a safe speed limit for trains under different seismic intensities. A finite element (FE) model of a simply supported railway BTS was established using the OpenSees software. A nonlinear seismic response analysis was performed under different ground motion intensities (0.1, 0.3, and 0.6 g for frequent, design, and rare earthquakes, respectively), and bridge damage, fastener damage, and residual deformation of the rail after the earthquakes were studied. An OpenSees-TRBF (train-rail-bridge-foundation coupled system dynamic analysis software, TRBF) co-simulation method was developed to analyze the running safety of trains after earthquakes under a damaged state of the BTS based on the TCP/IP communication interaction technology. A safe speed limit for trains considering the post-earthquake damage state and residual deformation was proposed, providing a reference for the post-earthquake capacity of trains. The results of the BTS seismic damage analysis showed that the residual displacement of the bearing was the fundamental reason for the change in the rail line shape, and fastener damage mainly occurred in the range of 2–4 fasteners at the end of the girder under the design and rare earthquakes. The results of the running safety analysis showed that, if damage to the BTS is ignored, the running safety after an earthquake will be misjudged. Based on the continuous overrun time limit index, the running safety indices for ground motion intensities of 0–0.4, 0.4–0.5, and 0.5–0.6 g could meet the speed requirements of 350, 300, and 150 km/h, respectively. This study provides some references and suggestions for the running safety of trains following an earthquake.

Modelling of critical speed of railway tracks on a multi-layered transversely isotropic saturated ground

The responses of railway tracks are significantly amplified when the high-speed train travels around the speed of waves propagating in underlying soils. The dynamic amplification phenomenon corresponding to the issue of the critical speed may compromise the stability and safety of operation and increase track damage. This paper proposes an analytical model to analyze the effect of the transverse isotropy of ground on the critical speed of railway tracks on stratified saturated soils. By using the Biot's theory, the general solutions of the transversely isotropic saturated porous medium are derived by employing the potential decomposition and Fourier transform. The transmission and reflection matrix method is extended to derive the three-dimensional fundamental solution for moving point loads acting on a multi-layered transversely isotropic saturated half-space. The models for railway tracks and wheel-axle loads are subsequently coupled to the ground. The proposed model is validated through a comparison with two existing models. Numerical studies demonstrate that the material anisotropy changes the critical speed and the corresponding dynamic amplification coefficient by up to 20%. The anisotropy in the shear modulus has the most significant influence on the critical speed, followed by Young's modulus and the permeability coefficient. The material anisotropy and soil layering cannot be ignored for the assessment of the critical speed of a track-ground system.

Evaluation of Spring Stiffness of Resilience Pads for Booted Sleeper Track System Using a Pressure Sensor

To date, the spring stiffness of resilience pads was mostly evaluated based on conventional (site measurement and laboratory tests) methods. Most studies in the past analyzed the effects of the deterioration of resilience pads on track damage. To examine the deterioration of resilience pads, evaluations were conducted based on laboratory tests using site measurements and samples were collected from the site, or based on loading tests using special equipment. such as TSS. However, no methodology was proposed to prove the theoretical equations of Zimmermann which compute the reaction force at the rail support point. Hence, this study aimed to prove that the reaction force increased if spring stiffness at the rail support point increased; this was achieved by using a pressure sensor according to the theoretical equations of Zimmermann. Furthermore, we aimed to propose a method to evaluate the spring stiffness of resilience pads to predict the extent of deterioration of the pads based on the increase in the pressure measured by a pressure sensor.

Feature Selection and Damage Identification for Urban Railway Track Using Bayesian Globally Sparse Principal Component Analysis

Urban railway track infrastructures often suffer from damage that affects their service performance due to a variety of factors. In this study, an unsupervised feature selection and damage identification method based on globally sparse probabilistic principal component analysis (PCA) is proposed for urban railway tracks using the monitoring data of train-induced dynamic responses. A Bayesian framework is proposed for generating principal components on a basis of vectors (original variables) with a global sparseness pattern instead of separate patterns in a traditional sparse PCA. In this framework, a variational expectation-maximization algorithm is employed to obtain the tractable calculation of the marginal likelihood function for learning all uncertain parameters of the Bayesian model. The obtained principal components are linear combinations of the very same set of important variables, making our method better interpretable than the traditional sparse PCA. We can clearly understand which original variables are most relevant for describing the data. The track damage is identified simply by discriminating the corresponding measured dynamic responses using the binary elements of the latent vector inferred from the Bayesian globally sparse PCA algorithm. The usefulness is demonstrated by successfully identifying the track bed plate crack damage through the actual train-induced dynamic responses collected from the structural health monitoring system of an urban railway track infrastructure, where the method is able to achieve F1 scores of 90% or higher for various scenarios.

TECHNOLOGY THE FIRE DETECTION SYSTEM ON THE RAILWAY LINE IS BASED ON IMAGE PROCESSING WITH THE COMPUTER VISION METHOD

The rail transportation system plays a role important as a medium of transportation for the movement of goods and people in large quantities and is one of the modes of cheap transportation, this transportation model evolved from a steam train until it evolves to become more sophisticated using electric and magnetic technology, trains system works well with support from several the first factor is human resources, supporting technology and facilities. The problem with the rail system is that damage to the rails can cause result in the transportation route being blocked and can cause a very fatal accident, Based on these problems, besides the feasibility of the rail system, rail maintenance is a very important key, the railroad track maintenance system is usually carried out periodically. The solution to handle this problem is to use a computer vision method by utilizing surveillance cameras or CCTV installed on railroad crossings able to detect damage, the detection of damage is categorized into a few types first is track damage, due to shifts, fires on rail lines and finally structural damage due to earthquakes or landslides in the railway line area, this technology has been applied to several developed countries. and can monitor a large area and can provide a quick response if a malfunction occurs, the system will be a smart monitoring system but doesn't replace the role of a railway officer but as a tool that will provide complete information where the location of the damage is so that prompt and more effective repair action can be taken.

Nonlinear responses of longitudinally coupled slab tracks exposed to extreme heat waves

Structural responses of longitudinally coupled slab tracks (LCSTs) under extreme heat waves (EHWs) and the adaptability of track reinforcement measures to cope with EHWs-related issues have been unprecedentedly investigated in this study. A novel finite element model (FEM) to assess nonlinear mechanical behaviours of LCSTs exposed to temperature rise has been established. The nonlinearities of material constitutional properties, interfacial behaviours and temperature distribution are taken into account, and the FEM has been fully validated by experimental data. This paper is the world's first to highlight nonlinear structural responses of LCSTs such as slab arching and interface failure under EHWs and under normal temperature rises (NTRs). More importantly, effectiveness of track reinforcement measures (such as post-installed anchors and interface adhesives) in mitigating track damage under EHWs are demonstrated to determine whether those measures are capable of making LCSTs adapt to EHWs. The new findings reveal that: (1) vertical buckling of LCST can be caused by atmospheric temperature rises; (2) the interface area between the mortar layer and the track slab adjacent to the joint with initial defect can fail under NTRs, while the interface delamination incurs under EHWs; (3) vertical displacements of track slabs under EHWs can be reduced by 97.3 % when post-installed anchors are introduced; and (4) the bond strength of interface adhesives should be larger than 0.02 MPa and 0.048 MPa to retain the vertical displacements within the threshold of level III interfacial gaps under NTRs and under EHWs, respectively.

Structural Damage and Recrystallization Response of Garnet Crystals to Intense Electronic Excitation (Adv. Funct. Mater. 8/2023)

Recrystallization Effects In article number 2212853, Peng Liu, Miguel L. Crespillo, Eva Zarkadoula, and co-workers demonstrate the track damage formation and recrystallization effects in garnet crystals under the intense electronic excitation, attributed to the key role of thermal parameters and cation radius ratio. The irradiation-induced nanostructures in garnet crystals enable the significant bandgap regulation and defect-related luminescence enhancement.