Search Results (74)

In railway infrastructure, particularly where concrete sleepers are employed, certain critical zones exhibit pronounced degradation of the ballast layer. Previous studies have identified several contributing factors, including the presence of welds, heterogeneity in the substructure beneath the sleepers, and variations in the track’s geometric parameters. Of these factors, the presence of welds seems to have the most significant influence. This article aims to determine whether differences in the ballast railway track’s response to traffic loads at weld locations can be identified in the initial phase, before obvious damage appears. Vibration responses in terms of displacement, velocity, and acceleration were measured on upgraded concrete sleepers equipped with rubber under-sleeper pads. The results indicate that velocities and accelerations at rail weld locations differ significantly from those in adjacent track sections, when the railway track is in an intact, undamaged condition. These results suggest a high likelihood of damage formation in these critical locations, indicating the necessity of preventive measures to mitigate damage. Possible mitigation measures that could help reduce the formation of damage are proposed. Full article

Defects formed during the thermite welding process of two sections of rails require the welded joints to be inspected for quality, and the most used non-destructive method for inspection is radiography testing. However, the conventional defect investigation process from the obtained radiography images is costly, lengthy, and subjective as it is conducted manually by trained experts. Additionally, it has been shown that most rail breaks occur due to a crack initiated from the weld joint defect that was either misclassified or undetected. To improve the condition monitoring of rails, the railway industry requires an automated defect investigation system capable of detecting and classifying defects automatically. Therefore, this work proposes a method based on image processing and machine learning techniques for the automated investigation of defects. Histogram Equalization methods are first applied to improve image quality. Then, the extraction of the weld joint from the image background is achieved using the Chan–Vese Active Contour Model. A comparative investigation is carried out between Deep Convolution Neural Networks, Local Binary Pattern extractors, and Bag of Visual Words methods (with the Speeded-Up Robust Features extractor) for extracting features in weld joint images. Classification of features extracted by local feature extractors is achieved using Support Vector Machines, K-Nearest Neighbor, and Naive Bayes classifiers. The highest classification accuracy of 95% is achieved by the Deep Convolution Neural Network model. A Graphical User Interface is provided for the onsite investigation of defects. Full article

This study examines factors affecting the thermal expansion behavior of continuous welded rails (CWRs) in urban rail systems and investigates conditions that lead to rail weld fractures. Parameters affecting CWR fractures near ventilation shafts in urban rail systems are identified through field investigations and machine learning analysis. Further, a computational fluid dynamics analysis is employed to evaluate the range of temperature variation around tunnel ventilation shafts that affects the CWR fractures. Load conditions, including temperature changes, were analyzed using a validated numerical model to determine the axial stress in the CWR, which resulted in a 23% reduction in the axial stress in the weld joint. The results confirm that increased localized temperature fluctuations around tunnel ventilation shafts lead to a higher frequency of CWR fractures. Full article

Driven by technological advancements and accelerated infrastructure development, an increase in the need to monitor the performance of prominent structures such as bridges, metro-corridors, and sea-link bridges is being advocated by experts to predict and minimize any hazards resulting from the degradation of the structures over time. However, accessing and replacing the batteries becomes problematic and expensive when the sensors are instrumented in remote areas of the bridge structures, especially when the sensors are embedded. For these reasons, a strong case can be made for harvesting and storing ambient energy from the surroundings to drive the sensors for structural health monitoring (SHM). This study aims to introduce a new trapezoidal strain-amplifying sensor/energy harvester (TSAH) for civil engineering structures that uses flexural strain amplification to enhance energy harvesting from structural vibrations. TSAH also serves as a sensor for integrated energy harvesting and SHM. This article examines the influence of the geometric properties of TSAH on strain amplification via numerical investigations under a specific set of external loads. Based on numerical studies, the sensors are bonded to the trapezoidal strain-amplifying plate to develop and assess the TSAH. Experimental investigations were carried out first in the laboratory to evaluate the effectiveness of the TSAH over the directly bonded (DB) sensors with two different types of piezo-transducers for energy harvesting. The host structure was exposed to impact and shaker vibrations for the laboratory research. For the various scenarios taken into consideration in the study, the typical amplification factor for peak voltage is determined to be between 1.45 and 3.75, while for the power, it is between 1.09 and 6.08. Further, for field verification, the TSAH configuration was evaluated on a real-life bridge structure, viz the Chipiyana rail over-bridge (ROB), Asia’s heaviest steel ROB located on the Delhi–Meerut expressway. The field experiments also establish the superior performance of TSAH, with an amplification factor ranging from 1.75 to 3.75 for peak voltage and 3.75 to 5.53 for peak power. As compared to the previously proposed curved configuration in the literature, the TSAH configuration is suitable for brittle sensors as well. Its ability to be permanently bonded by epoxy/welding, or temporarily using magnets, bolts, or clamps, offers it versatility over other surface bonded/embedded configurations. As a result of this, it imparts reusability in case of any damage, which promotes the goal of sustainability. Full article

To address the technical challenges, production quality issues, and inefficiencies caused by the heavy reliance on traditional manual processing of small assembly plates in the shipbuilding industry, this paper presents the design and analysis of a track-based automatic welding device. This equipment provides a solution for achieving batch and continuous welding in the field of automatic welding technology. The design section includes the mechanical design of the equipment’s core mechanisms, the design of the operating systems, the development of visual scanning strategies under working conditions, and the formulation of multi-layer and multi-pass welding processes. The analysis section comprises the static analysis of the equipment’s mechanical structure, kinematic analysis of the robotic arm, and inspection analysis of the device. Compared with manual welding, multi-layer and multi-pass welding experiments conducted using the equipment demonstrated stabilized welding quality for small assembly plates. Under the conditions of single plates with different groove positions and gaps, when the gap was 4 mm, processing efficiency increased by 7.35%, and processing time was reduced by 10.2%; when the gap was 5 mm, processing efficiency increased by 10.7%, and processing time decreased by 7.39%. The welding formation rate for the overall processing of single plate panels and web grooves increased by 11.48%, total material consumption decreased by 13.4%, and unit material consumption decreased by 13.5%. For mass production of small assembly plates of the same specifications, processing time was reduced by 16.7%, and there was a 41.4% reduction in costs. The equipment effectively addresses the low level of automation and heavy dependence on traditional manual processing in the shipbuilding industry, contributing to cost reduction and efficiency improvement. Full article

Paint-free bodywork has become an attractive alternative for rail vehicles, in the direction of easy maintainability and low manufacturing costs. However, conventional resistance spot welding inevitably leaves indentation marks to detrimentally reduce the optical homogeneity of the paint-free bodywork. In light of this, indentation-free resistance spot welding is proposed for joining SUS301L stainless steel sheets in order to achieve superior surficial integrity. A tiny SUS301L steel ball with a diameter of 1.5 mm was chosen as the intermediate filler between two steel sheets to avoid the formation of surficial indentation. The influence of welding current and welding time on the mechanical properties of joints was studied. The optimal parameters of the mechanical properties were obtained when the welding current was 8.0 kA, the welding time was 150 ms, the electrode pressure was 0.35 MPa, and the electrodes were cylindrical planar electrodes, which was determined by comparing the tensile shear test results. The surficial indentation depth was less than 1% of the plate thickness, and no observable indentations were seen on the surface of the optimized welding spots. Full article

Mg-Gd-Y-Zn-Mn (MVWZ842) is a kind of high rare earth magnesium alloy with high strength, high toughness and multi-scale strengthening mechanisms. After heat treatment, the maximum tensile strength of MVWZ842 alloy is more than 550 MPa, and the elongation is more than 5%. Because of its great mechanical properties, MVWZ842 has broad application potential in aerospace and rail transit. However, the addition of high rare earth elements makes the deformation resistance of MVWZ842 alloy increase to some extent. This leads to the difficulty of direct plastic processing forming and large structural part shaping. Friction stir welding (FSW) is a convenient fast solid-state joining technology. When FSW is used to weld MVWZ842 alloy, small workpieces can be joined into a large one to avoid the problem that large workpieces are difficult to form. In this work, a high-quality joint of MVWZ842 alloy was achieved by FSW. The microstructure and properties of this high-strength magnesium alloy after friction stir welding were studied. There was a prominent onion ring characteristic in the nugget zone. After the base was welded, the stacking fault structure precipitated in the grain. There were a lot of broken long period stacking order (LPSO) phases on the retreating side of the nugget zone, which brought the effect of precipitation strengthening. Nano-α-Mn and the broken second phase dispersed in the matrix in the nugget zone, which made the grains refine. A relatively complete dynamic recrystallization occurred in the nugget zone, and the grains were refined. The welding coefficient of the welded joint exceeded 95%, and the hardness of the weld nugget zone was higher than that of the base. There were a series of strengthening mechanisms in the joint, mainly fine grain strengthening, second phase strengthening and solid solution strengthening. Full article

Aluminum thermal welding joints are widely used in the maintenance welding of heavy-haul railways due to their easy handling and high efficiency. However, due to their inherent welding characteristics, welding results in certain differences in the material’s physical properties at the welding zone compared to adjacent base materials, leading to the occurrence of short-wave irregularity under long-term wheel–rail interactive forces. In order to explore the evolution characteristics of weld irregularity, dynamic characteristics, and plastic deformation under long-term wheel–rail impact, a detailed tracking test was conducted on a normal aluminum weld, and the process from being put on the track to being damaged and replaced was evaluated. At the same time, a rigid–flexible coupling model was established for subsequent analysis, and plastic damage was analyzed using the finite element model. The results show that the service life of the weld can be divided into three different stages: the initial stage, the intermediate stage, and the damage stage. In the damage stage, a temporary separation occurred between the wheel and rail, leading to a sudden change in the wheel–rail interaction. The weight of 250 MT at the weld reached the repairment control limit. The concentration effect of equivalent plastic deformation was most serious at 2~5 mm below the rail head. Full article

While the effect of ballast degradation on lateral resistance is noteworthy, limited research has delved into the specific aspect of ballast breakage in this context. This study is dedicated to assessing the influence of breakage on sleeper lateral resistance. For simplicity, it is assumed that ballast breakage has already occurred. Accordingly, nine granularity variations finer than No. 24 were chosen for simulation, with No. 24 as the assumed initial particle size distribution. Initially, a DEM model was validated for this purpose using experimental outcomes. Subsequently, employing this model, the lateral resistance of different particle size distributions was examined for a 3.5 mm displacement. The track was replaced by a reinforced concrete sleeper in the models, and no rails or rail fasteners were considered. The sleeper had a simplified model with clumps, the type of which was the so-called B70 and was applied in Western Europe. The sleeper was taken into consideration as a rigid body. The crushed stone ballast was considered as spherical grains with the addition that they were divided into fractions (sieves) in weight proportions (based on the particle distribution curve) and randomly generated in the 3D model. The complete 3D model was a 4.84 × 0.6 × 0.57 m trapezoidal prism with the sleeper at the longitudinal axis centered and at the top of the model. Compaction was performed with gravity and slope walls, with the latter being deleted before running the simulation. During the simulation, the sleeper was moved horizontally parallel to its longitudinal axis and laterally up to 3.5 mm in static load in the compacted ballast. The study successfully established a relationship between lateral resistance and ballast breakage. The current study’s findings indicate that lateral resistance decreases as ballast breakage increases. Moreover, it was observed that the rate of lateral resistance decrease becomes zero when the ballast breakage index reaches 0.6. Full article

This paper presents the concept of a modified 60E1 rail dedicated to continuous welded rail (CWR) track. The presented solution is the subject of a patent application by the authors of the publication. The paper describes problems associated with the operation of CWR track and the phenomena of so-called “rail stressing”, i.e., stresses created in the rail due to thermal shrinkage that, in extreme cases, can lead to the buckling of the rail track. Simulation calculations of longitudinal track loads to represent the occurrence of thermal force as a result of the occurrence of high air temperatures were carried out for the constructed conventional model of the railroad track as well as the track with the proposed solutions. A discussion of the simulation results is presented, indicating the possibility for the wider application of both varieties of modified rail. Full article

Pipeline welds typically do not have secondary reinforcement, rendering welds highly vulnerable to leakage accidents caused by the movement of gases or liquids. Therefore, identifying internal defects in welds through radiographic testing (RT) is critical for a visual and quantitative evaluation of weld defects. In this study, we developed a device that can automatically inspect the circumferential connection between pipes by applying a digital radiography testing (DRT) technique that can convert radiation signals into real-time electrical signals by using a digital detector array (DDA). Gamma rays were used to minimize spatial constraints in the inspection environment and optimization was performed to satisfy quality requirements set by international standards. Furthermore, FLUKA simulation was performed to predict radiation intensity for accurate radiation leakage identification to enable the shielding design to be supplemented with lead rubber. This measure considerably reduces the safe distance for radiation leakage during field testing. The results confirmed the feasibility of a novel automated inspection technique that integrates automatic inspection devices and ensures safety using radiation, the byproduct of which is a hazardous material. Full article

As an important part of the boundary conditions on both sides of the high-speed railway track–bridge system, the seismic response of the subgrade structure is different from that of the bridge structure. This difference has become increasingly significant with the widespread adoption of continuous welded rail technology in bridge construction. Therefore, investigating the seismic response of the bridge system, with a specific focus on the longitudinal constraint effects of the subsequent subgrade track structure, is of paramount importance. Utilizing finite element software, two distinct bridge models are developed: one incorporating the subsequent subgrade track structure and another excluding it. Through nonlinear time history analysis under varying seismic intensities, it is demonstrated that the longitudinal constraint of the subsequent subgrade track structure mitigates the longitudinal displacements and internal forces in critical components of the high-speed railway track–bridge system. Concurrently, acknowledging the heightened complexity and cost associated with post-earthquake repairs of the bridge structure compared to subgrade structure, this study uses a risk transfer connecting beam device. This device can redirect seismic damage from bridge structure to subgrade structure, thereby potentially reducing post-seismic repair expenses for the bridge. Full article

The azimuth track is an important component of the radio telescope wheel–rail system. During operation, the azimuth track is inevitably subject to phenomena such as track wear, track fatigue cracks, and impact damage to welded joints, which can affect observation accuracy. The 110 m QiTai radio telescope (QTT) studied in this paper is the world’s largest fully steerable radio telescope at present, and its track will bear the largest load ever. Since the welded joint of an azimuth track is the weakest part, an innovative welding method (multi-layer and multi-pass weld) is adopted for the thick welding section. Therefore, it is necessary to study the contact mechanical properties between the wheel and the azimuth track in this welded joint. In this study, tensile tests based on digital image correlation technology (DIC) and Vickers hardness tests are carried out in the metal zone (BM), heat-affected zone (HAZ), modified layer, and weld zone (WZ) of the welded joint, and the measured data are used to fit the elastic–plastic constitutive model for the different zones of the welded joint in the azimuth track. Based on the constitutive model established, a nonlinear finite element model is built and used to simulate the rolling mechanical performance between the wheel and azimuth track. Through the analysis of simulated data, we obtained the stress distribution of the track under different pre-designed loads and identified the locations most susceptible to damage during ordinary working conditions, braking conditions, and start-up conditions. The result can provide a significant theoretical basis for future research and for the monitoring of large track damage. Full article

Distributed optical fibre sensing (DOFS)-based strain measurement systems are now routinely deployed across infrastructure health monitoring applications. However, there are still practical performance and measurement issues associated with the fibre’s attachment method, particularly with thermoplastic pipeline materials (e.g., high-density polyethylene, HDPE) and adhesive affixment methods. In this paper, we introduce a new optical fibre installation method that utilises a hot-weld encapsulation approach that fully embeds the fibre onto the pipeline’s plastic surface. We describe the development, application and benefits of the new embedment approach (as compared to adhesive methods) and illustrate its practical performance via a full-scale, real-world, dynamic loading trial undertaken on a 1.8 m diameter, 6.4 m long stormwater pipeline structure constructed from composite spiral-wound, steel-reinforced, HDPE pipe. The optical frequency domain reflectometry (OFDR)-based strain results show how the new method improves strain transference and dynamic measurement performance and how the data can be easily interpreted, in a practical context, without the need for complex strain transfer functions. Through the different performance tests, based on UK rail-road network transport loading conditions, we also show how centimetre- to metre-scale strain variations can be clearly resolved at the frequencies and levels consistent with transport- and construction-based, buried infrastructure loading scenarios. Full article

Metal fabrication workshops (MFWs) are common businesses in Ugandan cities, and especially those producing metallic security gates, window and door frames (burglar-proof), and balcony and staircase rails. The objective of this study was to comparatively assess the pollution levels and potential health risks of manganese (Mn), chromium (Cr), cadmium (Cd), lead (Pd) and nickel (Ni) in pooled surface soil samples from four 5-, 7-, 8-, and 10-year-old MFWs (n = 28) and a control site (n = 8) in Mbarara City, Uganda. The concentration of the potentially toxic elements (PTEs) was determined using inductively coupled plasma–optical emission spectrometry. Contamination, ecological, and human health risk assessment indices and models were used to identify any risks that the PTEs could pose to the pristine environment and humans. Our results showed that PTE pollution of soils is occuring in the MFWs than at the control site. The mean concentrations of the PTEs (mg kg⁻¹) in the samples were: Mn (2012.75 ± 0.23–3377.14 ± 0.31), Cr (237.55 ± 0.29–424.93 ± 0.31), Cd (0.73 ± 0.13–1.29 ± 0.02), Pb (107.80 ± 0.23–262.01 ± 0.19), and Ni (74.85 ± 0.25–211.37 ± 0.14). These results indicate that the PTEs could plausibly derive from the fabrication activities in these workshops, which is supported by the high values of contamination factors, index of geoaccumulation, and the overall increase in pollution load indices with the number of years of operation of the MFWs. Human health risk assessment showed that there are non-carcinogenic health risks that could be experienced by children who ingest PTEs in the soils from the 7-, 8- and 10-year-old MFWs. The incremental life cancer risk assessment suggested that there are potential cancerous health effects of Cd and Ni that could be experienced in children (who ingest soils from all the four MFWs) and adults (ingesting soils from the 8- and 10-year-old MFWs). This study underscores the need to implement regulatory guidelines on the operation and location of MFWs in Uganda. Further research should be undertaken to investigate the emission of the PTEs during welding operations in the MFWs. Full article