This study aims to investigate the fatigue behavior and failure modes of bolted lap joints using Modified Tensile Specimens (MTS) under various cyclic load conditions. Emphasis is placed on identifying the relationship between load amplitude, fatigue life, and damage progression in low-carbon steel assemblies.

An experimental approach was adopted using MTS specimens fabricated from St 12 03 cold-rolled steel, joined with Grade 8.8 M4 bolts. Cyclic fatigue tests were conducted under zero-based loading at seven distinct force levels. Fracture surfaces were visually analyzed to identify dominant failure mechanisms.

The results revealed a strong inverse correlation between applied cyclic load and fatigue life. Three distinct failure modes were identified: bolt shear at high loads (5.4 kN), interface cracking and slippage at moderate loads (4.9-5.1 kN), and plate tearing or stable fatigue behavior at lower loads (=4.1 kN). The results highlight a progressive transition in failure mechanisms, from bolt shear at high loads to plate tearing and interface cracking at lower loads, providing essential insights for fatigue-resistant bolted joint design.

This study offers original insights into the fatigue behavior of bolted lap joints using MTS, a relatively underexplored configuration in fatigue assessment. By experimentally evaluating failure modes under varied cyclic load levels, the authors uncover critical transitions in damage mechanisms—from bolt shear to interface cracking and plate tearing—depending on the applied load. Unlike many existing studies focused on numerical modeling or bonded joints alone, this work provides empirical data rooted in real-world fastening conditions using cold-rolled low-carbon steel.

This study aims to propose a novel identification method to accurately estimate linear and nonlinear dynamics in permanent magnet synchronous linear motor (PMSLM) based on the time-domain analysis of relay feedback.

A mathematical model of the PMSLM-based servo-mechanical system was first established, incorporating the aforementioned nonlinearities. The model's velocity response was derived by analyzing its behavior as a first-order system under arbitrary input. To induce oscillatory dynamics, an ideal relay with artificially introduced dead-time components was then integrated into the servo-mechanism. Depending on the oscillations and the time-domain analysis, nonlinear formulas were deduced according to the velocity response of the servo-mechanism. Afterwards, the unknown model parameters can be solved on account of the cost function which utilizes the discrepancy between nominal position characteristics and temporary position characteristics, both of which are extracted from the oscillations. The proposed recognition method was validated through a two-stage process: (1) numerical simulation and calculation, followed by (2) real-time experimental verification on a direct-drive servo platform. Subsequently, leveraging the identification results, a novel control strategy was developed and its tracking performance was benchmarked against conventional control schemes.

Simulation results demonstrate that the proposed method achieves estimation accuracy within 8%. Building on this, a novel control strategy is developed by incorporating both friction pulsation and force pulsation identification results into the feedforward compensator. Comparative experiments reveal that this strategy significantly enhances tracking and positioning performance over traditional control schemes. In a word, this new identification method can be used in different process control and servo control systems. Moreover, parameter auto-tuning, feed forward compensation or disturbance observer can be investigated based on the obtained information to improve the system stability and control accuracy.

It is of great significance for the performance improvement of rail transit motor control equipment, such as electro-mechanical braking systems. By enhancing the efficiency of motor control, the performance of the product will be more outstanding.

This study aims to implement condition monitoring for urban rail train permanent magnet synchronous motors and inverter systems. Through the construction of a digital twin model, it performs fault diagnosis of potential system failures, enabling rapid fault localization and protection.

This research begins with a brief introduction to the structure and classification of permanent magnet synchronous motors (PMSMs), followed by a detailed analysis of their mathematical model. Subsequently, it thoroughly investigates the working principle of three-phase two-level inverters and the distribution of space voltage vectors. Based on the analysis of the main circuit topology, a digital twin model matching the external characteristics of the physical circuit is established using the model predictive control method, achieving accurate system simulation. Furthermore, through theoretical analysis and simulation verification of phase current characteristics under inverter switch tube faults, general patterns of phase currents under fault conditions are summarized. The established digital twin model is then employed to validate these patterns, confirming the model's effectiveness in fault diagnosis.

This study proposes a fault diagnosis method based on digital twins. Experimental and simulation results demonstrate that the established digital twin model can accurately simulate the external characteristics of the actual physical circuit, validating its effectiveness in inverter fault diagnosis. This approach offers practical value for condition monitoring in actual urban rail train systems.

The study innovatively starts from a mathematical model and simulates the actual physical model through a virtual model, requiring only external characteristics to achieve system fault diagnosis, thereby enhancing diagnostic efficiency.

Adding an appropriate pre-sag to the geometry of simple catenary systems for electric railways can improve their performance in dynamic interaction with the pantographs of trains operating under them. The value of pre-sag can be obtained by empirical approximation or computationally expensive optimisation. This study aims to define a simple but accurate method to determine a suitable pre-sag without dynamic simulations and to find its limitations.

A quasi-static method to determine the ideal value of pre-sag is described based on elasticity variations. It considers variations of the static contact force. The limits of this method are investigated by comparing it to a parametric dynamic simulation study. In the dynamic simulation, an optimal level of pre-sag is identified for each contact force level. The influence of the speed in the dynamic simulation results is expressed in two parameters: the quasi-static influence in the mean contact force and the dynamic influence in the ratio between the vehicle speed and the wave propagation speed in the contact wire.

The comparison between the suggested method and the dynamic simulations shows a high consistency up to a speed limit of around 40 % of the wave propagation speed. The best agreement with the dynamic results is achieved by calculating the optimal pre-sag based on the absolute elasticity variation.

The simplified approach for determining the pre-sag is valid for low-speed applications, such as suburban railway lines. For these cases, a highly suitable geometry can be obtained with the suggested method, meaning a significantly reduced computational effort. As a case study for this work, the results are applied to a Swedish suburban rail line upgrade case.

The static uplift force is added as a varied parameter in dynamic simulations. The shift in system behaviour from low to high dynamics is described, and how the benefits from pre-sag are visible and then disappear. The limit value of the low-dynamics regime is identified to be 40 %.

This study solves the key problem that the static level monitoring is susceptible to temperature interference and affects the accuracy in slope instability/deformation monitoring. The purpose is to develop a reliable temperature compensation method for the system, improve the accuracy of slope stability monitoring and provide support for improving the safety and safety monitoring of engineering spoil slope and other projects.

Combined with theoretical analysis and experimental verification, the temperature compensation method is explored. The working principle of the hydrostatic leveling monitoring system is analyzed and the data processing formula, the temperature error calculation formula and the calculation formula for eliminating the error settlement value are derived. The temperature compensation method is established and verified by the field test of the engineering spoil slope which is disturbed by a debris flow.

The experimental results show that this method can reduce the error of the static level monitoring system by about 40 %. The field test shows that the fluctuation of slope settlement monitoring value is reduced after temperature compensation and the monitoring value is consistent with the actual situation, which has certain practicability.

The originality of this study is to derive a theoretical formula for quantifying/eliminating temperature errors in static leveling and to establish a practical temperature compensation method. The accuracy of the system is improved, which provides a reference for slope stability monitoring under complex environment (especially railway geotechnical engineering) and promotes the development of precision monitoring technology.

This paper focuses on studying the reliability allocation for the railway system, aiming to improve the overall reliability of the railway system and ensure safety operation.

In view of the complex structure of the railway system, involving many subsystems, this paper analyzes the close dynamic coupling effect between railway subsystems. Based on this, taking the railway system failure as the top event, a fault tree is constructed in this paper. Then, a reliability allocation method based on the fault tree is employed to allocate the reliability index. Finally, a numerical experiment is implemented to show the performance of the reliability allocation method.

The results showed that each subsystem needs to improve its reliability to meet the specified railway system reliability requirements, and the traction power supply system is the most important subsystem, which is the most efficient in improving the reliability of the railway system.

For the first time, starting from a holistic perspective of the system, reliability allocation is carried out based on the importance of each railway subsystem.

Over the last decade, African rail sectors have applied hybrid reform models to catch up with the subregion's lagging rail performance compared to other regions. With this in mind, this paper aims to study the effect of deregulation on rail transport demand. Following an abundant literature on deregulation in Europe and Asia, this study focuses on structural and regulatory reforms.

The investigation methodology is in line with the investigations of Mizutani (2019) and Smith, Benedetto, and Nash (2018). This paper uses a seemingly unrelated model (SURE) for general estimation and a random effect least square model for regional block estimation on a panel of 26 countries for 15 years between 2000 and 2015.

The main results show that structural reforms positively affect passenger transport demand, but negatively affect freight transport demand. The level of competition stimulates demand for freight transport. Privatization of operators positively affects freight transport demand, but has no significant effect on passenger transport demand. The introduction of a regulatory authority has a positive effect on demand for passenger transport, and in certain regional blocs, it affects demand for freight transport, with the existence of corridors shared between several countries.

This study is carried out in the sub-Saharan African sub-region. Indeed, the importance of the rail sector and the dilapidated state of many of its infrastructures should prompt a more abundant literature on the subject of the effectiveness of deregulation movements. We also evaluate the effect of vertical or horizontal separation and the introduction of an independent regulator in the rail sector on overall demand for transport service.

Rail corrugation is still one of the unsolved challenges in the railway industry, and the abnormal vibration and high-frequency noise caused by it constitute serious adverse effects on the operating environment. How to control corrugation has been an important research theme, and understanding corrugation evolution features is the necessary prerequisite. This study aims to investigate the specific evolution characteristics of corrugation from the contact stick-slip perspective.

The formation and development processes of corrugation are analyzed by using a self-designed scale-down test device. Specifically, the contact stick-slip characteristics under different creepage conditions are analyzed and the formation mechanism of corrugation is summarized. On the basis of corrugation formation, the trend of corrugation development is further emphasized to completely describe the whole process of corrugation evolution.

The results show that, under the determined vertical load condition, the contact interface appears the creep force-creepage negative slope phenomenon in the transverse direction. The cause of short-pitch corrugation on the rail wheel surface under the smaller angles of attack may be related to the inherent vibration frequency of the test device, and the cause of corrugation on the rail wheel surface under the larger angles of attack is mainly related to the stick-slip vibration induced by contact creep saturation.

This research explores the evolution characteristics of corrugation by adopting a self-designed scale-down test device, and elucidates the mechanism of corrugation in detail.

With the rapid advancement of China's high-speed rail network, the density of train operations is on the rise. To address the challenge of shortening train tracking intervals while enhancing transportation efficiency, the multi-objective dynamic optimization of the train operation process has emerged as a critical issue.

Train dynamic model is established by analyzing the force of the train in the process of tracing operation. The train tracing operation model is established according to the dynamic mechanical model of the train tracking process, and the dynamic optimization analysis is carried out with comfort, energy saving and punctuality as optimization objectives. To achieve multi-objective dynamic optimization, a novel train tracking operation calculation method is proposed, utilizing the improved grey wolf optimization algorithm (MOGWO). The proposed method is simulated and verified based on the train characteristics and line data of CR400AF electric multiple units.

The simulation results prove that the optimized MOGWO algorithm can be computed quickly during train tracks, the optimum results can be given within 5s and the algorithm can converge effectively in different optimization target directions. The optimized speed profile of the MOGWO algorithm is smoother and more stable and meets the target requirements of energy saving, punctuality and comfort while maximally respecting the speed limit profile.

The MOGWO train tracking interval optimization method enhances the tracking process while ensuring a safe tracking interval. This approach enables the trailing train to operate more comfortably, energy-efficiently and punctually, aligning with passenger needs and industry trends. The method offers valuable insights for optimizing the high-speed train tracking process.

As a key structure in the railway power supply system, the overhead catenary pillar carries the entire weight and dynamic load of the contact suspension device and supporting equipment. Its stability and reliability are directly related to the operational safety and efficiency of electrified railways.

Regarding the phenomenon of abnormal shedding of coating above the support under the cantilever of the catenary pillar in the track running line, a three-dimensional model is established to analyse the rigid cantilever type catenary and the force analysis of the cantilever part is carried out by using ABAQUS to calculate the contact force of the bow network under different running speeds of the high-speed train. The load is applied at the locator end of the simplified model of the cantilever to get the support reaction force at the connection between the cantilever and the support.

The support reaction force is applied as a load to the three-dimensional model of the pillar support; the stress cloud and the stress extreme value of 86.14 MPa are obtained for the pillar and the support part and the fatigue life of the pillar's key parts is calculated to be 12.02 years, respectively.

The upper part of the lower support of the high-speed rail catenary pillar is subjected to the alternating load transmitted by the bow net, which causes the fretting damage at this position, resulting in the abnormal peeling of the coating on the upper part of the lower support. Through combining the ABAQUS analysis with the structural characteristics and operating conditions of the catenary system, the main causes of component failure are determined.