The installation of renewable energy is accelerating to achieve carbon neutrality by 2050. This paper proposes a control system for integrating charge/discharge of stationary and onboard energy storage systems on DC electrified railways. A simulation of the performance of a train operation power shows the effect of the demand response and effective use of renewable energy by adopting the control system for energy conservation.

In order to control electric wear of current collecting materials such as contact wires and contact strips in electric railways, it is necessary to understand the relationship between current and the molten volume at a contact loss point. In this paper, we propose a method for estimating the molten volume of the contact wire whose film resistance is taken into account, on the basis of the ϕ-θ theory. To verify the proposed method, we carried out wear tests under varying current conditions to measure the molten depth, molten radius, and molten volume. The wear test results showed that the experimental values of the molten volume of the contact wire are spread in the range where normalized potential at the contact boundary at which α was estimated to be 0.90 to 0.94.

In this study, we developed a nomogram to easily predict track settlement due to culvert pipe damage. First, a calculation method was developed to estimate the reduction ratio of the subgrade reaction coefficient under railway tracks. The accuracy of this method was verified by comparison with trap-door tests and field tests. Secondly, to produce the nomogram, we calculated track displacement under conditions of reduced subgrade reaction.

The allowable strain value for all types of contact wire, including high-strength contact wires, has been set to 500×10⁻⁶ based on the fatigue characteristics of a basic hard-drawn copper. However, as train speeds increase, the strain value of contact wires may increase to more than 500×10⁻⁶ in the future. Therefore, in this paper, we propose a method for setting allowable strain values for each contact wire, taking into account the probability of failure. This probability is consistent with the margins of the conventional allowable strain value of 500×10⁻⁶. In addition, using this method, we propose allowable strain values for four types of high-strength contact wires.

We performed simulations of ultrasonic wave propagation in cracked rails to investigate a method for detecting transverse cracks in the rail head using guided waves. The results show that 100-150 kHz input frequencies are suitable for detecting rail head cracks and that the peak intensity of the first few waves in the received signal waves decreases with the degree of cracking. Further investigation shows that transverse cracks greater than 20 mm that have grown below horizontal cracks can be detected by checking the intensity of the first three waves in the received waves at 100 kHz.

Currently, mowers are widely used for weed control along railway tracks. However, this method has some issues. For example, one of issues is that weeds regrow quickly after being cut during summer. Therefore, there is a need for more effective and efficient weed control methods. To address this need, we developed a specialized piece of steam weeding equipment. This equipment consists of a general-purpose steam cleaner and newly developed handheld nozzles. To verify the effectiveness of the developed equipment, it was tested in areas with vigorous weed growth. The test showed that this equipment provided effective usability with less labor and time. Furthermore, it was also confirmed that large weed regrowth was reduced by 70% after one year compared with mowers.

This paper describes a design optimization method for power generation systems for diesel vehicles consisting of a permanent magnet synchronous machine, a full-bridge rectifier and phase shift capacitors inserted between them. By combining an analysis method for the proposed systems and a multi-objective optimization method, a trial design optimization was carried out with the aim of minimizing indicators related to the size and weight of the system. Furthermore, the performance of the optimized design was verified by numerical simulations, and it was confirmed that the design achieved the required performance while satisfying the constraints of the system.

The authors are conducting research with the aim of establishing a numerical analysis method capable of evaluating vehicle behavior before and after derailment of a train set during an earthquake. In this paper, as a basic study, an analysis method is proposed that can represent seismic vehicle behavior before and after the derailment of a single vehicle in a stationary state. Then, in order to consider the coupling of multiple vehicles, the proposed method is also extended to include dynamic models for connecting members between vehicles such as couplers and inter-car yaw dampers. Furthermore, the influence of the interaction between vehicles on the derailment limit is investigated through trial calculations.

This paper describes a wheel-rail tangential contact force model for analyzing vehicle dynamics under running in rainy conditions. So far, vehicle dynamics analyses have only been conducted in dry conditions. In this study, we investigate and propose a wheel-rail tangential contact force model for analyzing vehicle dynamics under running in rainy conditions. The proposed model combines Kalker’s linear rolling contact theory with the relationship between adhesive coefficient and velocity measured in running experiments. The validity and generality of the proposed model was confirmed by a measurement experiment of tangential contact force using a twin-disc sliding-frictional rolling machine.

Squealing (below 10 kHz) and high-frequency noise (above 10 kHz) can occur when trains pass through curved sections of track. Measurements of these noises were carried out on commercial lines to understand how they are generated. It was found that these noises vary from wheel to wheel, having large dispersion. The analysis results showed that these noises are prominent when the outer wheel flanges are in contact with the outer rail at certain passing speeds. On the other hand, these noises are reduced when a train is running at equilibrium speed in curves.