Three-dimensional (3D) elastic vibrations in railway vehicle carbodies sometimes negatively impact ride comfort, and efficient numerical analysis methods are required to study effective countermeasures. The authors proposed in their former work a new vibration analysis model in which the railway vehicle carbody is modeled as a box-like structure composed of elastic plates, straight beams, and curved beams. This model can easily express complex 3D vibration shapes observed in actual carbody, such as the interaction between the roof, floor, and side structures. In this paper, an improved version of the previous model is proposed, firstly. Then, a series of numerical studies are carried out by changing the structural properties of each face of the carbody shell, including cross-sectional shapes or bending rigidities, to investigate their effect on the natural frequencies. According to the numerical results, it has been shown that the side pillars primarily affect the modes with cross-sectional deformation of the carbody. Additionally, as a general tendency, the bending and shear rigidities of the roof panel have been found to have a relatively significant effect on the first bending and the diagonal distortion modes.

The axle spring vibration isolator rubber installed on the axle box that encloses the axle bearings is subjected to loads corresponding to the wheel weight and vibration of the axle box during running. It is thought that the running condition of the bogie can be monitored by utilizing the axle spring vibration isolator rubber as a sensor to grasp the load and vibration. Therefore, we investigated a method of monitoring the running condition of the bogie by incorporating a piezoelectric element, which generates electric signals in response to applied loads and vibrations, in the axle spring vibration isolator rubber. In this paper, we made the rubber isolator with a built-in piezoelectric element (RIBP). As a result of running tests with the RIBP installed on a bogie, we found that the running condition of the bogie can be monitored by the time waveform of the electrical signal obtained from the piezoelectric element, and that the condition of the axle bearing can be monitored by the result of frequency analysis. In addition, as a result of examining the actual method of monitoring the running condition of a bogie using a RIBP, it was found that the condition could be monitored even if the number of RIBP installed on the bogie was reduced.

The aerodynamic characteristics of a conventional line pantograph in a crosswind were investigated by conducting large-eddy simulations (LESs). In a previous study, wind tunnel tests using a full-scale pantograph were performed at various attack angles of the crosswind to understand the lift force characteristics of a pantograph in crosswind conditions. These experiments revealed that the lift force increases significantly when the yaw angle is set to 56°; however, the mechanism of increment of the lift force has not been clarified. Therefore, the flow fields around the pantograph head were investigated. It was found that there are two main mechanisms: one is a stationary large-scale vortex generated on the upper surface of the pantograph head, and the other is a pressure increment on the lower surface of the pantograph head. In addition, LESs were conducted using modified pantograph head shapes to investigate methods for reducing the lift force of the pantograph head using the mechanisms above. Two changes to the pantograph head shape were considered: a diagonal cut on the lower surface of the pantograph head and opening sections on the upper and lower surfaces of the pantograph head. The former shape generates a negative pressure area under the pantograph head, while the latter attenuates the large-scale vortex on the upper surface of the pantograph head. Thus, they achieve lift reduction by different mechanisms and can be used together. The lift reduction rate reaches approximately 60% when both methods are used together, indicating that this is an effective lift force reduction method.

Research and development are actively conducted for recent advances in the self-driving and unmanned vehicles, along with further efficiency and safety. In such fields, obstacle avoidance is frequently addressed in control applications through the concept of active safety technology. This paper investigates the real-time optimal obstacle avoidance control that the optimal path generator embedded model predictive controller. By offline computation, a large number of optimal obstacle avoidance control solutions are calculated to generate the supervised learning data for the deep-learning neural network used for the optimal path generator. Then, constructed optimal path generator is embedded in the model predictive controller to generate the reference command for the tracking task during the optimization process. The utility of the proposed controller is evaluated by both the numerical simulation and experimental testing of the obstacle avoidance maneuver of the micro-unmanned vehicle. Results show that the proposed real-time optimal controller successfully performs obstacle avoidance.

The shortage of drivers for trucks and buses has become a critical problem in recent years, leading to active research and development on unmanned and manpower-saving operation of heavy-duty vehicles. However, due to their larger overhangs compared to passenger cars, heavy-duty vehicles are more difficult to maneuver on narrow roads and sharp curves, especially those commonly found in urban areas or parking lots. Consequently, path tracking control systems commonly applied to passenger cars cannot be directly used for heavy-duty vehicles. Thus, the objective of this study is to develop a path planning and motion control system for autonomous driving of heavy-duty vehicles on roads with large curvatures.

To design the control system, a risk potential is utilized to express the driver's sense of danger towards obstacles and road boundaries. Simulations are conducted on a course that replicates an actual intersection, and a parameter study is carried out. Finally, the simulation results of this approach are compared with those of a conventional path-following method. The results demonstrate that the proposed method is effective for obstacle avoidance in intersection situations.

This study aims to develop a numerical simulation-based method for predicting ductile crack growth resistance curve (R-curve) for pre-strained components for rational assessment of ductile crack growth controlling fracture for pre-strained structural component with any plastic constraint. Experiments on R-curve of 3-point bend specimen with a shallow crack for steel pre-strained by 6% over uniform elongation provides that the pre-strain does not significantly reduce ductile crack initiation and growth resistance, even though the pre-strain induces disappearance of uniform elongation and work hardening together with drastic reduction in elongation. Observations of damage evolution in terms of micro-void formation indicate that ductile crack growth behaviors in both virgin and pre-strained steels are based on a micro-void nucleation-controlled ductile fracture mechanism. These experimental results demonstrate that the ductile damage model that we have already proposed for predicting R-curve for virgin steel that exhibits micro-void nucleation-controlled ductile fracture behaviors can be applicable for these virgin and pre-strained steels used. Thus, based on the previously proposed ductile damage model, a simulation-based method to predict the R-curve of pre-strained specimens only from the properties of virgin steel is proposed taking material degradation (change in strength and damage properties) due to pre-strain into account. The applicability of the proposed method is verified by showing the predicted R-curve for pre-strained steel are in good agreement with experimental results.

Epoxy resins, one of the high-performance polymer materials, have been widely used as an adhesive because of their excellent strength and durability due to their cross-linked network structure. It is necessary to understand the adhesion mechanism to ensure their reliability as structural adhesives. It is concerned that environmental attacks, such as high temperature and humidity, degrade the bonding strength of the adhesive structure. In order to understand the degradation mechanism by environmental attacks, it is necessary to evaluate the intrinsic bonding strength of adhesive systems by a quantitative test method. This study proposed a novel test method to evaluate the shear bonding strength using a small columnar resin formed on the metal adherend's surface and investigated the adherend and environmental degradation effects on the bonding strength using the proposed method. The experimental results revealed that the bonding strength of the epoxy adhesive was affected by the environmental attack. The bonding strength increased regardless of the substrate material after the low-humidity and high-temperature exposure. On the other hand, the effect of the high humidity attack on the bonding strength was different depending on the adherend: the bonding strength of SUS304 decreased, on the other hand, that of A5052 increased. The fracture morphologies also changed in the case of A5052 adherend after the high humidity and temperature exposure. AlO(OH) was formed on the A5052 adherend surface after high humidity and temperature exposure, which might have affected its bonding strength.

Focusing on the cooling of the arc splitter plate after arc generation in the pole mounted switchgears, the heat transfer phenomenon was clarified. Experiments were carried out on a pole mounted switchgears with load currents of 600 A and 800 A, and the heat transfer phenomenon was evaluated from the surface temperature of the iron arc splitter plate measured with a radiation thermometer. From the analysis results, it was found that the plate was cooled by forced convection due to the expansion of the air due to the arc for about 5 s after arc interruption, and then cooled by natural convection. Immediately after the start of the experiment (about 600 s from the start), the effect of the arc on the air is large, and the ratio of cooling by forced convection to total cooling amount is about 0.5 to 0.75. When the melting area of the iron arc splitter plate increases, the ratio of heat transfer rate by forced convection becomes about 0.3 to 0.55. In addition, after the experiment with a load current of 800 A, it was confirmed that the iron arc splitter plate melted and melted down over a wide area. It is thought that at a load current of 600 A, the melting area of the iron arc splitter plate was small enough to melt down, but at 800 A, when the arc energy increased, the melting area of the iron arc splitter plate increased and melted down. It was clarified that the heat transfer phenomenon in the arc-extinguishing plate is affected by melting.

In this study, we aimed to stabilize premixed flame behaviors in a circular pipe with swirling flow. We constructed a system that automatically changes swirl vane angles according to the flame tip positions keeping the air ratio and flow rate. In addition, we tried to stabilize the flame behavior using this system, and simultaneously employed time-series PIV measurements in the flow fields in the circular pipe. The findings obtained in this study are shown below. (1) Under this experimental condition, it was shown that there was a positive and strong correlation between the flame tip positions and the integrated scattering intensity of tracer particles in a circular pipe with swirling flow. (2) Using the integrated scattering intensity of tracer particles as an index, the change of the flame tip positions was judged, and the swirl vane angle could be changed according to the behavior of the premixed flame. It was shown that keeping the flame tip positions within the circular pipe was possible. (3) While operating the flame position stabilization system, time-series PIV measurements simultaneously measured the flow fields near the flame tip. From the results, when the swirl vane angle was changed in the positive direction, an upstream-direction velocity region appeared by increasing the swirl intensity. After that, the flame propagated upstream along the formed upstream-direction velocity region.

There are few studies that have conducted comprehensive verification of the physiological and psychological effects of different textures of chilled confectioneries by means of biometric measurements and subjective evaluation. The effects of confectionery texture are still unclear. Therefore, this study aimed to clarify the effects of different textures on the activity of autonomic nervous system, the brain, and muscles, and emotion by simultaneously measuring changes over time in various biological information and assessing subjective evaluation given by the tasters during consumption of different types of ice cream with monaka shell with varying water content. Participants answered a subjective evaluation questionnaire and rested for 60 s, and then performed the task. The monaka ice cream consisted of 9 blocks, each of which was eaten in 20 s. Afterwards, the participants rested for 60 s and completed a subjective evaluation questionnaire. Near-infrared spectroscopy was used to measure brain activity during eating, electromyography to measure muscle activity, and electrocardiography equipment to analyze heart rate variability. Eating monaka shell with low water content significantly activated cerebral blood flow in the right hemisphere when the first and sixth blocks were eaten. A significant trend was observed in LF/HF, which is considered an index of sympathetic nerve activity. In the mastication force test, the participants chewed significantly more strongly on ice cream with a high water content monaka shell than those with a low water content. During mastication, the participants who consumed ice cream with the low water content shell tended to use slow muscles more than those who consumed ice creams with high water content shell. The questionnaire showed that both the increase in degree of emotions such as surprise and excitement and the decrease in the degree of emotions such as sadness and depression were larger when the participants consumed ice cream with a high water content shell than those with a low water content shell. The results suggest that monaka shells with a low water content induce a more relaxed state and pleasant emotions than those with a high water content.

In this study, we are attempting to create self-adhesive moldings made entirely from bamboo fibers extracted by a machining center in order to solve global environmental problems and the destruction of ecosystems caused by bamboo. However, the mechanical properties of the moldings are still insufficient. In the present report, we clarify the molding conditions that can improve the mechanical properties of the molded plates. First, the cause of fracture of the plates during tensile testing was investigated. As a result, it was considered that the cause was the fracture at the adhesion area or fiber withdrawal. To enhance the adhesive action, we focused on lignin, an adhesive component in bamboo, and its flow process during molding. We investigated the effects of in-mold temperature and pressure and molding time on the thermal flow of lignin. As a result, it was found that the thermal flow of lignin progressed and the mechanical properties improved as the time and pressure were increased. Therefore, we attempted to determine the molding conditions that maximize the tensile strength of the moldings by referring to a manufacturing process model for fiber-reinforced composites. Five specimens were fabricated, and a tensile strength of 32.37 MPa was achieved with a standard deviation of 0.55 MPa, which is equivalent to that of general-purpose plastics.

A simulation technique adaptable to calculating a laser-machined profile was proposed to develop microfabrication techniques for a cemented carbide using a focused picosecond pulsed laser. An experiment to obtain a defocus diagram, which shows the relationship between defocus and removal depth, was conducted by shifting the focal point upward to the work surface. The concept of zero cut, in which the laser beam was scanned repeatedly in the same path, was proposed, and it was verified using the proposed simulation technique that zero cut is useful for residual stock removal. In addition, a simulation technique adaptable to calculating both the laser-machined profile and the machining process conditions was developed using the defocus diagram as a machining condition. It was verified through a machining test by fabricating half-cut columns with radii of 30 and 50 μm formed on the upper half of a large base column that the dimensional error of the columns was less than 1% and the surface roughness was less than 0.1 μmRz. This means that the simulation technique using the defocus diagram as a machining condition is useful for the microfabrication of the cemented carbide using the focused picosecond pulsed laser.

This study proposes a multi-material topology optimization approach considering the effect of material cost. The proposed method can derive the optimized configuration, the choice of materials to use, and their arrangement, which can minimize material cost while satisfying a maximum displacement constraint. An approach based on Discrete Material Optimization with material definition independence and symmetry is employed to represent the arrangement and geometry of multiple materials for an isotropic linear elastic model. This structural representation method solves the problems of local minima solutions regarding the order of material definitions and the introduction of physically difficult-to-interpret parameters, which have been issued in the past. As a result, the proposed method is highly compatible with actual product design systems. As a strength constraint, a maximum displacement constraint based on the p-norm idea is introduced. The objective function is defined as the material cost function assuming the introduced structural representation approach. Finally, a study of several numerical examples is performed. The validity and effectiveness of the proposed approach is demonstrated.

In a section which a wireless train control system is installed and the track circuit is removed, it is difficult to detect rail broken. Under such circumstances, the vehicle is assumed to run repeatedly on rail gaps until rail broken is found by rail inspection or other means. Therefore, this study investigated the strength of the track components under condition of repeated passage at a rail broken section. Specifically, we fabricated a new falling weight test equipment which can apply the impact load of a vehicle passing through a rail broken section and then, the strength of track components was experimentally investigated by conducting repeated falling weight test. This test evaluates the plastic deformation of the rails and functional deterioration of the rail fastenings system in response to impact loads. In addition, in order to evaluate running safety considering repeated passage at a rail broken section, we created a vehicle running simulation model that takes into account damage condition of track components after a falling weight test. The results of the running simulation confirmed that the plastic deformation of the rails and damage to the rail fastening systems considered in this study do not have a significant impact on running safety.

In the installation process of an elevator, work performs to correct the bending of the rail in order to suppress the lateral vibration of the car due to the irregularity of the guide rail. In this work, each rail bracket is adjusted so that the cutting edge of the rail is in the specified horizontal position with respect to the piano wire. However, since the rail is bent at the joint, irregularities remain even if the brackets are lined up in a straight line. Such a method cannot suppress the lateral vibration of the car and may worsen it. In this research, we proposed a method of optimizing the rail shape to minimize the vibration of the car based on a rail behavior model in that adjustment process and a car vibration model. The effect was verified in an experiment using an actual elevator. In the elevator system, large vibration had been occurred because the periodic excitation force determined by the running speed and rail bending period matched the natural frequency of the car. By adjusting the rails based on proposed method, we avoided resonance and reduced lateral vibration by 37%. This verification showed that the use of the proposed method enabled significant vibration reduction in a short period of time.