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The wheel of the railway runs while coming into contact on a rail. Therefore, wear occurs in both. When these wears progress, the vibration is amplified. It leads to various problems such as a ride comfort and a noise. Many researchers examined the contact of a wheel and the rail so far. However, as for the shape of the abrasion to be formed on the surface of a wheel and the rail by progress of the abrasion, it is difficult to observe the abrasion situation to change each moment. It is necessary to investigate the process of shape change on wheel and rail in order to examine the influence of wear progress. In this study, we focused on a Discrete Element Method (DEM) that was effective for the dynamic behavior analysis of the granular material. The rail was expressed by replacing the irregularities of the rail surface to particles. A wheel ran on the particles replaced as a rail. Possibility of DEM was examined by comparing the calculated results with the experimental results of repetitive running. As a result, both showed that the acceleration level of the wheel increase and decrease repeatedly. In addition, it was found that the suggested analytical method of this study might be obtained the results similar to the tendency by the experiment.

In Japanese railway networks, the gauge corner cracking (GCC) occurs to the head hardened rail of the high rail in curved sections of R600 to R800m. In case of the GCC propagates deeply, it will be a possibility of causes rail broken. Therefore, the appearance of GCC is considered a serious problem from the viewpoint of safety transportation. Since GCC appears mixed with head checks, it is very difficult to find GCC in the early stages. Furthermore, GCC appears in the cluster conditions, it is very difficult to remove all cracks of GCC. Hence, it is very important to control the initiation of GCC. However, the countermeasure method for GCC initiation has not been developed. The aim of this study is to examine the reduction method for GCC initiation due to the relief of the contact pressure between wheel/rail. Therefore, the wear development of rail was focused, the influence of the worn profiles of rail on wheel/rail contact condition was examined. In the beginning of this study, rolling contact fatigue (RCF) test were conducted by use of the twin disc test equipment. Secondly, wear analysis of rail with multibody dynamics which was modeled the locations of GCC appearance was conducted. Finally, the effect of the worn profiles of rail on wheel/rail contact and the suppression of RCF initiation was examined by the wheel/rail contact analysis. In summary, the worn profiles of rail were confirmed the suppression effect for RCF by reducing the contact pressure between wheel/rail.

Rail wear does not develop in a short term, but it is closely related to crack initiation. Furthermore, there is a possibility that the worn profile of rail influences the curving performance or the running stability. However, worn profiles of rail changes complexity in each section (e.g. straight section, transition curve section, circular curve section) because the condition of wheel/rail contact changes gradually, according to the running condition of vehicle and track geometry conditions. Predicting the worn profiles of rail should be considered based on the results of the vehicle dynamics analysis. Therefore, it is very beneficial to predict the worn profiles of rail based on the analysis by using multibody dynamics. The purpose of this study is to develop the prediction model for worn profile of rail under the various angle of attack by using multibody dynamics. Especially, we focused on the wear development due to longitudinal slip and lateral slip. In the beginning of this study, the wear experiment was conducted by using the wheel/rail rolling contact equipment under the mixed slip conditions. Secondary, the prediction model with Simpack was developed. Then, wear predicting analysis was conducted in the same contact conditions as the experiments. Finally, we evaluated the results of analysis to validate the developed model under the various mixed slip conditions. As a result of the experiment and the analysis, it was revealed that the wear development under the mixed slip conditions can be evaluated by the contribution ratio of longitudinal slip and lateral slip.

This paper presents the experimental results of the transient characteristics of the tangential force between small cylindrical specimens assumed as a wheel after re-profiling and a new rail respectively, generated in the case where the frictional force is applied to the wheel/rail contact surface repeatedly, and also the results of the numerical analysis of the influence of the wheel/rail contact surface properties on the running performance of the railway vehicles. In the experiments, the tangential force characteristics in case of sweep under the different longitudinal slip change rate conditions have been obtained by means of a twin-disk sliding-frictional rolling machine equipped with the environmental device in RTRI. The experimental results show that the tangential force coefficient is smaller in the range of a low longitudinal slip ratio compared with the Kalker’s theoretical characteristics that are obtained by applying the Levi-Chartet’s formula of saturation, which are the steady characteristics of the tangential force, in case of the contact surface close to that after re-profiling, and that the tangential force coefficient becomes large when the frictional force is applied to the wheel/rail contact surface repeatedly. This means that the coefficient of friction becomes large due to the repetition of the rolling and sliding friction. In addition, in order to investigate the relation between the contact surface properties and the running performance of the railway vehicle, a numerical analysis using a simple wheel-rail dynamic model was carried out by comparing Kalker’s theoretical value with the experimental values. As a result of the numerical analysis, it’s clarified that in case of the power running, the wheel after re-profiling is more slippery than that without re-profiling after long run in the range of a low longitudinal slip ratio.

Rail is the peculiar element constructing the railway system. The phenomenon such as wear or defect of rail will be caused by the repeated wheel and rail rolling contact on the rail surface. Especially, the cracks called head checks are generated continuously on the gauge corner side of the high rail due to the plastic deformation caused by the severe contact with the wheels. The occurrence situations and the initiation factors of the head checks are widely known because the head checks are generated in many curved sections of which radii are about 800m. On the other hand, some head checks are confirmed to appear on the low rail in the curved section. However, the occurrence situations of the head checks of the low rail are not clarified because the appearance of this type of the head checks is limited. Furthermore, the initiation factors of this type of the head check are also not clarified. In this research, we conducted the site investigation and the analysis of the rail which has the head checks to clarify the appearance situations of the head checks of the low rail. In addition, we conducted the wheel and the rail contact analysis by use of the multi-body dynamics tool by constructing a model of the site of the head checks appearance of the low rail to examine the initiation factors of the head checks of the low rail.

Linkage mechanisms with 1 DOF consisting of links and lower pairs cannot completely generate the specified output motion. In order to solve that problem, the novel kinematic pair with 1 DOF is developed. This kinematic pair consists of two surfaces in line contact with each other and can generate relative rolling motion along the specified spatial trajectory. Thus, it is called the spatial rolling contact pair. The relative rolling motion along an arbitrary trajectory is specified so as to satisfy the kinematic condition of the spatial rolling motion. Rolling contact surfaces which can generate the specified motion are designed based on ruled surfaces of the instantaneous screw axis. Some norms to evaluate stability of rolling contact between designed pairing elements are introduced, and the pairing elements are constrained by many linear elastic elements so as to satisfy them. Some examples of the proposed kinematic pair are designed, and one of them is manufactured as a prototype. By some experiments, it is confirmed that the prototype generates the specified rolling motion and keeps rolling contact by designed elastic constraint. Finally, it is revealed that a spatial 4-bar mechanism with the spatial rolling contact pair can completely generate the specified output motion and can be synthesized more easily than the mechanism synthesized by conventional methods.

The rail is one of the most important elements in constructing railway system. The phenomenon such as wear or defect of rail will be caused by the repeated wheel/rail rolling contact. The wear of rail, which will not develop in a short period of time, has a close relation to crack initiation. Further, there is a possibility that the worn profile of rail influences the running stability or the curving performance of vehicle. Therefore, it is very important to analyze the wear development of the rail. Previously, we constructed the prototyped model for predicting worn profiles of rail with Simpack and validated of this model. At the same time, the wear of rail occurs more outstandingly in the curved section than in the straight section. In the curved section, the wheel passes with an attack angle, which gives rise to not only longitudinal slips but also lateral slips at the wheel/rail contact patch. In previous research, longitudinal slips and lateral slips have been treated as the equivalent. In this research, we conducted wear experiments by use of wheel/rail rolling contact test equipment to examine the influence of lateral slips on wear development. Moreover, we constructed wear predicting model considering lateral slip and analyzed the worn profile of rail in the same contact condition with the wear experiments. As a result of the experiments and the analysis, the analytical model was confirmed being valid to predict worn profile of rail considering lateral slip.

In recent years, railway system is attracting attention in terms of energy efficiency and environment friendliness. Rail of railway is one of the most important elements in constructing railway system. Railheads are subjected to severe contact with wheels during repeated passage of vehicles. As a results of severe contact with wheels, wear of rail or rail defect have been occurred on railheads. Rail profile will be changed due to wear development. Worn profiles of rail have changed complexity in each section because the condition of wheel/rail contact has changed gradually, according to the running condition of vehicle and track geometry condition. Therefore, it is very important to predict the worn profiles of rail based on the analysis of vehicle dynamics. Previously, we constructed the prototyped model for predicting worn profiles of rail with Simpack. However, the validation of this model has not been verified. In this study, we conducted the wear experiments by use of full-scaled wheel/rail rolling contact equipment to distinct the coefficient of wear and to measure the worn profiles for validating the prediction model. Moreover, we analyzed the worn profile of rail in the same contact condition with the wear experiments. Finally, we considered the results of wear depth and the contact patch of wheel/rail discs of this equipment in analysis and experiments. As a result of the analyses and experiment, the analytical model was confirmed being valid to predict worn profile of rail.