Hunting oscillation is unfavorable to the running stability because it can generate relatively large lateral force between the wheels and tracks. In addition, once hunting oscillation occurs, it lasts until the running speed is reduced to some degree. Therefore, we have studied global stability against hunting oscillation by conducting a hunting motion test using a real bogie on roller rigs. In this study, we confirmed that there exists a clear point where initial lateral displacement of the wheelset caused hunting oscillation. Then, we concluded that the point in question originated from unstable limit cycles, generated by subcritical hopf bifurcation. On the basis of the obtained global stability, we devised a simple method that could make the hunting oscillation converge on the equilibrium point by oscillating the roller rig, without slowing down the rotational speed of roller rigs.

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Wheel / rail wear of railway is one of the serious problems affecting running stability, ride comfort, and maintenance frequency. Especially in urban railway, heavy wear occurs on the sharp curve section, clarifying the mechanism of wear development is essential in reducing wear. Therefore, experiments to clarify the influence of contact position on wear development was conducted by using 1/5 scaled wheelset test stand which can systematically change various parameters and easily control wear influence factors. This experimental unit consists of a single wheelset and rail rollers, and the wheelset runs on rail rollers that simulate rail. The experiment simulated wheel wear in a R400m radius curvature on the worn rail by using two types of worn rail roller. By verifying the wear rate, determined between the amount of wheel wear and the passing tonnage, and the contact state between rail roller and wheel, we found that wheels traveling on worn rail roller has larger wear rate than on new rail roller.

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