车轮踏面磨耗导致车轮外形改变，使其滚动圆直径产生偏差，对车辆系统的动力学特性影响较大。

Wheel tread wear leads to change of the wheel profile and rolling diameter, which influences the dynamic behaviors of railway vehicles seriously.

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在曲线处的内轨和外轨通常打磨成不对称的形状，目的是改善共形接触，增大内外车轮滚动圆的直径差，利于导向。

Curves generally are ground with asymmetric profiles that promote conformal contact in order to take advantage of the rolling radius difference and enhance steering.

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鲁鲁想，既然圆环可以滚动，西瓜也可以滚动，因为它也是圆的。

Lulu thought since the round hoop can roll, the watermelon can roll too, because it was also round.

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