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列车速度的提高和车辆轴重的增加导致轮轨接触应力加大,引起车轮轮辋内部应力分布的变化。根据铸钢车轮轮辋金相分析结果,应用Goodier方程对轮辋处夹杂物和空穴周围的应力状态进行分析。在轮轨接触应力作用下,Al2O3球形夹杂物在其球体的“极点”位置产生应力集中,而空穴处于“赤道”位置,其应力更大。根据Murakami公式,以轴重为25 t的车轮为例,计算在不同运行速度下,距铸钢车轮踏面一定深度的夹杂物临界尺寸。其结果显示,在一定车速下,夹杂物的临界直径随距踏面深度的增加而增大;若深度一定,夹杂物的临界直径则随车速的提高而变小。当轮辋中夹杂物的尺寸大于该临界直径时,轮辋疲劳裂纹就可能萌生。
The increase of train speed and the increase of axle load lead to the increase of wheel-rail contact stress, which causes the change of stress distribution inside the wheel rim. According to the results of the metallographic analysis of wheel rim of cast steel, the Goodier equation is used to analyze the stress state around the inclusions and cavities at the wheel rim. Under the contact stress of the wheel and rail, Al2O3 spherical inclusions have stress concentration in the “pole” position of the sphere, while the holes are in the position of “equator” and the stress is greater. According to the Murakami formula, taking the wheel with 25t axle load as an example, the critical dimension of inclusions at a certain depth from the wheel tread of cast steel under different operating speeds is calculated. The results show that at certain speed, the critical diameter of inclusions increases with the increase of tread depth. If the depth is constant, the critical diameter of inclusions decreases with the increase of vehicle speed. When the size of the inclusions in the rim is larger than the critical diameter, rim fatigue cracks may initiate.