轨底坡对重载铁路钢轨疲劳裂纹萌生寿命的影响

Influence of track cant on fatigue crack initiation life of heavy-haul rails

合理的轨底坡参数可以优化轮轨间的接触状态,降低钢轨萌生裂纹的概率。为研究轨底坡参数对钢轨疲劳裂纹萌生寿命的影响,基于弹塑性接触理论,建立三维瞬态轮轨接触有限元模型,模拟不同轨底坡参数下(1:10,1:20,1:30,1:40,1:50和1:60)重载铁路轮轨间接触状态。根据Jiang-Sehitoglu损伤参量理论以及临界平面理论分析不同的轨底坡参数对钢轨疲劳裂纹萌生寿命的影响。研究结果表明:直线线路中,CHN75型钢轨采用1:20这一轨底坡参数时,轮轨间接触面积最大,钢轨表面的接触应力最小,轮轨间匹配程度最好,钢轨可通过轮对的极限次数最大;CHN60型钢轨采用1:40这一轨底坡参数时,轮轨间匹配程度最好,钢轨疲劳裂纹萌生寿命最大。对于重载铁路而言,2种类型钢轨均选用较为适配的轨底参数时,CHN75型钢轨与车轮的匹配程度优于CHN60型钢轨,疲劳裂纹萌生寿命也明显大于CHN60型钢轨。曲线线路中,轮对偏移量小于等于6 mm情况下,内外轨均选用1:20的轨底坡时,钢轨表面接触应力最小,轮轨间匹配状态最好,钢轨可通过轮对的极限次数最大,而当轮对偏移量达到9 mm时,选用1:30(外轨)、1:20(内轨)的非对称轨底坡形式可有效降低钢轨萌生疲劳裂纹的概率,延长钢轨的服役期限。

Reasonable rail cant parameters can optimize the wheel-rail contact state and reduce the probability of rail crack initiation.In order to research the influence of rail cant parameters on rail fatigue crack initiation life,a three-dimensional transient wheel-rail contact finite element model was established based on the elastic-plastic contact theory to simulate wheel-rail contact state under different rail cant parameters(1:10,1:20,1:30,1:40,1:50,1:60)of heavy railway.According to Jiang-Sehitoglu,s damage parameter theory and critical plane theory,the influence of different rail cant parameters on rail fatigue crack initiation life was analyzed.The results are drawn as follows.When CHN75 rail adopts the rail cant parameter of 1:20,the contact area between wheel and rail is the largest,the contact stress on the rail surface is the smallest,the matching degree between wheel and rail is the best,and the limit number that rail can pass through the wheels is the largest.When the CHN60 rail adopts rail cant parameter of 1:40,the wheel-rail matching degree is the best,and the rail fatigue crack initiation life is the largest.For heavy railway,the matching degree of CHN75 rail and wheel is better than CHN60 rail when they all choose suitable rail cant.Tthe fatigue crack initiation life is obviously longer than that of CHN60 rail.In the curve line,when the wheels,offset is less than or equal to 6 mm,the inner and outer rails both choose the rail cant parameters of 1:20,the rail surface contact stress is the minimum,the wheel-rail matching state is the best,and the limit number that rail can pass through the wheels is the maximum.When the wheels,offset reaches 9mm,the selection of 1:30(outer rail)and 1:20(inner rail)asymmetrical rail cant parameters can effectively reduce the probability of fatigue crack initiation and prolong the life of rail.