Continuum and atomistic scale computational mechanics for structures with small length scales. With on-demand call to molecular dynamics simulations and scale up to continuum level constitute models, where predictions can be made for laboratory accessible time and length scales.

Material systems including: crystal plasticity in singly/poly crystalline metals, interfacial/grain-boundary mechanics in nanostructured materials, amorphous solids, nanowires, soft materials.

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高速列车关键结构线路载荷谱特性研究进展

      

      近期,中科院力学所魏宇杰研究员团队在《国际疲劳》(International Journal of Fatigue)发表了题为 "A segmented load spectrum model for high-speed trains and its inflection stress as an indicator for line quality" 的研究文章,揭示了高速列车转向架结构线路载荷谱的分段特性及其与线路质量的内在联系。

       作为高速列车系统的主要承载构件,转向架结构的损伤状态由结构在服役过程中所承受的真实载荷谱决定,它将直接关系到列车运行的稳定性和安全性。理想情况下,人们希望获取转向架结构在全寿命周期内的载荷谱数据,以便对其进行准确的损伤和疲劳寿命估计。然而,由于开展全寿命周期监测的成本高昂,人们通常利用有限的试验数据来描述载荷谱,并将其扩展到全寿命周期。因此,在有限试验数据条件下准确掌握载荷谱特性并提高其表征精度对于提升高速列车服役安全性和结构可靠性具有重要意义。

       该研究以 CRH 380A 型高速动车组为试验平台,在京沪线、京广线、京太线和京成线(图1a)上开展了为期1年多的线路试验,线路涵盖了无砟(300 km/h)和有砟(200 km/h)两种轨道类型。通过分析转向架结构疲劳关键位置的线路应力谱,该团队发现随着分级级数的增加,不同运行线路、轨道类型和运行速度下的应力谱在对数坐标下均呈现出显著的分段特征,并提出了一种分段 Weibull 分布模型来描述该分段特征。与现有模型相比,分段 Weibull 分布模型简可以有效地捕捉应力谱的分段特征(图1b),具有更高的表征精度,且简单易用。更为重要的是,分段Weibull分布模型中的拐点应力可以被用作评价无砟轨道线路质量好坏的一个参数化指标,即线路条件越好,拐点应力越小,拐点应力的分散性越小,对应的单位损伤也越小(图2)。

       该研究对于深入理解高速列车关键结构线路载荷谱特性具有重要意义,同时也有利于关键结构线路载荷谱特性与线路条件之间内在联系的研究。该工作得到了国家自然科学基金委 "非线性力学的多尺度问题研究" 基础科学中心(Grants NO. 11988102),国家重点研发计划项目(2017YFB0202800)、中国科学院先导专项(XDB22020200) 以及复杂系统力学卓越创新中心的支持。

   论文链接:https://www.sciencedirect.com/science/article/pii/S0142112321000815

  

图 1: (a) 试验线路分布示意图,包括京沪线(BS-PDL)、京广线(BG-PDL)、京太线(BT-PDL)和京成线(BC-PDL)。(b) 至 (e) 分别为京广线、京太线、京沪线和京成线上试验获得的转向架应力谱(虚线)与分段 Weibull 分布模型拟合的应力谱(实线)的对比。

图 2:线路条件对分段 Weibull 分布模型中拐点应力的影响:(a) 不同线路分区间拐点应力分布。其中,京广线大部分为无砟轨道,京成线的北京至武汉段与京广线共线,武汉至成都段大部分为有砟轨道。由图可知,无砟轨道上的转向架关键位置应力谱的拐点应力明显大于有砟轨道上的拐点应力。(b) 不同无砟轨道线路区间上获得的线路应力谱的拐点应力与对应的每公里损伤的相关性:线路条件越好,拐点应力越小,相应的每公里损伤也越小。

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