The present paper studies fatigue crack growth (FCG) produced by a load pattern obtained numerically in a simulation of trains crossing a real bridge. It uses a model where the cyclic plastic deformation is assumed to be the main damage mechanism and that cumulative plastic strain at the crack tip is the driving parameter for FCG. The accumulation of damage was found to be very irregular along each load block, the major part occurring in the overload region. Plasticity induced crack closure is relatively high due to the periodic application of overloads, playing a major role. The overload produces crack tip blunting, increasing the effective load range in subsequent load cycles. The maximum elastic load range was quantified and used to eliminate load cycles not producing fatigue damage, which is important to reduce the numerical effort. The comparison of Finite Element Model (FEM) predictions with NASGRO results, showed that this gives a non-conservative difference of 23% in the number of load cycles after 1 mm of crack growth.

中文翻译：

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桥梁中火车产生的频谱载荷引起的疲劳裂纹扩展


本文研究了在火车穿越真实桥梁的仿真中以数值方式获得的载荷模式产生的疲劳裂纹扩展 （FCG）。它使用的模型假设循环塑性变形是主要损伤机制，裂纹尖端的累积塑性应变是 FCG 的驱动参数。发现沿每个负载块的损坏累积非常不规则，主要发生在过载区域。由于周期性施加过载，塑性诱导的裂纹闭合相对较高，起着重要作用。过载会产生裂纹尖端钝化，从而增加后续负载循环中的有效负载范围。最大弹性载荷范围被量化并用于消除不产生疲劳损伤的载荷循环，这对于减少数值工作量非常重要。有限元模型 （FEM） 预测与 NASGRO 结果的比较表明，在裂纹增长 1 mm 后，载荷循环次数的非保守差异为 23%。