中文摘要：

为了研究40CrNi2Si2MoVA低合金超高强度钢的跨尺度疲劳失效行为,以约束应力区描述材料的损伤过程,以跨尺度应变能密度因子作为疲劳裂纹扩展的控制参量,建立宏微观跨尺度疲劳裂纹扩展统一模型。采用上述模型,利用光滑试样（应力集中系数Kt=1）的试验S-N曲线,拟合出疲劳模型中的材料参数。当考虑材料微结构对疲劳寿命的影响时,该模型可精确再现出疲劳试验数据的发散特性。利用该模型对不同应力集中系数下（Kt=2,3）含缺口试样的疲劳寿命进行了预测,理论计算结果与试验结果吻合良好。研究结果表明,合金钢材料的初始缺陷及微结构的演化特性,对疲劳寿命有显著影响,是疲劳试验数据发散的主要原因。

英文摘要：

40CrNi2Si2MoVA steel material is a low alloy and super-high strength steel material and its trans-scale fatigue failure behavior is investigated.The fatigue damage process is described by a restraining stress zone.By taking the trans-scale strain energy density factor as the controlling parameter of fatigue crack growth,a unified micro/macro trans-scale fatigue crack growth model is proposed.The material fatigue parameters in the model are determined from the S-Ntest data for the smooth specimens with the stress concentration factor Kt =1.When the microscopic effects are taken into account,the scattered fatigue test data for smooth specimens are accurately re-produced by the proposed model.The fatigue lives for the notched specimens with different values of Kt（Kt=2,3）are predicted.The predicted results are in good agreement with the experimental results.The results show that the initial defects and the evolution of the material micro-structures have a large influence on the material fatigue life,which is the main reason of the scatter of fatigue test data.