The fatigue assessment of structural components, especially made of ductile cast iron subjected to complex loading conditions, heavily relies on analyzing fatigue damage resulting from stress concentrations induced by geometric irregularities like notches and shrinkage pores. Standard methodologies, encompassing the Theory of Critical Distances (TCD), Strain Energy Density (SED), and Critical Plane (CP), have played pivotal roles in predicting fatigue strength for components featuring such irregularities. In this work, the authors explore the applicability of the Effective Critical Plane (ECP) approach on ductile cast iron notched specimens subjected to multiaxial and non-proportional loading conditions. The method focuses on evaluating the critical plane factor, after averaging the stress and strain field within a given control volume or area (i.e. defined by a control radius), centered on the critical node. The study aims to enhance the accuracy of fatigue life prediction for structural components made of ductile cast iron, thereby contributing to the improvement and practical applicability of fatigue assessment under complex loading conditions. The methodology, integrating the Smith-Watson-Topper and Fatemi-Socie CP factor, was applied to several experimental fatigue data obtained from ductile cast iron notched specimens, tested under multiaxial non-proportional loading conditions. After establishing the control radius associated with the investigated material, the method was utilized to perform a fatigue life forecast analysis on a specimen with porous defects.

中文翻译：

---

有效临界平面方法在多轴和非比例载荷条件下球墨铸铁疲劳评估中的应用


结构部件的疲劳评估，尤其是由球墨铸铁制成的结构部件，在复杂的载荷条件下，在很大程度上依赖于分析由凹槽和缩孔等几何不规则性引起的应力集中引起的疲劳损伤。包括临界距离理论 （TCD）、应变能密度 （SED） 和临界平面 （CP） 在内的标准方法在预测具有此类不规则性的部件的疲劳强度方面发挥了关键作用。在这项工作中，作者探讨了有效临界平面 （ECP） 方法在多轴和非比例载荷条件下的球墨铸铁缺口试样的适用性。该方法侧重于在以临界节点为中心的给定控制体积或区域（即由控制半径定义）内对应力和应变场求平均值后，评估临界平面因子。该研究旨在提高球墨铸铁结构构件疲劳寿命预测的准确性，从而有助于改进复杂载荷条件下疲劳评估的改进和实际适用性。该方法整合了 Smith-Watson-Topper 和 Fatemi-Socie CP 因子，应用于从球墨铸铁缺口试样获得的几个实验疲劳数据，并在多轴非比例载荷条件下进行测试。在确定与所研究材料相关的控制半径后，该方法用于对具有多孔缺陷的试样进行疲劳寿命预测分析。