Abstract This study investigates the angles θ1, θ2, and θ3 that squat crack faces form with respect to three orthogonal planes: the rail top, the longitudinal-vertical cross-section and the lateral-vertical cross-section. Rail samples with squats of various severities are obtained from the field. Their three-dimensional crack networks are reconstructed using CT (computed tomography) scanning and serial cutting. A 3D visualization method, together with the necessary geometric definitions, is developed for enabling effective measurement and characterization of the squat cracks. It is found that the cracks can be characterized by four orientations (T1 – T4). The variation ranges of the crack angles are determined for each orientation that satisfies 132° ≤θ1 ≤ 150°, 6° ≤θ2 ≤ 36° and 67° ≤θ3 ≤ 81°. By investigating the occurrence frequency of the orientations, it is found that T4 and T1 together form the primary V-shaped cracks of the squats, and T2 and T3 together form the secondary V-shaped cracks. A finite element modelling of the wheel-track system, in combination with contact mechanics and multi-axial fatigue analysis, successfully relates the stress state to the RCF cracks.

中文翻译：

---

通过 CT 扫描和金相观察确定浅裂纹的角度

摘要 本研究研究了下沉裂纹面相对于三个正交平面形成的角度θ1、θ2和θ3：钢轨顶部、纵向垂直截面和横向垂直截面。从现场获得具有各种严重程度的深蹲的铁路样本。他们的三维裂缝网络是使用 CT（计算机断层扫描）扫描和连续切割重建的。开发了一种 3D 可视化方法以及必要的几何定义，以实现对深蹲裂缝的有效测量和表征。发现裂纹可以用四个方向（T1-T4）来表征。对于满足132°≤θ1≤150°、6°≤θ2≤36°和67°≤θ3≤81°的每个取向，确定裂纹角度的变化范围。通过考察取向的出现频率，发现T4和T1共同形成深蹲的初级V型裂纹，T2和T3共同形成次级V型裂纹。轮轨系统的有限元建模，结合接触力学和多轴疲劳分析，成功地将应力状态与 RCF 裂纹相关联。