Physics Department and Center for Interdisciplinary Research on Complex Systems, Northeastern University, Boston, Massachusetts 02115, USA.
Laboratoire FAST, Univ Paris Sud, CNRS, Université Paris-Saclay, F-91405 Orsay, France.
Phys Rev Lett. 2015 Dec 31;115(26):265503. doi: 10.1103/PhysRevLett.115.265503. Epub 2015 Dec 30.
A planar crack generically segments into an array of "daughter cracks" shaped as tilted facets when loaded with both a tensile stress normal to the crack plane (mode I) and a shear stress parallel to the crack front (mode III). We investigate facet propagation and coarsening using in situ microscopy observations of fracture surfaces at different stages of quasistatic mixed-mode crack propagation and phase-field simulations. The results demonstrate that the bifurcation from propagating a planar to segmented crack front is strongly subcritical, reconciling previous theoretical predictions of linear stability analysis with experimental observations. They further show that facet coarsening is a self-similar process driven by a spatial period-doubling instability of facet arrays.
当平面裂纹同时承受垂直于裂纹面的拉伸应力（I 型模式）和平行于裂纹前缘的剪切应力（III 型模式）时，通常会分裂成一系列倾斜的“子裂纹”。我们使用准静态混合模式裂纹扩展过程中不同阶段的断裂表面的原位显微镜观察和相场模拟来研究面的扩展和粗化。结果表明，从平面扩展到分段裂纹前缘的分叉是强烈亚临界的，这与先前线性稳定性分析的理论预测和实验观察结果一致。它们进一步表明，面的粗化是由面列的空间倍周期不稳定性驱动的自相似过程。
