Moulinet Sébastien, Adda-Bedia Mokhtar
Laboratoire de Physique Statistique, Ecole Normale Supérieure, UPMC Paris 6, Université Paris Diderot, CNRS, 24 rue Lhomond, 75005 Paris, France.
Phys Rev Lett. 2015 Oct 30;115(18):184301. doi: 10.1103/PhysRevLett.115.184301.
Understanding the physics of fragmentation is important in a wide range of industrial and geophysical applications. Fragmentation processes involve large strain rates and short time scales that take place during crack nucleation and propagation. Using rubber membranes, we develop an experimental analysis that enables us to track the fragmentation process in situ in both time and space. We find that bursting a highly stretched membrane yields a treelike fragmentation network that originates at a single seed crack, followed by successive crack tip-splitting events. We show that a dynamic instability drives this branching mechanism. Fragmentation occurs when the crack tip speed attains a critical velocity for which tip splitting becomes the sole available mechanism of releasing the stored elastic energy. Given the general character of the fragmentation processes, this framework should be applicable to other crack networks in brittle materials.
了解破碎的物理过程在广泛的工业和地球物理应用中都很重要。破碎过程涉及裂纹形核和扩展过程中出现的大应变率和短时间尺度。通过使用橡胶膜，我们开展了一项实验分析，使我们能够在时间和空间上原位追踪破碎过程。我们发现，使高度拉伸的膜破裂会产生一个树状破碎网络，该网络起源于单个种子裂纹，随后是连续的裂纹尖端分裂事件。我们表明，一种动态不稳定性驱动了这种分支机制。当裂纹尖端速度达到一个临界速度时就会发生破碎，此时尖端分裂成为释放储存弹性能量的唯一可用机制。鉴于破碎过程的一般特性，该框架应适用于脆性材料中的其他裂纹网络。
