When a dynamic crack front travels through material heterogeneities, elastic waves are emitted, which perturb the crack and change the morphology of the fracture surface. For asperity-free crystalline materials, crack propagation along preferential cleavage planes is expected to present a smooth crack front and form a mirror-like fracture surface. Surprisingly, we show here that in single crystalline silicon without material asperities, the crack front presents a local kink during high-speed crack propagation. Meanwhile, local oscillations of the crack front, which can move along the crack front, emerge at the front kink position and generate periodic fracture surface corrugations. They grow from angstrom amplitude to a few hundred nanometers and propagate with a long lifetime at a frequency-dependent speed, while keeping a scale-independent shape. In particular, the local front oscillations collide in a particle-like manner rather than proceeding with a linear superposition upon interaction, which presents the characteristic of solitary waves. We propose that such a propagating mode of the crack front, which results from the fracture energy fluctuation at a critical crack speed in the silicon crystal, can be considered as nonlinear elastic waves that we call “corrugation waves.”

当动态裂纹前沿穿过材料的非均质性时，会发出弹性波，从而扰动裂纹并改变断裂表面的形态。对于无粗糙结构的晶体材料，预期沿优先分裂面的裂纹扩展会呈现出平滑的裂纹前沿并形成镜面状的断裂表面。出乎意料的是，我们在这里表明，在没有材料粗糙的单晶硅中，裂纹前沿在高速裂纹扩展过程中呈现出局部扭结。同时，裂纹前沿的局部振荡可以沿着裂纹前沿移动，出现在前端的扭结位置，并产生周期性的断裂表面波纹。它们从埃的振幅增长到几百纳米，并以与频率有关的速度以长寿命传播，同时保持与尺寸无关的形状。特别地，局部前振荡以粒子状方式碰撞，而不是在相互作用时线性叠加，这表现出孤立波的特征。我们认为，这种由硅晶体临界裂纹速度下的断裂能波动引起的裂纹前沿的传播模式可以被视为非线性弹性波，我们称之为“波纹波”。