Albertazzi Bruno, Ozaki Norimasa, Zhakhovsky Vasily, Faenov Anatoly, Habara Hideaki, Harmand Marion, Hartley Nicholas, Ilnitsky Denis, Inogamov Nail, Inubushi Yuichi, Ishikawa Tetsuya, Katayama Tetsuo, Koyama Takahisa, Koenig Michel, Krygier Andrew, Matsuoka Takeshi, Matsuyama Satoshi, McBride Emma, Migdal Kirill Petrovich, Morard Guillaume, Ohashi Haruhiko, Okuchi Takuo, Pikuz Tatiana, Purevjav Narangoo, Sakata Osami, Sano Yasuhisa, Sato Tomoko, Sekine Toshimori, Seto Yusuke, Takahashi Kenjiro, Tanaka Kazuo, Tange Yoshinori, Togashi Tadashi, Tono Kensuke, Umeda Yuhei, Vinci Tommaso, Yabashi Makina, Yabuuchi Toshinori, Yamauchi Kazuto, Yumoto Hirokatsu, Kodama Ryosuke
Graduate School of Engineering, Osaka University, Suita, Osaka 565-0871, Japan.
LULI, École Polytechnique, CNRS, Commissariat à l'Energie Atomique et aux Energies Alternatives, Pierre and Marie Curie University (UPMC), 91128 Palaiseau, France.
Sci Adv. 2017 Jun 2;3(6):e1602705. doi: 10.1126/sciadv.1602705. eCollection 2017 Jun.
The understanding of fracture phenomena of a material at extremely high strain rates is a key issue for a wide variety of scientific research ranging from applied science and technological developments to fundamental science such as laser-matter interaction and geology. Despite its interest, its study relies on a fine multiscale description, in between the atomic scale and macroscopic processes, so far only achievable by large-scale atomic simulations. Direct ultrafast real-time monitoring of dynamic fracture (spallation) at the atomic lattice scale with picosecond time resolution was beyond the reach of experimental techniques. We show that the coupling between a high-power optical laser pump pulse and a femtosecond x-ray probe pulse generated by an x-ray free electron laser allows detection of the lattice dynamics in a tantalum foil at an ultrahigh strain rate of [Formula: see text] ~2 × 10 to 3.5 × 10 s. A maximal density drop of 8 to 10%, associated with the onset of spallation at a spall strength of ~17 GPa, was directly measured using x-ray diffraction. The experimental results of density evolution agree well with large-scale atomistic simulations of shock wave propagation and fracture of the sample. Our experimental technique opens a new pathway to the investigation of ultrahigh strain-rate phenomena in materials at the atomic scale, including high-speed crack dynamics and stress-induced solid-solid phase transitions.
对于从应用科学与技术发展到激光与物质相互作用及地质学等基础科学在内的广泛科学研究而言，理解材料在极高应变率下的断裂现象是一个关键问题。尽管其颇受关注，但其研究依赖于在原子尺度与宏观过程之间进行精细的多尺度描述，而到目前为止，这仅能通过大规模原子模拟来实现。以皮秒时间分辨率在原子晶格尺度上直接对动态断裂（层裂）进行超快实时监测超出了实验技术的能力范围。我们表明，高功率光学激光泵浦脉冲与由X射线自由电子激光产生的飞秒X射线探测脉冲之间的耦合，能够以高达[公式：见原文]~2×10至3.5×10 s的超高应变率检测钽箔中的晶格动力学。利用X射线衍射直接测量到，与在约17 GPa的层裂强度下开始层裂相关的最大密度下降为8%至10%。密度演化的实验结果与样品中冲击波传播和断裂的大规模原子模拟结果吻合良好。我们的实验技术为在原子尺度上研究材料中的超高应变率现象开辟了一条新途径，包括高速裂纹动力学和应力诱导的固 - 固相变。
