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A novel experimental technique for advanced materials

 

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. The team showed 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 Embedded Image ~2 × 108 to 3.5 × 108 s−1. 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. The 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.

 

More: B. Albertazzi, N. Ozaki, V. Zhakhovsky, A. Faenov, H. Habara, M. Harmand, N. Hartley, D. Ilnitsky, N. Inogamov, Y. Inubushi, T. Ishikawa, T. Katayama, T. Koyama, M. Koenig, A. Krygier, T. Matsuoka, S. Matsuyama, E. McBride, K. Petrovich Migdal, G. Morard, H. Ohashi, T. Okuchi, T. Pikuz, N. Purevjav, O. Sakata, Y. Sano, T. Sato, T. Sekine, Y. Seto, K. Takahashi, K. Tanaka, Y. Tange, T. Togashi, K. Tono, Y. Umeda, T. Vinci, M. Yabashi, T. Yabuuchi, K. Yamauchi, H. Yumoto and R. Kodama, Dynamic fracture of tantalum under extreme tensile stress, ScienceAdvances 3, e1602705 (2017)