5:15 PM - 7:15 PM
[PPS06-P19] High-velocity impact ejecta properties from rocks: Initial report of strain-rate dependence
Keywords:ejecta, strain rate
Impact events are major processes that play an important role in material transport across planetary bodies. In particular, high-velocity ejecta produced by impact events are essential for material transports between planetary and satellite systems. However, data on the relationship between ejecta size, ejection velocity, and ejection angle remain limited. Therefore, we conducted impact experiments using a secondary target method [1] to investigate these relationships. We found that no significant differences in ejecta velocity–angle relationships or maximum ejecta size at a given velocity, depending on the rock type. However, scale-dependent effects should be considered when extrapolating laboratory impact experiments to natural impact events.
In the physical processes occurring near the impact point, where high-velocity ejecta are produced, the strain rate (ε) serves as a key parameter reflecting differences in scale. This strain rate is expressed as ε≈via, where vi and a are the impact velocity and the projectile radius, respectively [2]. The strain rate significantly affects the crack growth processes in target materials [3] and even at the same impact velocity, the strain rate in laboratory experiments is approximately seven orders of magnitude higher than that of planetary impacts over a impactor radius of several tens of kilometers.
In this study, we aim to clarify the effects of strain rate on the relationships among ejecta size, ejection velocity, and ejection angle. To achieve this, we conduct laboratory impact experiments using a two-stage light-gas gun at the Institute of Space and Astronautical Science (ISAS) and a powder gun at Kobe University, varying the strain rate by two orders of magnitude.
This presentation reports on the development of the powder gun experimental setup and presents preliminary findings.
References
[1] Nakamura et al., submitted.
[2] Melosh et al. (1992) J. Geophys. Res. Planets 97, 14735-14759.
[3] Grady & Kipp (1980) Int. J. Rock Mech. Min. Sci. Geomech. Abstr. 17, 147-157.
Acknowledgments
This work was supported by JST SPRING Grant Number, JPMJSP2148, and the Hypervelocity Impact facility at ISAS, JAXA.
In the physical processes occurring near the impact point, where high-velocity ejecta are produced, the strain rate (ε) serves as a key parameter reflecting differences in scale. This strain rate is expressed as ε≈via, where vi and a are the impact velocity and the projectile radius, respectively [2]. The strain rate significantly affects the crack growth processes in target materials [3] and even at the same impact velocity, the strain rate in laboratory experiments is approximately seven orders of magnitude higher than that of planetary impacts over a impactor radius of several tens of kilometers.
In this study, we aim to clarify the effects of strain rate on the relationships among ejecta size, ejection velocity, and ejection angle. To achieve this, we conduct laboratory impact experiments using a two-stage light-gas gun at the Institute of Space and Astronautical Science (ISAS) and a powder gun at Kobe University, varying the strain rate by two orders of magnitude.
This presentation reports on the development of the powder gun experimental setup and presents preliminary findings.
References
[1] Nakamura et al., submitted.
[2] Melosh et al. (1992) J. Geophys. Res. Planets 97, 14735-14759.
[3] Grady & Kipp (1980) Int. J. Rock Mech. Min. Sci. Geomech. Abstr. 17, 147-157.
Acknowledgments
This work was supported by JST SPRING Grant Number, JPMJSP2148, and the Hypervelocity Impact facility at ISAS, JAXA.