IMPACT AGAINST ROCK. Takafumi Matsui*, Toshihiko Waza*, Kouki Kani** and Shoji Suzuki***, * Geophysical Institute, Faculty of Science, Univ
PHENOMENA ASSOCIATED WITH LOW-VELOCITY (10 Q 300 m/sec) IMPACT AGAINST ROCK. Takafumi Matsui*, Toshihiko Waza*, Kouki Kani** and Shoji Suzuki***, * Geophysical Institute, Faculty of Science, Univ. of Tokyo, ** Faculty of Education, Okayama Univ., *** Faculty of Engineering, Kyoto Univ.. It is believed that planets were formed by accretion of planetesimals. Matsui and Mizutani (1977) pointed out that the collisional behaviour of rocks composing planetesimals have play- ed an important role in the early stage of planetary formation. Collisional evolution-of mass-distribution spectrum of planetes- imals was shown to be influenced significantly by the relations characterizing the collisions-1 phenomena (Matsui, 1978, 1979). However, impact phenomena associated with collision have not been fully understood so far. It has been shown from the recent the- oretical studies on the random velocity distribution of planetes- imals that the mean impact velocity between planetesimals with the mass of 1018 g was in the range of 10 to 100 m/sec (e.g. Nakagawa, 1978). The collisional phenomena associated with such a low-velocity impact have, specifically, not been studied. Therefore, we performed the low-velocity impact experiment on rocks to reveal a nature of the collision process of planetes- imals. Using the 15 mm powder gun facility of faculty of Engi- neering, Kyoto University, projectiles of the cylindrical mild- steel (15CK, carbon content is 0.15 %) and rocks (tuff and basalt) were fired against four kinds of rocks (tuff, basalt, granite and dunite). Impact velocity ranges from%10 to~300m/sec. Mass ratio between projectile and target is almost 1. Thus, the im- parted energy to unit taget mass, ~i,ranges from 1.106 to %lo8 erg/g.- - The phenomena associated with the impact of the mild-steel against the spherical rock target were classified into five cat- egories.
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