5:15 PM - 6:30 PM
[PPS11-P20] Effects of oblique impacts on catastrophic disruption of rocky bodies simulated by quartz glass
Keywords:catastrophic disruption, oblique impact, impact strength
In this study, we conducted the impact experiments of quartz glass at the impact angle from 90 (head-on collision) to 0 (glancing impact) degrees, and studied the effect of oblique impacts on the degree of disruption and the ejection velocity of the ejecta fragments. We used quartz glass spheres with the size of 5cm and 8cm for the target, and a polycarbonate spherical projectile with the size of 4.75mm was launched at the impact velocity from 2 to 6km/s. The oblique impact was made at 15 to 90 degrees at 4.3km/s under the vacuum condition of 20Pa. After the impact, all the impact fragments were recovered to measure each weight in order to construct the size distribution of these fragments.
We found that the largest fragment mass was almost constant at the impact angle from 90 to 60 degrees, and it suddenly decreased from 60 to 45 degrees for the 5cm target, and then gradually increased up to 15 degrees: the largest fragment mass at 45 degrees was one order of magnitude larger that obtained from the impact between 90 and 60 degrees. Although the impact strength could be strongly affected by the impact angle at the high obliquity smaller than 45 degrees, the modified specific energy (Qc) defined by the normal component of the impact velocity on the impact surface was an appropriate parameter to scale the impact angle on the degree of the impact disruption, then the impact strength (Q*) could be refined by using this modified specific energy, Qc: The obtained impact strength defied by Qc including the oblique impacts is 1110 J/kg for the quartz glass. We also found a very unique feature on the quartz glass during the disruption, that is, the severe disruption and high velocity ejecta was discovered at the antipodal region. The mass of disrupted fragments originated from the antipodal region was almost same as that was originated from the cratered region near the impact site. This might be caused by the severe concentration of the shock wave at the antipodal region and it would be reflected on the free surface with the perfectly spherical shape of the quartz glass. But, further research would be necessary to understand this unique features discovered at the antipode.