镁合金弹丸10km/s撞击铝靶成坑特性实验

为获得10 km/s超高速撞击成坑特性，采用内爆发射器开展了长径比l/d_p为1/2、直径d_p为0.8 cm的镁合金弹丸撞击厚5 cm铝靶的超高速撞击实验，获得了铝靶的撞击成坑尺寸和形貌特性，结合文献数据，分析了成坑形貌与8 km/s以下速度撞击坑的差异和弹丸长径比、速度、动能对成坑尺寸的影响。结果表明:典型的撞击坑不仅包含中心成坑区，还包含了破坏区，成坑区近似半球形弹坑，破坏区为自由表面剥落形成的浅坑；坑深P_c/d_p为1.5～2.0，坑径d_c/d_p为3～3.5，坑形系数P_c/d_c为0.50，成坑效率E/V_c均值为3.74 kJ/cm3；对于l/d_p≤1的弹丸，采用等效直径对坑深进行归一化，归一化后坑深与长径比无关，与速度的2/3次幂成线性关系。

Experiment on crater characteristics of aluminium targets impacted by magnesium projectiles at velocities of about 10 km/s

Crater characteristics formed by the impact of the 5 cm thick Al 6061 targets with magnesium projectiles with length-diameter ratio l/d_p=1/2 and diameter d_p=0.8 cm at velocity of 10 km/s were investigated. The implosion-driven launcher designed by McGill University was manufactured by China Aerodynamics Research and Development Center. Eight experiments were carried out and the obtained maximal projectile velocities were in the range of 9.36?11.43 km/s. The profiles and flight attitude of projectile were snapped by use of the sequence laser shadowgraph imaging instrument. The results show that the projectiles deform obviously during the launching period in some experiments, but more than half projectiles could hold the initial shape well. Craters on targets were recovered and analyzed. A shallow damage area appeared around the semi-spherical crater. Such crater feature was compared with those craters impacted at velocity lower than 8 km/s in literatures and from other experiments with different projectile materials and aluminum types of targets. Typical dimensions of craters were measured. The crater depths P_c/d_p was 1.5?2.0, crater diameters d_c/d_p was 3.0?3.5, crater-shape coefficient P_c/d_c was about 0.50 and cratering efficiency E/V_c was about 3.74 kJ/cm3. Finally, the influences of l/d_p, impact velocity and energy of projectiles on crater dimensions were analyzed along with the experimental data from literatures. An effective diameter of cylindrical projectile was proposed to reduce the effect of l/d_p on the crater depth. And a crater depth formula of aluminum targets impacted by projectiles with different materials and velocities were fitted. Results show that the typical impact crater should not only be the central semi-sphere crater, but also contain shallow damage area formed by surface spallation. The type of target material influences the carter feature significantly. However, the projectile material and flight attitude have little influence on the crater feature. As for projectiles with l/d_p≤1, the crater depth normalized by effective diameter would not vary with l/d_p, but correlate with the impact velocity in form of 2/3 power law.