蓝宝石晶体七种晶向对16 ~ 86 GPa冲击应力的响应
Response of Seven Crystallographic Orientations of Sapphire Crystals to Shock Stresses of 16 to 86 GPa
摘要：
用时间分辨VISAR干涉法测量了在16 ~ 86 GPa冲击应力范围内具有7个晶向的蓝宝石（单晶Al 2 O3）的冲击波剖面。冲击波传播垂直于每个切口的表面。六方晶体结构的c轴和冲击传播方向之间的角度从0度的c切到90度的m切在基面。基于已发表的冲击诱导的光学透明度，冲击诱导的光学透明度与冲击波轮廓的平滑度相关。最终目标是找到冲击波在蓝宝石中传播的方向，这是最透明的窗口。在蓝宝石晶体和LiF窗口之间的界面处记录粒子速度历史。在大多数情况下，由于变形的不均匀性，测得的波形是有噪声的。Hugoniot弹性限度（HELS）的测量值取决于冲击压缩方向和峰值冲击应力。沿c轴和垂直于c的m方向的冲击载荷记录了最大HEL值。沿m和s方向的冲击压缩伴随着最小的变形不均匀性和最小的塑性冲击波上升时间。M-和S-切割蓝宝石最接近理想的弹塑性流动，这表明M-和S-切割蓝宝石可能是对最高冲击压力保持最透明的取向。在纯弹性形变下，蓝宝石具有非常高的层裂强度，其取决于载荷持续时间和峰值应力。蓝宝石的塑性形变导致其拉伸强度的损失。
英文摘要：
Shock-wave profiles of sapphire (single-crystal Al2O3) with seven crystallographic orientations were measured with time-resolved VISAR interferometry at shock stresses in the range 16 to 86 GPa. Shock propagation was normal to the surface of each cut. The angle between the c-axis of the hexagonal crystal structure and the direction of shock propagation varied from 0 for c-cut up to 90 degrees for m-cut in the basal plane. Based on published shock-induced transparencies, shock-induced optical transparency correlates with the smoothness of the shock-wave profile. The ultimate goal was to find the direction of shock propagation in sapphire that is most transparent as a window. Particle velocity histories were recorded at the interface between a sapphire crystal and a LiF window. In most cases measured wave profiles are noisy as a result of heterogeneity of deformation. Measured values of Hugoniot Elastic Limits (HELs) depend on direction of shock compression and peak shock stress. The largest HEL values were recorded for shock loading along the c-axis and perpendicular to c along the m-direction. Shock compression along the m- and s-directions is accompanied by the smallest heterogeneity of deformation and the smallest rise time of the plastic shock wave. m- and s-cut sapphire most closely approach ideal elastic-plastic flow, which suggests that m- and s-cut sapphire are probably the orientations that remains most transparent to highest shock pressures. Under purely elastic deformation sapphire has very high spall strength, which depends on load duration and peak stress. Plastic deformation of sapphire causes loss of its tensile strength.
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