边缘冲击(EOI)作用下透明陶瓷破坏特性研究

Failure characteristics of three transparent ceramics materials under the edge-on impact loading

相较于传统透明材料,相同面密度下透明陶瓷具有更优异的抗冲击性能,使其成为极具应用前景的透明装甲防护材料。研究透明陶瓷在冲击下的破坏响应及损伤演化规律,对透明陶瓷装甲的结构设计及防护能力的提高起到至关重要的作用。为了比较传统透明材料与典型透明陶瓷材料在冲击过程中的破坏特性差异,利用9 mm弹道枪发射平台进行了浮法玻璃、YAG透明陶瓷及镁铝尖晶石透明陶瓷3种透明材料的边缘冲击试验,破片发射速度为200~300 m/s。通过高速摄影捕捉破片的撞击过程,分析了粉碎区及主裂纹扩展距离随时间的变化规律。结果表明,3种材料在不同速度破片的冲击作用下,粉碎区面积与材料强度呈负相关性。对同种材料,在200~300 m/s速度范围内,破片撞击速度对主裂纹的扩展速度没有影响。同时比较了玻璃与透明陶瓷在宏观尺度上的损伤演化特征差异:玻璃在粉碎区两侧产生三角形的次裂纹区域,陶瓷材料则会产生细长的次裂纹簇,并会产生较明显的裂纹“分叉”现象。利用扫描电子显微镜对回收到的陶瓷碎片进行观测,并分析了2种透明陶瓷材料在细观尺度破坏特征的异同。2种透明陶瓷的径向裂纹断面上会出现从沿晶断裂到穿晶断裂的过渡变化,而环向断裂面上几乎都是沿晶和穿晶混合断裂。2种透明陶瓷中,仅YAG透明陶瓷在沿晶断裂时会出现晶体“剥落”现象。

Compared with traditional transparent materials,transparent ceramics have excellent impact resistance at the same areal density,which contributes to its giant potential in the field of transparent armor protection.The studies of the damage response and damage evolution law of transparent ceramics under impact play a vital role in the structural design and protection of transparent ceramic armors.In order to compare the difference between traditional transparent materials and typical transparent ceramic materials under the impact damage process,a 9 mm-ballistic gun launch platform was used to conduct edge-on impact(EOI)tests on three transparent materials,including float glass,YAG transparent ceramics and magnesium aluminum spinel transparent ceramics.The impact process of the fragments was captured by a high-speed video camera,and the change rule of the crushing zone and the propagation distance of the main crack over time was analyzed.The results show that the area of the crushing zone in three materials was negatively correlated with the strength of the material when the fragment impact velocity ranged from 200 to 300 m/s.For the same material,within this velocity range,the impact velocity of the fragments had no significant effect on the propagation velocity of the main crack.Besides,the macroscale differences on the damage evolution characteristics of three materials are investigated.Through the scanning electron microscope(SEM)observation on the recovered ceramic fragments,the similarities and differences on the damage characteristics of the two transparent ceramic materials at the mesoscale are analyzed in detail.The change that intergranular fracture transformed into transgranular fracture on the radial crack occurred in both spinel and YAG transparent ceramics,while the ring fracture surfaces were almost all along the intergranular fracture.Compared with the magnesium aluminum spinel transparent ceramics,YAG transparent ceramics possessed“peel off”phenomenon that fracture occurred along the grain boundary.Besides,the transgranular fracture surface in MgAl_(2)O_(4) transparent ceramics was in jagged irregular shape,while that of YAG transparent ceramics was smooth.