Impact Fracture Behavior and Fracture Criterion of Brittle Beams, plates and Circular Rings

夹层安全玻璃的方板，其夹层为聚乙烯醇缩丁醛，通过圆形钢冲头下落横向冲击并穿孔。通过与频闪仪相连的摄像机拍摄相应的断裂行为。夹层安全玻璃的穿透断裂由以下三个步骤组成：第一步是与冲击面相对的外层玻璃的脆性断裂，第二步是聚乙烯醇缩丁醛外层的脆性断裂。通过改变冲头的下落高度，测定了外层玻璃的起始冲击能U_1和U_2的极限值，即冲击能U_1和U_2的极限值。U_1与外层玻璃的厚度成比例地增加。U_p随夹层厚度的增加而增大。外层玻璃的U_p与裂纹扩展现象的关系最密切。考虑到上述关系和板的材料特性，提出了U_p的估算公式.

Square plates of laminated safety glass, of which interlayer is the polyvinyl butyral, are impacted transversely by dropping a circular steel punch and perforated. the corresponding fracture behaviors are photographed by a camera connected with the stroboscope. The penetration fracture of the laminated safety glasses consists of the following three steps;The first step is the brittle fracture of the opposite outerlayer glass to impact side, the second step is the brittle fracture of the outerlayer of the polyvinly butyral. The limits of the impact energies U_1 and U_2, which are the energy to initiate crack in the outerlayer glass and the penteration energy of punch, are measured by changing the dropping height of punch. U_1 increases proportionally to the thickness of outerlayer glass. U_p incrases proportionally to the thickness of interlayer. The strongest relation was observed between U_p and the crack propagation phenomena in outerlayer glasses. Considering the relations mentioned above and material properties of plate, the formula estimating U_p is proposed.