脆性PMMA板中高速裂纹与孔洞的相互作用

Interaction between High Speed Cracks and Holes in Brittle PMMA Plates

脆性断裂导致结构突然失效,为了保证结构安全,寻找一种方法来阻止动态裂纹传播是非常必要的。一个可能的止裂方法是在裂纹路径上布置弱化区,通过减小裂纹尖端应力集中来阻止裂纹传播。本文采用实验方法研究不同形状孔洞对动态传播裂纹的影响。研究表明:裂纹与孤立的孔洞汇交会发生止裂,如果预加荷载过大,或者孔洞有尖锐点,在裂纹所到达的孔洞对侧,可能会产生次生裂纹,导致试件完全破坏;孔洞边缘曲率在对于能否完全止裂起重要作用;采用内聚力单元的显式动态有限元程序能够较好地模拟实验现象。

As structural failure is frequently caused by cracks, reinforcements are then used on the structure to arrest the propagating cracks, thus finding a way to stop the dynamic crack from propagating is of much importance to guarantee the structural integrity. One possible way is to create cavities in the structure along the possible crack path so as to stop the propagating crack by reducing the stress at the tip of the crack. This paper presents the experimental results on the interactions of a dynamically propagating crack with a hole of different shapes. It is shown that the isolated hole can arrest the propagation of the main crack. However, if the applied loading is very high, or the hole has sharp corners, subsequent cracks may be initiated at the opposite side of the hole and propagate further. The side curvature of the hole plays an important role in controlling whether subsequent cracks will be initiated or not. Using the explicit FEM incorporating cohesive elements, the dynamic fractures of the plates are simulated. These numerical simulations provide results that are in agreement with the experimental observations.