Dynamic fracture of advanced ceramics under impact loading conditions using a miniaturized Kolsky bar

摘要

Advanced ceramic materials are frequently used in the machining of hardened steels, aerospace alloys and other abrasive materials. While these materials have many superior properties such as high hardness and abrasive resistance they are still prone to premature failure due to fracture. Accurate fracture properties of such materials are scarce, especially in the dynamic regime. The current work presents a novel combined experimental-numerical approach to determine dynamic fracture behavior. In recent years, much attention has been given to the study of dynamic behavior of materials under stress-wave loading. Experimentation with a modified Kolsky bar and a concurrent numerical investigation using the finite volume method was used in this study. The inherent difficulties in producing large amounts of advanced ceramic means that experiments must be carried out using very small samples. As a result the apparatus has been miniaturised to accommodate such specimen dimensions. The incident and reflected wave histories obtained experimentally in conjunction with the time to fracture of the specimen predicted numerically are used to determine fracture toughness at a number of loading rates. Presented is a novel and simple test method to determine fracture properties of advanced ceramics using a miniaturised Kolsky bar. Results indicate a change in fracture toughness at increased rates of loading. This may be due to the complicated underlying microstructure of the materials under investigation, which behave differently under varying loading rates.