13th International Conference on Fracture June 16–21, 2013, Beijing, China -1- Dynamic fracture of advanced ceramics under impact loading conditions using a miniaturized Kolsky bar Declan McNamara*, Patricia Alveen1, Declan Carolan1, Neal Murphy1, Alojz Ivanković1 1 School of Mechanical and Materials Engineering, University College Dublin, Ireland * Corresponding author: Declan.mc-namara@ucdconnect.ie Abstract 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. Keywords Dynamic Fracture, miniaturized Kolsky bar, advanced ceramics 1. Introduction As opposed to static fracture toughness, no standard methodology yet exists for the determination of the dynamic fracture toughness of materials. Under static conditions the stress intensity factor at the crack tip is proportional to the applied load, under dynamic loading this does not hold true. This is due to the inertial effects, which result from the transient loading conditions. Other factors affecting the determination of dynamic fracture toughness include wave propagation within the test specimen and the accurate determination of crack initiation. Traditionally dynamic fracture experiments were performed using the instrumented Charpy pendulum [1]. In this test setup strain gauges mounted on the hammerhead measure the response resulting from the impact on a specimen, [2, 3]. While this test method is well established and easily performed there exists a number of drawbacks. During the dynamic impact strong inertial forces affect the load applied at the crack tip. The hammer impact load is recorded by the strain gauge located at its head and this is used to determine the fracture parameters through the resulting load-time history. However due to the inertial forces present the applied load recorded by the
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