Wednesday, 13 October 2004 - 1:50 PM

This presentation is part of : Failure of Ceramics and Ceramic Composites

Fragmentation of a Dynamically Expanding Brittle Ring

Fenghua Zhou, K.T. Ramesh, and Jean-Francois Molinari. Johns Hopkins University, 232 Latrobe Hall, 3400 North Charles Street, Baltimore, MD 21218

Brittle materials break into many pieces under rapidly applied loading. The average fragment size and the size distribution are two inseparable characteristics of fragmentation. So far, most investigations on dynamic fragmentation are in two parallel tracks: studying the rate-dependences of fragment size, or studying the fragment size distributions.

We have developed an analytical-numerical approach to analyze the fragmentation process. The analysis renders the sizes of all fragments, from which average size and size distribution are obtained. We have simulated the fragmentation process of a one-dimensional straight bar over a broad strainrate region. In this presentation, we extend the previous work to study the fragmentation process of a circular ring that is dynamically expanded (e.g. by explosive loading). The expanding ring test is a convenient and effective technique to study the dynamic fracture and fragmentation properties of materials under high strain rate tensile loading. A significant advantage of this technique is that the specimen is stretched uniformly at a high loading rate, without significant azimuthal wave propagation in the specimen at the loading stage. We deduce the basic elastodynamic equations that govern the expansion of the ring and develop a numerical integration scheme based on characteristic line differential relationships to solve the governing equations. A dynamic crack initiation criterion and cohesive crack growth model are used to characterize the failure and fracture process. The fragment size and size distributions are discussed through statistical analyses of the results. The influences of the material parameters and the initial defect distributions are also investigated.

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