Wednesday, 13 October 2004 - 1:25 PM

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

Fragmentation of Ceramics under Dynamic Compressive Loading Using a Grain-Level Finite Element Method

Spandan Maiti and Philippe H. Geubelle. Department of Aerospace Engineering and Beckman Institute, University of Illinois at Urbana-Champaign, Urbana, IL 61801

Dynamic fragmentation of brittle materials can be observed in various applications from ore crushing to the failure of ceramic components in jet and rocket engines. Most of the analytical and numerical studies of this phenomenon have been performed assuming homogenized continuum properties. This study focuses on one class of brittle materials, ceramics, subjected to dynamic compressive loading conditions. The numerical analysis is performed at the mesoscale level taking into account the granular microstructure of the material. An explicit cohesive/volumetric finite element scheme is used to simulate the constitutive and failure response of the ceramic specimen subjected to uniform or impact-induced compressive loading. Failure is assumed to be of intergranular nature and the cohesive elements are placed only along the grain boundaries. A rate-independent, damage-dependent cohesive failure model is used to characterize the progressive failure of the cohesive surfaces. Contact between the fracture surfaces and between the fragments is captured through a cohesive element based penalty formulation. The damage evolution during the fragmentation process is characterized in terms of two different and complementary damage parameters: the first one takes into account the initiation and propagation of the distributed damage (or micro-cracks) as cohesive surfaces progressively fail under the effect of the dynamic loading conditions; the second one characterizes the coalescence of the micro-cracks and the creation of fragments. Special emphasis is placed on the analysis of the frictional contact effect on the initiation, propagation and final extent of the fragmentation process.

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