Dynamic Behavior of an Ordinary Chondrite: the Effects of Microstructure on Strength, Failure and Fragmentation

Article · August 2015with153 Reads
DOI: 10.1016/j.icarus.2015.07.027
Knowledge of the relationships between microstructure, stress-state and failure mechanisms is important in the development and validation of numerical models simulating large-scale impact events. In this study, we investigate the effects of microstructural constituent phases and defects on the compressive and tensile strength, failure, and fragmentation of a stony meteorite (GRO 85209). In the first part of the paper we consider the effect of defects on the strength and failure. Strengths are measured and linked with detailed quantification of the important defects in this material. We use the defect statistic measurements in conjunction with our current understanding of rate-dependent strengths to discuss the uniaxial compressive strength measurements of this ordinary chondrite with those of another ordinary chondrite, with a different defect population. In the second part of the paper, we consider the effects of the microstructure and defects on the fragmentation of GRO 85209. Fragment size distributions are measured using image processing techniques and fragments were found to result from two distinct fragmentation mechanisms. The first is a mechanism that is associated with relatively smaller fragments arising from individual defect grains and the coalescence of fractures initiating from microstructure defects. This mechanism becomes more dominant as the strain-rate is increased. The second mechanism is associated with larger fragments that are polyphase and polygrain in character and is dependent on the structural failure mechanisms that are activated during load. In turn, these are dependent on (for example) the strain-rate, stress state, and specimen geometry. The implications of these results are briefly discussed in terms of regolith generation and catastrophic disruption.
    • Spall, and failure in materials are of interest for a wide range of fields applications including ballistic penetration, dynamic fragmentation in hypervelocity particle target interactions, optical, diagnostic equipment hazards in high energy density (HED) facility chambers, and asteroid and meteor dynamics as they enter the atmosphere and break up[61][62][63]. Previous research by the U.S. Army Research Laboratory (ARL) has studied spall in several different metals, in order to provide protection from 'behind-armor debris'. There has been extensive study of spall strength and its mechanisms of dynamic failure in fcc metals.
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