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Pressure sensitive flow and constraint factor in amorphous materials below glass transition

Prasad, K Eswar and Keryvin, V and Ramamurty, U (2009) Pressure sensitive flow and constraint factor in amorphous materials below glass transition. In: International Symposium on Indentation Behavior of Materials, FEB, 2008, Hyderabad, pp. 890-897.

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The constraint factor, C (given by the hardness-yield strength ratio H/Y in the fully lastic regime of indentation), in metallic glasses, is greater than three, a reflection of the sensitivity of their plastic flow to pressure. Furthermore, C increases with increasing temperature. In this work, we examine if this is true in amorphous polymers as well, through experiments on amorphous poly(methyl methacrylate) (PMMA). Uniaxial compression as well as spherical indentation tests were conducted in the 248-348 K range to construct H/Y versus indentation strain plots at each temperature and obtain the C-values. Results show that C increases with temperature in PMMA as well. Good correlation between the loss factors, measured using a dynamic mechanical analyzer, and C, suggest that the enhanced sensitivity to pressure is possibly due to beta-relaxation. We offer possible mechanistic reasons for the observed trends in amorphous materials in terms of relaxation processes.

Item Type: Conference Paper
Publisher: Materials research society
Additional Information: Copyright for this article belongs to Materials research society.
Department/Centre: Division of Mechanical Sciences > Materials Engineering (formerly Metallurgy)
Date Deposited: 23 Dec 2009 09:41
Last Modified: 19 Sep 2010 05:37
URI: http://eprints.iisc.ac.in/id/eprint/21469

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