A Microcrack Model of Dilatancy in Brittle Materials

[+] Author and Article Information
S. Nemat-Nasser

University of California, San Diego, La Jolla, CA 92093

M. Obata

Department of Applied Mechanics and Engineering Sciences, University of California, San Diego, La Jolla, CA 92093

J. Appl. Mech 55(1), 24-35 (Mar 01, 1988) (12 pages) doi:10.1115/1.3173647 History: Received November 17, 1986; Revised August 21, 1987; Online July 21, 2009


For a solid containing preexisting flaws, overall nonlinear constitutive relations are developed on the basis of a model which endows a preexisting flaw with frictional and cohesive resistance, and which includes nucleation and growth of tension cracks at the preexisting flaw, as it deforms under the action of an overall compressive load. The preexisting flaws may be randomly distributed or may have an initial preferential distribution. They may be of varying sizes and orientations. Even when the flaws are randomly distributed, their preferential activation, and the nucleation and growth of tension cracks at preferential flaws, render the overall response of the solid highly anisotropic. As a first step toward a more complete constitutive micromechanical modeling, a dilute distribution of preexisting flaws is assumed, rate constitutive relations are developed for loading and unloading, which include hysteresis, dilatancy, and other characteristics observed experimentally in rocks, ceramics, concrete, and similar brittle materials. A number of illustrative examples are worked out, and the results are compared to relevant experimental observations.

Copyright © 1988 by ASME
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