9625406 This work, a collaboration between researchers at Cornell University and the University of Oklahoma, is focused on developing understanding about the mechanisms of rock fracture in compression. The research involves formulation and testing, with unique experiments and computer simulation, necessary to identify the evolution rules for the stable growth of three-dimensional cracks of arbitrary shape in brittle and rock materials. A laser will be used to induce three-dimensional cracks in transparent specimens. These specimens will be tested under compressive loading to induce stable growth and crack interactions. With transparent material, structural instabilities can be easily observed. Based on the test results, three-dimensional crack propagation criteria will be formulated. An existing computer simulator will be applied and extended for fully three-dimensional crack growth and interaction. Evolution rules for crack growth will be programmed into this simulator, which allows arbitrary trajectories of single internal cracks, cracks interacting with free surfaces, and with each other. The hypothesis to be tested within this objective is that, using computer simulation, an acceptable rule is one that will be able not only to reproduce experimental observations, but also will be able to predict evolving crack shapes in additional proof tests before performing them. ***
