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Research Abstracts Online
January 2010 - March 2011

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University of Minnesota Twin Cities
College of Science and Engineering
Department of Civil Engineering

PI: Jialiang Le

Scaling of Crack Growth Rate Law of Quasibrittle Structures Under Cyclic Compressive Loading

Many engineering structures, such as buildings, infrastructure, aircraft, and biomedical implants, are often subjected to cyclic compressive loading. Many of these structures are made of brittle heterogenous (quasibrittle) materials, which include concrete, fiber composites, toughened ceramics, bone, and many materials at micro- or nano-scales. Experiment investigations have shown that a crack would grow in brittle and quasibrittle materials, such as fine grain ceramics and mortar, under mode-I cyclic compressive loading. At the same time, it has also been shown that there is an intricate size effect on the crack growth rate of quasibrittle materials under mode-I cyclic tensile loading. However, no information is available on the effect of structure size on the fatigue crack growth under compressive cyclic loading. The objective of this project is to investigate the size effect on the rate of crack growth under compressive fatigue loading. A cyclic cohesive element will be developed to simulate the material behavior at the crack-tip region. Since the associated cohesive law involves an intrinsic characteristic length, it is expected that the crack growth rate under cyclic compressive loading would exhibit an intricate size effect, transiting from one power-law to another. The resulting size effect equation would provide a sound basis for the prediction of the fatigue lifetime of large-scale structures from the small-scale laboratory tests.