Viscoelasticity of brain corpus callosum in biaxial tension |
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| Institution: | 1. School of Biomedical Engineering, Colorado State University, Fort Collins, CO, USA;2. Department of Mechanical Engineering, Colorado State University, Fort Collins, CO, USA;3. Department of Clinical Sciences, Colorado State University, Fort Collins, CO, USA;1. Department of Surgery, Section of Minimally Invasive Surgery, Washington University in St. Louis, St. Louis, MO, USA;2. Department of Mechanical Engineering & Materials Science, Washington University in St. Louis, St. Louis, MO, USA;1. Institute of Biomechanics and Medical Engineering, AML, Department of Engineering Mechanics, Tsinghua University, Beijing 100084, PR China;2. Department of Ultrasonography, Peking University Third Hospital, Beijing 100191, PR China;1. Technical University of Munich, 85748 Garching, Germany;2. Universität Tübingen, 72076 Tübingen, Germany;1. School of Mechanical and Electronic Engineering, Soochow University, Suzhou 215021, Jiangsu, China;2. Robotics and Microsystems Center, Soochow University, Suzhou 215021, Jiangsu, China;3. School of Aerospace and Mechanical Engineering, The University of Oklahoma, Norman, OK 73019, United States;4. Institute for Computational Engineering and Sciences, The University of Texas at Austin, Austin, TX 78705, United States;5. Thayer School of Engineering, Dartmouth College, Hanover, NH 03755, United States;1. Department of Mechanical Engineering, Stanford University, Stanford, CA 94305, USA;2. Department of Mechanical Engineering, University of Erlangen-Nuremberg, 91058 Erlangen, Germany;3. Department of Aerospace and Mechanical Engineering, The University of Notre Dame, Notre Dame, IN 46556, USA;4. Department of Bioengineering, Stanford University, Stanford, CA 94305, USA |
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| Abstract: | Computational models of the brain rely on accurate constitutive relationships to model the viscoelastic behavior of brain tissue. Current viscoelastic models have been derived from experiments conducted in a single direction at a time and therefore lack information on the effects of multiaxial loading. It is also unclear if the time-dependent behavior of brain tissue is dependent on either strain magnitude or the direction of loading when subjected to tensile stresses. Therefore, biaxial stress relaxation and cyclic experiments were conducted on corpus callosum tissue isolated from fresh ovine brains. Results demonstrated the relaxation behavior to be independent of strain magnitude, and a quasi-linear viscoelastic (QLV) model was able to accurately fit the experimental data. Also, an isotropic reduced relaxation tensor was sufficient to model the stress-relaxation in both the axonal and transverse directions. The QLV model was fitted to the averaged stress relaxation tests at five strain magnitudes while using the measured strain history from the experiments. The resulting model was able to accurately predict the stresses from cyclic tests at two strain magnitudes. In addition to deriving a constitutive model from the averaged experimental data, each specimen was fitted separately and the resulting distributions of the model parameters were reported and used in a probabilistic analysis to determine the probability distribution of model predictions and the sensitivity of the model to the variance of the parameters. These results can be used to improve the viscoelastic constitutive models used in computational studies of the brain. |
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| Keywords: | Stress relaxation Anisotropic material Biological material Constitutive behavior Viscoelastic material |
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