Journal
JOURNAL OF THE MECHANICAL BEHAVIOR OF BIOMEDICAL MATERIALS
Volume 65, Issue -, Pages 490-501Publisher
ELSEVIER SCIENCE BV
DOI: 10.1016/j.jmbbm.2016.09.020
Keywords
Soft tissue; Mechanical properties; Transversely isotropic material; Indentation; Genetic algorithm
Funding
- National Natural Science Foundation of China [61503267]
- Jiangsu Province [BK20140356, 16KJB460018]
- Scientific Research Foundation for the Returned Overseas Chinese Scholars, State Education Ministry [K511701515]
- NIH [R01 NS092853]
- School of Aerospace and Mechanical Engineering (AME) at the University of Oklahoma (CHL)
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Characterizing the mechanical properties of white matter is important to understand and model brain development and injury. With embedded aligned axonal fibers, white matter is typically modeled as a transversely isotropic material. However, most studies characterize the white matter tissue using models with a single anisotropic invariant or in a small-strain regime. In this study, we combined a single experimental procedure asymmetric indentation with inverse finite element (FE) modeling to estimate the nearly incompressible transversely isotropic material parameters of white matter. A minimal form comprising three parameters was employed to simulate indentation responses in the large-strain regime. The parameters were estimated using a global optimization procedure based on a genetic algorithm (GA). Experimental data from two indentation configurations of porcine white matter, parallel and perpendicular to the axonal fiber direction, were utilized to estimate model parameters. Results in this study confirmed a strong mechanical anisotropy of white matter in large strain. Further, our results suggested that both indentation configurations are needed to estimate the parameters with sufficient accuracy, and that the indenter-sample friction is important. Finally, we also showed that the estimated parameters were consistent with those previously obtained via a trial-and-error forward FE method in the small-strain regime. These findings are useful in modeling and parameterization of white matter, especially under large deformation, and demonstrate the potential of the proposed asymmetric indentation technique to characterize other soft biological tissues with transversely isotropic properties. (C) 2016 Elsevier Ltd. All rights reserved.
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