Abstract
The mechanical characterization of brain tissue has been generally analyzed in the frequency and time domain. It is crucial to understand the mechanics of the brain under realistic, dynamic conditions and convert it to enable mathematical modelling in a time domain. In this study, the compressive viscoelastic properties of brain tissue were investigated under time and frequency domains with the same physical conditions and the theory of viscoelasticity was applied to estimate the prediction of viscoelastic response in the time domain based on frequency-dependent mechanical moduli through Finite Element models. Storage and loss modulus were obtained from white and grey matter, of bovine brains, using dynamic mechanical analysis and time domain material functions were derived based on a Prony series representation. The material models were evaluated using brain testing data from stress relaxation and hysteresis in the time dependent analysis. The Finite Element models were able to represent the trend of viscoelastic characterization of brain tissue under both testing domains. The outcomes of this study contribute to a better understanding of brain tissue mechanical behaviour and demonstrate the feasibility of deriving time-domain viscoelastic parameters from frequency-dependent compressive data for biological tissue, as validated by comparing experimental tests with computational simulations.
Highlights
Brain tissue is soft and complex, and its mechanical characterization has been studied for decades
The frequency dependent mechanical behaviors of brain white and grey matter were characterized through dynamic mechanical testing, and our results show that the storage modulus is greater than the loss modulus over all tested frequencies
The Finite element (FE) models in the frequency domain were capable of capturing the trend for both storage and loss moduli across the frequencies investigated
Summary
Brain tissue is soft and complex, and its mechanical characterization has been studied for decades. The mechanical behavior of brain tissue has been studied under various test conditions. Oscillations of the head leading to brain shaking within the skull can produce brain trauma.[26]. Comparison of the mechanical properties of brain tissue in the literature shows that there is a lack of standard testing protocols.[12] Some studies investigated brain tissue in the time domain[50] while dynamic sweep tests on brain tissue in the frequency domain have been performed.[16] Further, the mechanical results depend on sample preparation, indenter geometry and measurement length-scale. Compressive loading can lead to brain trauma[1,54] and compressive waves were found on the impact site of brain tissue during the course of head dynamics.[36]. A range of dynamic mechanical data are available for various materials in the literature, it has rarely been applied in
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