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TECHNICAL BRIEFS

Modified Bilston Nonlinear Viscoelastic Model for Finite Element Head Injury Studies

[+] Author and Article Information
F. Shen1

Division of Bioengineering, National University of Singapore, 9 Engineering Drive 1, Singapore 117576mpesf@nus.edu.sg

T. E. Tay, J. Z. Li, S. Nigen

Division of Bioengineering, National University of Singapore, 9 Engineering Drive 1, Singapore 117576

P. V. Lee, H. K. Chan

 Defence Medical and Environmental Research Institute, 27 Medical Drive, Singapore 117510

1

Corresponding author.

J Biomech Eng 128(5), 797-801 (Mar 08, 2006) (5 pages) doi:10.1115/1.2264393 History: Received October 13, 2005; Revised March 08, 2006

This paper proposes a modified nonlinear viscoelastic Bilston model (Bilston, 2001, Biorheol., 38, pp. 335–345). for the modeling of brain tissue constitutive properties. The modified model can be readily implemented in a commercial explicit finite element (FE) code, PamCrash. Critical parameters of the model have been determined through a series of rheological tests on porcine brain tissue samples and the time-temperature superposition (TTS) principle has been used to extend the frequency to a high region. Simulations by using PamCrash are compared with the test results. Through the use of the TTS principle, the mechanical and rheological behavior at high frequencies up to 104rads may be obtained. This is important because the properties of the brain tissue at high frequencies and impact rates are especially relevant to studies of traumatic head injury. The averaged dynamic modulus ranges from 130Pato1500Pa and loss modulus ranges from 35Pato800Pa in the frequency regime studied (0.01radsto3700rads). The errors between theoretical predictions and averaged relaxation test results are within 20% for strains up to 20%. The FEM simulation results are in good agreement with experimental results. The proposed model will be especially useful for application to FE analysis of the head under impact loads. More realistic analysis of head injury can be carried out by incorporating the nonlinear viscoelastic constitutive law for brain tissue into a commercial FE code.

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Copyright © 2006 by American Society of Mechanical Engineers
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Figures

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Figure 1

Finite element models for shear relaxation and compression simulation. (a) Model for shear relaxation; (b) Model for compression.

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Figure 2

The linear viscoelastic regime (LVR) in strain at 37°C(ω=10rad∕s)

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Figure 3

Brain tissues properties as measured in oscillation tests at different temperatures

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Figure 4

Small strain oscillatory results predicted by the model

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Figure 5

Comparison between theoretical and numerical and experimental results on shear relaxation (in the figure, E denotes experimental data, T denotes theoretical predictions, N denotes FE numerical results)

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Figure 6

Comparison between numerical and experimental results on unconfined compression (strain rate=0.01s−1)

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