Constitutive Properties Determination of Human Cranium by an Experimental-Computational Modal Analysis

In this paper, we identified the material constitutive parameters of the human skull from reported tensile test results. Initially, we applied both linear-elastic and Mooney-Rivlin nonlinear hyperelastic constitutive models to the available tensile test data at different strain rates of 0.005, 0.10, 10, and 150 1/sec. It was shown that the suggested hyperelastic model fitted the test results with higher accuracy in comparison with the linear-elastic model. In the next step, the experimental modal analysis was carried out through roving hammer-impact tests on a dried human skull. The first four natural frequencies of the skull were measured to be 496, 543, 1250, and 1287 Hz, and these values were verified by the modal assurance criterion. Then, a 3D finite element (FE) model of that human skull was created by a 3D scanner and discretized to carry out a computational modal analysis. The performance of the determined material properties for the human skull from both linear and hyperelastic material models was evaluated using FE modal analysis. The calculated modal frequencies were then compared to the experimentally measured frequencies. It was shown that the material parameters from both the linear and hyperelastic constitutive models obtained at a strain rate of 0.10 1/sec, provided the best performance in computational modal analysis with minimum deviations relative to the experimental results. These results confer a better understanding of the human skull behavior among different strain rates, which could increase the accuracy of nonlinearity dynamic simulations on the skull.