Application of Optimization Methodology and Specimen-Specific Finite Element Models for Investigating Material Properties of Rat Skull

State Key Laboratory of Advanced Design and Manufacturing for Vehicle Body, Hunan University, Hunan, China.
Annals of Biomedical Engineering (Impact Factor: 3.23). 01/2011; 39(1):85-95. DOI: 10.1007/s10439-010-0125-0
Source: PubMed


Finite element (FE) models of rat skull bone samples were developed by reconstructing the three-dimensional geometry of microCT images and voxel-based hexahedral meshes. An optimization-based material identification method was developed to obtain the most favorable material property parameters by minimizing differences in three-point bending test responses between experimental and simulation results. An anisotropic Kriging model and sequential quadratic programming, in conjunction with Latin Hypercube Sampling (LHS), are utilized to minimize the disparity between the experimental and FE model predicted force-deflection curves. A selected number of material parameters, namely Young's modulus, yield stress, tangent modulus, and failure strain, are varied iteratively using the proposed optimization scheme until the assessment index 'F', the objective function comparing simulation and experimental force-deflection curves through least squares, is minimized. Results show that through the application of this method, the optimized models' force-deflection curves are closely in accordance with the measured data. The average differences between the experimental and simulation data are around 0.378 N (which was 3.3% of the force peak value) and 0.227 N (which was 2.7% of the force peak value) for two different test modes, respectively. The proposed optimization methodology is a potentially useful tool to effectively help establish material parameters. This study represents a preliminary effort in the development and validation of FE models for the rat skull, which may ultimately serve to develop a more biofidelic rat head FE model.

Download full-text


Available from: Xu Han, Apr 30, 2015
  • Source
    • "The material properties of impact surfaces can be determined by FE simulation and optimisation method through matching the simulation results with those from the drop tests. This method has been used in the literature [10] [12] [34]. Figure 3 shows the processes of determining the material properties of impact surfaces using this method. "
    [Show abstract] [Hide abstract]
    ABSTRACT: The mechanism and tolerance of paediatric head injuries are not well established mainly due to the limited cadaveric tests available. Weber's studies [Experimental studies of skull fractures in infants, Z Rechtsmed. 92 (1984), pp. 87–94; Biomechanical fragility of the infant skull, Z Rechtsmed. 94 (1985), pp. 93–101] in mid 1980s contained the most extensive paediatric cadaver test data under various fall conditions in the literature. However, the limited injury measurements and the unknown material properties of the impact surfaces in Weber's tests limited their application in paediatric fall protection. In the present study, drop tests, inverse finite element modelling and optimisation were first conducted to quantify the material characteristics of four impact surfaces (carpet, vinyl, foam and blanket) used in the Weber's tests. With the impact surface material determined, five cadaver tests from Weber's studies were reconstructed using a parametric paediatric head finite element model. Results showed that the simulated strain and stress distributions on the skulls correlated well with the fracture patterns reported in the cadaver tests. The impact surface material properties developed in this study and the methods of using the parametric paediatric head model to reconstruct the cadaver tests provided valuable information for future ground surface designs for child fall protection and development of paediatric head injury criteria.
    Full-text · Article · Aug 2013 · International Journal of Crashworthiness
  • Source
    • "Due to its importance in clinical and research applications, subject-specific finite element (FE) modelling of bone is a fast growing domain. A number of specimen-specific modelling procedures were proposed in the past decade (Weinans et al. 2000; Anderson et al. 2005; Wullschleger et al. 2010; Guan et al. 2011). However, the assessment of the reliability of the mechanical predictions obtained using such models remains a challenging issue as it depends on both the methods applied and the research discipline. "
    [Show abstract] [Hide abstract]
    ABSTRACT: The authors propose a protocol to derive finite element (FE) models from micro computer tomography scans of implanted rat bone. A semi-automatic procedure allows segmenting the images using specimen-specific bone mineral density (BMD) thresholds. An open-source FE model generator processes the segmented images to a quality tetrahedral mesh. The material properties assigned to each element are integrated from the BMD field. Piecewise, threshold-dependent density-elasticity relationships are implemented to limit the effects of metal artefacts. A detailed sensitivity study highlights the coherence of the generated models and quantifies the influence of the modelling parameters on the results. Two applications of the protocol are proposed. The stiffness of bare and implanted rat tibiae specimens is predicted by simulating three-point bending and inter-implant displacement, respectively. Results are compared with experimental tests. The mean value and the variability between the specimens are well captured in both tests.
    Full-text · Article · Jun 2013 · Computer Methods in Biomechanics and Biomedical Engineering
  • [Show abstract] [Hide abstract]
    ABSTRACT: The finite element (FE) method is a powerful tool to study brain injury that remains to be a critical health concern. Subject/patient-specific FE brain models have the potential to accurately predict a specific subject/patient's brain responses during computer-assisted surgery or to design subject-specific helmets to prevent brain injury. Unfortunately, efforts required in the development of high-quality hexahedral FE meshes for brain, which consists of complex intracranial surfaces and varying internal structures, are daunting. Using multi-block techniques, an efficient meshing process to develop all-hexahedral FE brain models for an adult and a paediatric brain (3-year old) was demonstrated in this study. Furthermore, the mesh densities could be adjusted at ease using block techniques. Such an advantage can facilitate a mesh convergence study and allows more freedom for choosing an appropriate brain mesh density by balancing available computation power and prediction accuracy. The multi-block meshing approach is recommended to efficiently develop 3D all-hexahedral high-quality models in biomedical community to enhance the acceptance and application of numerical simulations.
    No preview · Article · Dec 2011 · Computer Methods in Biomechanics and Biomedical Engineering
Show more