Finite element models of rib as an inhomogeneous beam structure under high-speed impacts

Fracture of ribs commonly occurs during blunt impacts and can lead to serious injuries or even fatality. The finite element (FE) modeling of ribs under impacts, however, is difficult due to the complex geometry, the difficulty in determining material parameters, and the amount of the computational time required. This study develops a method of modeling ribs as inhomogeneous beam structures. The geometries are reconstructed from images acquired with X-ray computed tomography. Bone material properties, orthotropic or isotropic, are determined from the CT pixel values. From the material distribution inside the cross-section, generalized classical beam formulations use to determine the local homogenized stiffness of the nodes along the rib. To compare the accuracy and efficiency of the method, detailed three-dimensional (3D) FE models of ribs are also developed. Simulations of three benchmark problems that represent different loading or impact conditions demonstrate that the beam FE model is very efficient and is at least as accurate as a very finely meshed 3D FE model. Finally, the rib FE model is used to study blunt trauma injury of animal tests under high-speed impacts. The consistency between predictions and experimental results shows that the developed rib model is a great value to study of blunt trauma caused by high-speed impacts.