Hexahedral elements with a single integration point have been the solid elements of choice to represent organs in human finite element models for impact. While those elements have been known to be efficient in terms of stability and computational cost, they are difficult to generate and meshing represents a significant part of a model development time. The ever increasing level of details of biomechanical models further increases these meshing difficulties. In recent years, computing power has become affordable and new formulations of tetrahedral elements – that can be generated automatically even for complex shapes – have been introduced in the explicit finite element codes. The aim of this study was to evaluate the performance of two meshing approaches – semiautomatic hexahedron meshing vs. automatic tetrahedron meshing – for a simple biomechanical application. In this study, a kidney model was build based on the geometry from Visible Human Project dataset. Five types of 3D solid elements (8 node bricks with a single and 8 integration points, 20 node bricks, 4 and 10 node tetrahedrons) and two material laws (linear visco-elastic, hyperelastic viscous) were used to simulate a kidney blunt impact described in Schmitt and Snedeker .
While the drawbacks of tetrahedral elements were observed in particular in terms of computing cost, the difference in model response was found to be acceptable in a biomechanical characterized by large specimen to specimen variability. Furthermore, the tetrahedral element stability was found to be excellent.
For more complex shapes, the increased computing cost may be largely outweighed by the advantages of an automatic meshing approach.
|2005||Vezin P, Verriest JP. Development of a set of numerical human models for safety. In: Proceedings of the 19th International Technical Conference on the Enhanced Safety of Vehicles (ESV). June 6-9, 2005; Washington, DC.|
|2005||Snedeker JG, Barbezat M, Niederer P, Schmidlin FR, Farshad M. Strain energy density as a rupture criterion for the kidney: impact tests on porcine organs, finite element simulation, and a baseline comparison between human and porcine tissues. J Biomech. May 2005;38(5):993-1001.|
|2005||Snedeker JG, Niederer P, Schmidlin FR, Farshad M, Demetropoulos CK, Lee JB, Yang KH. Strain-rate dependent material properties of the porcine and human kidney capsule. J Biomech. May 2005;38(5):1011-1021.|
|2006||Ramos A, Simões JA. Tetrahedral versus hexahedral finite elements in numerical modelling of the proximal femur. Med Eng Phys. November 2006;28(9):916.|