MSEN 681 Seminar Series 4:10 PM, Monday, April 13, 2015 • 202 Reed-McDonald Building Fracture Processes in Cortical Bone Professor Vadim Silberschmidt Loughborough University, United Kingdom abstract Understanding of bone fracture can improve medical and surgical procedures. Therefore, investigation of the effect of bone’s microstructure and properties as well as loading parameters on initiation and propagation of crack is of great importance. In this paper, several modelling approaches are used to study fracture of cortical bone tissue at various length scales and different types of loading. Two major problems are tackled: crack propagation under impact loading and bone cutting in surgical procedures. In the former case, a micro-scale finite-element fracture model is suggested accounting for bone’s microstructure and using X-FEM for crack propagation analysis. Several formulations are used: effective homogeneous medium and three- and four-component heterogeneous one. The topology of a transverse-radial cross section captured with optical microscopy is used to generate the models in two last cases; extensive experimental studies provide necessary mechanical input data. The effect of dynamic loading is analyzed separately, employing both experimental analysis and numerical simulations. Two areas are covered: tensile impact tests to quantify a bone’s behavior under impact loading, and a 3D finite-element model simulating these tests. In the first area the effect of three different parameters -– a cortex position, a notch depth and an energy level – on the bones tissue’s response is investigated. Additionally, a 3D numerical model for the tensile impact test is developed using Abaqus/Explicit finite-element software. The problem of bone cutting is treated within the framework of tool-bone interaction analysis. A twodomain approach is used, with a process zone treated using the smooth-particle hydrodynamics method. This zone is embedded in a continuum domain with macroscopic anisotropic properties obtained in experiments. This study is supported by analysis of damage induced by the interaction between the cutting tool and bone tissue using wedge and indentation tests and considering also the anisotropic behavior of the bone. Indentation tests are performed on several anatomical positions of a bovine cortical bone to observe damage initiation and effect of mechanical anisotropy on damage characteristics. Each anatomical position is tested with a load ranging from 1 kg to 100 kg. The wedge testing provides a broader perspective on damage evolution, especially in the direction of tool motion. http://msen.tamu.edu