Inelastic constitutive modelling of cortical bone taking account of anisotropy and damage

An anisotropic inelastic constitutive model of cortical bone was formulated to predict deformation and failure behavior in traffic accidents or falling by utilizing the framework of viscoplasticity and damage mechanics. The model can represent characteristic features of cortical bone, such as anisotropic elastic coefficients with strain rate dependency, viscoplasticity with strength anisotropy as well as strength asymmetry of tension and compression. The damage evolution equation also enables us to predict bone failure with rate dependency. Experimental data of uniaxial compressive or tensile loading tests of human cortical bone at various strain rates were used to validate the proposed model. Predicted stress-strain curves and failure points agreed well with those of experimental data at wide range of strain rates. This shows the present model can be used to predict bone failure in various impact simulations of traffic accidents or falling.