Deformation and fracture behaviour of cortical bone based on anisotropic yield criteria using finite element method.
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Date
2016
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Publisher
Universiti Teknologi Malaysia
Abstract
Bone fractures have long been studied by clinicians and biomedical engineering researchers. Despite the widespread use of different fracture criteria to evaluate the fracture behaviour of bone, yet the proposed models mostly consider the ultimate load as the failure point which is not practical and realistic for the natural quasi brittle behaviour of bone. In this study, a finite element based anisotropic failure criterion coupled with quasi brittle damage law model was proposed. The developed model aims to analyse the progressive failure of bone under different loading modes and to improve the prediction of both deformation and failure of cortical bone. Both experimental works and computational simulation were carried out under two type of loading modes: compression and bending. To validate the nature of quasi brittle bone behaviour and the experimental works, an available isotropic Brittle Damaged Plasticity (BDP) model in finite element software (ABAQUS) was implemented and the comparison was made with the experimental data. Then, anisotropic Liu-Huang-Stout (LHS) yield criterion and quasi brittle damage model were implemented through user subroutine code: user subroutine to define material behaviour (VUMAT) to display a complete force displacement curve as well as to characterise the damage and failure of full femur bovine bone. Experimental results showed that the trend of force-displacement exhibits the same trend with finite element BDP model. It also highlighted the damage propagation was corresponded to the accumulation of plastic strain. From the developed model, the force-displacement curve, the damage evolution and plastic strain distribution were in good agreement with the experimental works and the previous literatures. The accuracy of the proposed model is achieved up to 15% over the BDP model. This indicates that the proposed model could be more accurate in the prediction of bone deformation and fracture behaviour. Therefore, this model will provide better analysis in designing orthopaedic implants that will attach to the bone.
Description
Thesis (PhD. (Mechanical Engineering))
Keywords
Biomedical engineering, Fracture mechanics, Biomaterials